Every time someone tells me something like, “Non-monogamy is naive. Life’s not that simple.” I want to point them to this image showing just how unsimple non-monogamy is. This is why Cacilda and I encourage people (even couples who write books about sex) to insist on our right to discretion. If it’s highly personal, extremely complex, changing all the time, and really nobody’s business but yours, why answer the question at all? If Bill and Hillary had gone on 60 Minutes back in 1992 with that message, American culture might have taken a big step into maturity.


Preface: A Primate Meets His Match (a note from one of the authors)
Introduction: Another Well-Intentioned Inquisition (below)
– A Few Million Years in a Few Pages

Part I: On the Origin of the Specious
1. Remember the Yucatán!
– You Are What You Eat
2. What Darwin Didn’t Know About Sex (below)

– The Flintstonization of Prehistory
– What Is Evolutionary Psychology and Why Should You Care?
– Lewis Henry Morgan
3. A Closer Look at the Standard Narrative of Human Sexual Evolution
– How Darwin Insults Your Mother (The Dismal Science of Sexual Economics)
– The Famously Flaccid Female Libido
– Male Parental Investment (MPI)
– “Mixed Strategies” in the War Between the Sexes
– Extended Sexual Receptivity and Concealed Ovulation
4. The Ape in the Mirror
– Primates and Human Nature
– Doubting the Chimpanzee Model
– In Search of Primate Continuity

Part II: Lust in Paradise (Solitary?)
5. Who Lost What in Paradise?
– On Getting Funky and Rockin’ Round the Clock
6. Who’s Your Daddies?
– The Joy of S.E.Ex.
– The Promise of Promiscuity
– Bonobo Beginnings
7. Mommies Dearest
– Nuclear Meltdown
8. Making a Mess of Marriage, Mating, and Monogamy
– Marriage: The “Fundamental Condition” of the Human Species?
– On Matrimonial Whoredom
9. Paternity Certainty: The Crumbling Cornerstone of the Standard Narrative
– Love, Lust, and Liberty at Lugu Lake
– On the Inevitability of Patriarchy
– The March of the Monogamous
10. Jealousy: A Beginner’s Guide to Coveting Thy Neighbor’s Spouse
– Zero-Sum Sex
– How to Tell When a Man Loves a Woman

Part III: The Way We Weren’t
11. “The Wealth of Nature” (Poor?)
– Poor, Pitiful Me
– The Despair of Millionaires
– Finding Contentment “at the Bottom of the Scale of Human Beings”
12. The Selfish Meme (Nasty?)
– Homo Economicus
– The Tragedy of the Commons
– Dreams of Perpetual Progress
– Ancient Poverty or Assumed Affluence?
– On Paleolithic Politics
13. The Never-Ending Battle over Prehistoric War (Brutish?)
– Professor Pinker, Red in Tooth and Claw
– The Mysterious Disappearance of Margaret Power
– The Spoils of War
– The Napoleonic Invasion (The Yanomami Controversy)
– The Desperate Search for Hippie Hypocrisy and Bonobo Brutality
14. The Longevity Lie (Short?)
– When Does Life Begin? When Does It End?
– Is 80 the New 30?
– Stressed to Death
Who’re You Calling a Starry-Eyed Romantic, Pal? (below)

Part IV: Bodies in Motion
15. Little Big Man
– All’s Fair in Love and Sperm War
16. The Truest Measure of a Man
Hard Core in the Stone Age (below)
17. Sometimes a Penis Is Just a Penis
18. The Prehistory of O (below)

– “What Horrid Extravagancies of Minde!”
– Beware the Devil’s Teat
– The Force Required to Suppress It
19. When Girls Go Wild
– Female Copulatory Vocalization
– Sin Tetas, No Hay Paraíso
– Come Again?

Part V: Men Are from Africa, Women Are from Africa
20. On Mona Lisa’s Mind
21. The Pervert’s Lament
– Just Say What?
– Kellogg’s Guide to Child Abuse
– The Curse of Calvin Coolidge
– Ten More Reasons Why I Need Somebody New (Just Like You)
22. Confronting the Sky Together
– Everybody Out of the Closet
– The Marriage of the Sun and the Moon

References and Suggested Further Reading


Introduction: Another Well-Intentioned Inquisition

Forget what you’ve heard about human beings having descended from the apes. We didn’t descend from apes. We are apes. Metaphorically and factually, Homo sapiens is one of the five surviving species of great apes, along with chimpanzees, bonobos, gorillas, and orangutans (gibbons are considered a “lesser ape”). We shared a common ancestor with two of these apes—bonobos and chimps—just five million years ago. That’s “the day before yesterday” in evolutionary terms. The fine print distinguishing humans from the other great apes is regarded as “wholly artificial” by most primatologists these days.

If we’re “above” nature, it’s only in the sense that a shaky-legged surfer is “above” the ocean. Even if we never slip (and we all do), our inner nature can pull us under at any moment. Those of us raised in the West have been assured that we humans are special, unique among living things, above and beyond the world around us, exempt from the humilities and humiliations that pervade and define animal life. The natural world lies below and beneath us, a cause for shame, disgust, or alarm; something smelly and messy to be hidden behind closed doors, drawn curtains, and minty freshness. Or we overcompensate and imagine nature floating angelically in soft focus up above, innocent, noble, balanced, and wise.

Like bonobos and chimps, we are the randy descendents of hypersexual ancestors. At first blush, this may seem an overstatement, but it’s a truth that should have become common knowledge long ago. Conventional notions of monogamous, till-death-do-us-part marriage strain under the dead weight of a false narrative that insists we’re something else. What is the essence of human sexuality and how did it get to be that way? In the following pages, we’ll explain how seismic cultural shifts that began about ten thousand years ago rendered the true story of human sexuality so subversive and threatening that for centuries it has been silenced by religious authorities, pathologized by physicians, studiously ignored by scientists, and covered up by moralizing therapists.

Deep conflicts rage at the heart of modern sexuality. Our cultivated ignorance is devastating. The campaign to obscure the true nature of our species’ sexuality leaves half our marriages collapsing under an unstoppable tide of swirling sexual frustration, libido-killing boredom, impulsive betrayal, dysfunction, confusion, and shame. Serial monogamy stretches before (and behind) many of us like an archipelago of failure: isolated islands of transitory happiness in a cold, dark sea of disappointment. And how many of the couples who manage to stay together for the long haul have done so by resigning themselves to sacrificing their eroticism on the altar of three of life’s irreplaceable joys: family stability, companionship, and emotional, if not sexual, intimacy? Are those who aspire to these joys cursed by nature to preside over the slow strangulation of their partner’s libido?

The Spanish word 
esposas means both “wives” and “handcuffs.” In English, some men ruefully joke about the ball and chain. There’s good reason marriage is often depicted and mourned as the beginning of the end of a man’s sexual life. And women fare no better. Who wants to share her life with a man who feels trapped and diminished by his love for her, whose honor marks the limits of his freedom? Who wants to spend her life apologizing for being just one woman? 

Yes, something is seriously wrong. The American Medical Association reports that some 42 percent of American women suffer from sexual dysfunction, while Viagra breaks sales records year after year. Worldwide, pornography is reported to rake in anywhere from fifty-seven to a hundred-
billion-dollars annually. In the United States, it generates more revenue than CBS, NBC, and ABC combined, and more than all professional football, baseball, and basketball franchises. According to U.S. News and World Report,“Americans spend more money at strip clubs than at Broadway, off-Broadway, regional and nonprofit theaters, the opera, the ballet and jazz and classical music performances—combined.”

There’s no denying that we’re a species with a sweet tooth for sex. Meanwhile, so-called traditional marriage appears to be under assault from all sides—as it collapses from within. Even the most ardent defenders of 
normal sexuality buckle under its weight, as never-ending bipartisan perp-walks of politicians (Clinton, Vitter, Gingrich, Craig, Foley, Spitzer, Sanford) and religious figures (Haggard, Swaggert, Bakker) trumpet their support of family values before slinking off to private assignations with lovers, prostitutes, and interns.

Denial hasn’t worked. Hundreds of Catholic priests have confessed to thousands of sex crimes against children in the past few decades alone. In 2008, the Catholic Church paid $436 million in compensation for sexual abuse. More than a fifth of the victims were under ten years old. This we know. Dare we even imagine the suffering such crimes have caused in the seventeen centuries since a sexual life was perversely forbidden to priests in the earliest known papal decree: the 
Decreta and Cum in unum of Pope Siricius (c. 385)? What is the moral debt owed to the forgotten victims of this misguided rejection of basic human sexuality?

On threat of torture, in 1633, the Inquisition of the Roman Catholic Church forced Galileo to state publicly what he knew to be false: that the Earth sat immobile at the center of the universe. Three and a half centuries later, in 1992, Pope John Paul II admitted that the scientist had been right all along, but that the Inquisition had been “well-intentioned.”

Well, there’s no Inquisition like a 
well-intentioned Inquisition.

Like those childishly intransigent visions of an entire universe spinning around an all-important Earth, the standard narrative of prehistory offers an immediate, primitive sort of comfort. Just as pope after pope dismissed any cosmology that would remove humankind from the exalted center of the endless expanse of space, just as Darwin was (and in some crowds, still is) ridiculed for recognizing that human beings are the creation of natural laws, many scientists are blinded by their emotional resistance to any account of human sexual evolution that doesn’t revolve around the monogamous nuclear family unit.

Although we’re led to believe we live in times of sexual liberation, contemporary human sexuality throbs with obvious, painful truths that must not be spoken aloud. The conflict between what we’re 
told we feel and what we really feel may be the richest source of confusion, dissatisfaction, and unnecessary suffering of our time. The answers normally proffered don’t answer the questions at the heart of our erotic lives: Why are men and women so different in our desires, fantasies, responses, and sexual behavior? Why are we betraying and divorcing each other at ever increasing rates when not opting out of marriage entirely? Why the pandemic spread of single-parent families? Why does the passion evaporate from so many marriages so quickly? What causes the death of desire? Having evolved together right here on Earth, why do so many men and women resonate with the idea that we may as well be from different planets?

Oriented toward medicine and business, American society has responded to this ongoing crisis by developing a marital-industrial complex of couples therapy, pharmaceutical hard-ons, sex-advice columnists, creepy father-daughter purity cults, and an endless stream of in-box come-ons (“Unleash your LoveMonster! She’ll thank you!”). Every month, truckloads of glossy supermarket magazines offer the same old tricks to get the spark back into our moribund sex lives.

Yes, a few candles here, some crotchless panties there, toss a handful of rose petals on the bed and it’ll be just like the very first time! What’s that you say? He’s still checking out other women? She’s still got an air of detached disappointment? He’s finished before you’ve begun?

Well, then, let the experts figure out what ails you, your partner, your relationship. Perhaps his penis needs enlarging or her vagina needs a retrofit. Maybe he has “commitment issues,” a “fragmentary superego,” or the dreaded “Peter Pan complex.” Are you depressed? You say you love your spouse of a dozen years but don’t feel sexually attracted the way you used to? One or both of you are tempted by another? Maybe you two should try doing it on the kitchen floor. Or force yourself to do it every night for a year. Maybe he’s going through a midlife crisis. Take these pills. Get a new hairstyle. 
Something must be wrong with you.

Ever feel like the victim of a well-intentioned Inquisition?

This split-personality relationship with our true sexual nature is anything but news to entertainment corporations, who have long reflected the same fractured sensibility between public pronouncement and private desire. In 2000, under the headline “Wall Street Meets Pornography,”
 The New York Times reported that General Motors sold more graphic sex films than Larry Flynt, owner of the Hustler empire. Over eight million American subscribers to DirecTV, a General Motors subsidiary, were spending about $200 million a year on pay-per-view sex films from satellite providers. Similarly, Rupert Murdoch, owner of the Fox News Network and the nation’s leading conservative newspaper, The Wall Street Journal, was pulling in more porn money through a satellite company than Playboy made with its magazine, cable, and Internet businesses combined. AT&T, also a supporter of conservative values, sells hard-core porn to over a million hotel rooms throughout the country via its Hot Network.

The frantic sexual hypocrisy in America is inexplicable if we adhere to traditional models of human sexuality insisting that monogamy is natural, marriage is a human universal, and any family structure other than the nuclear is aberrant. We need a new understanding of ourselves, based not on pulpit proclamations or feel-good Hollywood fantasies, but on a bold and unashamed assessment of the plentiful scientific data that illuminate the true origins and nature of human sexuality.

We are at war with our eroticism. We battle our hungers, expectations, and disappointments. Religion, politics, and even science square off against biology and millions of years of evolved appetites. How to defuse this intractable struggle?

In the following pages, we reassess some of the most important science of our time. We question the deepest assumptions brought to contemporary views of marriage, family structure, and sexuality—issues affecting each of us every day and every night.

We’ll show that human beings evolved in intimate groups where almost everything was shared—food, shelter, protection, child care, even sexual pleasure. We don’t argue that humans are natural-born Marxist hippies. Nor do we hold that romantic love was unknown or unimportant in prehistoric communities. But we’ll demonstrate that contemporary culture misrepresents the link between love and sex. With and without love, a casual sexuality was the norm for our prehistoric ancestors.

Let’s address the question you’re probably already asking: how we can possibly know anything about sex in prehistory? Nobody alive today was there to witness prehistoric life, and since social behavior leaves no fossils, isn’t this all just wild speculation? 

Not quite. There’s an old story about the trial of a man charged with biting off another man’s finger in a fight. An eyewitness took the stand. The defense attorney asked, “Did you actually see my client bite off the finger?” The witness said, “Well, no, I didn’t.” “Aha!” said the attorney with a smug smile. “How then can you claim he bit off the man’s finger?” “Well,” replied the witness, “I saw him spit it out.”

In addition to a great deal of circumstantial evidence from societies around the world and closely related nonhuman primates, we’ll take a look at some of what evolution has spit out. We’ll examine the anatomical evidence still evident in our bodies and the yearning for sexual novelty expressed in our pornography, advertising, and after-work happy hours. We’ll even decode messages in the so-called “copulatory vocalizations” of thy neighbor’s wife as she calls out ecstatically in the still of night.


Readers familiar with the recent literature on human sexuality will be familiar with what we call the standard narrative of human sexual evolution (hereafter shortened to “the standard narrative”). It goes something like this:

1. Boy meets girl.

2. Boy and girl assess one another’s mate value from perspectives based upon their differing reproductive agendas/capacities:

a) He looks for signs of youth, fertility, health, absence of previous sexual experience, and likelihood of future sexual fidelity. In other words, his assessment is skewed toward finding a fertile, healthy young mate with many childbearing years ahead and no current children to drain his resources.

b) She looks for signs of wealth (or at least prospects of future wealth), social status, physical health, and likelihood that he will stick around to protect and provide for their children. Her guy must be willing and able to provide materially for her (especially during pregnancy and breastfeeding) and their children (known as male parental investment).

3. Boy gets girl: assuming they meet one another’s criteria, they “mate,” forming a long-term pair bond—the “fundamental condition of the human species,” as famed author Desmond Morris put it. Once the pair bond is formed:

a) She will be sensitive to indications that he is considering leaving (vigilant toward signs of infidelity involving intimacy with other women that would threaten her access to his resources and protection)—while keeping an eye out (around ovulation, especially) for a quick fling with a man genetically superior to her husband.

b) He will be sensitive to signs of her sexual infidelities (which would reduce his all-important paternity certainty)—while taking advantage of short-term sexual opportunities with other women (as his sperm are easily produced and plentiful).

Researchers claim to have confirmed these basic patterns in studies conducted around the world over several decades. Their results seem to support the standard narrative of human sexual evolution, which appears to make a lot of sense. But they don’t, and it doesn’t.

While we don’t dispute that these patterns play out in many parts of the modern world, we don’t see them as elements of human nature so much as adaptations to social conditions—many of which were introduced with the advent of agriculture no more than ten thousand years ago. These behaviors and predilections are not biologically programmed traits of our species; they are evidence of the human brain’s flexibility and the creative potential of community. 

To take just one example, we argue that women’s seemingly consistent preference for men with access to wealth is 
not a result of innate evolutionary programming, as the standard model asserts, but simply a behavioral adaptation to a world in which men control a disproportionate share of the world’s resources. As we’ll explore in detail, before the advent of agriculture a hundred centuries ago, women typically had as much access to food, protection, and social support as did men. We’ll see that upheavals in human societies resulting from the shift to settled living in agricultural communities brought radical changes to women’s ability to survive. Suddenly, women lived in a world where they had to barter their reproductive capacity for access to the resources and protection they needed to survive. But these conditions are very different from those in which our species had been evolving previously.

It’s important to keep in mind that when viewed against the full scale of our species’ existence, ten thousand years is but a brief moment. Even if we ignore the roughly two million years since the emergence of our 
Homo lineage, in which our direct ancestors lived in small foraging social groups, anatomically modern humans are estimated to have existed for about 200,000 years. With the earliest evidence of agriculture dating to about 8000 BCE, the amount of time our species has spent living in settled agricultural societies represents just 5 percent of our collective experience, at most. As recently as a few hundred years ago, most of the planet was still occupied by foragers.

So in order to trace the deepest roots of human sexuality, it’s vital to look beneath the thin crust of relatively recent human history. Until agriculture, human beings evolved in societies organized around an insistence on sharing just about everything. But all this sharing doesn’t make anyone a 
noble savage. These pre-agricultural societies were no nobler than you are when you pay your taxes or insurance premiums. Universal, culturally imposed sharing was simply the most effective way for our highly social species to minimize risk. Sharing and self-interest, as we shall see, are not mutually exclusive. Indeed, what many anthropologists call fierce egalitarianism was the predominant pattern of social organization around the world for many millennia before the advent of agriculture. 

But human societies changed in radical ways once they started farming and raising domesticated animals. They organized themselves around hierarchical political structures, private property, densely populated settlements, a radical shift in the status of women, and other social configurations that together represent an enigmatic disaster for our species: human population growth mushroomed as quality of life plummeted. The shift to agriculture, wrote author Jared Diamond, is a “catastrophe from which we have never recovered.”

Several types of evidence suggest our pre-agricultural (prehistoric) ancestors lived in groups where most mature individuals would have had several ongoing sexual relationships at any given time. Though often casual, these relationships were not random or meaningless. Quite the opposite: they reinforced crucial social ties holding these highly interdependent communities together.

We’ve found overwhelming evidence of a decidedly casual, friendly prehistory of human sexuality echoed in our own bodies, in the habits of remaining societies still lingering in relative isolation, and in some surprising corners of contemporary Western culture. We’ll show how our bedroom behavior, porn preferences, fantasies, dreams, and sexual responses all support this reconfigured understanding of our sexual origins. Questions you’ll find answered in the following pages include:


  • Why is long-term sexual fidelity so difficult for so many couples?
  • Why does sexual passion often fade, even as love deepens?
  • Why are women potentially multi-orgasmic, while men all too often reach orgasm frustratingly quickly and then lose interest?
  • Is sexual jealousy an unavoidable, uncontrollable part of human nature?
  • Why are human testicles so much larger than those of gorillas but smaller than those of chimps?
  • Can sexual frustration make us sick? How did a lack of orgasms cause one of the most common diseases in history, and how was it treated?


The Flintstonization of Prehistory

“Judging from the social habits of man as he now exists” is anything but a reliable method for understanding prehistory (though admittedly, Darwin had little else to go on). The search for clues to the distant past among the overwhelming detail of the immediate present tends to generate narratives closer to self-justifying myth than to science.

The word myth has been debased and cheapened in modern usage; it’s often used to refer to something false, a lie. But this use misses the deepest function of myth, which is to lend narrative order to apparently disconnected bits of information, the way constellations group impossibly distant stars into tight, easily recognizable patterns that are simultaneously imaginary and real. Psychologists David Feinstein and Stanley Krippner explain, “Mythology is the loom on which [we] weave the raw materials of daily experience into a coherent story.” This weaving becomes tricky indeed when we mythologize about the daily experience of ancestors separated from us by twenty or thirty-thousand years or more. All too often, we inadvertently weave our own experiences into the fabric of prehistory. We call this widespread tendency to project contemporary cultural proclivities into the distant past “Flintstonization.” 

Just as the Flintstones were “the modern stone-aged family,” contemporary scientific speculation concerning prehistoric human life is often distorted by assumptions that seem to make perfect sense. But these assumptions can lead us far from the path to truth.

Flintstonization has two parents: a lack of solid data and the psychological need to explain, justify, and celebrate one’s own life and times. But for our purposes, Flintstonization has at least three intellectual grandfathers: Hobbes, Rousseau, and Malthus. 

Thomas Hobbes (1588–1679), a lonely, frightened war refugee in Paris, was Flintstoned when he looked into the mists of prehistory and conjured miserable human lives that were “solitary, poor, nasty, brutish and short.” He conjured a prehistory very much like the world he saw around him in seventeenth-century Europe, yet gratifyingly worse in every respect. Propelled by a very different psychological agenda, Jean-Jacques Rousseau (1712–1778) looked at the suffering and filth of European societies and thought he saw the corruption of a pristine human nature. Travelers’ tales of simple savages in the Americas fueled his romantic fantasies. The intellectual pendulum swung back toward the Hobbesian view a few decades later when Thomas Malthus (1766–1834) claimed to mathematically demonstrate that extreme poverty and its attendant desperation typify the eternal human condition. Destitution, he argued, is intrinsic to the calculus of mammalian reproduction. As long as population increases exponentially, doubling each generation (2, 4, 8, 16, 32, etc.), and farmers can increase the food supply only by adding acreage mathematically (1, 2, 3, 4, etc.), there will never—can never—be enough for everyone. Thus, Malthus concluded that poverty is as inescapable as the wind and the rain. Nobody’s fault. Just the way it is. This conclusion was very popular with the wealthy and powerful, who were understandably eager to make sense of their good fortune and justify the suffering of the poor as an unavoidable fact of life.

eureka moment was a gift from two terrible Thomases and one friendly Fred: Hobbes, Malthus, and Flintstone, respectively. By articulating a detailed (albeit erroneous) description of human nature and the sorts of lives human beings lived in prehistory, Hobbes and Malthus provided the intellectual context for Darwin’s theory of natural selection. Unfortunately, their thoroughly Flintstoned assumptions are fully integrated into Darwin’s thinking and persist to the present day.

The sober tones of serious science often mask the mythical nature of what we’re told about prehistory. And far too often, the myth is dysfunctional, inaccurate, and self-justifying.

Our central ambition for this book is to distinguish some of the stars from the constellations. We believe that the generally accepted myth of the origins and nature of human sexuality is not merely factually flawed, but destructive, sustaining a false sense of what it means to be a human being. This false narrative distorts our sense of our capacities and needs. It amounts to false advertising for a garment that fits almost no one. But we’re all supposed to buy and wear it anyway.

Like all myths, this one seeks to define who and what we are and thus what we can expect and demand from one another. For centuries, religious authorities disseminated this defining narrative, warning of chatty serpents, deceitful women, forbidden knowledge, and eternal agony. But more recently, it’s been marketed to secular society as hard science.

Examples abound. Writing in the prestigious journal 
Science, anthropologist Owen Lovejoy suggested, “The nuclear family and human sexual behavior may have their ultimate origin long before the dawn of the Pleistocene [1.8 million years ago].” Well-known anthropologist Helen Fisher concurs, writing, “Is monogamy natural?” She gives a one-word answer: “Yes.” She then continues, “Among human beings … monogamy is the rule.” 

Many different elements of human prehistory seem to nest neatly into each other in the standard narrative of human sexual evolution. But remember, that Indian seemed to answer Cortés’s question, and it seemed indisputable to Pope Urban VIII and just about everyone else that the Earth remained solidly at the center of the solar system. With a focus on the presumed nutritional benefits of pair-bonding, zoologist and science writer Matt Ridley demonstrates the seduction in this apparent unity: “Big brains needed meat … [and] food sharing allowed a meaty diet (because it freed men to risk failure in pursuit of game) … [and] food sharing demanded big brains (without detailed calculating memories, you could easily be cheated by a free-loader).” So far, so good. But now Ridley inserts the sexual steps in his dance: “The sexual division of labor promoted monogamy (a pair bond now being an economic unit); monogamy led to neotenous sexual selection (by putting a premium on youthfulness in mates).” It’s a waltz, with one assumption spinning into the next, circling round and round in “a spiral of comforting justification, proving how we came to be as we are.” 

Note how each element anticipates the next, all coming together in a tidy constellation that seems to explain human sexual evolution.
The distant stars fixed in the standard constellation include:


  • what motivated prehuman males to “invest” in a particular female and her children;
  • male sexual jealousy and the double standard concerning male versus female sexual autonomy;
  • the oft-repeated “fact” that the timing of women’s ovulation is “hidden”;
  • the inexplicably compelling breasts of the human female;
  • her notorious deceptiveness and treachery, source of many country and blues classics;
  • and of course, the human male’s renowned eagerness to screw anything with legs—an equally rich source of musical material.

This is what we’re up against. It’s a song that is powerful, concise, self-reinforcing, and playing on the radio all day and all night … but still wrong, baby, oh so wrong.

The standard narrative is about as scientifically valid as the story of Adam and Eve. In many ways, in fact, it is a scientific retelling of the Fall into original sin as depicted in
Genesis—complete with sexual deceit, prohibited knowledge, and guilt. It hides the truth of human sexuality behind a fig leaf of anachronistic Victorian discretion repackaged as science. But actual—as opposed to mythical—science has a way of peeking out from behind the fig leaf.The Flintstonization of Prehistory

“Judging from the social habits of man as he now exists” is anything but a reliable method for understanding prehistory (though admittedly, Darwin had little else to go on). The search for clues to the distant past among the overwhelming detail of the immediate present tends to generate narratives closer to self-justifying myth than to science.

The word myth has been debased and cheapened in modern usage; it’s often used to refer to something false, a lie. But this use misses the deepest function of myth, which is to lend narrative order to apparently disconnected bits of information, the way constellations group impossibly distant stars into tight, easily recognizable patterns that are simultaneously imaginary and real. Psychologists David Feinstein and Stanley Krippner explain, “Mythology is the loom on which [we] weave the raw materials of daily experience into a coherent story.” This weaving becomes tricky indeed when we mythologize about the daily experience of ancestors separated from us by twenty or thirty-thousand years or more. All too often, we inadvertently weave our own experiences into the fabric of prehistory. We call this widespread tendency to project contemporary cultural proclivities into the distant past “Flintstonization.” 

Just as the Flintstones were “the modern stone-aged family,” contemporary scientific speculation concerning prehistoric human life is often distorted by assumptions that seem to make perfect sense. But these assumptions can lead us far from the path to truth.

Flintstonization has two parents: a lack of solid data and the psychological need to explain, justify, and celebrate one’s own life and times. But for our purposes, Flintstonization has at least three intellectual grandfathers: Hobbes, Rousseau, and Malthus. 

Thomas Hobbes (1588–1679), a lonely, frightened war refugee in Paris, was Flintstoned when he looked into the mists of prehistory and conjured miserable human lives that were “solitary, poor, nasty, brutish and short.” He conjured a prehistory very much like the world he saw around him in seventeenth-century Europe, yet gratifyingly worse in every respect. Propelled by a very different psychological agenda, Jean-Jacques Rousseau (1712–1778) looked at the suffering and filth of European societies and thought he saw the corruption of a pristine human nature. Travelers’ tales of simple savages in the Americas fueled his romantic fantasies. The intellectual pendulum swung back toward the Hobbesian view a few decades later when Thomas Malthus (1766–1834) claimed to mathematically demonstrate that extreme poverty and its attendant desperation typify the eternal human condition. Destitution, he argued, is intrinsic to the calculus of mammalian reproduction. As long as population increases exponentially, doubling each generation (2, 4, 8, 16, 32, etc.), and farmers can increase the food supply only by adding acreage mathematically (1, 2, 3, 4, etc.), there will never—can never—be enough for everyone. Thus, Malthus concluded that poverty is as inescapable as the wind and the rain. Nobody’s fault. Just the way it is. This conclusion was very popular with the wealthy and powerful, who were understandably eager to make sense of their good fortune and justify the suffering of the poor as an unavoidable fact of life.

eureka moment was a gift from two terrible Thomases and one friendly Fred: Hobbes, Malthus, and Flintstone, respectively. By articulating a detailed (albeit erroneous) description of human nature and the sorts of lives human beings lived in prehistory, Hobbes and Malthus provided the intellectual context for Darwin’s theory of natural selection. Unfortunately, their thoroughly Flintstoned assumptions are fully integrated into Darwin’s thinking and persist to the present day.

The sober tones of serious science often mask the mythical nature of what we’re told about prehistory. And far too often, the myth is dysfunctional, inaccurate, and self-justifying.

Our central ambition for this book is to distinguish some of the stars from the constellations. We believe that the generally accepted myth of the origins and nature of human sexuality is not merely factually flawed, but destructive, sustaining a false sense of what it means to be a human being. This false narrative distorts our sense of our capacities and needs. It amounts to false advertising for a garment that fits almost no one. But we’re all supposed to buy and wear it anyway.

Like all myths, this one seeks to define who and what we are and thus what we can expect and demand from one another. For centuries, religious authorities disseminated this defining narrative, warning of chatty serpents, deceitful women, forbidden knowledge, and eternal agony. But more recently, it’s been marketed to secular society as hard science.

Examples abound. Writing in the prestigious journal 
Science, anthropologist Owen Lovejoy suggested, “The nuclear family and human sexual behavior may have their ultimate origin long before the dawn of the Pleistocene [1.8 million years ago].” Well-known anthropologist Helen Fisher concurs, writing, “Is monogamy natural?” She gives a one-word answer: “Yes.” She then continues, “Among human beings … monogamy is the rule.” 

Many different elements of human prehistory seem to nest neatly into each other in the standard narrative of human sexual evolution. But remember, that Indian seemed to answer Cortés’s question, and it seemed indisputable to Pope Urban VIII and just about everyone else that the Earth remained solidly at the center of the solar system. With a focus on the presumed nutritional benefits of pair-bonding, zoologist and science writer Matt Ridley demonstrates the seduction in this apparent unity: “Big brains needed meat … [and] food sharing allowed a meaty diet (because it freed men to risk failure in pursuit of game) … [and] food sharing demanded big brains (without detailed calculating memories, you could easily be cheated by a free-loader).” So far, so good. But now Ridley inserts the sexual steps in his dance: “The sexual division of labor promoted monogamy (a pair bond now being an economic unit); monogamy led to neotenous sexual selection (by putting a premium on youthfulness in mates).” It’s a waltz, with one assumption spinning into the next, circling round and round in “a spiral of comforting justification, proving how we came to be as we are.” 

Note how each element anticipates the next, all coming together in a tidy constellation that seems to explain human sexual evolution.
The distant stars fixed in the standard constellation include:


  • what motivated prehuman males to “invest” in a particular female and her children;
  • male sexual jealousy and the double standard concerning male versus female sexual autonomy;
  • the oft-repeated “fact” that the timing of women’s ovulation is “hidden”;
  • the inexplicably compelling breasts of the human female;
  • her notorious deceptiveness and treachery, source of many country and blues classics;
  • and of course, the human male’s renowned eagerness to screw anything with legs—an equally rich source of musical material.

This is what we’re up against. It’s a song that is powerful, concise, self-reinforcing, and playing on the radio all day and all night … but still wrong, baby, oh so wrong.

The standard narrative is about as scientifically valid as the story of Adam and Eve. In many ways, in fact, it is a scientific retelling of the Fall into original sin as depicted in
Genesis—complete with sexual deceit, prohibited knowledge, and guilt. It hides the truth of human sexuality behind a fig leaf of anachronistic Victorian discretion repackaged as science. But actual—as opposed to mythical—science has a way of peeking out from behind the fig leaf.

the first casualty of war

Professor Pinker, Red in Tooth and Claw

Imagine a high-profile expert stands before a distinguished audience and argues that Asians are warlike people. In support of his argument, he presents statistics from seven countries: Argentina, Poland, Ireland, Nigeria, Canada, Italy, and Russia. “Wait a minute,” you might say, “those aren’t even Asian countries—except, possibly, Russia.” The expert would be laughed off the stage—as he should be.

In 2007, world-famous Harvard professor and best-selling author Steven Pinker gave a presentation built upon similarly flawed logic at the TED conference (Technology, Entertainment, Design) in Long Beach, California. 
Pinker’s presentation provides both a concise statement of the neo-Hobbesian view of the origins of war and an illuminating look at the dubious rhetorical tactics often used to promote this bloodstained vision of our prehistory. The twenty-minute talk is available at the TED website. We encourage you to watch at least the first five minutes (dealing with prehistory) before reading the following discussion. 

Though Pinker spends less than 10 percent of his time discussing hunter-gatherers (a social configuration, you’ll recall, that represents well over 95 percent of our time on the planet), he manages to make a real mess of things.


Three and a half minutes into his talk, Pinker presents a chart based on Lawrence Keeley’s War Before Civilization: The Myth of the Peaceful Savage. The chart shows “the percentage of male deaths due to warfare in a number of foraging or hunting and gathering societies.” He explains that the chart shows that hunter-gatherer males were far more likely to die in war than are men living today.

But hold on. Take a closer look at that chart. It lists seven “hunter- gatherer” cultures as representative of prehistoric war-related male death. The seven cultures listed are the Jivaro, two branches of Yanomami, the Mae Enga, Dugum Dani, Murngin, Huli, and Gebusi. The Jivaro and both Yanomami groups are from the Amazon region, the Murngin are from northern coastal Australia, and the other four are all from the conflict-ridden, densely populated highlands of Papua New Guinea.
Are these groups representative of our hunter-gatherer ancestors? Not even close.

Only one of the seven societies cited by Pinker (the Murngin) even approaches being an immediate-return foraging society (the way Russia is 
sort of Asian, if you ignore most of its population and history). The Murngin had been living with missionaries, guns, and aluminum powerboats for decades by the time the data Pinker cites were collected in 1975—not exactly prehistoric conditions.

None of the other societies cited by Pinker are immediate-return hunter-gatherers, like our ancestors were. They cultivate yams, bananas, or sugarcane in village gardens, while raising domesticated pigs, llamas, or chickens. Even beyond the fact that these societies are not remotely representative of our nomadic, immediate-return hunter-gatherer ancestors, there are still further problems with the data Pinker cites. Among the Yanomami, true levels of warfare are subject to passionate debate among anthropologists, as we’ll discuss shortly. The Murngin are not typical even of Australian native cultures, representing a bloody exception to the typical Australian Aborigine pattern of little to no intergroup conflict. Nor does Pinker get the Gebusi right. Bruce Knauft, the anthropologist whose research Pinker cites on his chart, says the Gebusi’s elevated death rates had nothing to do with warfare. In fact, Knauft reports that warfare is “rare” among the Gebusi, writing, “Disputes over territory or resources are extremely infrequent and tend to be easily resolved.”

Despite all this, Pinker stood before his audience and argued, with a straight face, that his chart depicted a fair estimate of typical hunter- gatherer mortality rates in prehistoric war. This is quite literally unbelievable.

But Pinker is not alone in employing such sleight-of-hand to advance of Hobbes’s dark view of human prehistory. In fact, this selective presentation of dubious data is disturbingly common in the literature on human blood-lust.

In their book 
Demonic Males, Richard Wrangham and Dale Peterson admit that war is unusual in nature, “a startling exception to the normal rule for animals.” But because intergroup violence has been documented in both humans and chimps, they argue, a propensity for war must be an ancient human quality, going back to our last common ancestor. We are, they warn, “the dazed survivors of a continuous, 5-million-year habit of lethal aggression.” Ouch.

But where are the bonobos? In a book of over 250 pages, the word bonobo appears on only eleven of them, and the species is dismissed as offering a less relevant sense of our last common ancestor than the common chimpanzee does—although many primatologists argue the opposite. But at least they 
mentioned the bonobo.

In 2007, David Livingstone Smith, author of 
The Most Dangerous Animal: Human Nature and the Origins of War, published an essay exploring the evolutionary argument that war is rooted in our pri- mate past. In his grisly accounts of chimps pummeling one another to a bloody pulp and eating each other alive, Smith repeatedly refers to them as “our closest non-human relative.” You’d never know from reading his essay that we have an equally close nonhuman relative. The bonobo was left strangely—if typically—unmentioned.

Amid the macho posturing about the brutal implications of chimpanzee violence, doesn’t the equally relevant, nonwarring bonobo rate a mention, at least? Why all the yelling about yang with nary a whisper of yin? All darkness and no light may get audiences excited, but it can’t illuminate them. This oops-forgot-to-mention-the-bonobo technique is distressingly common in the literature on the ancient origins of war.

But the bonobo’s conspicuous absence is notable not just in discussions of war. Look for the missing bonobo wherever someone claims an ancient pedigree for human male violence of any sort. See if you can find the bonobo in this account of the origins of rape, from 
The Dark Side of Man: “Men did not invent rape. Instead, they very likely inherited rape behavior from our ape ancestral lineage. Rape is a standard male reproductive strategy and likely has been one for millions of years. Male humans, chimpanzees, and orangutans routinely rape females. Wild gorillas violently abduct females to mate with them. Captive gorillas also rape females.”

Leaving aside the complications of defining rape in nonhuman species unable to communicate their experiences and motivations, rape— along with infanticide, war, and murder—has never been witnessed among bonobos in several decades of observation. Not in the wild. Not in the zoo. Never.

Doesn’t that warrant a footnote, even?

what darwin didn't know

What Darwin Didn’t Know About Sex

“We are not here concerned with hopes or fears, only with truth as far as our reason permits us to discover it.”
Charles Darwin (
The Descent of Man)

A fig leaf can hide many things, but a human erection isn’t one of them. The standard narrative of the origins and nature of human sexuality claims to explain the development of a deceitful, reluctant sort of sexual monogamy. According to this oft-told tale, heterosexual men and women are pawns in a proxy war directed by their opposed genetic agendas. The whole catastrophe, we’re told, results from the basic biological designs of males and females. Men strain to spread their cheap and plentiful seed far and wide (while still trying to control one or a few females in order to increase their paternity certainty). Meanwhile, women are guarding their limited supply of metabolically expensive eggs from unworthy suitors. But once they’ve roped in a provider-husband, they’re quick to hike up their skirts (when ovulating) for quick-and-dirty clandestine mating opportunities with square-jawed men of obvious genetic superiority. It’s not a pretty picture.

Biologist Joan Roughgarden points out that it’s an image little changed from that described by Darwin 150 years ago. “The Darwinian narrative of sex roles is not some quaint anachronism,” she writes. “Restated in today’s biological jargon, the narrative is considered proven scientific fact…. Sexual selection’s view of nature emphasizes conflict, deceit, and dirty gene pools.” 

No less an authority than 
The Advice Goddess herself (syndicated columnist Amy Alkon) voices the popularized expression of this oft-told tale:

“There are a lot of really bad places to be a single mother, but probably one of the worst ever was 1.8 million years ago on the savanna. The ancestral women who successfully passed their genes on to us were those who were choosy about who they went under a bush with, weeding out the dads from the cads. Men had a different genetic imperative—to avoid bringing home the bison for kids who weren’t theirs—and evolved to regard girls who give it up too easily as too high risk for anything beyond a roll on the rock pile.” 

Note how so much fits into this tidy package: the vulnerabilities of motherhood, separating dads from cads, paternal investment and jealousy, the sexual double standard. But as they say at the airport, beware of tidy packages you didn’t pack yourself.



“As for an English lady, I have almost forgotten what she is — something very angelic and good.”
– Charles Darwin, in a letter from the 
HMS Beagle

“Gentry had to be pitied. They had so few advantages in respect of love. They could say they longed for a kiss from a bouncy wife in a vicarage garden. They couldn’t say she roared under me and clutched my back, and I shot my specimen to blazes.”
– Roger McDonald, 
Mr. Darwin’s Shooter

The best place to begin a reassessment of our conflicted relationship with sexuality may be with Charles Darwin himself. Darwin’s brilliant work inadvertently lent an enduring scientific patina to what is essentially anti-erotic bias. Despite his genius, what Darwin didn’t know about sex could fill volumes. This is just one of them.

On the Origin of Species was published in 1859, a time when little was known about human life before the classical era. Prehistory, the period we define as the 200,000 or so years when anatomically modern people lived without agriculture and writing, was a blank slate theorists could fill only with conjecture. Until Darwin and others began to loosen the link between religious doctrine and scientific truth, guesses about the distant past were restricted by church teachings. The study of primates was in its infancy. Given the scientific data Darwin never saw, it’s not surprising that this great thinker’s blind spots can be as illuminating as his insights. 

For example, Darwin’s ready acceptance of Thomas Hobbes’s still-famous characterization of prehistoric human life as having been “solitary, poor, nasty, brutish, and short” left these mistaken assumptions embedded in present-day theories of human sexuality. Asked to imagine prehistoric human sex, most of us conjure the hackneyed image of the caveman dragging a dazed woman by her hair with one hand, a club in the other. As we’ll see, this image of prehistoric human life is mistaken in every one of its Hobbesian details. Similarly, Darwin eagerly incorporated Thomas Malthus’s unsubstantiated theories about the distant past into his own theorizing, leading to dramatic overestimations of early human suffering (and thus, of the comparative superiority of Victorian life). These pivotal misunderstandings persist in many contemporary evolutionary scenarios.

Though he certainly didn’t originate this narrative of the interminable tango between randy male and choosy female, Darwin beat the drum for its supposed “naturalness” and inevitability. He wrote passages like, “The female…with the rarest exception, is less eager than the male… [She] requires to be courted; she is coy, and may often be seen endeavoring for a long time to escape the male.” While this female reticence is a key feature in the mating systems of many mammals, it isn’t particularly applicable to human beings or, for that matter, the primates most closely related to us.

In light of the philandering he saw going on around him, Darwin wondered whether early humans might have been polygynists (one male mating with several females), writing, “Judging from the social habits of man as he now exists, and from most savages being polygamists, the most probable view is that primeval man aboriginally lived in small communities, each with as many wives as he could support and obtain, whom he would have jealously guarded against all other men.” 

Evolutionary psychologist Steven Pinker appears to be “judging from the social habits of man as he now exists” as well (though without Darwin’s self-awareness) when he bluntly asserts, “In all societies, sex is at least somewhat ‘dirty.’ It is conducted in private, pondered obsessively, regulated by custom and taboo, the subject of gossip and teasing, and a trigger for jealous rage.” We’ll show that while sex is indeed “regulated by custom and taboo,” there are multiple exceptions to every other element of Pinker’s overconfident declaration.

Like all of us, Darwin incorporated his own personal experience—or its absence—into his assumptions about the nature of all life. In 
The French Lieutenant’s Woman, John Fowles gives a sense of the sexual hypocrisy that characterized Darwin’s world. Nineteenth-century England, writes Fowles, was “an age where woman was sacred; and where you could buy a thirteen-year-old girl for a few pounds—a few shillings, if you wanted her for only an hour or two. … Where the female body had never been so hidden from view; and where every sculptor was judged by his ability to carve naked women. …Where it was universally maintained that women do not have orgasms; and yet every prostitute was taught to simulate them.” 

In some respects, the sexual mores of Victorian Britain replicated the mechanics of the age-defining steam engine. Blocking the flow of erotic energy creates ever-increasing pressure which is put to work through short, controlled bursts of productivity. Though he was wrong about a lot, it appears Sigmund Freud got it right when he observed that, “civilization” is built largely on erotic energy that has been blocked, concentrated, accumulated, and redirected.

“To keep body and mind untainted,” explains Walter Houghton in 
The Victorian Frame of Mind, “the boy was taught to view women as objects of the greatest respect and even awe. He was to consider nice women (like his sister and mother, like his future bride) as creatures more like angels than human beings—an image wonderfully calculated not only to dissociate love from sex, but to turn love into worship, and worship of purity.” 

When not in the mood to worship the purity of their sisters, mother, daughters, and wife, men were expected to purge their lust with prostitutes, rather than threatening familial and social stability by “cheating” with “decent women.” Nineteenth-century philosopher Arthur Schopenhauer observed that “there are 80,000 prostitutes in London alone; and what are they if not sacrifices on the altar of monogamy?” 

Charles Darwin was certainly not unaffected by the erotophobia of his era. In fact, one could argue that he was especially sensitive to its influence, inasmuch as he came of age in the intellectual shadow of his famous—and shameless—grandfather, Erasmus Darwin, who had flouted the sexual mores of his day by openly having children with various women and even going so far as to celebrate group sex in his poetry. The death of Charles’s mother when he was just eight years old may well have enhanced his sense of women as angelic creatures floating above earthly urges and appetites. 

Psychiatrist John Bowlby, one of Darwin’s most highly regarded biographers, attributes Darwin’s lifelong anxiety attacks, depression, chronic headaches, dizziness, nausea, vomiting, and hysterical crying fits to the separation anxiety created by the early loss of his mother. This interpretation is supported by a strange letter the adult Charles wrote to a cousin whose wife had just died: “Never in my life having lost one near relation,” he wrote, apparently repressing his memories of his own mother’s death, “I daresay I cannot imagine how severe grief such as yours must be.” Another indication of this psychological scarring was recalled by his granddaughter, who remembered how confused Charles had been when someone added the letter “M” to the word OTHER in a game similar to Scrabble. Charles looked at the board for a long time before declaring, to everyone’s confusion, that no such word existed. 

A hyper-Victorian aversion to (and obsession with) the erotic seems to have continued in Charles’s eldest surviving daughter, Henrietta. “Etty,” as she was known, edited her father’s books, taking her blue crayon to passages she considered inappropriate. In Charles’s biography of his free-thinking grandfather, for example, she deleted a reference to Erasmus’s “ardent love of women.” She also removed “offensive” passages from 
The Descent of Man and Darwin’s autobiography.

Etty’s prim enthusiasm for stamping out anything sexual wasn’t limited to the written word. She waged a bizarre little war against the so-called stinkhorn mushroom (
Phallus ravenelii) that still pops up in the woods around the Darwin estate. Apparently, the similarity of the mushroom to the human penis was a bit much for her. As Etty’s niece (Charles’s granddaughter) recalled years later, “Aunt Etty … armed with a basket and a pointed stick, and wearing a special hunting cloak and gloves,” would set out in search of the mushrooms. At the end of the day, Aunt Etty “burn[ed them] in the deepest secrecy on the drawing room fire with the door locked—because of the morals of the maids.” 


“He will hold thee, when his passion shall have spent its novel force, something better than his dog, a little dearer than his horse.”
– Alfred, Lord Tennyson

Don’t get us wrong. Darwin knew plenty, and he deserves his place in the pantheon of great thinkers. If you’re a Darwin-basher looking for support, you’ll find little here. Charles Darwin was a genius and a gentleman for whom we have endless respect. But as is often the case with male gentleman geniuses, he was a bit clueless when it came to women.

In questions of human sexual behavior, Darwin had little to go on other than conjecture. His own sexual experience appears to have been limited to his vehemently proper wife, Emma Wedgwood, who was also his first cousin and sister-in-law. During his circumnavigation of the globe on the 
Beagle, the young naturalist appears never to have gone ashore in search of the sexual and sensual pleasures pursued by many seafaring men of that era. Darwin was apparently far too inhibited for the decidedly hands-on data collection Herman Melville hinted at in his best-selling novels Typee andOmoo, or to sample the dusky South Pacific pleasures that had inspired the sexually frustrated crew of The Bounty to mutiny.

Darwin was far too buttoned-up for such carnal pursuits. His by-the-book approach to such matters is evident in his careful consideration of marriage in the abstract, before he even had any particular woman in mind. He sketched out the pros and cons in his notebook: 
Marry and Not Marry. On the Marry side he listed, “Children—(if it Please God)—Constant companion, (&friend in old age) who will feel interested in one, —object to be loved and played with. —Better than a dog anyhow … female chit-chat … but terrible loss of time.”

On the other side of the page, Darwin listed concerns such as “Freedom to go where one liked—choice of Society & little of it. … Not forced to visit relatives & to bend in every trifle … fatness & idleness—Anxiety & responsibility. … Perhaps my wife wont [sic] like London; then the sentence is banishment & degradation into indolent, idle fool.” 

Though Darwin proved to be a very loving husband and father, these pros and cons of marriage suggest he very seriously considered opting for the companionship of a dog instead.

on starry-eyed romantics

Who Are You Calling a Starry-Eyed Romantic, Pal?

Many otherwise reasonable people seem to have a burning need to locate the roots of war deep in our primal past, to see self-sufficient foragers as poor, and to spread the misbegotten gospel that three or four decades was a ripe old age for a human being in pre-agricultural times. But this vision of our past is demonstrably false. ¿Que pasa?

If prehistoric life was a perpetual struggle that ended in early death, if ours is a species motivated almost exclusively by self-interest, if war is an ancient, biologically embedded tendency, then one can soothingly argue, as Steven Pinker does, that things are getting better all the time—that, in his Panglossian view, “we are probably living in the most peaceful moment of our species’ time on Earth.” That would be encouraging news, indeed, which is what most audiences want to hear, after all. We all want to believe things are getting better, that our species is learning, growing, and prospering. Who refuses congratulations for having the good sense to be alive here and now?

But just as “patriotism is the conviction that your country is superior to all others because you were born in it” (G. B. Shaw), the notion that we live in our species’ “most peaceful moment” is as intellectually baseless as it is emotionally comforting. Journalist Louis Menand noted how science can fulfill a conservative, essentially political function by providing “an explanation for the way things are that does not threaten the way things are.” “Why,” he asks rhetorically, “should someone feel unhappy or engage in anti-social behavior when that person is living in the freest and most prosperous nation on Earth? It can’t be the system!” What’s your problem? Everything’s just fine. Life’s great and getting better! Less war! Longer life! New and improved human existence!

This Madison Avenue vision of the super-duper present is contrasted with a fictional, blood-smeared Hobbesian past. Yet it’s marketed to the public as the “clear-eyed realist” position, and anyone who questions its founding assumptions, as we do, risks being dismissed as delusional romantics still grieving over the death of Janis Joplin and the demise of bell-bottoms. But that “realistic” argument is riddled with misunderstood data, mistaken interpretations, and misleading calculations. A dispassionate review of the relevant science clearly demonstrates that the tens of thousands of years before the advent of agriculture, while certainly not a time of uninterrupted utopian bliss, was for the most part characterized by robust health, peace between individuals and groups, and high levels of overall satisfaction for most of our ancestors.

Having made this argument, have we outed ourselves as card-carrying comrades in the Delusional Utopian Movement (DUM)? Is it Rousseauian fantasy to assert that prehistory was not an unending nightmare? That human nature leans no more toward violence, selfishness, and exploitation than toward peace, generosity, and cooperation? That most of our ancient ancestors probably experienced a sense of communal belonging few of us enjoy today? That human sexuality probably evolved and functioned as a social bonding device and a pleasurable way to avoid and neutralize conflict? Is it silly romanticism to raise the fact that ancient humans who survived their first few years often lived almost as long as the richest and luckiest of us do today, even with our high-tech coronary stents, diabetes medication, and titanium hips?

No. If you think about it, the neo-Hobbesian vision is far sunnier than ours. To have concluded, as we have, that our species has an innate capacity for love and generosity at least equal to our taste for destruction, for peaceful cooperation as much as coordinated attack, for an open, relaxed sexuality as much as for jealous, passion-smothering possessiveness … to see that both these worlds were open to us, but that around ten thousand years ago a few of our ancestors wandered off the path they’d been on forever into an inescapable garden in which our species has been trapped ever since… well, this is not exactly a rose-colored view of the overall trajectory of humankind. 

Who are the naïve romantics here, anyway? 

The Prehistory of O

Now there you have a sample of man’s “reasoning powers,” as he calls them. He observes certain facts. For instance, that in all his life he never sees the day that he can satisfy one woman; also, that no woman ever sees the day that she can’t overwork, and defeat, and put out of commission any ten masculine plants that can be put to bed to her. He puts those strikingly suggestive and luminous facts together, and from them draws this astonishing conclusion: The Creator intended the woman to be restricted to one man. 
Mark Twain, Letters from the Earth

We recently spotted a young man strolling down Las Ramblas in Barcelona proudly sporting a T-shirt proclaiming that he was Born to F*ck. One wonders whether he has a whole set of these shirts at home: Born to Bre*the, Born to E*t, Born to Dr*nk, Born to Sh*t, and of course the depressing but inevitable Born to D*e.

But maybe he was making a deeper point. After all, the argument central to this book is that sex has long served many crucial functions for Homo sapiens, with reproduction being only the most obvious among them. Since we human beings spend more time and energy planning, executing, and recalling our sexual exploits than any other species on Earth, maybe we all should wear such shirts.

Or maybe just the women. 

When it comes to sex, men may be trash-talking sprinters, but it’s the women who win all the marathons. Any marriage counselor will tell you the most common sex-related complaint women make about men is that they are too quick and too direct. Meanwhile, men’s most frequent sex-related gripe about women is that they take too damned long to get warmed up. After an orgasm, a woman may be anticipating a dozen more. A female body in motion tends to stay in motion. But men come and go. For them, the curtain falls quickly and the mind turns to unrelated matters.

This symmetry of dual disappointment illustrates the almost comical incompatibility between men’s and women’s sexual response in the context of monogamous mating. You have to wonder: if men and women evolved together in sexually monogamous couples for millions of years, how did we end up being so incompatible? It’s as if we’ve been sitting down to dinner together, millennium after millennium, but half of us can’t help wolfing everything down in a few frantic, sloppy minutes, while the other half are still setting the table and lighting candles.

Yes, we know: 
mixed strategies, lots of cheap sperm versus a few expensive eggs in one basket, and so on. But these flagrantly maladjusted sexual responses make far more sense when viewed as relics of our having evolved in promiscuous groups. Rather than spinning theories within theories in an effort to prop up an unstable paradigm—monogamy withmistakesmild polygyny, mixed mating strategies, serial monogamy—can we simply face the one scenario where none of this self-defeating, inconsistent special pleading is necessary?

Okay, fine, it’s embarrassing. Maybe even humiliating, if you’re prone to that sort of thing. But 150 years after 
On the Origin of Species was published, isn’t it time to accept that our ancestors evolved along a sexual trajectory similar to that of our two highly social, very intelligent, closely related primate cousins? With any other question we have about the origins of human behavior, we look to chimps and bonobos for important clues: language, tool use, political alliances, war, reconciliation, altruism … but when it comes to sex we turn away from these models to the distantly related, antisocial, low-I.Q. but monogamous gibbon? Really?

We’ve pointed out how the agricultural revolution triggered radical social reconfigurations from which we’re still reeling. Perhaps the far-fetched denial of our promiscuous sexual prehistory expresses a legitimate fear of social instability, but insistent demands for a stable social order (based, as we’re often reminded, upon the nuclear family unit) cannot erase the effects of the hundreds of thousands of years that came before our species settled into stable villages.

If female chimps and bonobos could talk, do we really think they’d be griping to their hairy girlfriends about prematurely ejaculating males who don’t bring flowers anymore? Probably not, because as we’ve seen, when a female chimp or bonobo is in the mood, she’s likely to be the center of plenty of eager male attention. And the more attention she gets, the more she attracts, because as it turns out, our male primate cousins get turned on by the sight and sound of others of their species having sex. Imagine that.

hard core, b.c.

Hard Core in the Stone Age

Here’s a head-scratcher. Why do so many heterosexual men get off on pornography featuring groups of guys having sex with just one woman? It doesn’t add up, if you think about it. It’s more cone than ice cream. And the suggestive strangeness doesn’t end with the counterintuitive male-to-female ratio; it’s male ejaculate that puts the money in the money shot.

Researchers have confirmed what most men already know: men tend to get turned on by images depicting an environment in which sperm competition is clearly at play (though few, we imagine, think of it in quite these terms). Images and videos showing one woman with multiple males are far more popular on the Internet and in commercial pornography than those depicting one male with multiple females. A quick peek at the online offerings at Adult Video Universe lists over nine hundred titles in the Gangbang genre, but only twenty-seven listed under Reverse Gangbang. You do the math. Why would the males in a species that’s been wearing the shackles of monogamy for 1.9 million years be sexually excited by scenes of groups of men ejaculating with one or two women? 

Skeptics may argue that this arousal could reflect nothing more than commercial interests or a passing fashion. Fair enough, but what to make of experimental evidence that men viewing erotic material suggestive of sperm competition (two men with one woman) produce ejaculates containing a higher percentage of motile sperm than men viewing explicit images of only three women? And why does being cuckolded consistently appear at or near the top of married men’s sexual fantasies, according to experts ranging from Alfred Kinsey to Dan Savage?

As far as we know, there is no corresponding taste among women for erotica featuring multiple overweight middle-aged ladies with cheap tattoos, bad haircuts, and black socks having sex with one hot guy. Go figure.

Could this male appetite for multimale scenes be an echo of the porn of the Pleistocene? Keep in mind the variety of societies discussed previously in which women assist and inspire teams of workers or hunters by making themselves sexually available. The same dynamic is enacted on any given Sunday with fluttering pom-poms, the shortest of shorts, and the highest of kicks ending with sexy young legs spread right down to the Astroturf. While there are other conceivable explanations for such oddities of contemporary life, they certainly align well with a prehistory characterized by sperm competition. 

Go Trojans!

notes to readers

1. After Sex at Dawn came out, we started receiving emails from women readers saying something along the lines of, “Loved the book, except for that last part, where your focus on ‘Phil’ seemed to contradict everything you’d been saying about women’s sexuality and rights.” Good point. So, in addition to writing back to those women, we convinced our publisher to let us add a Note to the Reader that will appear in the paperback. This is the note we added:

This section, centered around “philandering Phil” struck some readers of previous editions of this book as imbalanced, in light of the importance of sexual satisfaction for both women and men. "Why only talk about an affair from a man’s perspective," we've been asked, “when the rest of your book is so balanced and supportive of women’s sexuality?” That's a fair and direct question for which we can offer only unfair and indirect answers. 

First, many men report that they had affairs simply because opportunities arose, while women—for whom such opportunities tend to be more plentiful—generally report a more complex confluence of motivations. For example, when Shirley Glass and Thomas White anonymously interviewed 300 men and women about their extramarital affairs, they found that men tended to see their affairs as more sexual, while women were motivated more by emotional considerations and reported greater levels of dissatisfaction with their marriages. These findings have been echoed repeatedly in other research.

Secondly, as we’ve discussed in previous chapters, women’s libidinous motivations tend to be far more fluid, and thus are more difficult to quantify or discuss adequately. Recall that women are more likely to engage in extra-marital sex when they’re ovulating, for example, and are less likely to use birth control than at other points in their menstrual cycle. A woman in her 40s may well approach a “friends with benefits” situation completely differently than she would have two decades earlier, for reasons relating both to hormonal levels and life experience. 

In addition to these internal factors, women tend to be more responsive to external conditions (Are the kids grown and out of the house? Is she financially independent? What would her friends and family say? Does she suspect that he’s having an affair?). Men—even highly intelligent, otherwise cautious and calculating men—often blunder into these situations blinded by something that doesn’t seem to render women quite so helpless.

Of course, none of these statements are definitive or universal. Whatever generalizations we make about motivations will be belied by many exceptions among both men and women. Every person is an ever-changing world and every relationship a universe. Nothing we say here is meant to simplify or minimize anyone's experience, male or female.

Our purpose is merely to briefly explore how some of the theories we've discussed play out in many modern lives by looking at the scenario married couples confront most frequently: the middle-aged man who strays. A similar assessment of women's motivations and experiences of extra-marital affairs would require far more space than we have. 

Finally, we actually know "Phil," who was willing to discuss his experiences with us. If we know any women who are having affairs as we write this, they've chosen not to share their secret with us, perhaps wisely.

In addition to the note above, the paperback contains this extended conversation with Dan Savage:

The following is a heavily edited extract based on two Savage Love podcasts recorded with Dan Savage in 2010 and an unpublished conversation. The full, unedited, raunchy, NSFW podcast recordings can be found (free) at the iTunes store or at www.thestranger.com. Episode 194 was broadcast on July 6th, and episode 210 on October 27th. Dan Savage is the best-known sex advice columnist in the United States. His podcast and syndicated column reach millions of readers weekly.

* * *

DS: You know how every once in a while you see a movie or you read a book or an article in a magazine—or perhaps some advice in an advice column—and you think, “Oh my god, I’m not crazy!”? I’ve just had that experience reading your book. I don’t know how to start this interview with you but by gushing. I understand that you’re married to a woman but, where have you been all my life?

CPR: (laughing) I’ve been trying to get your attention for the past couple of years!

DS: I’ve been reading your book and screaming and yelling and jumping up and down. I feel so vindicated by the research that you guys have done because for years, I’ve been pointing out just from observation and anecdotal evidence that monogamy is hard, doesn’t work, and makes people kind of miserable. And yet we’re told it should come easily and naturally when we’re in love, that a monogamous commitment is effortless where there’s love. And you guys have demonstrated that this is simply not true.

CPR: That’s our conclusion.

DS: What inspired you to write this book, to paint this bull’s eye on your backs? Because you are going to get criticized from all sides.

CPR: I guess what got me into this line of thinking initially was the Clinton/Lewinsky situation. I was thinking, how is it possible that if men have had all the power—political, economic, even physical power—since the beginning of time, how is it that the most powerful man in the world is being publicly humiliated for having a consensual sexual relationship with someone? It just didn’t make sense. So that led me to investigate evolutionary psychology. For the first year or so, I had the passion of the convert. I thought it explained everything. Luckily, at the time, I was living in San Francisco, working for a non-profit organization called Women in Community Service. I was one of the only men working there. Consequently, I had lots of very intelligent, outspoken women around me who helped me see that the depiction of female sexuality that is fundamental to evolutionary psychology really doesn’t make much sense at all.

DS: And what is the picture painted of female sexuality? You say in the book that “women are whores.” That’s what they’re telling us.

CPR: WE don’t say that! We half-jokingly say that Darwin says women are whores, in that they supposedly trade sex for stuff: protection, food, status, and so on, according to the conventional Darwinian view. We argue that women aren’t whores by nature; they’re sluts … and we mean that as a compliment! In other words, women evolved to have sex for the same reasons men do—because they like it. It feels good. Not because they’re trying to get something from men.

DS: There’s stuff in this book that will make people’s heads explode, like the concept of partible paternity. Instead of women trading sexual exclusivity and the assurance of paternity to men, that what was actually going on was that women may have been fucking as many men as possible so all the men in the group could believe that the kid could be theirs.

CPR: Right. This is something that Sarah Hrdy writes about in several of her books on alloparenting. She explains that it’s actually better for that child if lots of adults feel they have a direct connection to the child.

DS: You guys argue that this was the natural order of things, sort of a polyamorous, all for one and one for all, sex culture. So, if monogamy wasn’t our natural state, and now it’s an “ill-fitting garment,” and so on, now what?

CPR: Well, this is a book about how we are and how we got to be this way, but it’s not about what anyone should do about it.

DS: Yes, but don’t you think it will help people just to know the reason that they’re falling short? That they’re not doing anything wrong, necessarily? That it’s their inner nature, their inner bonobo? These ideals our culture has created about monogamy and faithfulness and fidelity are nice, but they’re not very functional and our own libidos and reptile brains are at war with them.

CPR: Exactly. People often say to us, “But we’re human beings. We can choose how to behave.” That’s true, to a certain extent, but our bodies rebel against decisions that go against our evolved nature. You can choose to wear shoes that are too small, but you can’t choose to be comfortable in them. You can choose to wear a corset, but you may well pass out because you can’t breathe properly… The human body and mind have evolved for a certain kind of life. The further we diverge from that path, the greater the cost, in terms of mental, emotional, and physical health. There’s just no getting away from this. We examine all this in greater detail in our next book.

Getting back to your earlier question, “Now what?”, the ambition we have for this book is humble, but important, I think. We hope it encourages and empowers people to give themselves a break, to cut themselves and their partners some slack. It actually promotes family stability to not be so rigid concerning fidelity. A zero tolerance policy doesn’t help anyone.

DS: I’m constantly arguing that! If we’re interested in preserving marriages and keeping families intact, we need to be less psychotic about never seeing anyone else naked ever again once we’re married. If we make certain allowances, the marriage is more likely to survive over the long run. If the only way you can ever have sex with anyone else is to end the marriage, many people will end or sabotage the marriage.

CPR: Well put.

DS: OK, let’s talk about how the book’s been received so far. I’ve seen some negative reaction concerning jealousy and love. What do you say to people who say this vision of prehistory can’t possibly be right, cause we’re “by nature” possessive about love.

CPR: Well, I generally avoid making sweeping statements about these issues, but I’ll give it a shot for you, Dan. Cacilda and I believe that real love isn’t primarily about sex. If you’re lucky enough to find love in your life, you quickly realize how relatively unimportant sex is. Love is about a lot of unerotic things: getting old together, taking care of each other when we’re sick or grieving, raising a child together, paying the bills … sharing the dailyness of life. It’s not primarily about orgasms. So many people confuse these things. They mistake good sexual chemistry for soulmating, for a reason to sign up for a life together. Then, a few years later, when the chemical thrill has dissipated—as it does—they find they’ve made a horrible mistake. So, even though our book is largely about sex, one of the central points we wanted to make is that most of us take sex way too seriously. We need to chill out. Like music, sex can be sacred, but doesn’t always have to be. Sometimes we hear God in a Bach toccata, but sometimes we’re just dancing and having a good time listening to the Rolling Stones. Nothing sacred about it.

DS: You heard it here first, folks! Other than those quibblers, how’s the book been received so far?

CPR: To be honest, we’re surprised and thrilled at the reception. Of course, I’ve got a Google alert set to the title, so I see most of the blog discussions, reviews on Amazon.com and GoodReads, etc. Overall, people seem to be very positive about the book. Much more than we’d expected. We figured we’d get about 50% hate mail and 50% non-hate mail, but probably 90% of the people who’ve written to us have been very, very kind in their comments. Some of the emails are heartbreaking. A lot of them along the lines of, “Damn, I wish I’d known all this when I was young!” One I’ll never forget said, simply, “I’m a 63 year-old widow and I consider this one of the most important books I’ve ever read. I wish I could live my life over with this information.” We get a lot of messages that relate to what you said earlier, about how people feel better when they can understand why they feel as they do. Why they can honestly love their partner but still feel attracted to other people. Seriously, the response from readers has been mind-blowing.

DS: But surely not ALL positive.

CPR: No, and maybe this is still the calm before the storm. There hasn’t been much negative response from the academic community—at least not the evolutionary psychology crowd we critique in our book: Pinker, Buss, Chagnon, and those guys. 

We’ve received lovely messages from people like Frans de Waal and Sarah Hrdy—certainly two of the most prominent authorities in the evolution of human sexuality—although they don’t necessarily agree with everything we wrote. On the other hand, Alan Dixson, a prominent primatologist we quote extensively, trashed us in an interview he gave to a paper in New Zealand, but he admitted he hadn’t read the book, he was just responding to what he’d heard about it. That’s been sort of typical of the most negative critical responses so far. They admit they haven’t read Sex at Dawn, but they dismiss it anyway. Megan McArdle, the business and economics editor at The Atlantic wrote what is probably the most negative review to date, and she openly admitted she was only half-way through the book when she wrote it.

DS: I saw that! “Humans aren’t like bonobos because we’re not like bonobos!”

CPR: Right. Rock-solid logic there, no? She apparently felt so threatened by the book that she couldn’t think straight. I mean, she accused us of leaving out any discussion of jealousy, as it didn’t fit our model, somehow missing Chapter 10, which is called: “Jealousy, A Beginner’s Guide to Coveting Thy Neighbor’s Spouse.” 

But as I said, the negative response has been much less than we were expecting, and is understandable; lots of people feel threatened by the arguments we’ve made. 

We’ve received lots of support from academics and clinicians. We’ve heard from scholars at the Kinsey Institute, professors all over the country who are assigning the book to their students, and we were honored when Sex at Dawn was chosen as the best consumer book of 2010 by the Society for Sex Therapy and Research (SSTAR).

DS: I’m so sorry Cacilda couldn’t join you on this trip. What was her role in the book?

CPR: Cacilda is one of two psychiatrists who run a psychiatric facility with close to a hundred patients. So she’s pretty tied to her day job these days, much as she’d love to participate more in interviews and meet readers. Strangely, a few people have interpreted her non-presence in interviews as evidence that I made her up just to give the book some cover with women readers. Seriously! 

I’d done a lot of this research before meeting Casi, about ten years ago. Still, what she brought to the book was crucial. First, she’d done her own research into human sexual behavior in rural Mozambique for the World Health Organization in the first years of the AIDS crisis, so she had extensive “real life” understanding of how things work in that part of the world. She grew up in a mixed Muslim/Hindu Indian family in Africa, so she brought a lot of multi-cultural nuance to the project, and of course, being a medical doctor, she was integral to the discussions of diet, longevity, infant care, and so on. Portuguese is her native language, and English is actually one of six that she speaks. As the native English speaker and professional writer, I did the writing, but she read every draft, again and again, before it went to anyone else. To call her anything other than a co-author would be inadequate.

DS: You’ve lived in Spain for a long time. Have you seen any major differences in the way Americans and Spanish deal with sex?

CPR: Oh yeah. In fact, that may be why I’ve lived in Spain for so long! Despite the history of Catholicism as the “official religion,” urban Spanish people, at least, are far less conflicted about sex than the typical American. One of the first things that struck me was how openly and unashamedly Spanish people flirt. I’m not, and never have been, a particularly great-looking guy, but after a few weeks walking around in Barcelona, I felt like Brad Pitt! It’s not sleazy or even necessarily sexual, but women look in your eyes and, if they like what they see, they smile. So simple. There’s not that fear and suspicion of strangers one finds so often in American cities, where eye contact is to be avoided at all costs. In the U.S., there seems to be an assumption that any man you don’t know could very well be a rapist/pervert/murderer or creep of some sort. I’m not blaming women for having that fear, of course, but it’s pretty depressing for men and women. In Barcelona, you can walk down the street and be smiled at by three or four lovely women per block. It sure makes walking a lot more fun!

Cacilda gets the same sort of ego-boosts all the time. (But she is particularly beautiful, so it’s less surprising.) Nothing sleazy, mind you, but just guys who say things like, “Hi. I just wanted to introduce myself and ask if you’d like to have a drink sometime. You’re really lovely.” There’s an innocence around flirting here that’s been lost in the States. It’s a shame, as it’s very much a win-win situation that dramatically improves quality of life for everyone involved.

DS: What was the most surprising thing you learned while working on Sex at Dawn?

CPR: So many things come to mind, but probably the most mind-blowing was the information about the first “key parties” having been started by elite WWII pilots who were facing very high fatality rates, the highest in the whole military. It was so moving to think about what motivated them to open their marriages with other couples. They were cultivating these webs of love, or at least real affection, because they knew that some of the men wouldn’t survive the war, and they wanted the widows to have as much support and love as possible. This confluence of selflessness and sexuality seemed to connect so directly to the hunter-gatherer groups, where men also have a high mortality rate from hunting accidents, falls, animal attacks, and so on. It was an unexpected, yet very clear reflection of the distant past.

DS: Has the experience of publishing this book changed you in any way? 

CPR: Interesting question. It has. It’s made me much less critical of other people’s books. I don’t think I could write a negative review at this point. When I was younger, it was easy to point out the flaws in books, but at this point, I’m much more aware that there’s a person on the other side who did their best. If I were writing Sex at Dawn again, I’d probably tone down some of the snarkier bits. 

I’m also more aware of just how impossible it is to please everyone. We’ve been incredibly fortunate in the response to this book, but still, for every nine comments we get congratulating us for writing the book with humor, we’ll get one or two describing the writing style as “sophomoric” or “unserious.” Some people think serious issues can only be discussed in serious tones. It’s interesting to have become a public figure, even in the very limited way I’m experiencing it. People have the right to their responses to your work, positive or negative. I’ve learned not to take it personally, in either case.

Sometimes people ask how we managed to write a book together without killing each other, or why the voice sounds like mine and not much like Cacilda’s. Here’s an explanation that was included in the original manuscript, but which our editor thought was superfluous.

Over the years, like many couples, Cacilda and I have settled into a comfortable division of labor. I clean the cat boxes, take out the garbage, and do the writing. Cacilda does everything else.

As you might imagine, I'm not eager to renegotiate our deal.

But at a certain point pretty early on, it became clear to me that there was no way I could claim to be the only author of this book. The realization hit me one night when I was lying awake trying to think of how I could adequately acknowledge Cacilda's contribution to 
my book. No matter how purple the prose I imagined, how cheesy the heartfelt thanks I envisioned, nothing conveyed an honest and honorable acknowledgement of the insight, patience, experience, and care my best friend, colleague, and wife had contributed to transforming this from a collection of half-considered ideas to the book you hold in your hands. It was then that I finally remembered what a wiser man would never have forgotten: sitting in front of a computer day after day is only the most obvious part of creating a book. Coming home from a long day working with troubled patients and their families, Cacilda spent countless evenings carefully reading, rereading, and reading again drafts of the same chapters again and again (in her sixth language, no less), offering smart advice and gentle correction, questioning questionable conclusions, and providing often-unwarranted encouragement. Without her participation, this would be much less of a book – if a book at all.

So, for better or worse, the voice you hear in these pages is mine, as are any mistakes of fact and judgment, tone and organization. But whatever is worthwhile in these pages comes from us both and was born, as most worthwhile things are, in loving collaboration.


We shifted a lot of the more scientific discussion to the endnotes of Sex at Dawn. This seemed like a good way to include the sorts of information students and other specialized readers would need while not overloading more casual readers less concerned with sources and methodological issues. Since many of the papers we cited are available on line, we’ve got lots of links in the endnotes. Here you’ll find a regularly updated version of that part of the book. Please let us know if you come across any dead links, either here or in the book itself. We’ll add new references (stuff that’s come out since publication) at the end of the relevant sections.


1. Maybe as recently as 4.5 million years ago. For a recent review of the genetic evidence, see Siepel (2009).

2. de Waal (1998), p. 5. 

3. Some of these numbers are reported in McNeil et al. (2006) and Yoder et al. (2005). The hundred billion figure comes from http:// www.latimes.com/news/nationworld/nation/la-fg-vienna-porn25- 2009mar25,0,7189584.story.

4. See “Yes, dear. Tonight again.” Ralph Gardner, Jr. The New York Times (June 9, 2008): http://www.nytimes.com/2008/06/08/fashion/08nights.html

5. Full disclosure: Murdoch also owns HarperCollins, the publisher of this book.

6. Diamond (1987). 

7. Such relationships would have been among many group-identity-boosting techniques, including participation in group bonding rituals still common to shamanistic religions characteristic of foraging people. Interestingly, such collective-identity-affirming rituals are often accompanied by music (which—like orgasm—releases oxytocin, the hormone most associated with forming emotional bonds). See Levitin (2009) for more on music and social identity.

8. The precise timing of this shift has recently been called into question. See White and Lovejoy (2009).

9. For more on the sharing-based economies of foragers, see Sahlins (1972), Hawkes (1993), Gowdy (1998), Boehm (1999), or Michael Finkel’s National Geographic article on the Hadza, available here: http://ngm.nationalgeographic.com/2009/12/hadza/finkel-text.

10. Mithen (2007), p. 705.

11. Taylor (1996), pp. 142–143. Taylor’s book is an excellent archaeological account of human sexual origins.

Part I: On the Origin of the Specious

Chapter 1: Remember the Yucatán!

1. This account comes from Todorov (1984), but Todorov’s version of events is not universally accepted. See http://www.yucatantoday.com/ culture/esp-yucatan-name.htm, for example, for a review of other etymologies (in Spanish).

2. From the FDA’s Macroanalytical Procedures Manual—Spice Methods. Accessed online at: http://www.fda.gov/Food/ScienceResearch/ LaboratoryMethods/MacroanalyticalProceduresManualMPM/ ucm084394.htm.

Chapter 2: What Darwin didn’t Know About Sex

1. Originally published in Daedalus, Spring 2007. Article can be found here: http://www.redorbit.com/news/science/931165/challenging_darwins_theory_of_sexual_selection/index.html. For more of her uniquely informed view of sexual diversity in nature, see Roughgarden (2004). For her deconstruction of self-interest as the engine of natural and sexual selection, see Roughgarden (2009). For more on homosexuality in the animal world, see Bagemihl (1999).

2. http://www.advicegoddess.com/ag-column-archives/2006/05. 

3. Not everyone would agree, of course. When Darwin’s brother Erasmus first read the book, he found Charles’s reasoning so compelling that he wasn’t bothered by the lack of evidence, writing, “If the facts won’t fit in, why so much the worse for the facts is my feeling.” For a thorough (but reader-friendly) look at how Darwin’s Victorianism affected his own and subsequent science, see Hrdy (1996). 

4. Darwin (1871/2007), p. 362. 

5. Pinker (2002), p. 253. 

6. Fowles (1969), pp. 211-212. 

7. Houghton (1957). Quoted in Wright (1994), p. 224. 

8. Quoted in Richards (1979), p. 1244. 

9. Writing in Scientific American Online (February 2005, p. 30), science historian Londa Schiebinger explains: “Erasmus Darwin . . . did not limit sexual relations to the bonds of holy matrimony. In his “Loves of the Plants” (1789), Darwin’s plants freely expressed every imaginable form of heterosexual union. The fair Collinsonia, sighing with sweet concern, satisfied the love of two brothers by turns. The Meadia—an ordinary cowslip—bowed with ‘wanton air,’ rolled her dark eyes and waved her golden hair as she gratified each of her five beaux. . . . Darwin may well have been using the cover of botany to propagandize for the free love he practiced after the death of his first wife.”

10. From Hrdy (1999b). 

11. Raverat (1991). 

12. Desmond and Moore (1994), p. 257. Also, see Wright (1994) for excellent insights into Darwin’s thought process and family life. 

13. The Flintstones occupies a unique place in American cultural history. It was the first prime-time animated series for adults, ABC’s first series to be shown in color, the first prime-time animated series to last more than two seasons (not matched until The Simpsons in 1992), and the first animated program to show a man and woman in bed together. 

14. Lovejoy (1981). 

15. Fisher (1992), p. 72. 

16. Ridley (2006), p. 35. 

17. See, for example, Steven Pinker’s assertion that human societies have become progressively more peaceful through the generations (discussed in detail in Chapter 13). 

18. Wilson (1978), pp. 1–2. 

19. A view Steven Pinker resuscitated decades later, long after more nuanced positions had become prevalent. 

20. See, for example, Thornhill and Palmer (2000). 

21. “A Treatise on the Tyranny of Two,” New York Times Magazine, October 14, 2001. You can read the essay online at http://www.nytimes.com/2001/10/14/magazine/14AGAINSTLOVE.html

22. Quoted in Flanagan (2009). 

23. Real Time with Bill Maher (March 21, 2008). Ironically, the panelist who suggested “moving on” was Jon Hamm who, at the time, played a serial womanizer on TV’s Mad Men. 

24. For more on Morgan’s life and thought, see Moses (2008). 

25. Morgan (1877/1908), p. 418, 427. 

26. Darwin (1871/2007), p. 360. 

27. Morgan (1877/1908), p. 52. 

28. Dixson (1998), p. 37.

Chapter 3: A Closer Look at the Standard Narrative of Human Sexual Evolution

1. With apologies to John Perry Barlow, author of “A Ladies’ Man and Shameless.” At: http://www.nerve.com/personalEssays/Barlow/ shameless/index.asp?page=1.

2. Wilson (1978), p. 148 

3. Pinker (2002), p. 252. 

4. Barkow et al. (1992), p. 289. 

5. Barkow et al. (1992), pp. 267–268. 

6. Acton (1857/62), p. 162. 

7. Symons (1979), p. vi. 

8. Bateman (1948), p. 365. 

9. Clark and Hatfield (1989).

10. Wright (1994), p. 298. 

11. Buss (2000), p. 140. 

12. Wright (1994), p. 57. 

13. Birkhead (2000), p. 33. 

14. Wright (1994), p. 63. 

15. Henry Kissinger—just our opinion. Nothing personal. 

16. Wright (1994), pp. 57–58.

17. Symons (1979), p. v. 

18. Fisher (1992), p. 187.

Chapter 4: The Ape in the Mirror

1. See Caswell et al. (2008) and Won and Hey (2004). Rapid advances in genetic testing have reopened the debate over the timing of the chimp/bonobo split. We use the widely accepted estimate of 3 million years, though it may turn out to have occurred less than a million years ago.

2. This account from de Waal and Lanting (1998). 

3. Harris (1989), p. 181. 

4. Symons (1979), p. 108. 

5. Wrangham and Peterson (1996), p. 63.

6. Sapolsky (2001), p. 174. 

7. Table based on de Waal (2005a) and Dixson (1998). 

8. Stanford (2001), p. 116. 

9. Berman (2000), pp. 66–67.

10. Dawkins (1976), p. 3.

11. http://www.edge.org/3rd_culture/woods_hare09/woods_hare09_ index.html.

12. de Waal (2005), p. 106. 

13. Theroux (1989), p. 195. 

14. Pusey (2001), p. 20. 

15. Stanford (2001), p. 26. 

16. McGrew and Feistner (1992), p. 232.

17. de Waal (1995). 

18. de Waal and Lanting (1998), p. 73. 

19. de Waal (2001a), p. 140. 

20. The quote appears here: http://primatediaries.blogspot.com/2009/03/bonobos-in-garden-of-eden.html. 

21. Fisher (1992), p. 129. 

22. Fisher (1992), pp. 129–130. 

23. Fisher(1992). These quotes are all taken from an endnote on page 329. 

24. Fisher (1992), p. 92. 

25. Fisher (1992), pp. 130–131. 

26. de Waal (2001b), p. 47. 

27. de Waal (2005), pp. 124–125. 

28. A true man of science, de Waal was kind enough to review and critique parts of this book, including sections where we disagree with some of his views. 

29. The information in this chart is taken from various sources (Blount, 1990; Kano, 1980 and 1992; de Waal and Lanting, 1998; Savage- Rumbaugh and Wilkerson, 1978; de Waal, 2001a; de Waal, 2001b).

Relevant research published after Sex at Dawn.

1. Paternity and relatedness in wild chimpanzee communities. Authors: Linda Vigilant, Michael Hofreiter, Heike Siedel, and Christophe Boesch. This paper questions the high levels of extra-group mating other researchers have reported among wild chimps, as well as the centrality of male coalitions in chimp social organization, suggesting that male-female interactions are more important than previously believed.

Part II: Lust in Paradise (Solitary)

Chapter 5: Who Lost What in Paradise?

1. For readers interested in further understanding how and why the shift from foraging to cultivation happened, Fagan (2004) and Quinn (1995) are both great places to start.

2. Cochran and Harpending (2009) point out some of these parallels: “In both [domesticated] humans and domesticated animals,” they write, “we see a reduction in brain size, broader skulls, changes in hair color or coat color, and smaller teeth.” (p. 112.)

3. Anderson is quoted in “Hellhole,” by Atul Gawande in The New Yorker, March 30, 2009. The article is very much worth reading for its
examination of whether solitary confinement is so anti-human that it qualifies as torture. Gawande concludes it clearly does, writing, “Sim- ply to exist as a normal human being requires interaction with other people.”

4. Jones et al. (1992), p. 123. 

5. Although only humans and bonobos appear to have sex throughout
the menstrual cycle, both chimps and some types of dolphins seem to share our predilection for engaging in sex for pleasure, as opposed to reproduction alone.

6. These tidbits come from Ventura’s wonderful essay on the origins of jazz and rock music, “Hear That Long Snake Moan,” published in Ventura (1986). The book is out of print, but you can access this essay and other writing at Ventura’s website: http://www.michaelventura. org/. The Thompson material can be found both in Ventura’s essay and in Thompson (1984).

Chapter 6: Who’s Your Daddies?

1. Harris (1989), p. 195. 

2. Beckerman and Valentine (2002), p. 10. 

3. Beckerman and Valentine (2002), p. 6. 

4. Kim Hill is quoted in Hrdy (1999b), pp. 246–247. 

5. Among the Bari people of Colombia and Venezuela, for example, researchers found that 80 percent of the children with two or more socially recognized fathers survived to adulthood, whereas only 64 percent of those with one official father made it that far. Hill and Hurtado (1996) reported that among their sample of 227 Aché chil- dren, 70 percent of those with only one recognized father survived to age ten, while 85 percent of those with both a primary and secondary father made it that far.

6. The quote is from an article by Sally Lehrman posted on AlterNet .org. Available at http://www.alternet.org/story/13648/?page=entire.

7. Morris (1981), pp. 154–156. 

8. In Beckerman and Valentine (2002), p. 128. 

9. See Erikson’s chapter in Beckerman and Valentine (2002).

10. Williams (1988), p. 114. 

11. Caesar (2008), p. 121. 

12. Quoted in Sturma (2002), p. 17.

13. See Littlewood (2003). 

14. At this point, naysayers will point out that Margaret Mead’s famous claims of South Seas libertines were debunked by Derek Freeman (1983). But Freeman’s debunking has been debunked as well, thus leaving Mead’s original claims, what, rebunked? Hiram Caton (1990) and others have argued, quite compellingly, that Freeman’s relentless attacks on Mead were likely motivated by a psychiatric disorder that also led to several paranoid outbursts of such intensity that he was forcibly removed from Sarawak by Australian diplomatic officials. The general consensus in the anthropological community seems to be that it’s unclear to what extent, if any, Mead’s findings were mistaken. Freeman’s purported debunking took place after decades of Christian indoctrination of Samoans, so it should surprise no one if the stories he heard differed significantly from those told to Mead half a century earlier. For a brief review, we recommend Monaghan (2006).

15. Ford and Beach (1952), p. 118. 

16. Small (1993), p. 153.

17. de Waal (2005), p. 101. 

18. Morris (1967), p. 79. 

19. http://primatediaries.blogspot.com/2007/08/forbidden-love.html. 

20. Kinsey (1953), p. 415. 

21. Sulloway (1998). 

22. For a review of other mammals that practice sharing behavior, see Ridley (1996) and Stanford (2001). 

23. Bogucki (1999), p. 124. 

24. Knight (1995), p. 210. 

25. The extent to which ovulation truly is hidden in humans is not as settled a matter as many authorities claim. There is good reason to beieve that olfactory systems are still able to detect ovulation in women and that such systems are significantly atrophied when compared with those of ancestral humans. See, for example, Singh and Bronstad (2001). Furthermore, there is reason to believe that women advertise their fertility status via visual cues such as jewelry and changes in facial attractiveness. See, for example, Roberts et al. (2004).

26. Daniels (1983), p. 69. 

27. Gregor (1985), p. 37.

28. Crocker and Crocker (2003), pp. 125–126. 29. Wilson (1978), p. 144.

Chapter 7: Mommies Dearest

1. Pollock (2002), pp. 53–54. 

2. The quote is taken from an interview by Sarah van Gelder, “Remembering Our Purpose: An Interview with Malidoma Somé,” In Context: A Quarterly of Humane Sustainable Culture, vol. 34, p. 30 (1993). Available online at http://www.context.org/ICLIB/IC34/Some.htm.

3. Hrdy (1999), p. 498. 

4. Darwin (1871), p. 610. 

5. Leacock (1981), p. 50. 

6. http://www.slate.com/id/2204451/. 

7. Erikson (2002), p. 131. 

8. Chernela (2002), p. 163. 

9. Lea (2002), p. 113.

10. Chernela (2002), p. 173. 

11. Morris (1998), p. 262. 

12. Malinowski (1962), pp. 156–157. 

13. See Sapolsky (2005). 

14. Drucker (2004). 

15. Even Jean-Jacques Rousseau, poster-boy for the Romantic ideal of the Noble Savage, made use of these baby disposals. In 1785, Benjamin Franklin 
visited the hospital where Rousseau had deposited his five illegitimate children and discovered a mortality rate of 85 percent among the babies there (“Baby Food,” by Jill Lepore, in The New Yorker, January 19, 2009).

16. McElvaine (2001), p. 45. 

17. Betzig (1989), p. 654.

Chapter 8: Making a Mess of Marriage, Mating, and Monogamy

1. As we write this, Tiger Woods is being accused of having “slept with” more than a dozen women in cars, parking lots, on sofas. . . . Are we to think he’s a narcoleptic?

2. de Waal (2005), p. 108. 

3. Trivers’s paper is seen as the foundational text in establishing the importance of male provisioning (investment) as a crucial factor in female sexual 
selection, among other things. It’s well worth a read if you want a deeper understanding of the overall development of evolutionary psychology.

4. Ghiglieri (1999), p. 150.

5. Small (1993), p. 135. 

6. Roughgarden (2007). Available online: http://www.redorbit.com/news/science/931165/challenging_darwins_theory_of_sexual_selection/index.html.

7. The New Yorker, November 25, 2002. 

8. Cartwright’s article is available here: http://www.pbs.org/wgbh/aia/part4/4h3106t.html. 

9. Symons (1979), p. 108. 

10. Valentine (2002), p. 188.

11. Article by Souhail Karam, Reuters, July 24, 2006. 

12. The New Yorker, April 17, 2007. 

13. Vincent of Beauvais Speculum doctrinale 10.45. 

14. Both from Townsend and Levy (1990b).

Chapter 9: Paternity Certainty: the Crumbling Cornerstone of the Standard Narrative

1. Edgerton (1992), p. 182. 

2. In Margolis (2004), p. 175. 

3. Pollock (2002), p. 53. 

4. For more on the deep connections between a society’s levels of violence and its eroticism, see Prescott (1975). 

5. Quoted in Hua (2001), p. 23. 

6. Namu (2004), p 276. For an excellent look at Mosuo culture, check out PBS Frontline World, “The Women’s Kingdom,” available at www.pbs.org/frontlineworld/rough/2005/07/introduction_to.html. 

7. Namu (2004), p. 69. 

8. Namu (2004), p. 8. 

9. This sacred regard for each individual’s autonomy is characteristic of foragers, too. For example, when Michael Finkel visited the Hadza recently in Tanzania, he reported, “the Hadza recognize no official leaders. Camps are traditionally named after a senior male . . . but this honor does not confer any particular power. Individual autonomy is the hallmark of the Hadza. No Hadza adult has authority over any other.” (National Geographic, December 2009.)

10. Hua (2001), pp. 202–203. 

11. Namu (2004), pp. 94–95.

12. China’s Kingdom of Women, Cynthia Barnes. Slate.com (November 17, 2006): http://www.slate.com/id/2153586/entry/2153614.

13. Goldberg (1993), p. 15. 

14. (Photo: Christopher Ryan.) When I saw this old woman, I knew her face contained the feminine strength and humor I was hoping to convey in a photo. I gestured to ask if it would be all right to take her picture. She agreed, but asked me to wait, and immediately started calling. These two little girls (granddaughters? Great- granddaughters?) came running. Once she had them in her arms, she gave me the go-ahead to take the shot.

15. The book was published in 2002, while Goldberg’s came out almost a decade earlier, but all of Sanday’s work on the Minangkabau, including the paper Goldberg cites, argues against his position—a point certainly deserving of mention.

16. Source: http://www.eurekalert.org/pub_releases/2002-05/uop-imm050902.php.

17. Source: www.eurekalert.org/pub_releases/2002-05/uop-imm050902 .php.

18. Most of these quotes are from an article by David Smith that appeared in 
The Guardian, September 18, 2005, available online at http://www.guardian.co.uk/uk/2005/sep/18/usa.filmnews, or Stephen Holden’s review in The New York Times, June 24, 2005, available online at http://movies.nytimes.com/2005/06/24/movies/24peng.html?_r=2.

The San Diego Union-Tribune: “Studies Suggest Monogamy Isn’t for the Birds—or Most Creatures,” by Scott LaFee, September 4, 2002.

20. “Monogamy and the Prairie Vole,” Scientific American online issue, February 2005, pp. 22–27.

21. Things have become a bit more muddled since Insel said that. More recently, Insel and others have been working on trying to discover the hormonal correlations underlying the fidelity or lack thereof among prairie, montane, and meadow voles. As reported in the October 7, 1993 issue of Nature, Insel and his team found that vasopressin, a hormone released during mating, seemed to trigger protective, nest- guarding behavior in some species of male voles, but not others, lead- ing to speculation about “monogamy genes.” See http://findarticles .com/p/articles/mi_m1200/is_n22_v144/ai_14642472 for a review. In 2008, Hasse Walum of the Karolinska Institute in Sweden found that a variation in the gene called RS3 334 seemed to be associated
 with how easily men bonded emotionally with their partners. Most interestingly, the gene appears to have some association with autism as well. The reference for Walum’s paper is Proceedings of the National Academy of Sciences, DOI: 10.1073pnas.0803081105. A news article summarizing the findings is online at http://www.newscientist.com/ article/dn14641-monogamy-gene-found-in-people.html.

Chapter 10: Jealousy: a Beginner’s Guide to Coveting thy Neighbor’s Spouse

1. Darwin (1871/2007), p. 184. 

2. Hrdy (1999b), p. 249. 

3. Known to historians as The Wicked Bible or The Adulterous Bible, the mistake led to the royal printers losing their license and a £300 fine. 

4. Confusingly, the tribe that came to be known as the Flatheads was not one of them, as their heads were “flat,” like the white trappers’, while the neighboring tribes’ heads were bizarrely conical. 

5. Grayscale reproduction scanned from Eaton, D.; Urbanek, S.: Paul Kane’s Great Nor-West, University of British Columbia Press; Vancouver, 1995. 

6. In fact, Maryanne Fisher and her colleagues found the opposite; distress was greater if the infidelity involved someone with familial bonds (see Fisher, et al. [2009]). 

7. Buss (2000), p. 33. 

8. Buss (2000), p. 58. 

9. Jethá and Falcato (1991).

10. Harris (2000), p. 1084. 

11. For an overview of Buss’s research on jealousy, see Buss (2000). For research and commentary rebutting his work, see Ryan and Jethá (2005), Harris 
and Christenfeld (1996), and DeSteno and Salovey (1996).

12. www.epjournal.net/filestore/ep06667675.pdf. 

13. Holmberg (1969), p. 161. 

14. From an “On Faith” blog post in The Washington Post, November 29, 2007: http://newsweek.washingtonpost.com/onfaith/panelists/richard_dawkins/2007/11/banishing_the_greeneyed_monste.html.

15. Wilson (1978), p. 142.

Part III: The Way We Weren’t

Chapter 11: “The Wealth of Nature” (Poor?)

1. Presumably, he was reading the sixth edition, published in 1826. 

2. Barlow (1958), p. 120. 

3. It’s no accident that Darwin was well aware of Malthus’s thinking. Harriet Martineau, an early feminist, economic philosopher, and out-spoken opponent of slavery, had been close to Malthus before striking up a friendship with Darwin’s older brother, Erasmus, who introduced her to Charles. Had Charles not been “astonished to find how ugly she is,” some, including Matt Ridley, suspect their friendship might have led to marriage. It would surely have been a marriage with lasting effects on Western thought (see Ridley’s article, “The Natural Order of Things,” in The Spectator, January 7, 2009).

4. Shaw (1987), p. 53. 

5. Darwin (1871/2007), p. 79. Both Malthus and Darwin would have profited from familiarity with MacArthur and Wilson’s (1967) thoughts on r/K reproduction and selection. Briefly, they posit that some species (like many insects, rodents, etc.) reproduce quickly to fill an empty ecological niche. They don’t expect most of their young to survive to adulthood, but they flood the environment quickly (r-selected). K-selected species have fewer young and invest heavily in each of them. Such species are generally in a state of Malthusian equilibrium, having already reached a population/food supply stasis point. Thus, these questions: as Homo sapiens is clearly a K-selected species, at what point did our environmental niche become saturated? Or have we continually found ways to expand our niche as human population expanded? If so, what does this mean for the underlying mechanisms of natural selection when applied to human evolution?

6. For example: “In the roughly 2 million years our ancestors lived as hunters and gatherers, the population rose from about 10,000 protohumans to about 4 million modern humans. If, as we believe, the growth pattern during this era was fairly steady, then the population must have doubled about every quarter million years, on average.” Economics of the Singularity, Robin Hanson, http://www.spectrum.ieee.org/jun08/6274.

7. Source: U.S. Census Bureau: http://www.census.gov/ipc/www/ worldhis.html.

8. Lilla (2007).

9. Smith’s essay is online at http://realhumannature.com/?page_id=26. 

10. Hassan (1980). 

11. For a different take on how and why prehistoric population levels grew so slowly, see Harris (1977), particularly Chapter 2. For yet another take see Hart and Sussman (2005), who argue that our ancestors did in fact live in Hobbesian fear—but not from each other so much as from constant predation. Malthus acknowledged the low population growth of Native Americans, but he attributed it to lack of libido caused by food shortages, “phlegmatic temperament,” or “a natural defect in their bodily frame” (I. IV. P. 3).

12. Most of the other species of hominids that had spread from Africa to Asia and Europe previously were already long gone by the time modern humans wandered out of Africa. Those still hanging on, Neanderthals and (possibly) 
Homo erectus, would have been at a huge disadvantage if there was interspecies competition—which is unclear. One could argue that the presence of Neanderthals in Europe and parts of Central Asia may have led to competition over hunting areas, but the extent of contact between our ancestors and Neanderthals, if any, is unresolved. Also, any overlap would have been partial, as Neanderthals appear to have been top-level carnivores, while Homo sapiens are and were enthusiastic omnivores (see, for example, Richards and Trinkaus, 2009).

13. The question of when humans first arrived in the Americas is unresolved. Recent archaeological finds in Chile suggesting human settlements dating to about 35,000 years ago have thrown open the question of how and when the first humans arrived in the western hemisphere. See, for example, Dillehay et al. (2008).

14. See Amos and Hoffman (2009), for example. Paleoanthropologist John Hawkes isn’t convinced that population bottlenecks necessarily imply sparse prehistoric human populations overall, proposing that “many small groups of humans were in fact competing intensively, and many of them failed to persist over the long term. In other words, a small effective size is hardly evidence of no ancient competition or warfare. It may be the result of intense competition leading to many local extinctions” (see his blog: http://johnhawks.net/node/1894). Given the persistence of hunter-gather populations in the world’s least habitable zones, the 
the genetic evidence of just a few hundred breeding pairs after the Toba eruption 70,000 years ago (Ambrose, 1998), we aren’t convinced by Hawkes’s scenario of “many local extinctions” due to competition— as opposed to planetary catastrophe.

15. Agriculture itself can be seen as a response to ecological saturation brought about by the combined effects of gradually rising regional population and catastrophic climate change. For example, Nick Brooks, a researcher at the University of East Anglia, argues, “Civilization was in large part an accidental by-product of unplanned adaptation to catastrophic climate change.” Brooks and others argue that the agricultural shift was a “last resort” response to deteriorating environmental conditions. For a comprehensive discussion of how climate change might have provoked agriculture, see Fagan (2004).

16. Known as “geophagy,” dirt eating is common in societies around the world—especially among pregnant and lactating women. Additionally, many otherwise toxic foods containing poisonous alkaloids and tannic acids are cooked along with alkaloid-binding clays. Clay can be a rich source of iron, copper, magnesium, and calcium—all critical during pregnancy.

17. August 5, 2007. 

18. http://moneyfeatures.blogs.money.cnn.com/2009/04/30/millionaires-arent-sleeping-well-either/?section=money_topstories. 

19. See Wolf et al.(1989) and Bruhn and Wolf (1979). Malcolm Gladwell (2008) also discusses Roseto. 

20. Sahlins (1972), p. 37. 

21. http://www.newyorker.com/online/blogs/books/2009/04/the-exchange-david-plotz.html. 

22. Malthus (1798), Book I, Chapter IV, paragraph 38. 

23. Darwin (1871/2007), p. 208. 

24. For a more detailed analysis of how modern economic theory plays out (or doesn’t) among non-state societies, see Henrich et al. (2005) and Richard Lee’s chapter titled “Reflections on Primitive Communism,” in Ingold et al. (1988).

Chapter 12: The Selfish Meme (Nasty?)

1. In A Theory of Moral Sentiments, Smith wrote, “How selfish soever man may be supposed, there are evidently some principles in his nature, which interest him in the fortune of others, and render their happiness necessary to him, though he derives nothing from it, except the pleasure of seeing it.”

2. Gowdy (1998), p. xxiv. 

3. From Mill (1874). 

4. New York Times, July 23, 2002, “Why We’re So Nice: We’re Wired to Cooperate.” http://www.nytimes.com/2002/07/23/science/ why-we-re-so-nice-we-re-wired-to-cooperate.html. For the original research, see Rilling et al. (2002).

5. We’ve drawn from an excellent analysis of Hardin’s paper by Ian Angus, which can be found at http://links.org.au/node/595.

6. See Ostrom (2009), for example. 

7. See Dunbar (1992 and 1993). 

8. Harris (1989), pp. 344–345. 

9. Bodley (2002), p. 54.

10. Harris (1989), p. 147. 

11. van der Merwe (1992), p. 372. Also see Jared Diamond, “The Worst Mistake in the History of the Human Race” (widely available online; see here, for example: http://www.awok.org/worst-mistake/). 

12. Le Jeune (1897), pp. 281–283. 

13. Gowdy (1998), p. 130. 

14. Quoted in Menzel and D’Aluisio, p. 178. 

15. Harris (1977), p. x. Also see Eaton, Shostak, and Konner (1988). 

16. Gowdy (1998), p. 13.

17. Gowdy (1998), p. 23. 

18. Harris (1980), p. 81. 

19. Ridley (1996), p. 249. 

20. See de Waal (2009) for much more on the biological origins of empathy and instinctive justice. 

21. Dawkins (1998), p. 212. 

22. de Waal and Johanowicz (1993). 

23. Sapolsky and Share (2004). Also see Natalie Angier, “No Time for Bullies: Baboons Retool Their Culture, New York Times, April 13, 2004. 

24. Boehm (1999), p. 3, 68. 

25. Fromm (1973), p. 60. 

26. Gowdy (1998), p. xvii.

Relevant research published after Sex at Dawn.

1. Here’s a paper that supports our contention that egalitarian social organization is more functional for small scale social groups like those of the EEA (see references to Dunbar’s number) and that more hierarchical power structures emerge when the group gets too big for consensus rule.

A theory of leadership in human cooperative groups
Journal of Theoretical Biology
Available online 2 June 2010.
Paul L. Hooper Hillard S. Kaplan a and James L. Boone


Two types of models aim to account the origins of rank differentiation and social hierarchy in human societies. Conflict models suggest that the formation of social hierarchies is synonymous with the establishment of relationships of coercive social dominance and exploitation. Voluntary or 'integrative' models, on the other hand, suggest that rank differentiation—the differentiation of leader from follower, ruler from ruled, or state from subject—may sometimes be preferred over more egalitarian social arrangements as a solution to the challenges of life in social groups, such as conflict over resources, coordination failures, and free-riding in cooperative relationships. Little formal theoretical work, however, has established whether and under what conditions individuals would indeed prefer the establishment of more hierarchical relationships over more egalitarian alternatives. This paper provides an evolutionary game theoretical model for the acceptance of leadership in cooperative groups. We propose that the effort of a leader can reduce the likelihood that cooperation fails due to free-riding or coordination errors, and that under some circumstances, individuals would prefer to cooperate in a group under the supervision of a leader who receives a share of the group's productivity than to work in an unsupervised group. We suggest, in particular, that this becomes an optimal solution for individual decision makers when the number of group members required for collective action exceeds the maximum group size at which leaderless cooperation is viable. 

2. Here’s an article about a paper demonstrating hormonal differences in how male chimps and male bonobos respond to stress, with chimps gearing up for battle and bonobos chilling out. Quite interesting, in light of the never-ending debate about the relevance of these two primates to human nature:


Chapter 13: The Never-Ending Battle over Prehistoric War (Brutish?)

1. From his closing argument in the Scopes case. 

2. Wade (2006), p. 151. 

3. Recent studies of mitochondrial DNA suggest that even before the human migrations out of Africa that began about 60,000 years ago, human populations were largely isolated from each other for as much as 100,000 years, localized in eastern and southern Africa. Only about 40,000 years ago did these two lines reunite, becoming a single pan-African population, according to this research. See Behar et al. (2008). Full paper available online at http://www.cell.com/AJHG/ fulltext/S0002-9297%2808%2900255-3#.

4. Readers interested in further exploration of the critique of Hobbesian assumptions regarding war in prehistory could begin with Fry (2009) and Ferguson (2000).

5. Pinker’s talk was based upon an argument he presents in The Blank Slate (2002), particularly in the last few pages of the third chapter. 

6. The link to Pinker’s presentation is http://www.ted.com/index.php/talks/steven_pinker_on_the_myth_of_violence.html. You can find many other interesting presentations at this site. You might want to search Sue Savage-Rumbaugh’s talks on bonobos, for example. If you prefer to read Pinker’s remarks, an essay based upon the talk can be found at www.edge.org/3rd_culture/pinker07/pinker07_index.html.

7. Note that Pinker’s chart represents part of a chart in Keeley’s book (1996), and that Keeley refers to these societies as “primitive,” “prestate,” and “prehistoric” in his charts (pp. 89–90). Indeed, Keeley distinguishes what he calls “sedentary hunter-gatherers” from true “nomadic hunter-gatherers,” writing, “Low-density, nomadic hunter-gatherers, with their few (and portable) possessions, large territories, and few fixed resources or constructed facilities, had the option of fleeing conflict and raiding parties. At best, the only thing they would lose by such flight was their composure” (p. 31).
As we’ve established, these nomadic (immediate-return) hunter-gatherers are most representative of human prehistory—a period that is, by definition, before the advent of settled communities, cultivated food, domesticated animals, and so on. Keeley’s confusion (and thus, Pinker’s) is largely due to his referring to horticulturalists, with their gardens, domesticated animals, and settled villages, as “sedentary hunter-gatherers.” Yes, they do occasionally hunt and they sometimes gather, but because these activities are not their sole source of food, their lives are dissimilar to those of immediate-return hunter-gatherers. Their gardens, settled villages, and so on make territorial defense necessary and fleeing conflict much more problematic than it was for our ancestors. They—unlike true immediate-return foragers—have a lot to lose by simply fleeing aggression.
Keeley acknowledges this crucial difference, writing, “Farmers and sedentary hunter-gatherers had little alternative but to meet force with force or, after injury, to discourage further depredations by taking revenge” (p. 31).
The point bears repeating. If you live a settled life in a stable village, have a labor-expensive shelter, cultivated fields, domesticated animals, and too many possessions to carry easily, you’re not a hunter-gatherer. Prehistoric human beings did not have any of these things, which is, after all, precisely what made them “prehistoric.” Pinker either fails to appreciate this essential point, or simply ignores it.

8. Societies in Pinker’s chart:
Jivaro cultivate yams, peanuts, sweet manioc, maize, sweet potatoes, peanuts, tuber beans, pumpkins, plantains, tobacco, cotton, banana, sugarcane, taro, and yam. They also traditionally domesticate llamas and guinea pigs and later the introduced dog, chicken, and pig.
Yanomami are foraging, “slash-and-burn” horticulturists. They cultivate plantains, cassava, and bananas.
Mae Enga grow sweet potatoes, taro, bananas, sugarcane, Pandanus nuts, beans, and various leaf greens, as well as potatoes, maize, and peanuts. They raise pigs, used not only for meat but for important ritualistic celebrations.
—About 90 percent of the 
Dani diet is sweet potatoes. They also cultivate banana and cassava. Domestic pigs are important both for currency used in barter and for the celebration of important events. Pig theft is a major cause of conflict.
 Murngin economy was based primarily on fishing, collecting shellfish, hunting, and gathering until the establishment of missions and the gradual introduction of market goods in the 1930s and 1940s. While hunting and gathering remain important for some groups, motor vehicles, aluminum boats with outboard engines, guns, and other introduced tools have replaced indigenous techniques.
Huli’s staple food is the sweet potato. Like other groups in Papua New Guinea, domestic pigs are prized for meat and status.

9. This, according to Fry (2009). 

10. Knauft (1987 and 2009). 

11. To make matters even worse, Pinker juxtaposes these bogus “hunter-gatherer” mortality rates with a tiny bar showing the relatively few war-related deaths of males in twentieth-century United States and Europe. This is misleading in many respects. Perhaps most important, the twentieth century gave birth to “total war” between nations, in which civilians (not just male combatants) were targeted for psycho- logical advantage (Dresden, Hiroshima, Nagasaki . . .), so counting only male mortalities is meaningless.
Furthermore, why did Pinker not include the tens of millions who died in some of the most vicious and deadly examples of twentieth-century warfare? In his discussion of “our most peaceful age,” he makes no mention of the Rape of Nanking, the entire Pacific theater of World War II (including the detonation of two nuclear bombs over Japan), the Khmer Rouge and Pol Pot’s killing fields in Cambodia, several consecutive decades-long wars in Vietnam (against the Japanese, French, and Americans), the Chinese revolution and civil war, the India/Pakistan separation and subsequent wars, or the Korean war. None of these many millions are included in his assessment of twentieth-century (male) war fatalities.
Nor does Pinker include Africa, with its never-ending conflicts, child soldiers, and casual genocides. No mention of Rwanda. Not a Tutsi or Hutu to be found. He leaves out every one of South America’s various twentieth-century wars and dictatorships infamous for torturing and disappearing tens of thousands of civilians. El Salvador? Nicaragua? More than 100,000 dead villagers in Guatemala? Nada. Absolutamente nada. 

12. For example, see Zihlman et al. (1978 and 1984). 

13. Why War?, available online at http://realhumannature.com/?page_id=26. After we contacted him to ask how he could possibly justify the omission, Smith at first cited Wrangham and Peterson’s dismissal of bonobos as being less representative than chimps of our last common ancestor. When we pointed out that many primatologists argue that bonobos are probably more representative), that even Wrangham had revised his opinion on the point, and in any case, it is factually wrong to say that chimps are our “closest non-human relative” without mentioning bonobos, he finally relented and added two brief references to bonobos to his lurid descriptions of chimps’ “bloody wars of attrition.” Since the online essay was an extract from his book, which was already in print, it seems unlikely these reluctant changes are reflected there.

14. Ghiglieri (1999), pp. 104–105. 

15. For a review, see Sussman and Garber’s chapter in Chapman and Sussman (2004). 

16. The quote is from de Waal (1998), p. 10.

17. Goodall (1971), cited in Power (1991), pp. 28–29. 

18. Strangely,even though he agrees with this central point made by Power, de Waal barely mentions her work—and only to dismiss her, at that. In an endnote in his 1996 book, 
Good Natured: The Origins of Right and Wrong in Humans and Other Animals, he writes, “On the basis of her reading of the literature, Power (1991) has argued that provisioning at some field sites (such as Gombe’s banana camp) turned the chimpanzees more violent and less egalitarian, and thus changed the ‘tone’ of relationships both within and between communities. Power’s analysis—which blends a serious reexamination of available data with nostalgia for the 1960s image of apes as noble savages—raises questions that will no doubt be settled by ongoing research on unprovisioned wild chimpanzees.”
This dismissal of Power’s analysis strikes us as unjustified and uncharacteristically ungenerous. Regardless of whether or not she felt “nostalgia for the 1960s” (an emotion we didn’t detect in her book), de Waal admits her analysis “raises questions” that merit investigation. These questions threaten to recast a great deal of data concerning chimpanzee social interactions—of great interest to de Waal, one of the world’s leading authorities on chimpanzee behavior and a man whose scholarship demonstrates deep respect for critical analysis.

19. Ghiglieri (1999), p. 173. 

20. For a review of these reports and a rebuttal to Power’s argument, see Wilson and Wrangham (2003). The paper is available online at http://anthro.annualreviews.org. 

21. Nolan (2003). 

22. Behar et al. (2008). Also, for an excellent review of this material, see Fagan (2004). 

23. Turchin (2003 and 2006). 

24. Readers with mental images of Sioux (Lakota) chiefs with eagle-feather war bonnets rippling in the wind should keep in mind that in the generations before first contact with whites, disease spread through many tribes and the arrival of horses brought severe cultural disruptions, leading to conflict between groups that had been at peace previously (see Brown, 1970/2001).

25. Edgerton (1992), pp. 90–104. 

26. Ferguson (2003).

27. On Christmas Day, 1968, Apollo 8 astronaut Frank Borman read this prayer to a world audience: “Give us, O God, the vision which can see thy love in the world in spite of human failure. Give us the faith to trust the goodness in spite of our ignorance and weakness. Give us the knowledge that we may continue to pray with understanding hearts, and show us what each one of us can do to set forth the coming of the day of universal peace. Amen.”

28. Tierney (2000), p. 18. Tierney’s book sparked a conflagration that makes any chimpanzee community seem downright pacific in comparison. The bulk of the controversy concerns Tierney’s charges that Chagnon and his colleague, James Neel, may have caused a fatal epidemic among the Yanomami. Not having examined these charges in detail, we have nothing to add to that discussion, limiting our critique to Changnon’s methodology and scholarship as it applies to Yanomami warfare.

29. By comparison, Chagnon’s total time among the Yanomami adds up to about five years. Readers interested in knowing more about the Yanomani might start with Good (1991). This is a very personal and accessible account of his time living with them (and ultimately, taking a wife there). Tierney (2000) outlines the case against Chagnon, though going far beyond the critiques we’ve outlined here. Ferguson (1995) offers an in-depth analysis of Chagnon’s calculations and conclusions. For more of Ferguson’s views on the origins of war, the following two papers can be downloaded from his departmental web page (http://andromeda.rutgers.edu/socant/brian.htm): Tribal, “Ethnic,” and Global Wars, and Ten Points on War, which includes a broad discussion of biology, archaeology, and the Yanomami controversy. Borofsky (2005) offers a balanced account of the controversy and the context in which it occurred. Of course, Chagnon’s work is readily available as well.

30. Quoted in Tierney (2000), p. 32. 

31. Washington Post review of Darkness in El Dorado: Jungle Fever, by Marshall Sahlins, Sunday, December 10, 2000, p. X01. 

32. Chagnon (1968), p. 12. 

33. Tierney (2000), p. 14. 

34. Sponsel (1998), p. 104. 

35. October 23, 2008.

Relevant research published after Sex at Dawn.

1. Quitting the hominid fight club: The evidence is flimsy for innate chimpanzee--let alone human--warfare
By John Horgan 


Chapter 14: The Longevity Lie (Short?)

1. Note that these numbers are for demonstration purposes only. To keep it simple (and since it’s meaningless anyway), we haven’t adjusted for male/female size differences, regional variations in average infant skeleton sizes, and so on.

2. October 6, 2008. 

3. Adovasio et al. (2007), p. 129. 

4. Gina Kolata, “Could We Live Forever?,” November 11, 2003. 

5. Scientific American, March 6, p. 57. 

6. Harris (1989), pp. 211–212. 

7. http://www.gendercide.org/case_infanticide.html. 

8. These numbers don’t include the selective abortion of female fetuses, which is widespread in these countries. For example, Agence-France Presse 
reports that selective abortions have left China with 32 million more men than women, and that in just one year (2005), more than 1.1 million more boys than girls were born in China.

9. Philosopher Peter Singer has written thought-provoking books and essays on the question of how to calculate the value of human versus nonhuman life. See, for example, Singer (1990).

10. Cited in Blurton Jones et al. (2002). 

11. Blurton Jones et al. (2002). 

12. See Blurton Jones et al. (2002). 

13. An excellent paper highly recommended to readers interested in these matters is Kaplan et al. (2000). The paper can be downloaded at Kaplan’s faculty website: www.unm.edu/~hebs/pubs_kaplan.html. 

14. From the paper by Kaplan et al. cited above, p. 171.

15. Readers interested in seeing how these same agricultural curses are playing out in the modern world might want to read Michael Pollan’s 
In Defense of Food: An Eater’s Manifesto(2009).

16. Larrick et al. (1979). 

17. Source: Diamond (1997).

18. Edgerton (1992), p. 111. 

19. Cohen et al. (2009). 

20. Horne et al. (2008).

21. While we’re on the subject of hammocks, we’d like to take this opportunity to formally propose that hammocks—not spear points or stone blades—were the first example of human technology. That no hard evidence for this proposal has been unearthed is due to hammocks being made of perishable fibers. (Who wants a stone hammock?) Even chimps and bonobos fashion primitive hammocks by weaving together tree branches for sleeping platforms.

22. See Sapolsky (1998) for an excellent overview of how stress affects us. On the question of human/bonobo similarities concerning stress, it’s interesting to note that when bombs fell near them in World War II, all the bonobos in the zoo died from the stress the explosions caused, while none of the chimps perished (according to de Waal and Lanting, 1998).

The New Yorker, June 26, 2006, p. 76.

Part IV: Bodies in Motion

1. This quote is taken from a debate between Gould on one side and Steven Pinker and Daniel Dennett on the other. Well worth reading, if you like high-brow discussion with plenty of low blows, is “Evolution: The Pleasures of Pluralism,” The New York Review of Books 44(11): 47–52.

2. Potts (1992), p. 327.

Chapter 15: Little Big Man

1. Miller (2000), p. 169. 

2. Though not always, as other factors can influence body-size dimorphism, apart from the intensity of male-male mating conflict. See Lawler (2009), for 

3. Male 
Australopithecus (between three and four million years ago) are thought to have been about fifty percent larger than females. Recent papers suggest Ardipethicus ramidus, another supposed human ancestor (thought to be a million or so years older than Australopithecus) was closer to our 15 to 20 percent levels. But keep in mind that the much-ballyhooed reconstruction of Ardipethicus ramidus relied upon bits and pieces of many different individuals, so our sense of body size dimorphism 4.4 million years ago is based upon educated guesses, at best (White et al., 2009).

4. Lovejoy (2009). 

5. http://www.psychologytoday.com/articles/200706/ten-politically-incorrect-truths-about-human-nature. 

6. Supplemental note. On sexual selection in relation to monkeys. Reprinted from 
Nature, November 2, 1876, p. 18. http://sacred-texts.com/aor/darwin/descent/dom25.htm. 

7. As we’ll discuss in the next chapter, the genital echo theory posits that women developed pendulous breasts so that the cleavage would mimic the (is there a scientific term for this?) butt-crack that so enticed our primate ancestors. Following that line of reasoning, some argue that fancily named lipstick serves to re-create the bright red “hinder ends” that so perplexed poor Darwin.

8. See Baker and Bellis (1995) or Baker (1996) for the sperm-team theory. 

9. Hrdy (1996) is a wonderfully erudite and engaging discussion of how some of Darwin’s personal sexual hang-ups are reflected still in evolutionary theory. 

10. Supplemental note. On sexual selection in relation to monkeys. Reprinted from Nature, November 2, 1876, p. 18. http://sacred-texts.com/aor/darwin/descent/dom25.htm. 

11. Diamond (1991), p. 62.

Chapter 16: The Truest Measure of a Man

1. de Waal (2005), p. 113. 

2. In Barkow et al. (1992), p. 299. 

3. Barash and Lipton (2001), p. 141. 

4. Pochron and Wright (2002). 

5. Wyckoff et al. (2000). Other research looking into primate testicular genetics has reinforced the impression that ancestral human mating behavior more closely resembled the promiscuity of chimps than the one-male-at-a-time gorillas. See, for example, Kingan et al. (2003), who conclude that although “predicting the expected intensity of sperm competition in ancestral Homo is controversial, . . . we find patterns of nucleotide variability at SgI in humans to resemble more closely the patterns seen in chimps than in gorillas.”

6. Short (1979). 

7. Margulis and Sagan (1991), p. 51. 

8. Lindholmer (1973). 

9. For more on this, see work by Todd Shackelford, particularly Shackelford et al. (2007). Shackelford generously makes most of his published work available for free download at http://www.toddkshackelford .com/publications/index.html.

10. Symons (1979), p. 92. Although we probably disagree with half of his conclusions, and much of the science is out of date, Symons’s book is well worth reading for its wit and artistry alone.

11. Harris (1989), p. 261. 

12. Sperm competition is an area of passionate debate. Space limitations (and quite possibly, readers’ interest) preclude us from a more thorough discussion—especially concerning the highly controversial claims of Baker and Bellis regarding sperm teams composed of specialized cells acting as “blockers,” “kamakaze,” and “egg-getters.” For a scientific review of their findings, see Baker and Bellis (1995). For a popularized review, see Baker (1996). For a balanced discussion of the controversy written by a third party, see Birkhead (2000), especially pp. 21–29.

13. Data primarily from Dixson (1998). 14. See, for example, Pound (2002). 15. Kilgallon and Simmons (2005). 16. Some readers will argue that these conventions in contemporary pornography are expressions of female subjugation and degradation rather than eroticism. Whether or not this is the case (a discussion we’re going to sidestep at this juncture), one must still ask why it is being expressed in this way, with these images, given that there are so many ways of visibly humiliating a person. Some authorities believe the practice of bukkake originated as a way of punishing adulterous women in Japan—a somewhat less Puritanical Scarlet Letter, if you will (see, for example, “Bake a Cake? Exposing the Sexual Practice of Bukkake,” poster presented at the 17th World Congress of Sexology, by Jeff Hudson and Nicholas Doong: http://abstracts.co.allenpress.com/ pweb/sexo2005/document/50214). If you don’t know what bukkake is, and you’re even slightly prone to being offended, please forget we even mentioned it.

Chapter 17: Sometimes a Penis Is Just a Penis

1. Frans de Waal suspects that bonobos have longer penises than humans, at least relative to body size, but most other primatologists seem to disagree with his assessment. In any case, there is no question that the human penis is far thicker than that of any other ape, in absolute terms or relative to body size, and far longer than that of any primate not clearly engaged in extreme sperm competition.

2. Sherfey (1972), p. 67. 

3. One species of gibbon, the black-crested gibbon (Hylobates concolor), does in fact have an external, pendulous scrotum. Interestingly, this type of gibbon may also be exceptional in not being strictly monoga- mous (see Jiang et al., 1999).

4. Gallup (2009) offers an excellent summary of this material. 

5. Dindyal (2004). 

6. http://news.bbc.co.uk/go/pr/fr/-/2/hi/health/7633400.stm2008/09/24. 

7. Harvey and May (1989), p. 508. 

8. Writing in the 
Encyclopedia of Human Evolution, Robert Martin notes, “Relative to body size, humans have a very low value for rmax—even in comparison with other primates. This suggests that selection has favoured a low breeding potential during human evolution. Any model of human evolution should take this into account.” A low rmax value along with the very high levels of sexual activity typical of humans is yet another indication that sex has long functioned for nonreproductive purposes in our species.
Similarly, while Dixson (1998) characterizes the seminal vesicles of monogamous and polygynous primates (except the gelada baboon) as vestigial or small, he classifies the human seminal vesicles as medium—noting that “it is reasonable to propose that natural selection might have favoured reduction in size of the vesicles under conditions where copulation is relatively infrequent and the need for large ejaculate volume and coagulum formation is reduced.” He goes on to propose that “this might explain the very small size of the vesicles in primarily monogamous [primates].”

9. BBC News online, July 16, 2003.

10. BBC News online, October 15, 2007. 

11. Psychology Today, March/April 2001. 

12. Barratt et al. (2009). 

13. Hypothetically, one could try to falsify this hypothesis using data on testicular volume and sperm production from some of the societies we’ve discussed where sperm competition and partible paternity are in effect. To this end, we’ve contacted every anthropologist we could locate who has worked in the Amazon (or anywhere else with hunter-gatherers), but no one seems to have managed to gather these delicate data. Still, even if it were found that males in these societies showed higher testicular volume and sperm production, as our hypothesis predicts, definitive confirmation of the hypothesis would be precluded by the relative absence of the environmental toxins that are presumably at least partly responsible for testicular atrophy in industrialized societies.

14. BBC News online, December 8, 2006. 

15. Diamond (1986). 

16. W. A. Schonfeld, “Primary and Secondary Sexual Characteristics. Study of Their Development in Males from Birth through Maturity, with Biometric Study of Penis and Testes,” American Journal of Diseases in Children 65, 535–549 (cited in Short, 1979).

17. Harvey and May (1989). 18. Baker (1996), p. 316. 19. Bogucki (1999), p. 20.

Chapter 18: The Prehistory of O

1. Maines’s book has become an underground sensation. Written as a serious cultural history of the vibrator, the story she tells is surprising and compelling. As we write, a play based on the book written by Sarah Ruhl (In the Next Room) is playing on Broadway. A National Public Radio story on the play is here: http://www.npr.org/templates/ story/story.php?storyId=120463597&ps=cprs.

2. Quotes taken from Margolis (2004). 

3. See Money (2000). Interestingly, semen depletion is central to the ancient Taoist understanding of male health and sexuality as well. See, for example, Reid (1989). 

4. On Baker Brown, see Fleming (1960) and Moscucci (1996). 

5. Coventry (2000).

6. Although the clitoris is often referred to as “the only organ in the human body whose sole function is to provide pleasure,” there are two problems with this observation. First, if female orgasm (pleasure) is functional in the senses we outline (increases chances of fertilization, inspires vocalizations, and thereby promotes sperm competition), then there is clearly a purpose to the pleasure. Secondly, what about male nipples? Not all men find them to be a site of pleasure, but they are certainly highly enervated and serve no functional purpose.

7. Margolis (2004), pp. 242–243. 

8. Ironically, according to archaeologist Timothy Taylor (1996), this image of the Devil is thought to be derived from Cernunnos, the horned god, who was the Celtic translation of Indian tantric practice and thus originally a symbol of spiritual transcendence via sexual practice.

9. Coventry (2000). 

10. Hrdy (1999b), p. 259. 

11. Sherfey (1972), p. 113.

Chapter 19: When Girls Go Wild

1. Pinker (2002), p. 253. 

2. Not to exclude women or gay men, but there is a dearth of scientific data on this particular angle. Interestingly, though, several people have reported to us anecdotally that when they’ve overheard their neighbors (both gay male and lesbian couples) having sex, the partner they considered to be the more feminine was the one who was making more noise.

3. When the director, Rob Reiner, showed the screenplay to his mother, she suggested that at the end of that scene, the camera cut to an older woman in the restaurant about to order, who says, “I’ll have what she’s having.” The line was so brilliant that Reiner told his mother he’d insert it, but only if she agreed to deliver the line in the film, which she did.

4. Semple (2001). 

5. Small (1993), p. 142. 

6. Small (1993), p. 170. 

7. Dixson (1998), pp. 128–129. 

8. Pradhan et al. (2006). 

9. These quotes are from Hamilton and Arrowood (1978).

10. The intensity of the female’s vocalizations could, for example, guide the discerning male’s orgasmic response—thus increasing the chances of simultaneous or near-simultaneous orgasm. As we discuss below, there is evidence such timing could be to the male’s reproductive advantage.

11. The title, far from being the frat-boy declaration it may seem (“Without tits, there is no paradise.”), is the name of a Colombian television drama about young women who get breast implants hoping to attract the attentions of local drug lords and thereby escape poverty.

12. For example, Symons (1979) and Wright (1994). 

13. See Morris (1967), Diamond (1991), and Fisher (1992). 

14. http://dir.salon.com/story/mwt/style/2002/05/28/booty_call/. 

15. Though they can be considered permanently swollen, this is not to say that breasts don’t change throughout a woman’s life (and menstrual) cycle. They typically swell further at pregnancy, menstruation, and orgasm (up to 25 percent greater than normal, according to Sherfey), and diminish in size and fullness with age and breastfeeding.

16. Small (1993), p. 128. 

17. Haselton et al. (2007). Available online at www.sciencedirect.com.

18. Many accounts of human sexuality incorporate this explanation, but that of Desmond Morris is probably still the most widely known.

19. Dixson (1998), pp. 133–134. 

20. Dixson refers specifically to macaques and chimps in this passage, though he’s speaking of the capacity for multiple orgasm in female primates in general in the section where the passage appears. Passages like this led us to wonder why Dixson hadn’t followed the data to where they seem to so clearly lead. We sent him an email outlining our argument and requesting his comments and criticisms, but if he received our message, he chose not to respond.

21. Symons (1979), p. 89. 

22. Lloyd, a former student of Stephen Jay Gould, recently published an entire book in which she reviews (and rather contemptuously dismisses) the various adaptive arguments for the female orgasm (
The Case of the Female Orgasm: Bias in the Science of Evolution). For a sense of why we don’t recommend her book, take a look at David Barash’s review, available online (“Let a Thousand Orgasms Bloom”). Download at http://www.epjournal.net/filestore/ep03347354.pdf.

23. As noted above, some of the findings of Baker and Bellis are highly controversial. We mention them because they are known to many in the general audience, but none of their findings are necessary to our argument. 

24. Barratt et al. (2009). Available online at http://jbiol.com/content/8/7/63. 

25. Pusey (2001). 

26. Both quotes appear in Potts and Short (1999). The first quote is from the main text, page 38, and the second is quoting Laura Betzig, p. 39. 

27. Dixson (1998), pp. 269–271. An excellent review of the development of the concept of postcopulatory sexual selection can be found in Birkhead (2000). Copious evidence for this filtering function can be found in Eberhard (1996), where the author presents dozens of examples of females exerting “post-copulatory control” over which sperm fertilize
their eggs. 

28. Dixson (1998), p. 2. 

29. Small (1993), p. 122. 

30. Gallup et al. (2002).

Other Relevant Research

Nicholas A, Brody S, de Sutter P, and de Carufel F. A woman's history of vaginal orgasm is discernible from her walk. J Sex Med 2008;5:2119–2124.

Conclusions. The discerning observer may infer women's experience of vaginal orgasm from a gait that comprises fluidity, energy, sensuality, freedom, and absence of both flaccid and locked muscles. Results are discussed with regard to previous research on gait, the effect of the musculature on sexual function, the special nature of vaginal orgasm, and implications for sexual therapy. 

Part V: Men Are from Africa, Women Are from Africa

1. Wright (1994), p. 58.

Chapter 20: On Mona Lisa’s Mind

1. Kendrick et al. (1998). 

2. Baumeister (2000). 

3. Chivers et al. (2007). 

4. Much of the research reviewed here is mentioned in Bergner’s excellent article “What Do Women Want?—Discovering What Ignites Female Desire,” 
January 22, 2009. Link: http://www.nytimes .com/2009/01/25/magazine/25desire-t.html.

5. Anokhin et al. (2006). 

6. Georgiadis et al. (2006). Or, for a review: Mark Henderson, “Women Fall into a ‘Trance’ During Orgasm,” Times Online, June 20, 2005. http://www.timesonline.co.uk/tol/life_and_style/health/article535521.ece. 

7. Tarin and Góomez-Piquer (2002). 

8. Little’s quote is from BBC News article: http://news.bbc.co.uk/2/hi/health/2677697.stm. 

9. Wedekind et al. (1995). A more recent follow-up that confirms these results is Santos et al. (2005).

10. Birth control pills don’t just interfere with women’s ability to sense MHC in men, but appear to affect other feedback systems as well. See Laeng and Falkenberg (2007), for example.

11. For a recent survey of this research, see Alvergne and Lummaa (2009). 

12. This isn’t meant as an indictment of the pill. But in light of these changes, we’d strongly recommend that couples spend several months together using alternate forms of birth control before making long-term plans. 

13. Lippa (2007). Available online at http://psych.fullerton.edu/rlippa/bbc_sexdrive.htm. 

14. See Safron et al. (2007). A good review of related research is here: http://www.wired.com/medtech/health/news/2004/04/63115?currentPage=all. 15. Alexander and Fisher (2003).

Chapter 21: The Pervert’s Lament

1. Dixson (1998), p. 145. 

2. Both these interviews appear on NPR’s This American Life, Episode #220. Available via free download at iTunes or at www.thislife.org. 

3. According to Reid (1989), it was considered wise and healthful for young Chinese men to share their abundant sexual energies with older women, who would benefit from absorbing the energy released by male orgasm; likewise, it was felt that young women’s orgasms would infuse older men with increased vitality. The same pattern is found in some foraging societies, as well as among some South Pacific island cultures. 

4. One example among many: Dabbs et al. (1991,1995) found, “Offenders high in testosterone committed more violent crimes, were judged more harshly by the parole board, and violated prison rules more often than those low in testosterone.” 

5. Gibson (1989). 

6. One wonders about the long-term social repercussions of widespread sexual frustration in adolescent males. To what extent, for example, is this frustration a contributing factor to the misogynistic rage many men experience? How does this frustration affect young men’s willingness to fight wars or join street gangs? While we don’t agree with arguments like those advanced by Kanazawa (2007) claiming that Islam sanctions polygyny in order to increase the male sexual frustration that creates a pool of available suicide bombers, it’s hard to dismiss the notion that intense frustration will often be expressed as misdirected rage.

7. Georgia has a serious problem with oral sex. Until 1998, it was illegal—even between a married couple in their own bedroom—and punishable by up to twenty years in prison.

8. For example, http://www.npr.org/templates/story/story.php?storyId= 102386952&ft=1&f=1001.

9. Fortenberry (2005). 

10. All quotes from this section are taken from Prescott (1975). 

11. See Elwin (1968) and Schlegel (1995). 

12. “Some Thoughts on the Science of Onanism,” a speech delivered to the Stomach Club, a society of American writers and artists. 

13. Money (1985). 

14. See http://www.cirp.org/library/statistics/USA/. 

15. Money (1985), pp. 101–102. 

16. These men believed that any spices or strong flavors excited sexual energies, so they recommended bland diets to dampen the libido. Graham crackers and unsweetened breakfast cereal were originally marketed to parents of adolescent boys as foods that would help them evade the evils of masturbation. For a fictionalized—though largely accurate— depiction of these men and their movement, see Boyle (1993).

17. Interestingly, Freud’s nephew, Edward Bernays, is considered one of the founders of public relations and modern advertising. Among his many famous ad campaigns was the first to associate cigarettes with increased autonomy for women. In the 1920s, Bernays staged a legendary publicity stunt still taught in business classes today. He arranged to have fashion models march in New York’s Easter parade, each with a lit cigarette and wearing a banner calling it a “torch of liberty.” For more on this, see Ewen (1976/2001).

18. Farmers know that in order to get a bull to mate with the same cow more than a few times, the bull has to be tricked into thinking it’s a different cow. They do this by rubbing a blanket on another cow to absorb her scent and then throwing it on top of the cow to be mated. If the bull isn’t fooled into it, he’ll simply refuse—no matter how attractive the cow may be.

19. Sprague and Quadagno (1989). 

20. See, for example, the documentary film “Rent a Rasta,” written and directed by J. Michael Seyfert: www.rentarasta.com, or the feature film “Heading South,” directed by Laurent Cantet, 

21. The New Yorker, July 6 and 13, 2009, p. 68. 

22. Additionally, the so-called Westermark effect appears to strongly dissuade sex between close familiars. 

23. See, for example, Gray et al. (1997 and 2002) and Ellison et al. (2009). 

24. See, for example, Glass and Wright (1985). 

25. Roney et al. (2009), but also see Roney et al. (2003, 2006, and 2007). 

26. Davenport (1965). 

27. Kinsey et al. (1948), p. 589. 

28. Symons (1979), p. 232. 

29. Bernard (1972/1982). 

30. Berkowitz and Yager-Berkowitz (2008). 

31. Symons (1979), p. 250. 

32. See, for example, Roney et al. (2003). Regular aerobic exercise, lots of garlic, stress avoidance, and plenty of sleep are also good ways to “keep it up.” We should note that despite the anecdotal evidence, few scientists have risked ridicule by applying for grants to study the hormonal changes in philanderers. The phenomenon is well documented in other mammals, however (see, for example, Macrides et al., 1975). It’s possible the effect may be mediated not by actual intercourse so much as by pheromones, which might explain the bulusela shops where Japanese men purchase girls’ vaccum-packed (but used) panties from vending machines. Enterprising graduate students might want to consider research similar to Wedekind’s “Sweaty T-shirt study,” but with women’s panties instead of men’s shirts in the plastic bags, to see whether exposure to novel women’s genital pheromones alone is enough to affect testosterone blood concentrations in men.

33. For example, for depression: Shores et al. (2004); heart disease: Malkin et al. (2003); dementia: Henderson and Hogervorst (2004); mortality: Shores et al. (2006).

34. Squire quoted by Phillip Weiss in his provocative article in New York magazine: “The affairs of men: The trouble with sex and marriage.” May 18, 2008. Available here: http://nymag.com/relationships/sex/47055.

Chapter 22: Confronting the Sky Together

1. Wilson (1978), p. 148. 

2. Holmberg (1969), p. 258.

3. “Is There Hope for the American Marriage?” Caitlin Flanagan Time, July 2, 2009. http://www.time.com/time/nation/article/0,8599,1908243,00 .html.

4. These quotes from Druckerman were taken from a review of her book in The Observer, July 8, 2007.

5. Jaynes (1990), p. 67. 

6. “What does marriage mean?” Dan Savage. In Salon.com, July17, 2004: http://www.salon.com/mwt/feature/2004/07/17/gay_marriage/index.html. 

7. Squire quoted by Weiss in New York magazine: “The affairs of men: The trouble with sex and marriage.” May 18, 2008. Available here: http://

8. “Only You. And You. And You. Polyamory—relationships with multiple, mutually consenting partners—has a coming-out party.” By Jessica Bennett. Newsweek (Web Exclusive) July 29, 2009. http://www .newsweek.com/id/209164.

9. Hrdy (2001), p. 91. 

10. “Scenes from a group marriage.” By Laird Harrison. Salon.com. http://mobile.salon.com/mwt/feature/2008/06/04/open_marriage/index.html. 

11. http://andrewsullivan.theatlantic.com/the_daily_dish/2009/01/ted-haggard-a-1.html. 

12. McElvaine (2001), p. 339. 

13. Perel (2006), p. 192. 

14. Gould (2000), pp. 29–31. 

15. After all, in the 1970s, somebody bought nearly four million copies of 
Open Marriage, by Nena and George O’Neill. 

16. Perel (2006), pp. 192–194.

17. Burnham and Phelan (2000), p. 195. 

18. Perel (2006), p. 197. 

19. Bergstrand and Blevins Williams (2000). 

20. Easton and Liszt (1997). 

21. You can hear the press conference at www.thisamericanlife.org/Radio_Episode.aspx?episode=95. 

22. We first learned of this striking sun/moon relation in Weil (1980), a fascinating book on the consciousness-altering potential of everything from solar eclipses to perfectly ripe mangoes.


References and Suggested Further Reading

Abbott, E. (1999). A History of Celibacy. Cambridge, MA: Da Capo Press.

Abramson, P. R., and Pinkerton, S. D. (Eds.). (1995a). 
Sexual Nature Sexual Culture. Chicago: University of Chicago Press.
With Pleasure: Thoughts on the Nature of Human Sexuality. New York: Oxford University Press.

Acton, W. (1857/2008). 
The Functions and Disorders of the Reproductive Organs in Childhood, Youth, Adult Age, and Advanced Live Considered in their Physiological, Social, and Moral Relations. Charleston, SC: BiblioLife.

Adovasio, J. M., Soffer, O., and Page, J. (2007). 
The Invisible Sex: Uncovering the True Roles of Women in Prehistory. New York: Smithsonian Books.

Alexander, M. G., and Fisher, T. D. (2003). Truth and consequences: Using the bogus pipeline to examine sex differences in self-reported sexuality. 
The Journal of Sex Research, 40: 27–35.

Alexander, R. D. (1987). 
The Biology of Moral Systems. Chicago: Aldine.

Alexander, R. D., Hoogland, J. L., Howard, R. D., Noonan, K. M., and Sherman, P. W. (1979). Sexual dimorphisms and breeding systems in pinnepeds, ungulates, primates and humans. In N. Chagnon and W. Irons (Eds.), 
Evolutionary Biology and Human Social Behavior: An Anthropological Perspective (pp. 402–435). New York: Wadsworth.

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