"Sex at Dawn": Why monogamy goes against our nature

From testicle size to our slutty ancestors, a new book explains what human history teaches us about sex and couples

Published June 27, 2010 6:01PM (EDT)

According to Christopher Ryan and Cacilda Jethá, the authors of the new book "Sex at Dawn: The Prehistoric Origins of Modern Sexuality," the state of the American marriage is awfully grim. We have a stratospheric divorce rate and a surge of single parents. Couples who stay together are often trapped in sexless, passionless unions. An entire industry — from couples therapy to sex supplements — has emerged to help people "rekindle the spark" without straying from the confines of monogamy.

But Ryan and Jethá also have a theory for what's causing this misery: From a biological perspective, men and women simply aren't meant to be in lifelong monogamous unions. In "Sex at Dawn," which uses evidence gathered from human physiology, archaeology, primate biology and anthropological studies of pre-agricultural tribes from around the world, they argue that monogamy and the nuclear family are more recent inventions than most of us would expect — and far less natural than we've come to believe.

Before the advent of agriculture, they argue, prehistoric humans lived in a much less sexually possessive culture, without the kind of lifelong coupling that currently exists in most countries. They also point to the bonobos, our closest relatives, who live in egalitarian and peaceful groups and have astronomical rates of sexual interaction, as evidence of our natural inclinations. While Ryan and Jethá's book (Ryan is a psychologist, and Jethá a practicing psychiatrist, in Spain) is often a bit scattered and hard to follow, its provocative argument is also impossible to dismiss.

Salon spoke to Ryan over the phone from Barcelona about the problem with American marriages, why gay men understand relationships better than straight men, and the hidden meaning of human testicle size.

You paint a bleak picture of the state of marriage in the West, particularly in the United States. What makes it so bad?

Marriage in the West isn’t doing very well because it’s in direct confrontation with the evolved reality of our species. What we argue in the book is that the best way to increase marital stability, which in the modern world is an important part of social stability, is to develop a more tolerant and realistic understanding of human sexuality and how human sexuality is being distorted by our modern conception of marriage. Certainly growing up in the '70s and '80s there were very few kids I knew whose parents weren’t divorced at least once. The economic, emotional, psychological cost of fractured relationships is a major problem in American society — with single mothers and single-parent families.

You argue that much of this misery stems from changes that occurred when humans developed agriculture, around 8000 B.C. What happened?

The advent of agriculture changed everything about human society, from sexuality to politics to economics to health to diet to exercise patterns to work-versus-rest patterns. It introduced the notion of property into sexuality. Property wasn’t a very important consideration when people were living in small, foraging groups where most things were shared, including food, childcare, shelter and defense. It makes perfect sense that sexuality would also be shared — why wouldn’t it be when paternity wasn’t an issue?

When you have agriculture, men started to worry about whether or not certain children were theirs biologically, because they wanted to leave their accumulated property to their own child. At that point, people also made a very clear connection between sexual behavior and birth. Lots of people didn't have a very clear understanding of the cause and effect of sex and birth, but when you have domesticated animals living side by side with people, they start to notice that the characteristics of a certain male that has mated with a certain female show up in the offspring.

One of the central ideas of much biological and genetic theory is that animals will expend more energy protecting those they’re genetically related to — siblings, parents, offspring — as opposed to those they're not related to. Why wouldn't that apply to humans?

There are many, many exceptions to that rule in nature. One of the exceptions we talk about in the book are the vampire bats that share blood with each other. They go out and they suck the blood at night and then they come back to the cave and the bats that didn’t get any blood will receive blood from other bats. They share, and that has nothing to do with genetic connection. And in terms of animals that are much more closely related to humans, when you look at bonobos and their promiscuous interaction, it’s virtually impossible for a male to know which of his offspring are related to him biologically. So to say that there’s this inherent concern with paternity within our species, I just don’t see evidence for that.

Does this mean that humans didn't form couples before the advent of agriculture?

Because human groups at the time knew each other so well and spent their lives together and were all interrelated and depended upon each other for everything, they really knew each other much better than most of us know our sexual partners today. We don’t argue that people didn’t form very special relationships — you can see this even in chimps and bonobos and other primates, but that bond doesn’t necessarily extend to sexual exclusivity. People have said that we’re arguing against love — but we're just saying that this insistence that love and sex always go together is erroneous.

Given that these people have been dead for thousands of years, and we don't have a fossil record of sexual activity, isn't this hard to prove?

The evidence comes from several different areas. We look at pre-agricultural people who have been studied today and horticultural people who have been studied by anthropologists. There’s a fair amount of information about the sexuality of people who haven’t been deeply exposed to Western influence. There are accounts from travelers and colonialists, first-contact accounts from historical records, that we rely on. But you can also extract a great deal of information from the human body itself — from the design of the penis to the volume of the testicles to the sperm-producing potential of the testicular tissue and the way we have sex.

What does our testicle size tell us about the way we have sex?

Our testicles aren’t as big as those of chimps and bonobos, but our ejaculation is about four times as big in terms of volume. The theory is that when males compete on the level of the sperm cell, they develop much larger testicles, because in promiscuous animals, the sperm of the different males is competing with the sperm of other males to get to be the first to the egg. And the fact that our testicles are not as small relative to our body as the monogamous gibbon or gorillas reinforces the idea that we have been non-monogamous for a long time.

Plus the design of our penis strongly suggests that it evolved to create a vacuum in the female reproductive system, thereby pulling out the semen of anyone who was there previously. There are all kinds of indications of sperm competition in the human male. And one of the things that we suggest in the book that no one else has suggested is that because the testicles are genetically the part of the body that adapts fastest to environmental pressure, it’s quite possible that our testicles are much smaller than they were as recently as fifteen or twenty thousand years ago, to reflect the historical cultural imposition of monogamy. And of course we all know that sperm count is dropping precipitously even as we speak.

But that drop in sperm count has been reported over the last few decades, and I don't think American culture has becoming less sexualized since the 1950s — I think the opposite is true.

Well, it’s hard to say because it’s only been measured for about the last 100 years. So it’s very difficult to know what was happening before that. But yeah, it does seem to be plummeting faster and faster, and there are indications that it has a lot to do with industrial contaminants in the environment, and antibiotics and growth hormones in the food supply and so on.

But I think there’s this bifurcation of American culture where you’ve got the liberalization on one side with states passing gay marriage, but then you have other states veering off in the other direction. I think the Bill Clinton and Lewinsky situation could have been such a great opportunity for the culture to grow up instead of wasting so much time and money and political capital in this investigation of a victimless crime. If the Clintons had gone on their "60 Minutes" interview and just said, "You know what, our sex life is nobody’s business but ours," I think the country would have been so much better off.

I think from a cultural standpoint the idea of strict monogamy has far less currency within the gay male world than it does within the straight world. I’m a gay man, and I think probably about half the gay male couples I know are in open relationships. Why do you think that is?

First of all, they’re both men, so they both know what it’s like to be a man. They both know from experience that love and sex are two very different things, and it seems that for women the experience of sexuality is much more embedded in narrative, in emotion, in emotional intimacy. But also it’s really hard to judge what women would be like if they hadn’t been persecuted for the last five or six thousand or ten thousand years for any hint of infidelity.

Gay men in the United States have also by definition gone through a process of self-examination. The whole process of coming out is a process of integrating sexuality into your life in a way that takes courage, and it’s not something that happens naturally. I think gay people have an advantage because they’ve already gone through a process of saying: "Look, my sexuality is what it is. I’m not ashamed of it. I’m going to live openly and in accord with it." That puts them on a different level than most heterosexual people who are able to pass along and pretend that they fit into the normal parameters.

It seems like many Americans, in particular, have a very strong notion that a marriage must remain monogamous at all costs — and that any infidelity is grounds for divorce. In other countries, like France, for example, that doesn't seem to be the case.

I’ve been living off and on for almost 20 years here in Barcelona, and from outside, the United States looks very adolescent, in a positive and negative sense. There's its adolescent energy — its idealism — but there’s also an immaturity and intolerance toward the ambiguity of life and the complexity of relationships. The American sense of relationships and sexuality tends to be very informed by Hollywood: It’s all about the love story. But the love story ends at the wedding and doesn't go into the 40 years that comes after that.

So if monogamous marriage isn't the right arrangement for us, what is?

We’re not really arguing for any particular arrangement. We don’t even really know what to do with this information ourselves. What we’re trying to do in the book is give people a more accurate sense of where we came from, why we are the way we are, and why certain aspects of life feel like a bad fit. I think a lot of people make a commitment when they’re in love, which is a sort of a delusional state that lasts a couple of years at most. I think it was Goethe who said that love is an unreal thing, and marriage is a real thing, and any confusion of the real with the unreal always leads to disaster.

All we’re really hoping for is to encourage more tolerance and more open discussion between men and women about sexuality and about marriage, and to come to see that marriage isn’t about sex. It's about things that are much deeper and more lasting than sex, especially if you have children. And the American insistence on mixing love and sex and expecting passion to last forever is leading to great suffering that we think is tragic and unnecessary.

By Thomas Rogers

Thomas Rogers is Salon's former Arts Editor. He has written for the Globe & Mail, the Village Voice and other publications. He can be reached at @thomasmaxrogers.

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