Christopher Ryan

Are we designed to be sexual omnivores?

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I'm going to go off script and make Chris quite nervous here by making this audience participation. All right. Are you with me? Yeah. Yeah. All right.


So what I'd like to do is have you raise your hand if you've ever heard a heterosexual couple having sex. Could be the neighbors, hotel room, your parents. Sorry. Okay. Pretty much everybody. Now raise your hand if the man was making more noise than the woman. I see one guy there. It doesn't count if it was you, sir. (Laughter) So his hand's down. And one woman. Okay. Sitting next to a loud guy.


Now what does this tell us? It tells us that human beings make noise when they have sex, and it's generally the woman who makes more noise. This is known as female copulatory vocalization to the clipboard crowd. I wasn't even going to mention this, but somebody told me that Meg Ryan might be here, and she is the world's most famous female copulatory vocalizer. So I thought, got to talk about that. We'll get back to that a little bit later.


Let me start by saying human beings are not descended from apes, despite what you may have heard. We are apes. We are more closely related to the chimp and the bonobo than the African elephant is to the Indian elephant, as Jared Diamond pointed out in one of his early books. We're more closely related to chimps and bonobos than chimps and bonobos are related to any other primate — gorillas, orangutans, what have you. So we're extremely closely related to them, and as you'll see in terms of our behavior, we've got some relationship as well. So what I'm asking today, the question I want to explore with you today is, what kind of ape are we in terms of our sexuality? Now, since Darwin's day there's been what Cacilda and I have called the standard narrative of human sexual evolution, and you're all familiar with it, even if you haven't read this stuff. The idea is that, as part of human nature, from the beginning of our species' time, men have sort of leased women's reproductive potential by providing them with certain goods and services. Generally we're talking about meat, shelter, status, protection, things like that. And in exchange, women have offered fidelity, or at least a promise of fidelity. Now this sets men and women up in an oppositional relationship. The war between the sexes is built right into our DNA, according to this vision. Right? What Cacilda and I have argued is that no, this economic relationship, this oppositional relationship, is actually an artifact of agriculture, which only arose about 10,000 years ago at the earliest. Anatomically modern human beings have been around for about 200,000 years, so we're talking about five percent, at most, of our time as a modern, distinct species. So before agriculture, before the agricultural revolution, it's important to understand that human beings lived in hunter-gatherer groups that are characterized wherever they're found in the world by what anthropologists called fierce egalitarianism. They not only share things, they demand that things be shared: meat, shelter, protection, all these things that were supposedly being traded to women for their sexual fidelity, it turns out, are shared widely among these societies. Now I'm not saying that our ancestors were noble savages, and I'm not saying modern day hunter-gatherers are noble savages either. What I'm saying is that this is simply the best way to mitigate risk in a foraging context. And there's really no argument about this among anthropologists. All Cacilda and I have done is extend this sharing behavior to sexuality. So we've argued that human sexuality has essentially evolved, until agriculture, as a way of establishing and maintaining the complex, flexible social systems, networks, that our ancestors were very good at, and that's why our species has survived so well.


Now, this makes some people uncomfortable, and so I always need to take a moment in these talks to say, listen, I'm saying our ancestors were promiscuous, but I'm not saying they were having sex with strangers. There were no strangers. Right? In a hunter-gatherer band, there are no strangers. You've known these people your entire life. So I'm saying, yes, there were overlapping sexual relationships, that our ancestors probably had several different sexual relationships going on at any given moment in their adult lives. But I'm not saying they were having sex with strangers. I'm not saying that they didn't love the people they were having sex with. And I'm not saying there was no pair-bonding going on. I'm just saying it wasn't sexually exclusive.


And those of us who have chosen to be monogamous — my parents, for example, have been married for 52 years monogamously, and if it wasn't monogamously, Mom and Dad, I don't want to hear about it— I'm not criticizing this and I'm not saying there's anything wrong with this. What I'm saying is that to argue that our ancestors were sexual omnivores is no more a criticism of monogamy than to argue that our ancestors were dietary omnivores is a criticism of vegetarianism. You can choose to be a vegetarian, but don't think that just because you've made that decision, bacon suddenly stops smelling good. Okay? So this is my point. (Laughter) That one took a minute to sink in, huh?


Now, in addition to being a great genius, a wonderful man, a wonderful husband, a wonderful father, Charles Darwin was also a world-class Victorian prude. All right? He was perplexed by the sexual swellings of certain primates, including chimps and bonobos, because these sexual swellings tend to provoke many males to mate with the females. So he couldn't understand why on Earth would the female have developed this thing if all they were supposed to be doing is forming their pair bond, right? Chimps and bonobos, Darwin didn't really know this, but chimps and bonobos mate one to four times per hour with up to a dozen males per day when they have their sexual swellings. Interestingly, chimps have sexual swellings through 40 percent, roughly, of their menstrual cycle, bonobos 90 percent, and humans are among the only species on the planet where the female is available for sex throughout the menstrual cycle, whether she's menstruating, whether she's post-menopausal, whether she's already pregnant. This is vanishingly rare among mammals. So it's a very interesting aspect of human sexuality. Now, Darwin ignored the reflections of the sexual swelling in his own day, as scientists tend to do sometimes.


So what we're talking about is sperm competition. Now the average human ejaculate has about 300 million sperm cells, so it's already a competitive environment. The question is whether these sperm are competing against other men's sperm or just their own. There's a lot to talk about in this chart. The one thing I'll call your attention to right away is the little musical note above the female chimp and bonobo and human. That indicates female copulatory vocalization. Just look at the numbers. The average human has sex about 1,000 times per birth. If that number seems high for some of you, I assure you it seems low for others in the room. We share that ratio with chimps and bonobos. We don't share it with the other three apes, the gorilla, the orangutan and the gibbon, who are more typical of mammals, having sex only about a dozen times per birth. Humans and bonobos are the only animals that have sex face-to-face when both of them are alive. (Laughter) And you'll see that the human, chimp and bonobo all have external testicles, which in our book we equate to a special fridge you have in the garage just for beer. If you're the kind of guy who has a beer fridge in the garage, you expect a party to happen at any moment, and you need to be ready. That's what the external testicles are. They keep the sperm cells cool so you can have frequent ejaculations. I'm sorry. It's true. The human, some of you will be happy to hear, has the largest, thickest penis of any primate.


Now, this evidence goes way beyond anatomy. It goes into anthropology as well. Historical records are full of accounts of people around the world who have sexual practices that should be impossible given what we have assumed about human sexual evolution. These women are the Mosuo from southwestern China. In their society, everyone, men and women, are completely sexually autonomous. There's no shame associated with sexual behavior. Women have hundreds of partners. It doesn't matter. Nobody cares. Nobody gossips. It's not an issue. When the woman becomes pregnant, the child is cared for by her, her sisters, and her brothers. The biological father is a nonissue. On the other side of the planet, in the Amazon, we've got many tribes which practice what anthropologists call partible paternity. These people actually believe — and they have no contact among them, no common language or anything, so it's not an idea that spread, it's an idea that's arisen around the world — they believe that a fetus is literally made of accumulated semen. So a woman who wants to have a child who's smart and funny and strong makes sure she has lots of sex with the smart guy, the funny guy and the strong guy, to get the essence of each of these men into the baby, and then when the child is born, these different men will come forward and acknowledge their paternity of the child. So paternity is actually sort of a team endeavor in this society. So there are all sorts of examples like this that we go through in the book.


Now, why does this matter? Edward Wilson says we need to understand that human sexuality is first a bonding device and only secondarily procreation. I think that's true. This matters because our evolved sexuality is in direct conflict with many aspects of the modern world. The contradictions between what we're told we should feel and what we actually do feel generates a huge amount of unnecessary suffering. My hope is that a more accurate, updated understanding of human sexuality will lead us to have greater tolerance for ourselves, for each other, greater respect for unconventional relationship configurations like same-sex marriage or polyamorous unions, and that we'll finally put to rest the idea that men have some innate, instinctive right to monitor and control women's sexual behavior. (Applause) Thank you. And we'll see that it's not only gay people that have to come out of the closet. We all have closets we have to come out of. Right? And when we do come out of those closets, we'll recognize that our fight is not with each other, our fight is with an outdated, Victorian sense of human sexuality that conflates desire with property rights, generates shame and confusion in place of understanding and empathy. It's time we moved beyond Mars and Venus, because the truth is that men are from Africa and women are from Africa.


Thank you.




Chris Anderson: Thank you. Christopher Ryan: Thank you.


CA: So a question. It's so perplexing, trying to use arguments about evolutionary history to turn that into what we ought to do today. Someone could give a talk and say, look at us, we've got these really sharp teeth and muscles and a brain that's really good at throwing weapons, and if you look at lots of societies around the world, you'll see very high rates of violence. Nonviolence is a choice like vegetarianism, but it's not who you are. How is that different from the talk you gave?


CR: Well first of all, the evidence for high levels of violence in prehistory is very debatable. But that's just an example. Certainly, you know, lots of people say to me, just because we lived a certain way in the past doesn't mean we should live that way now, and I agree with that. Everyone has to respond to the modern world. But the body does have its inherent evolved trajectories. And so you could live on McDonald's and milkshakes, but your body will rebel against that. We have appetites. I think it was Schopenhauer who said, a person can do what they want but not want what they want. And so what I'm arguing against is the shame that's associated with desires. It's the idea that if you love your husband or wife but you still are attracted to other people, there's something wrong with you, there's something wrong with your marriage, something wrong with your partner. I think a lot of families are fractured by unrealistic expectations that are based upon this false vision of human sexuality. That's what I'm trying to get at.


CA: Thank you. Communicated powerfully. Thanks a lot.


CR: Thank you, Chris. (Applause)

An idea permeates our modern view of relationships: that men and women have always paired off in sexually exclusive relationships. But before the dawn of agriculture, humans may actually have been quite promiscuous. Author Christopher Ryan walks us through the controversial evidence that human beings are sexual omnivores by nature, in hopes that a more nuanced understanding may put an end to discrimination, shame and the kind of unrealistic expectations that kill relationships.

About the speaker
Christopher Ryan · Psychologist

The co-author of "Sex at Dawn," Christopher Ryan explores the prehistoric roots of human sexuality.

The co-author of "Sex at Dawn," Christopher Ryan explores the prehistoric roots of human sexuality.