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Sexuality and gender are often at the forefront of cultural and political debate today. In his new book, The Sexual Evolution: How 500 Million Years of Sex, Gender, and Mating Shape Modern Relationships (Mariner Books), evolutionary biologist Nathan H. Lents details how the animal world may hold many answers to these concepts. In this Q&A, Lents details how animal relationships can offer perspective on sexual diversity, social monogamy and gender identity.
Newsweek: What drew you to the field of evolutionary biology?
Lents: I've loved both history and biology since childhood. Evolutionary biology is the study of the natural history of life, and humans have always been fascinated by our history. In previous eras, cultures developed various creation myths to explain our origins. But now, science is developing tools and methodologies to probe our biological history and it is a thrill to play a small role in that.
Why is looking at human sexuality and relationships through that lens useful?
I maintain that the evolutionary lens is essential for understanding anything about us. Furthermore, sex and sexuality have likely played an outsized role in our evolution because of how directly they impact reproductive success. Humans have many relationships that dearly matter to them. Parental relationships, sibling relationships, friendships, extended family, business partnerships and so on. But our romantic partners—the ones we have sex with—usually take priority over all others. I think that is a reminder of how sex connects our past to our future.
How does your book challenge traditional views on sex, gender and mating in humans?
Over the past few centuries, the dominant forces in our culture placed sharp restrictions on how humans engage their gender and sexuality, which led to a narrowing of our sexual potential. We were told that only heterosexuality is natural, that humans are built strictly for monogamy, that sexual activity is mostly for procreation, that diverse gender expression is aberrant and that there is only one correct way to make a family. This was so ingrained that biologists saw nature that way as well. Aided by advances in technology and methodology, we have now begun to observe animals—and ourselves—more objectively and, lo and behold, we had been missing a lot of the larger picture. We're still at the beginning of this revolution, but it is already clear that sex, gender and sexuality are much more diverse and creative than we realized. Sexual diversity is good for animals and it's good for us too.
Monogamy in humans is largely based on cultural constructions, not evolutionary ones. Are you saying we would be better off if we shed these conventions?
I am definitely not saying that. First off, biology aims to describe how things are, not how they should be. Secondly, of the various mating systems we see in animals, social monogamy is one that often places individuals on equal footing and binds them together in mutual parental investment. It's a pretty good deal for all involved. I am not saying that humans are not evolved for monogamy. Rather, I argue that humans are evolved for flexibility, that different systems emerge in different environments and that humans can thrive in many different arrangements. We know that in animals, sexual exclusivity rarely accompanies social monogamy, and we know that our ancestors have lived and thrived under different mating systems. Social monogamy may be the most common, but there is nothing inherently unnatural with other types of sexual relationships.
Can you suggest a few behaviors from the animal kingdom that humans should specifically seek to emulate? Or avoid?
The Barbary macaque society is enviable because it is egalitarian, cooperative and mostly gregarious. Bonobo society is similarly peaceful, affectionate and sexual, and I think it is a beautiful way to live, although neither of these are completely free of hierarchy, conflict or violence. The societies of gorillas and common chimpanzees are more aggressive and violent, and I don't think we want to live like that. The good news is that there is a lot that we can do to build a peaceful and egalitarian society through various social incentives. Perhaps more than any other species, humans adapt their behavior in response to the social environment. I agree with David Sloan Wilson and others who argue that humans are at our best when we are working in cooperative groups in which the fates of all involved are tied together. I think the happiest places to live are those with individual freedom but with close financial and social cooperation.
What is the most surprising thing you learned while researching and writing this book?
I was very surprised to learn how common diverse genders, sexualities and mating strategies are among animals. We've all been so immersed in anthropocentric biases that we tend to view animal sex and mating through our own lens. But the theme of nature is diversity, creativity and adaptability.
Valentine's Day is approaching. What animal courting behaviors can humans learn from to enhance our own relationships?
What's great about how animals approach pair-bonding is that it is largely free of taboos, expectations and other cultural baggage. Therefore, I think the best gift we can give our romantic partner is our judgment-free understanding of how they wish to express their gender and sexuality. When we let each other explore our inner drives and passions, we get closer to the ideal of living as our authentic selves. It can be difficult to resist the instinct to restrict and coerce our partners' behaviors, but offering autonomy and acceptance instead is an empowering act of unselfish love.
