The Evolution of Sex: Gender, Mating, and Social Relations

Source: Iurii Laimin/Pexels.

The evolution of sex, gender, mating strategies, and social relationships are hot topics in the study of nonhuman and human behavior.¹ People from many different disciplines are weighing on these and related topics and a new and easy-to-read book titled The Sexual Evolution: How 500 Million Years of Sex, Gender, and Mating Shape Modern Relationships by evolutionary biologist Dr. Nathan Lents is an excellent science-based summary of what we know.

Among his major messages are that many of our supposedly modern ideas about gender and human sexuality are, in fact, deeply rooted in our animal ancestors and that we can learn a lot about ourselves from the incredible array of sexual diversity among other animals. Here's what he had to say about his fascinating and eye-opening book.

Marc Bekoff: Why did you write The Sexual Evolution?

Nathan Lents: There were two primary motivations for writing this book, one directed at my fellow scientists, and one directed at the general public. Firstly, I am critiquing how much bias has impacted how scientists interpret their observations and discuss their findings.

That bias is anthropomorphic, patriarchal, heteronormative, gender critical, and sex-negative. It is distressing to me how much these biases have infected otherwise good solid biology research. For far too long, biologists collapsed animal reproductive behaviors into overly simplified categories and failed to grasp the diversity right in front of their eyes. Only recently have we begun to see how creatively animals can engage sexed bodies, gendered behaviors, and sexual interactions, and this is puzzling given that we have long known that the whole purposes of sex and sexual reproduction is to generate and spread diversity. Finally, we are starting to appreciate that the same logic of “diversity wins” applies to sex itself.

Source: Mariner Books/with permission.

And secondly, I am trying to show the general public that the current moment of sexual upheaval in our society is actually a rediscovery of a more expansive relationship with sex and gender that our ancestors once had and that other animals enjoy today.

As young people take creative approaches to gender expression and sexuality, and explore different relationship styles, many reactionaries are left clinging to outdated notions that sexual diversity is somehow wrong and unnatural, but nothing could be further from the truth. Sex is more than a binary, gender is supposed to be creative, and there is no one right way to make a family. These ideas are not so radical when we appreciate how recent the narrow view of sex really is.

MB: How does your book relate to your background and general areas of interest?

NL: In my research laboratory, I study the evolution of the human genome and some of our unique genes that make us distinct from our closest relatives. But in my teaching as well as most of my writing, I emphasize how much we have in common with other animals. Although this may seem like a contradiction, that’s not how I see it. Rather, I think that only by appreciating what we have in common with other animals, and what is different about us, can we get the full picture of what it means to be human. I have been teaching the biology of sex, gender, and sexuality for about 15 years now, and this book is, in many ways, the culmination of everything I have learned in the process.

MB: Who do you hope to reach?

NL: I think this is a book for everyone, but the people I most hope will read it are biologists, nature and animal lovers, feminists, the LGBTQ community and its allies, and those who are interested in the biology of sex and gender. Everyone has a stake in these conversations because we all have sexed bodies, gender identity and expression, and we pursue sexual relationships. Personally, I think we are all better off in understanding the natural history of these things that are so core to who we are.

MB: What are some of the topics you consider and what are some of your major messages?

NL: In part one of my book, I offer five chapters on animal biology and behavior covering these topics: biological sex, gender, sexuality, sexual relationships, and the many purposes of sexual interactions. And the major messages of those chapter are diversity, diversity, diversity. It’s everywhere! And then in part two, I bring things back to the human experience and offer three chapters that focus on how the animal biology that I already discussed bears on the human experience of sex and gender. And then in the concluding chapter I provide a little bit of “what I really think” about all of this.

MB: How does your work differ from others that are concerned with some of the same general topics?

NL: I think my book offers a unique perspective on sex and gender by emphasizing its long history, literally 500 million years of evolution. Others have discussed the biology of these topics, of course, but I think my perspective is unique in that it places these behaviors in their full evolutionary context and specifically seeks and highlights how diverse sex and gender is in nature.

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MB: Are you hopeful that as people learn more about this topic they will appreciate how all animals, including ourselves, make more of themselves?

NL: Yes, I am hopeful that this book will be perspective-altering for many people because, for whatever reason, we see animals as more pure manifestations of biology than humans are. I guess this is because most people see human behavior as totally contaminated by societal expectations, cultural indoctrination, and social control. It’s hard to argue with that because many humans truly have done everything they can to remove themselves from “nature.” I think that is very much to our detriment.

Besides educating about the true nature and history of sex and gender, I hope the book will help to instill a love and appreciation for animals and the richness of their social lives. Animals are so fascinating and they have so much to teach us about ourselves.