A look at our evolutionary history with 'Sex at Dawn'

For many people, monogamy is the standard in modern relationships. One partner, lifelong commitment, exclusivity. It feels “natural” — but is it really? Or is it mainly a cultural agreement that we have built over time? In the influential book Sex at Dawn, Christopher Ryan and Cacilda Jethá argue that our view of monogamy may actually conflict with our evolutionary origins.

The conventional view: humans as faithful partners

The classic evolutionary theory goes something like this: men want to spread their genes as widely as possible, while women seek a reliable provider who helps raise offspring. The result: monogamy as an evolutionary strategy. Two people, one family, faithfulness to each other — supposedly rooted deeply in our biology. It is a story that aligns with how many of us were raised. It is also a story that Ryan and Jethá challenge in Sex at Dawn.

Hunter-gatherers and sexual flexibility

Ryan and Jethá describe how many insights from anthropology and primatology suggest that early human societies were likely far less strictly monogamous than we often assume today. Rather than the idea of “one man, one woman,” early human groups may have:

• Shared childcare more broadly within the community
• Organized sexuality in a less exclusive way
• Developed strong social bonds between multiple partners within the group

The idea is not that there was “chaos,” but rather a form of shared intimacy and cooperation, where exclusivity played a less central role than we are used to today.

Back to the beginning: how did our ancestors really live?

Ryan bases his argument on a wide range of sources: studies of contemporary hunter-gatherer societies, comparative primatology, archaeological findings, and human sexual anatomy itself. His central argument: for most of human history, people lived in small, mobile groups characterized by shared food, shared childcare, and — most likely — shared sexuality.

Some key insights from the book:

1. Our closest relatives do things differently
   Chimpanzees and bonobos are our closest genetic relatives. Bonobos live in matriarchal communities where sex serves a social function — it resolves conflicts, strengthens bonds, and has little to do with exclusivity. Ryan asks: if our closest relatives live this way, why would humans be naturally monogamous?
2. Our bodies tell a story
   According to Ryan, human testicle size, penis anatomy, and certain aspects of female sexuality point toward what biologists call sperm competition — a characteristic of species where females mate with multiple males. In strictly monogamous species (such as gibbons), there are no signs of these anatomical adaptations.
3. Hunter-gatherers lived differently
   Communities such as the Mosuo in China and the Aché in Paraguay have known or still know forms of shared parenting and sexual freedom that differ greatly from the Western ideal of monogamy. Children are raised by the wider community, not exclusively by a nuclear family.
4. The agricultural revolution changed everything
   Around 10,000 years ago, with the rise of agriculture, something new emerged: private property. And with ownership came inheritance, possession, and the question: who do these children belong to? Ryan argues that monogamy may be less of a natural instinct and more of a cultural invention — useful for transferring property, but not necessarily rooted in our deepest nature.

But... does this mean monogamy is “unnatural”?

Does this mean monogamy is “unnatural”? No, and this is an important nuance. The book does not argue that monogamy is wrong, but rather that it is not the only “natural” form of human romantic or sexual behavior. Humans are incredibly flexible. We can:

• Create deep, long-lasting emotional bonds
• Experience curiosity and variety at the same time
• Develop culturally diverse forms of relationships

This flexibility may actually be our true evolutionary strength.

In conclusion

Whether humans are naturally monogamous is not a simple yes-or-no question. It is a story about evolution, culture, and human flexibility. What Sex at Dawn mainly shows is that there may not be one single “natural” way of loving — but rather a broad spectrum of possibilities. And perhaps that is where the true essence lies: not in following one fixed model, but in consciously choosing how we want to create connection.

Curious to learn more? Pick up the book. Start a conversation with your partner. Or begin with the most fundamental question: what do I truly want, and why?