Sex at Dawn

Almost everyone grows up hearing the same narrative. Men are supposedly naturally interested in spreading their seed, women are supposedly more selective and looking for a provider, and the faithful, stable couple is said to be the natural result of evolution. Psychologist Christopher Ryan and psychiatrist Cacilda Jethá call this the standard narrative of human sexuality.

The book is born from the suspicion that this narrative is wrong on important points. According to the authors, it was assembled by thinkers who lived in agricultural societies, with private property and inheritance, and who projected their own world back into prehistory. It would be as big a mistake as picturing cavemen as a sitcom family.

The authors give a playful name to this reading habit: the Flintstones fallacy, the assumption that the remote past was a rougher version of our present. From there, they try to reconstruct what human sexual life was like before agriculture changed the rules.

The book's main bet is that, for most of our species' history, humans lived in small bands of hunter-gatherers, with little property and a great deal of sharing. Food, childcare and, according to the authors, even sexual partners circulated more freely than we assume.

They argue that, in a world with no land to inherit and no cattle to fence in, no one needed to guarantee that children were exclusively theirs. Security came from the group's support network, not from an exclusive contract between two adults.

This reconstruction depends on indirect evidence, since no one filmed life fifty thousand years ago, and all we have are bones, tools and comparisons. The reader should note that the authors' work is, in part, interpretation, built from present-day groups, fossils and comparisons with other primates.

For the authors, the turning point came with the agricultural revolution, about ten thousand years ago. When land came to have owners, concerns about inheritance appeared, and knowing who fathered each child became a matter of property. The control of female sexuality, they say, was born from that.

The authors draw on thinkers who linked property and exclusive marriage, and they point out that agricultural life brought inequality, disease and long working hours. Imposed fidelity would be one of the social technologies created to protect assets.

This reading has appeal, because it connects intimacy to money, something Americans see clearly in estate disputes and alimony battles. Still, the relationship between agriculture and marriage is debated, and many anthropologists see pair bonds in societies without farming.