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Thursday, February 07, 2019

Review: Sex At Dawn

Sex At Dawn is a book with an argument, so let me summarize the argument in the book:

Traditional views on the evolutionary nature of sex in humans are that humans are a naturally monogamous species, with rampant cheating. This view does not line up with the following evidence:

  • Human male-female dimorphism is about 20% (men are about 20% larger than women on average), making us more like Chimpanzees and Bonobos than like Gorillas and Gibbons.
  • Human male sexual organs display signs of having been evolved for sperm competition, rather than monogamy/harem-like structures: these includes testicles hanging outside the body in vulnerable locations, high sperm count, with coupious amounts of seminal fluid (which can actually vary depending on how recently the male has seen its mate), and preference.
  • Human females also display signs of having evolved for non-monogamous mating: human females are the louder of the couple when having sex (i.e., issuing calls for more mates to join in the sperm competition), human females can keep having orgasms far longer than a single male can keep it up, and human females also do not display any overt signs of ovulation but remain sexually active throughout the month.
  • Studies of humans in hunter-gatherer societies that are nomadic show that extreme egalitarianism is practiced: this includes sharing of food, and even rituals of observed sex and group rearing of children, contrary to the "selfish-gene" hypothesis where time, energy, and resources spent raising kids that don't carry your genes are considered "wasted." In practice, entire tribes would raise the children collectively, with men not necessarily knowing whose child is whose. Children in such societies experience a much more stable childhood life than the traditional "nuclear family" with a high chance of divorce.
There's lots of evidence in the book hammering in the details of each of the arguments made above, but that's the gist of the argument. Extraordinary claims demand extraordinary evidence, and much time in the book is spent on both producing evidence (some of it cultural and observational: at one point they mention the famous "fake orgasm" scene in "When Harry Met Sally" wouldn't have been funny if it was Harry who was faking it), and pointing out that the traditional view of human monogamy doesn't have nearly as much evidence supporting it as previously supposed.

One interesting observation the authors make is that these traditional forager societies tend to be female oriented rather than male dominated, and they hypothesize that the creation of agriculture was what drove the current patriarchal society we see in the modern world. The book ends with a call to action for families to explore alternative structures rather than live unhappily in (sexual or otherwise) frustration. There are a few examples, but they do observe that children of 2 parent households do better by far than children of divorced households, and plead for parents to use their understanding of this book to design better (or at least less frustrating) lives for themselves.

I thought the book was very well argued and the evidence in favor of their view of human sexuality compelling. The book has revolutionized my thinking about human reproduction and evolution, and definitely makes many other books I've read about human sexuality that rely on the traditional, male-oriented patriarchy model of family formation obsolete. It also explains many phenomenon that might have puzzled you or me, such as why are relationships so hard, even between couples that really like each other, and why human fertility seems to be decreasing. Highly Recommended. I wouldn't be surprised if at the end of this year I named this book to be the book of the year.

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