The Evolution and Future of the Human Animal Jared Diamond
It's 15 years old now, so I think there have probably been a lot of new relevant results since then. The stuff on human sexual behavior and mate selection is definitely relevant, but where there is overlap with my ideas, the fit is disappointingly bad.
One thing is that he says that in a state of nature humans are “mildly polygynous”, which he argues is supported by purely physical observations of male/female size difference as well as the common tendency of modern hunter-gatherer tribes. And he talks about some of the extreme harem arrangements that were used in china and the mideast. Clearly in the past status could increase your genetic fitness if you are a man (or still if you're in a Mormon cult.) Somehow culture has sublimated our libido. It seems like the instinct that status will increase your reproductive success is still there and is still at least one factor driving men's social striving, even though this actually the opposite of the truth.
So far as infidelity, he cites the 10% number for children unrelated to the nominal father, but he also points out that the infidelity rate must be significantly higher and cites survey data for the 20-30% range, which was surprisingly high to me. He puzzles over why women would want to be unfaithful, and somehow never considers the obvious point that they might be looking for better genes, or at least for different genes to hedge their genetic bet.
He does observe the obvious male qandry of being unsure they are the father, and discusses of traditional practices that make a lot of sense when interpreted as ways of keeping women from “pursuing a mixed sexual strategy”, such as the harem, and also practices such as “female circumcision”, etc., and observes that traditional laws about infidelity (made by men) considered the offending party to be the woman and the wronged party to be the husband. So far as mate selection, he considers it to be “maximum similarity while avoiding incest.” He cites results for significant correlations on many appearance factors, including very subtle ones such as index finger length. He does observe that the similarity-to-self is entirely consistent with choosing a partner similar to your opposite-sex parent (since of course you resemble them.) He talks about a bunch of studies of mate choice in mice, mentioning without much comment the “optimal difference” results, but also citing cases where by artificially scenting the parents they were able to create a preference for a similarly scented mate. So in mice there is a general preference for similarity.
He explains the observed preference for similar mates as “imprinting”, curiously neglecting to consider what the evolutionary value of this behavior is. I offer the solution that recreating the family is an obvious conservative strategy. Of course, in the extreme, you want to choose a mate of the right species, so clearly issues of sexual selection and speciation come in here, but those considerations which must emerge from mate choice happen on a longer timescale.
The most interesting additional parts were the chapter about proto-indo-european and the implicit story of conquest eradicating almost all of the indigenous languages of europe. Likely this also resulted in a greater general cultural homogeneity in Europe, with (for example) militaristic values. The invading horsemen's culture wasn't adopted in its entirety because it seems that it had to be adapted to local climactic conditions, and this resulted in some cultural hybridization, with the locals also evidently making significant genetic contribution to the population. Also, the chapter on genocide, especially the observations about historical genocide, Genghis Kahn, the bible, Greek story, suggest that at least by the time of city-states, killing at least the men and children in conquered cities was the norm. Whether the conquered peoples are killed or merely assimilated, it's clear that the stakes were very high in inter-cultural competition. Genocide is just the thing to encourage genetic evolution to aid the culture. A self-sacrificing willingness to fight to defend the polity is the first thing you'd expect to see, and we do see this in historical and modern cultures. Of course, in the presence of genocide, fighting to save your children is clearly genetically adaptive.
The description of the life in the New Guinea highlands was also interesting, especially insofar as it can be considered the human condition in “a state of nature”, as Diamond suggests. One point is that there was very little mobility, with each tribe or village only knowing their immediate neighbors, and often those not very well. Often they supposed that their valley contained the only people on earth. Also the huge cultural diversity, with languages as different as English and Chinese within 60 miles of each other. There was also huge diversity in lifeways, such as family patterns and sexual behavior. This kind of stuff suggests that though family and economic behavior are presumably influenced by instinct, there are a huge number of vastly different cultures that can work,and the instinctual contribution must be very broad. At the end of the chapter he mourns this loss of cultural diversity and notes in a single sentence that our culture was selected for military and economic power, and is not necessarily the culture that makes people happiest.