This review will be lackluster not only because Scott Alexander covered Joseph Henrich’s book so extensively it required five posts (one, two, three, four, five) but also because I was moving data including notes on the book back & forth between computers while reading and lost much of them in the process through carelessness. I still figure it’s better than nothing, for my own purposes at least.

The title of the book refers to what separates human beings from other species, particularly our closest primate relatives. Henrich intends to argue that can’t simply be chalked up to our larger brains or any other individual capacity of our bodies (though he does discuss the importance of many such features in tracking how our secret caused us to diverge from chimps). Indeed, he insists that if a group of humans were dropped into an unfamiliar jungle in a survival competition against as primitive a relation as colobus monkeys, we would lose against monkeys. This would be the case even if the humans were permitted to cooperate alongside each other in a group against the monkeys (who of course never form social organizations as large as we do). Instead the secret is our accumulated culture, which we possess due to social learning and only a relatively infrequent amount of individual learning to move the knowledge frontier forward.

While much of the book (particularly the discussion of the importance of social status, and prestige specifically) reminded me of Robin Hanson, in other ways this is an overtly anti-Hansonian work. Henrich decidedly rejects viewing humans as “homo hypocritus“, arguing that we are actually worse than chimpanzees in Machiavellian out-smarting of peers. His reasoning is that the human faculty for imitation is so powerful that we can’t zig when others zag to get an advantage over them, whereas other animals can randomize more easily (rather cultural evolution produced rituals to randomize our decision-making, typically at the scale of a collective). In some ways this reminded me of Steve Sailer emphasizing that “chimps aren’t chumps” who teach other (an enormous difference, per Henrich).

It is surprising how many scenarios researchers have set up in which chimps can outperform bigger-brained humans, but when Henrich derided human reasoning abilities on the basis that we believe in the “hot-hand fallacy” that just showed the limits of his own understanding, since I knew from Andrew Gelman that it’s not a fallacy. The book was published in 2016, so maybe that was close enough to the vindication of the hot-hand that it’s understandable he wasn’t up to date on that. But a lot of the material on how easily our minds are affected drew on the social psychology priming literature hit hard by the replication crisis, and one experiences something like the (Murray) Gell-Man amnesia effect when after reading a lot of plausible claims confidently stated one reads similarly confident proclamations one knows now are unreliable (like his citation of a behavioral econ study on Israeli daycares). I did look at all the end-notes while reading (though I didn’t always match the citations to the corresponding entries in the bibliography), and was surprised both that urls (to youtube, of all places) made repeated appearances in this on-paper book to be manually copied into a browser, and that there were citations saying to “see” an unnamed “forthcoming” work from Henrich & co-authors. Perhaps those urls would be clickable in an electronic version and the citations could be updated to reflect the correct citations for those works once published.

Prior to reading I had already read Kevin Simler’s argument (also published shortly before this book, but criticizing a Henrich paper cited in there) for a more cynical take on prestige than Henrich, as well as Hanson’s even more cynical take. I recommend readers check out the former for the fascinating case of “babbler birds”. Those are the most important things to note in this review, while what follows will just be unorganized notes I didn’t lose while reading the later chapters of the book.

Something that might have gone unnoticed if I hadn’t read so much online from the disreputable/pseudonymous and otherwise is the claim that U.S counties with more Scotch-Irish settlers centuries ago have higher homicide rates… but ONLY in the south, not New England or the Mid-Atlantic. No mention at all of how a county’s homicide rate correlates with percentage African-American regardless of region. The book goes out of its way to emphasize that while there has been recent selection in small populations for things like lactose tolerance, this does not translate to continental-scale racial differences, so perhaps Henrich is covering himself for possible cancellation after attributing WEIRD distinctiveness to Catholic marriage laws (possibly erroneously, though I can’t remember where I saw it argued that the distinctive regional marriage pattern he was purporting to explain predated the Church’s laws in question).

As part of his emphasis on how our minds are affected by others he discusses the placebo effect. Greg Cochran (whose book with Harpending is cited here) doesn’t believe in it, attributing it instead to regression to the mean. What was particularly striking was that Henrich also discusses “nocebos” that harm people, and despite giving explanations earlier about how our distinctive features could evolve there’s no thought as to how something as deleterious as our capacity to be harmed by the evil eye could be (though the discussion of cultural evolution would suffice to explain why people could believe in supernatural harm even if they weren’t actually harmed at all).

One place where Henrich didn’t express complete confidence in his explanations is when he first attributed chimpanzees using more tools than orangutans to their spending more time on the ground rather than in trees (where orangutans usually are, and where tools could be dropped), but then had an endnote adding “Admittedly, [the advantages of terrestriality in explaining the relatively complex tools of chimpanzees to more arboreal orangutans] leaves open the question of why bonobos and gorillas don’t use tools more than orangutans.” He himself has cited Richard Wrangham, so I’m surprised he didn’t note that bonobos are limited precisely to an area without gorillas, where they can occupy the occupy the ecological niche normally taken up by gorillas (who are large enough to spend their lives on the ground). Wrangham attributes the lower homicide rates of bonobos to that (gorillas also rarely kill other adults, though they do fight in a less lethal manner for dominance, as their preferred source of food isn’t such a concentration of nutrients to fight over), and it could also be related to their shared disinterest in tools.

Lastly, I found unpersuasive his analogy of the transition from independent free-floating molecules to DNA, and from single-celled organisms to multicellular ones being like that of humans developing a “collective brain” via cultural evolution. DNA all gets copied together, and the cells of multicellular organisms share the same DNA. Yes, there are de novo mutations and things like meiotic drive and selfish genes trying to create more copies of themselves than others, but it’s significantly different from culture. Group selection doesn’t work on a genetic level because the variance between groups is rarely large enough relative to the variance within (a cheater mutation can always emerge and win in a population of altruistic cooperators). It can on a cultural level because it’s much more common for neighboring groups to be completely discordant along the lines of something like language. The incentives of individuals & groups remains different, and those people can (and do, when they can get away with it) cheat. Not just WEIRD people either, which is why we’re mentally attuned to detecting cheating (something Henrich discusses, though not why it would be necessary if we’re naturally bad at cheating).