Gene-culture co-evolution 1: the secret of cultural evolution’s success

I’ve just finished reading Joseph Henrich, The Secret of our Success, the first book I’ve read on gene-culture co-evolution, an emerging academic field. (I’ve also seen it described as evolutionary culture anthropology (ECA)). Henrich’s book is a very interesting read, written in a populist way, but with citations of a substantial amount of original research. It’s also the first book I’ve found which has me thinking that possibly evolutionary approaches could be of use to historians.

Most of what I’ve previously read on evolutionary approaches to human life is evolutionary psychology and much of it is frankly both poor science and reactionary crap. Because it’s working via a mechanism which assumes change can come only from differential reproductive survival, it has to claim that all sorts of behaviours exist only because they improve one’s chances of getting a mate or getting a woman pregnant. (Most of the models used are so unsophisticated they don’t even consider issues of long-term survival. In evolutionary terms it’s no good having lots of children if they are all going to die before reproducing themselves, so there’s always a trade-off between the quality and quantity of offspring). And it also claims cultural universality for many traits that clearly aren’t universal.

In contrast, Henrich is looking primarily at the interaction of two different forms of reproduction of traits: genetic evolution via reproduction, but also cultural evolution via what he calls cultural learning. Or in less formal terms, people copying one another. Unlike some earlier versions of ECA, he’s not distinguishing between different forms of cultural transmission, but arguing that humanoid brains evolved to copy others and that’s one of the secrets of our success.

The evidence comes from a mix of primatology, anthropology, archaeology, neuroscience and a variety of psychological experiments, especially economic games and studies of young children. Henrich’s central idea is that humans have evolved to copy and learn from others and that it is primarily this that enables the accumulation of culture and the great advances we have made, rather than our innately being much smarter than chimpanzees. Henrich has a nice quote on this, riffing off Bernard of Chartres’s  idea of humans as “dwarfs standing on the shoulders of giants”:

we [humans] are smart, but not because we stand on the shoulders of giants or are giants ourselves. We stand on the shoulder of a very large pyramid of hobbits. The hobbits do get a bit taller as the pyramid ascends, but it’s still the number of hobbits, not the height of particular hobbits, that’s allowing us to see further (p. 323).

I obviously don’t have the expertise to evaluate the reliability of Henrich’s theories and experiments, but the outlines seem plausible and he’s avoided some of the obvious problems with cultural evolution. Firstly, he sidesteps the idea of memes, which have a lot of problems. Sometimes Henrich talks vaguely about “cultural packages”, but most of what he’s talking about is how cultural learners copy other people, and one of his most interesting insights is how there’s a tendency to copy “prestigious” people as a whole, rather than an attempt to isolate the factors where there’s a definite causal connection to their success. For example, this is the basis of using celebrities to endorse products. It’s also one of the methods by which maladaptions can spread: Henrich mentions the potent effect of celebrity suicides as encouraging copycat actions as an extreme example.

Henrich also points out that our tendency to take on cultural packages as a whole was probably evolutionarily advantageous in the past. His example is food processing: there are a lot of plants which need extensive processing to make them safely edible. People who experimented with omitting these stages could easily end up with long-term health problems (e.g. you can get pellagra if you eat a lot of maize which hasn’t undergone nixtamalization).

Brains adapted to cultural learning of this type produce cultures that are simultaneously “sticky” and “fluid”, i.e. ones that are both conservative in preserving traditions, but can also under certain circumstances  change rapidly, when there’s copying of those who are more successful. That certainly fits with both the long-term survival of cultures in a particular ecological niche and examples of rapid change that can’t be explained by reproductive success.

Henrich’s second main theme is that cultural learning and gene-culture co-evolution leads to “self-domestication” of humans. In other words, we have become better at co-operating within groups, as we have evolved. His first point is that our brains’ adaptation for cultural learning also means that social norms usually develop: people in a group converge on accepted behaviour and those who don’t adhere to these norms are sanctioned in some way. You can demonstrate this in adults via game theory experiments. But Henrich also discusses experiments with young children that show that even three-year olds will try to enforce arbitrary norms for playing with toys that they’ve seen modelled by an adult. The urge to “get it right” and make sure that others do seems to develop very young.

This willingness to abide by rules/norms and to sanction those who don’t leads to self-domestication. In small-scale societies, people who don’t co-operate with others and don’t abide by norms have reputational damage, which affects their marriage prospects and the help they get from others. As a result, they’re less likely to be able to pass their genes on. Groups which co-operate internally can grow larger and tend to out-compete ones with less co-operation. In particular, larger groups and larger social networks, with a larger collective brain, are much better at preserving culture and improving it. In contrast, small groups can gradually lose parts of their culture and their abilities: the classic example is the Aboriginal Tasmanians, whose tool set simplified after they were separated from mainland Australia.

The result of such multi-level selection (at the group as well as the individual level) is the development over millennia of humans as more co-operative and less aggressive towards strangers (at least as compared to e.g. a troupe of chimpanzees). But as well as culture creating genetic change in this long-term way, Henrich points out that the brain is sufficiently plastic that individual brains can also be changed by the culture around them. For example, learning to read affects our visual processing system, but the specific changes vary between languages: people’s brains react differently to seeing Hebrew characters if they’re Hebrew speakers rather than unfamiliar with the Hebrew alphabet.

How does all this affect historians? I think there are both broad and narrow possibilities. One broad effect is that culture-gene evolution gives us a model of human psychology that isn’t either “people in other societies are just like us” (as evolutionary psychology and universalism claim) or “they’re nothing like us” (as cultural anthropology sometimes seem to claim). Instead it suggests ways in which recurring practices can “hook into” the cultural learning tendencies of our brains without needing to be universally applicable. (Henrich, for example, discusses how incest taboos extend what seem to be common innate brother-sister incest taboos to wider kin by analogy).

The second broad effect seems to me at least a partial rehabilitation of functionalism. One of the problems with traditional functionalism in anthropology/history is that it relies on groups not understanding why they do a particular practice. (I’ve quoted Mary Douglas on such a definition before). But cultural learning theories suggest practices work whether or not you “know” how they do: if you build a better mousetrap by chance or by deliberate planning, if it works and people come to accept that, they’ll still learn from you. Alhough in the way that cultural learning works, if you paint it green just because that’s the paint you’ve got handy, other people will probably paint their mousetraps green as well, and in a generation or so there’ll be explanations as to why it “has” to be green. Causal models seem to follow after practices, which is another idea I’m interested in at the moment.

As regards the specific aspects of history that I’m interested in, Henrich has some interesting ideas about how ethnicity and sex affect cultural learning, which I might talk about at a later date. And because one of the topics I work on is the history of morals, I need to look at how cultural evolutionary ideas about social norms might fit in with that. All in all, the book has given me a lot of specific material to think about, as well as a potentially quite useful framework for human psychology and I’m grateful for that.











One thought on “Gene-culture co-evolution 1: the secret of cultural evolution’s success

  1. Suggestions here of an acquired lemmings culture. I have never thought of painting a mousetrap any colour, but I guess in the current ‘green’ climate, green as a colour, any shade would do I suppose, might subliminally make the mouse trapper feel a bit better about their catching/hunting methods.


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