Who are you with? With Harari or with Henrich?

Joseph Heath critiques in this article the account of human evolution presented by Yuval Noah Harari in “Sapiens” for being unscientific and outdated. He contrasts it with the much more solid and current theory, according to him, of Joseph Henrich (“The Secret of Our Success”), which completely reverses the explanatory order.

Heath identifies four unique capacities that differentiate humans:

• Superior intelligence (including abstract and mathematical reasoning).
• Complex and grammatical language.
• Ultrasocial cooperation (with non-kin).
• Cumulative culture (continuous transmission and improvement of knowledge and artifacts).

Any serious theory must explain how these traits evolved in a very short evolutionary time (Homo erectus appeared about 2 million years ago or so).

Harari’s sequence follows the classic order:

Intelligence → Language → Cooperation → Culture.

But Heath sees many problems with it:

• A large brain is very costly (energy and mortality in childbirth). It’s not clear what compensatory benefit it would have had on the savanna.
• Language as a “random mutation” (Tree of Knowledge) has serious problems: the first mutant wouldn’t have anyone to talk to (bootstrapping problem).
• Without prior cooperation, language would be “cheap talk” (cheap talk) and not very credible.
• Cooperation doesn’t easily arise from intelligence (game theory and the prisoner’s dilemma demonstrate this).
• Culture isn’t just “more people working together”; it’s cumulative cultural evolution.

So Heath prefers the sequence proposed by Henrich (following Boyd and Richerson):

Culture → Cooperation → Language → Intelligence.

The story would be more or less as follows. The initial tweak that kickstarted everything was a greater capacity for faithful imitation: humans copy complex behaviors with great precision, even without fully understanding them, unlike chimpanzees. This capacity allowed the emergence of cumulative cultural evolution, that is, tools, techniques, and knowledge improving and being transmitted from generation to generation. Conformist imitation (“do what the majority does”) and the tendency to imitate the most successful increased cultural homogeneity within groups, which boosted selection between groups: those that were more culturally cooperative dominated the others, favoring the emergence of prosocial norms. This, in turn, triggered a process of self-domestication, in which the most aggressive individuals were reproductively marginalized, making humans more prosocial by nature. With greater cooperation, language became useful and credible. Finally, intelligence (including the large brain) was driven by the cultural explosion: it was worth investing in better memory and cognition because it allowed absorbing and leveraging an increasingly complex culture.

In summary, the article is a clear defense of gene-culture co-evolution.