Alex Zakharov's Reviews > The Secret of Our Success: How Culture Is Driving Human Evolution, Domesticating Our Species, and Making Us Smarter

A well-articulated case for gene-culture coevolution, and as good of an argument for culture driving genetic evolution as you are going to get. For starters Henrich’s book effectively debunks the once-orthodox and badly mistaken view (espoused by the likes of Stephen Jay Gould) that human biological evolution basically stopped 50K years ago and we’ve since been adapting via cultural evolution. Henrich does stress that accumulated culture is the driving force of human evolution but he also demonstrates the resulting and quite strong effects on human genome thus setting stage for autocatalytic gene-culture co-evolutionary process.

In my view many genes vs culture debates can be resolved by simply looking at culture as part of the environment, and then we are back to classic dynamics of natural selection and adaptation. In this sense Henrich’s emphasis on culture at the expense genes can be misleading to a cursory reader. At a high level Henrich’s perspective is actually in line with Cochran and Harpending (“10000 year explosion”) – humans have always genetically adapted to various environments and if anything the rate in the last 10K years have only increased due to culture-driven selection.

Notes to self:

- A big theme that humans unlike other species adapt to various environments via cultural “downloads” and learning rather than raw biological adaptation. That resulted in genetic changes that biologically optimized humans for knowledge acquisition from the surrounding environment/culture (extended childhood, menopause, cortex-folding and density limited by head size, selection for sociability, mimicry etc)

- Fascinating chapter on biological changes due to selection for running and hunting (humans can vary speed smoothly while animals got “gears”, special muscle fibers, skeletal changes, neck rotation, sweat glands changes)

- Outsourcing body functions in general is another theme (e.g. “water source” for running, food digestion - shorter stomachs, colons, smaller teeth, jaw changes etc). Outsourcing frees up the energy for optimizing the brain...

- Other adaptions – skin color, lactose tolerance, efficient alcohol processing in Asia, blue eyes in Balkans, infection resistance (malaria-sickle cell story, virus resistance in Europe vs Americas or Europe vs Africa). Cochran/Harpending have a different spin on lactose tolerance arguing for pastoral cultures with dairy outcompeting pastorals without dairy and on the margin outcompeting early farmers as well. They link it to emergence of Indo-European language family.

- Very big theme - opaque cumulative knowledge. Henrich explanation is clearer and more developed than Taleb’s “grandmothers wisdom” or “religion/faith as a hedge”. Results in selection for and wiring up of mimicry, norm following (to copy opaque knowledge without understanding it) and reputation maintenance. Finally a sensible argument for human tendency to follow norms and punish violators. Also need to know whom to copy from – prestige plus automatic selection for group affiliation markers such as ethnicity in choosing the model.
o Lesson to be learned: experiment, don’t design (humans are bad at top-down design, institutions and otherwise)
o Lack of causal models may be a plus in early phases of practice adoption but you do need them eventually.
o Interesting comment is increased need to “mentalize” other person’s state of mind (improves knowledge acquisition/download?), which could plausibly lead to dualism and farther down the road to religion(?)

- Cooperation is a big theme of course:
o Nice somewhat-plausible argument for “outsourcing” child raising and optimizing knowledge intake. Extended childhood increases cost on mother giving rise to pair-ponding. Learning from multiple models helps (from adults and same age group), perhaps leading to increased intra-tribal cooperation. Pair-bonding/family clans can also lead to cooperation among groups once daughters from one tribe marry the other.
o Intergroup competition with or without warfare also fosters cooperation within group. For more modern version of it see Tilly's european state formation via war.

- On one hand it is nice that Henrich’s argument doesn’t hinge on group vs individual selection as a mechanism for culture-driven evolution. On the other avoiding group selection subject altogether sometimes leads him down incredibly speculative alleys. For example he tries to justify kin selection as a special case of group selection driven by cultural selection, highly implausible. You don’t need culture for kin-selection at all, but yes you would most likely would need culture to increase trust among unrelated groups.

- Excellent section on “startup” problem, i.e. under what conditions does a species switch to cultural evolution (crossing the “rubicon”). Need to have enough knowledge around you to accumulate in the first place, at least enough knowledge that one can’t learn it on his own in single lifetime, chicken-and-egg problem. Tries to link to it to terrestrially (freeing up the hands), predation pressures (eliciting cooperation), fluctuating environments (forcing adaptation). Reducing workload on mother, emergence of pair-bonding may modulate this threshold crossing via cooperation feedback loops. Group size matters increasing probability of encountering or generating a successful practice. We probably almost crossed it a few times unsuccessfully. Very speculative, I’m not fully sold, but quite interesting. Perhaps needs synthesis with Cochran/Harpending that on the margin gives more weight to biological factors (human expansions, viruses).

- Cute bit on differences in bias towards forefront vs background in europeans vs asians (determining absolute line lengths vs relative sizes experiments)

- Distinguishes between biology and genetics, correctly warns about confusing the two when discussing effects of culture. In case for biology brings up thickening of neural connections due to reading (ok) and famous Nisbett/Cohen study of honor cultures and violence in American South as an import from Scots-Irish immigration (eh... don't hold your breath on this one).

- Henrich’s constant theme is that over multiple generations in a given specific environment and in the process of optimizing knowledge/culture for that environment a human subpopulation would undergo genetic changes. But then he often treats culture as the primary differentiating aspect between different populations. You can’t have your cake and eat it too. Just think European diseases having a massive impact on colonization of America or compare populations that spend 8K years doing agriculture vs a few of hundred.

- Cute bit on division of labor as division of information in the face of vast amounts of accumulated knowledge, once you can’t learn it all specialization is inevitable and is only bound to increase. Even in pre-history division of labor between men and women was driven by this information and skill asymmetry.

- Another big theme collective brain. Larger groups, more connections, more experimentation, better solutions found quicker. Smells like another flavor of Garett Jones’ “Hive Mind”. OK, perhaps all else being equal larger group and more connections probably do make you smarter. But “all else being equal” is a tall order and is rarely the case. By Henrich’s own logic wouldn’t yours and your group’s achievement potential relative to where it is now be influenced by the evolutionary path that culture/population took to get to this point?

For a given point in time it seems that Cochran/Harpending idea of step jumps driven by right tail of IQ distribution may matter more relative to sheer group size and number of connections (small differences in average gives rise to large differences in the tails, and it is the tails that matter for significant progress). Joel Mokyr in his "Culture of Growth" makes a somewhat similar argument for a post-renaissance Bacon-inspired 200 year run of a transnational community of highly intelligent, constantly-communicating, knowledge-sharing tinkerers eventually bringing about industrial revolution. So yes connections and group size matter but it matters the most in the right tail.

Anyway, terrific book, often speculative but highly recommended. Read it together with "10000 year explosion" and you'll have a blast.