Darwin’s Unfinished Symphony

In one kind of book, a smooth talker who has published many books takes a fraction of a year to explore a topic that has newly piqued their curiosity. In another kind of book, someone who has spend a lifetime wrestling with a big subject tries to put it all together into an integrated synthesis. Sometimes they even synthesize an entire research group or tradition. Kevin Laland’s book Darwin’s Unfinished Symphony is this second kind of book, a kind I much prefer.

Laland’s research group has for decades studied the origins of human cultural evolution. They’ve learned a lot. In particular they attribute humanity’s unique ability to accumulate culture over a long time to our very high reliability in transferring practices. Humans achieve such high reliability both by being smart, and by our unusual ability to teach, i.e., changing our behavior to make it easier for others to copy our practices. Just how high a reliability is required is shown by the example of Tasmania, where several thousand isolated humans slowly lost many skills and tools over thousands of years. It seems even human level intelligence and teaching isn’t good enough if your population is only a few thousand.

In both this book and in Henrich’s The Secret of our Success, I detect a tone of conflict between those who emphasize the value of smart brains for evolving culture, and those who emphasize the value of smart brains for managing the complex politics of large social groups. For example, in his book Laland says:

The currently dominant view is that the primate brain expanded to cope with the demands of a rich social life, including the aforementioned Machiavellian skills required to deceive and manipulate others, and the cognitive skills necessary to maintain alliances and trans third-party relationships. The most important data supporting this hypothesis is a positive relationship between measures of group sizes and relative brain size. In our analyses, group size remained as an important predictor of relative brain size, but also proved a significant secondary predictor of primate intelligence and social learning. However, group size was neither the sole, not the most important, predictor of brain size or intelligence in our models. Combined with our earlier find that social group sizes does not predict the performance of primates in laboratory tests of cognition, this reinforced our view that there was more to primate brain evolution than selection for social intelligence. (p.144)

As far as I can remember, all of the cultural learning examples in both the Laland and Henrich books are outside of the domain of Machiavellian social competition. But cultural learning can also be useful there, and so even if the strongest selection pressure on brains was for social competition, that is completely consistent with a strong selection for increasingly reliable abilities to learn and teach. Of course the overall long term increase in humanity’s power and scope is probably less directly due to better social competition skills. But from each creature’s point of view that is mostly a side effect relative to their struggle to survive and reproduce.

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