Jason Soon has an interesting link to an interview with Arthur Jensen, a leading hereditarian and advocate of the idea that intelligence is dominated by a single ‘g’ factor. It struck me that, although Steven Pinker gives generally favorable references to Jensen, this is the exact opposite to the Cosmides-Tooby idea of intelligence as a ‘modular’ bag of tricks which Pinker strongly supports.

This lead to me to another thought – an egalitarian implication of evolutionary psychology that I don’t think has been noticed before. Hereditarians like Jensen, Herrnstein & Murray etc argue that some people have ‘better genes’ than others – superior intelligence, greater physical strength etc. and that these advantages seem to be positively correlated.

But strong versions of Darwinism imply (roughly speaking) that evolution proceeds so rapidly that, most of the time, animals are optimally adapted to their environments. This involves trade-offs, and when the environment changes,so do the optimal trade-offs. In humans, intelligence is clearly the biggest single concern, and if you buy the Cosmides-Tooby story, you’d expect to see some environments favoring more allocation of resources to the spatial module, others to the interpersonal module and so on. (A nice feature of this argument is that it doesn’t rely on any particular hypothesis about the environments in which humans evolved, only that they varied and the variations made different demands on intelligence.)

This leads to the conclusion that insofar as ability is determined by genetic endowments, ability in one area should be negatively correlated with ability in others. This is a standard feature of popular ‘folk’ psychology, which assumes, for example, negative correlations between math ability and interpersonal skills. In my case, it’s pretty clear that whatever environment shaped my genes, it didn’t place a lot of weight on fine motor skills.