> Intelligence and other personality traits are of course heritable, but controlled by thousands of genes that are unlikely to shift significantly over the course of around 50,000 years.

This sounds pretty convincing, but it seems to prove too much. Doesn't this also refute the idea of individual gentic differences in intelligence? Which we know exist due to the incredibly high heritability of intelligence?

Couldn't whatever allows these differences to exist not vary in strength depending on the emvironmental pressures sustained over thousands of years?