>>11760297There are two good theories that I've heard on this:
One is that even the smallest amounts of technology, like pottery and bows, massively increase the disparities in reproductive success between the more and less intelligent members of a population. The more intelligent you are, the better you can exploit technology. Additionally as societies become larger and specialization increases, societies become stratified. Those with high social intelligence can reap massive rewards by exploiting other people to increase their own reproductive success. Thus the more technology you have and the more stratified society becomes, the faster overall intelligence increases because of MASSIVE selection pressures. Blacks have only had access to postpaleolithic technology for a couple thousand years, thanks to their isolation in Africa, and for most of that time they still had their hands on very little. Asians and Europeans, on the other hand, went into the mesolithic tens of thousands of years ago, and that's what really got the ball rolling.
The other theory is that hot, tropical climates are a bad place for intelligence to evolve, since so many smart people get killed off by infectious diseases. Colder, drier climates may have less food, but you're not getting wrecked by malaria 24/7, so your intelligent people are more likely to reproduce.
