Uh, no, this subject is a tangent and we shouldn't really get into it here.

However, a couple of general statements: There are reams of genetic and psychometric data available. More than enough to develop pretty good idea when and where the most probable selection events for good brain genes occurred and how fast they spread. Your word 'premature' tells me something about your acquaintance with that data.

Also, there is one very simple rule: totally genetically isolated communities only have access to their own mutations. Their population is small, so the number of mutations is also small. Non-isolated communities get swept by every positive selection event that comes along.