A unresolved question about evolution

[Minimalist]

I remember the uproar which broke out in the late 60's when Arthur Jensen suggested that sub-saharan blacks were less intelligent because they had been "cut off" from genetic interaction with the rest of the world.  Such research has been largely discredited now but it should be noted that in spite of this alleged "isolation" the reason that blacks were brought to the new world as slaves was that the native-americans had the effrontery to keep dying in droves on their new masters from imported diseases but blacks didn't.  The New World really was "isolated" by the oceans.  There was plenty of contact between sub-saharan africa, either by caravan across the Sahara or as a result of Arab traders on the East Coast and later European explorers on the West Coast.