NYT's Nick Wade reports that lactose tolerance in East Africans appeared as recently as 3,000 years ago. It spread through Europe somewhere between 5,000 and 6,000 years ago.
Lactose intolerance in the African heat and drought is conceivably a severe disadvantage, not only in limiting the amount of available fluid intake, but also in causing bowel problems and water loss in those unable to tolerate it. Such an advantage should spread like wildfire. In evolutionary terms, 3,000 years approximates that pace (though the time thought to be required for major evolutionary change continues to lessen)--about four-fifths of African Tutsis (historical herders) are lactose tolerant.
ASPM and microcephalin have also cropped up recently in varying degrees by ancestral population. Stubbornly feral silver foxes have become as amicable toward humans as golden retrievers in a mere thirty generations. That comes to about 750 years for us--less time than Dr. Cochran and crew hypothesize it took Ashkenazi Jews to obtain a one standard deviation advantage in intelligence over their Gentile brethren.
We're a work in progress--moving at difference paces and in different directions. The differences are more than skin deep.