There was evidence that as much as 75,000 years ago, the human population experienced a sudden drop in genetic population, a "bottleneck" catastrophe. Was the supereruption of the volcano Toba to blame? Or did different shifts in climate, those that gave Africa repeated periods of drought, really do the job? Whatever the culprit, this bottleneck changed the destiny of human history. As a result, one race of people has a far smaller genetic distinction from another than two chimpanzees in one same troop.
Let us assume that, in an alternate timeline, the bottleneck catastrophe happened at a later date, preferably during the Younger Dryas climate chaos 11,000 years ago. At that time, there was a four-to-thirteen-degree-Fahrenheit drop in global temperature at a span of 1200 years, too quick for ice age plant and animal species to deal with. It most certainly brought an end to the Clovis culture.
Delay the bottleneck to the Younger Dryas, and how much of a population growth would we have seen between 75,000 and 11,000 years ago? Would human history, preferably history taking place during the Bronze Age, be reset on an earlier date? Would a higher genetic diversity give humans significant differences in their appearances and anatomies?