That argument is misleading. For it to be true, Modern Africans would have to remain exactly the same as their common ancestor, Proto Homo Sapiens. What is left out in that discussion is that Modern Africans and Asians developed at the same time, with Asians evolving from a group that left Africa way way earlier than the group that stayed. Factor in 10,000+ years of environmental adaptation, and you have what we have today. The original argument is faulty because pretty much all Modern Humans share those same ancestors.