In addition to the Khoasan information, this is another study that talks about the recent gene flow between archaic hominid, who evolved separately for hundreds of thousands of years, and the ancestors of modern negroids. Only negroes have these genes, because it happened recently, when our ancestors had already left Africa. In addition, they have these genes in an absurd amount because they have up to 19%, where aborigines have up to 8% denisovans, north Asians up to 4% neanderthal and a little denisovan, and whites up to 1%, often 0.1%, neanderthal and nothing more. They have 19%, and some studies indicate that the Leyham of Kenya have up to 31%. That's 1/3 of their genes evolved 1.5million years apart from the rest of humans. In any case, genetic studies of southern African populations have shown that groups speaking non-Bantu languages with clicking consonants have some of the most archaic genetic lines in humans. In addition, hunter-gatherer populations in Africa retain unique information about human history - unique is such a nice term for 19% of hominid genes evolving separately for up to 1.5million years. Diversity, uniqueness, fascinating, how we know it.