AfriGeneas World Research Forum
" In the recent past, each of us is descended from a small fraction of the people who were then alive. We're descended from our parents one generation ago, our grandparents two generations ago, our great-grandparents three generations ago, and so on. We tend to think that the same exclusivity holds for the more distant past—that a European-American, for example, is descended from a few clusters of people who lived in Europe many centuries ago, or that an African-American has ancestors from just a handful of African villages.
"But that presumption is wrong. Imagine that you could identify all of your great-great-great-great- … grandparents 20 generations back—from about the time Columbus stepped ashore in the New World. (You would never be able to, of course, because no paper records connect you to virtually any of those people, but pretend that God handed you a perfect genealogical record.) Assuming typical human mating patterns, your direct ancestors 20 generations ago consisted of somewhere between 600,000 and 1,000,000 different people. Taking the lower figure, perhaps 480,000 of the ancestors of the average African-American were living in Africa in the year 1492, and approximately 120,000 were living in Europe, the Americas, and Asia. For the average European-American, more than a half-million ancestors were living in Europe, with the rest scattered through Africa, Asia, and the Americas."