this stems from the analogy that the earliest known remains of a human being were from a skeleton they found in Africa ... they calculated she lived over 150,000 years ago..
and once they did the DNA tests on this skeleton and compared them to the genes of over a large percentage of people of ALLL races whites included it turned out that the DNA results of this skeleton also matched the genenomes of all the participants of the study .. this is how they tracked the path of life on earth STARTING in africa and then showing the path made to each area of the world... the mediterranean first making its rounds to asia europe and america... all stemming from the remains of this one african woman ...
rent the documentary titled The Real Eve "5 billion people from one woman" at the library or blockbusters.. or buy it online
and youll get your answer
heres a couple links to information on it
and heres an excerpt from the documentary:
"Unfolding like a scientific detective story, THE REAL EVE enlists top scientists and cutting-edge research to prove that everyone on the planet today can trace one part of his or her genetic heritage back to one woman who lived in Africa, more than 150,000 years ago, through a unique part of our DNA. Unlike the DNA that dictates height or eye color, mitochondrial DNA (mtDNA) provides the chemical energy in nearly all human cells; humans cannot survive without it. The mtDNA of "mitrochondrial Eve" has come down through evolution, from mother to daughter (men are carriers but don't pass it on). Although she was not the only woman living at the time, nor necessarily the most fertile, this "Eve" had the one successful mtDNA type - it was the only strain to survive. Genetic evidence, combined with recent archaeology and oceanography, shows that a small group of modern human ancestors, including later female descendants of this "Eve," left Africa 80,000 years ago (earlier than was originally thought) - and that from this exodus, the rest of the world was populated. "