That means everybody on Earth descends from somebody who was around as recently as the reign of Tutankhamen, maybe even during the Golden Age of ancient Greece. There's even a chance that our last shared ancestor lived at the time of Christ.
'It's a mathematical certainty that that person existed,' said Steve Olson, whose 2002 book 'Mapping Human History' traces the history of the species since its origins in Africa more than 100,000 years ago.
and later in the article:
With the help of a statistician, a computer scientist and a supercomputer, Olson has calculated just how interconnected the human family tree is. You would have to go back in time only 2,000 to 5,000 years - and probably on the low side of that range - to find somebody who could count every person alive today as a descendant.
Furthermore, Olson and his colleagues have found that if you go back a little farther - about 5,000 to 7,000 years ago - everybody living today has exactly the same set of ancestors. In other words, every person who was alive at that time is either an ancestor to all 6 billion people living today, or their line died out and they have no remaining descendants.
It's an interesting and thought provoking article, please read the whole thing.
I agree with the article on the conclusion that there is probably a shared ancestor for everybody currently living back several millenia - and it may be as recent as 2,000 years ago.
I disagree with the conclusion that everybody living today has exactly the same set of ancestors (living 5,000 to 7,000 years ago). According to all the archaeologists and other experts, there were groups of humans in many places on Earth in that time, but the migration to these places occurred over a long period of time and usually long before 7,000 years ago. I can believe that everyone living in a certain place, say England or China, has substantially the same set of ancestors back 7,000 years ago, but they certainly cannot be identical to everybody living today, no matter what the probability experts claim. It doesn't make sense to me.
Of course, some people will claim that the common ancestor 5,000 years ago was Noah and his wife. That flies in the face of the archaeological data available, showing groups of humans in many places after the last ice age some 10,000 or more years ago.
The book "Mapping Human History" sounds interesting, and is on my list of Books to Buy.
Just my two cents - I am not an expert in these fields. What do you think?