I think the analysis might be shallow

Roots of human family tree are shallow

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.

Let’s consider, say, a 100% Native American and a 100% Australian Aborigine. Wouldn’t their common ancestor go back quite a bit further than 5,000 to 7,000 years?

Native Americans are descend from peoples from Siberia around16,000 years ago.^[1] Australian Aborigines descend from peoples who arrived in Australia around 40,000 – 50,000 ago.^[2] The populations have been isolated from the rest of the world until fairly recently, so the 5,000 to 7,000 year figure doesn’t make sense.

“Had you entered any village on Earth in around 3,000 B.C., the first person you would have met would probably be your ancestor,” Hein marveled.

I doubt this would be true for me if I encountered a goup of people in Australia around 3000 B.C.