This lends support to Chang's calculation that by expanding his model from living Europeans to everyone alive on Earth, an all-ancestor generation would have occurred some 3,400 years ago.


What about the separation of New World and Old World?

"Thus DNA sequences shared with parents are the longest, those shared with grandparents are half as long and those shared with great-grandparents half as long again and so on.

"So the longer ago an ancestor is, the shorter the chunk is likely to be."

Until you run again into the problem of the first few paragraphs where distantly related people intermingle/share grandparents. Then the halving (or even the shortenning) should stop altogether.

This lends support to Chang's calculation that by expanding his model from living Europeans to everyone alive on Earth, an all-ancestor generation would have occurred some 3,400 years ago.
Bit queaesy about that number, as it doesn't take into acount hard geographical boundaries that can keep populations apart for quite some time.

It's interesting research - but I feel it should be taken with a grain of salt.

@ Sean and Ant

This lends support to Chang's calculation that by expanding his model from living Europeans to everyone alive on Earth, an all-ancestor generation would have occurred some 3,400 years ago.


this does not say that the N. American indian tribes are ancestors of Native Australian tribes.

It says if you were alive 3400 years ago and had children -- then you and everyone else in your generation are the ancestors of everyone alive today.

Not that you are directly related to everyone today...

If it was a math function it would be surjective or onto. If you are alive today -- then you have an ancestor that was alive 3400 years ago that had children.

Not

If you were alive 3400 years ago and had children you are an ancestor of someone today.

But

If you were alive 3400 years ago and had children - you are part of a generation that is the common ancestors of everyone alive today... even though your lines may have died out, others in your generation survived.

[quote]"Our research confirmed what Chang suspected—that everybody who was alive in Europe a thousand years ago and who had children, is an ancestor of everyone alive today who has some European ancestry," Ralph said.[/quote]

We know that family lines can die out completely after several generations, so this statement is obviously not true. However, I remember reading about a study a couple of years ago that shows that if a family line produces offspring for at least six generations, the descendants will be so numerous and widely spread that the line almost certainly will continue to produce offspring. Thus, any individual who has had descendants for at least six generations, will probably have descendants today regardless of when s/he lived.