[Modernman]

If a human generation is 20 years, then for a human population to be genetically isolated for 50 generations that would take 1,000 years! I don't think that any group of Homo sapiens were ever isolated from their neighbors for that long

How about Australian aborigines or American natives?

[jennyp]

How about Australian aborigines or American natives?

As I understand it, aborigines had some contact with Polynesians. I don't know if American native eskimos had any contact with Russian eskimos, but there surely was some gene flow traveling up & down the Americas.