Expert: John Shea - 3/1/2006

Question
Paul asked about direct decendents. However; how doesn't migration, trade, immigration affect the degree of "relatedness" and can it really be understood on the level of a population like "greeks" or "egyptians"?
is Paul's question refering to discovering an individuals lineage? and can one, depending on how fragmentary a record is, truely distinguish the degree of "greekness" through a fossil record?

Thank you,
Donna

Answer
Dear Donna
You are correct that in-migration and out-migration will affect the genetic composition of any regional population, so the chances of an individual living person being descended from some ancient population in a particular region are small.  However, if you are considering the question at a population level, -that is, are some modern Greeks/Egyptians etc. descended from the people who lived in that same region a few thousand years previously, then the probability that they are is higher.
Ultimately, with DNA from fossils and sub-fossils one could compare modern and recent populations, if one wanted to, but I don't see what one would learn from such a study other than what one might reasonably deduce (as outlined above).
Another, consideration is that the Nile and Mediterranean Basins have had large populations for thousands of years.  Significant genetic changes tend to occur slowly in such large populations. The odds that there are marked differences between living populations and ones merely a few thousand years ago seem (to me at least) vanishingly small.
You are correct, there are no genes for "greekness" or "egyptianity" but there may be polymorphisms that mark particular regional populations that would allow one to link them to ancestral populations.  I don't know why one would want to do this, but it is a theoretical possibility.
Cheers,
John Shea