Military movements also let favorable alleles vault over long distances and geographical barriers. Alexander the Great furnished one of the more dramatic examples. In the course of a remarkable career of conquest (dying undefeated), he marched as far east as Pakistan.
In addition to settling Greeks over much of the Middle East, his legacy included Greek kingdoms that survived for several centuries in Afghanistan and Pakistan. Those kingdoms didn't just influence the artistic development of Buddhism; they also transmitted alleles. Today we see a few Greek Y chromosomes among the Pathans, the dominant ethnic group in Af-ghanistan.13 Of course, we also see some Y chromosomes that are directly descended from Genghis Khan himself in the Pathans' despised neighbors, the Hazara.14 Local marriage could never have spread genes as rapidly as that—but Genghis and Alexander could.
If regional Y-chromosome variants (which as far as we know have no special inherent fitness advantage) could spread that far, you can be sure that any advantageous mutation that had become common in Greece in Alexander's time did as well. Every such allele has had a good chance of becoming common in Afghanistan by the present day. This isn't quite as true for those Mongol alleles, since they've only had a third as long to spread as those of Alexander and his merry men. In these longdistance transfers, the earlier the connection, the more important. And in the same way, large population transfers have a greater effect than small ones.
Was this article helpful?