PDA

View Full Version : Y Chromosome J Haplogroups trace post glacial period expansion from Turkey and Caucas



J Man
09-20-2012, 04:04 PM
A very interesting looking new study that has yet to hit the press.

http://www.ashg.org/2012meeting/abstracts/fulltext/f120121642.htm

Paleoclimate reconstructions have shown that several glacial refugia formed around the Mediterranean and Black Sea during the last glacial period (LGP) that dramatically affected the distribution of the populations of Eurasia and the Middle East. Post-glacial warming, beginning around 12,000 years ago, resulted in population migrations out of those refugia, and drove the Neolithic revolution. The timing and routes of these migrations and their specific regions of expansion remain elusive. The genetic signals marking the initial settlement following the LPG are also unclear. On the Y chromosome, there is significant regional variation among subhaplogroups of J within the Middle East that are informative about these events, which were investigated in more detail. 2774 samples were analyzed, including 941 newly genotyped, to characterize populations where J haplogroups have expanded geographically. Haplogroup J diversity was measured by coancestry using Y-STR haplotype effective number. Reduced Median networks were calculated for each of the J subhaplogroups and SNP coalescence times were estimated by BATWING. The J subhaplogroups’ frequencies show substantial variation across the Mediterranean Basin. J subhaplogroups show little organization of their haplotypes by geography, suggesting that diversity evolved primarily within a pool of ancestral populations for a larger part of its history, then post-glacial expansions carried this diversity throughout their modern geographical range. Coalescence time estimates indicate longer evolution of J haplogroups in northern populations, in agreement with co-ancestry diversity. Population divergence time estimates are recent compared to coalescence times, supporting long evolution times prior to post-glacial expansions. Our data provide evidence for the timing and differential routes of post glacial repopulation of the region. When combined with archaeological and linguistic evidence, these genetic data allow us to reconstruct the spread of agriculture and the origins of various Neolithic cultures of the Middle East. The Neolithic expansion has been marked by haplogroups characteristic of the Middle East, with J haplogroups showing geographically differential frequency distributions and haplotype diversities. These results are suggestive of evolution within the Anatolian Peninsula and the Black Sea basin during the LGP, followed by multiple expansions taking distinct routes at different times subsequent to the LGP.