February 06, 2007

Clinal Y chromosome variation in Italy

Warning bells always go off in my head when I read that modern populations, especially in "central" world areas such as Italy are the result of prehistoric events and untouched by modern events. In particular, this seems to be the result of phylogenetic resolution within haplogroups, as well as the indiscriminate use of relevant "source" populations for proposed historical movements. A recent article on Indian Y chromosomes was a prime example of this tendency, rejecting the contribution of Central Asian Indo-Aryan speakers on the basis of modern Central Asians, who as I pointed out, possess Y chromosome types that were added in recent historical times by Altaic speakers who inundated the area.

I will restate my thesis that modern gene pools, especially for Y chromosome ones, were shaped to a much greater extent by historical events than is currently accepted. So far, the mtDNA evidence is accumulating about sharp differences between modern and ancient inhabitants in various localities, making the idea of continuity since the Neolithic or even the Paleolithic more doubtful. The caricature of genetic history as a Paleolithic substratum with limited Neolithic adstrata and negligible historical influences will no doubt be revealed in the years to come.

Mol Phylogenet Evol. 2006 Dec 13; [Epub ahead of print]

Y chromosome genetic variation in the Italian peninsula is clinal and supports an admixture model for the Mesolithic-Neolithic encounter.

Capelli C, Brisighelli F, Scarnicci F, Arredi B, Caglia' A, Vetrugno G, Tofanelli S, Onofri V, Tagliabracci A, Paoli G, Pascali VL.

The Italian peninsula, given its geographical location in the middle of the Mediterranean basin, was involved in the process of the peopling of Europe since the very beginning, with first settlements dating to the Upper Paleolithic. Later on, the Neolithic revolution left clear evidence in the archeological record, with findings going back to 7000 B.C. We have investigated the demographic consequences of the agriculture revolution in this area by genotyping Y chromosome markers for almost 700 individuals from 12 different regions. Data analysis showed a non-random distribution of the observed genetic variation, with more than 70% of the Y chromosome diversity distributed along a North-South axis. While the Greek colonisation during classical time appears to have left no significant contribution, the results support a male demic diffusion model, even if population replacement was not complete and the degree of Neolithic admixture with Mesolithic inhabitants was different in different areas of Italy.


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