May 14, 2010

The Mediterranean as barrier to gene flow (Athanasiadis et al. 2010)

A very limited number of markers, but a relatively wide assortment of populations.

BMC Evolutionary Biology 2010, 10:84doi:10.1186/1471-2148-10-84

The Mediterranean Sea as a barrier to gene flow: evidence from variation in and around the F7 and F12 genomic regions

Georgios Athanasiadis et al.


The Mediterranean has a long history of interactions among different peoples. In this study, we investigate the genetic relationships among thirteen population samples from the broader Mediterranean region together with three other groups from the Ivory Coast and Bolivia with a particular focus on the genetic structure between North Africa and South Europe. Analyses were carried out on a diverse set of neutral and functional polymorphisms located in and around the coagulation factor VII and XII genomic regions (F7 and F12).

Principal component analysis revealed a significant clustering of the Mediterranean samples into North African and South European groups consistent with the results from the hierarchical AMOVA, which showed a low but significant differentiation between groups from the two shores. For the same range of geographic distances, populations from each side of the Mediterranean were found to differ genetically more than populations within the same side. To further investigate this differentiation, we carried out haplotype analyses, which provided partial evidence that sub-Saharan gene flow was higher towards North Africa than South Europe.

As there is no consensus between the two genomic regions regarding gene flow through the Sahara, it is hard to reach a solid conclusion about its role in the differentiation between the two Mediterranean shores and more data are necessary to reach a definite conclusion. However our data suggest that the Mediterranean Sea was at least partially a barrier to gene flow between the two shores.



Andrew Oh-Willeke said...

"[O]ur data suggest that the Mediterranean Sea was at least partially a barrier to gene flow between the two shores."

I would be dumbfounded if the conclusion were different. The interesting questions are (1) how much gene flow was there in the historic era, (2) how much gene flow was there in the pre-historic era, and (3) which genes moved in which directions.

princenuadha said...

The samples were mostly from NW Africa and SW Europe. I'm sure their is less differentiation between NE Africa and SE Europe. Not sure how the differentiation of sub Sahara would be in the east.

Ponto said...

How do you know that prince? You know something we don't?

We all know the history that has come down to us about the Minoans, Mycenaeans, Egyptians, Hittites, Phoenicians, the other Greeks and so on in the cast of characters in this history play. I am skeptical as always, don't really believe all that I am told or taught or read. A lot of history of the Levant area comes out of the Bible, which is hardly an authoritative source.

The study is a waste of time and money. Of course Europeans had contacts with Africans, and Africans with Europeans. The Mediterranean is not really any more of a barrier than a stream, river, large mountains, desert conditions, freezing temperature - people always find a way to cross these barriers. What the study should have concluded is this: Europeans and Africans has contact for millenia, and with respect to genetic or racial admixture, the brunt of sub Saharan admixture was borne by North Africans, and it was North Africans who introduced sub Saharan admixture, highly attenuated by them, into Europe principally Southern Europeans. Of course the opposite is true, North Africans have introduced European admixture to sub Saharans.

princenuadha said...

the study showed that there is more genetic differentiation per distance going from a S. Europe directly towards N Africa than from S Europe to Central europe. Thus there is a S Europe cluster separate from N Africa (geography might have dictated that anyways).

The lands of the Easter Mediterranean are connected by land, giving one extra way of gene flow. many migrations to S europe and N Africa came from the middle east, the founder effect would get stronger as you move west and leave more people behind. Thus the west would be less like the original migrants from the middle east and the people of the western Mediterranean would be less like each other. lastly a recent migration from the middle east (Neolithic) produced more continuity in the eastern Med than it did in the western Med because of "dilution" of the Neolithic elements as you move west.

and as you say, I am a prince, so I do know things that most don't. don't question me boy : )