Obviously, these days, there is no real genetic gap between Northern and Southern Europe. Populations across the middle of the continent merge into their Northern and Southern neighbors, bridging the two. So all we have are places where genetic distances are somewhat more pronounced than expected based on geographic proximity, such as the Alpine zone. However, was this the case before the "barbarian" migrations of the early middle ages, when Germanic and Slavic tribes moved south in great numbers? There's no way to tell, because it's not possible to get samples from that era. But I thought I'd see what happens in an MDS analysis if I took away all the groups supposedly affected by these population movements, and just ran the Northern Europeans against Southern Europeans and Middle Easterners. So I dropped the French, Swiss, Hungarians and Romanians, and got this...
That's quite a gap. However, it's possible to create such things on many plots with a bit of selective sampling. Nevertheless, I really like the analysis for a number of reasons, including the fact that it also shows a clear difference within Northern Europe in terms of southern influence. The cline that runs from Germany to Finland and the Baltic States gels extremely well with the lack of Neolithic influence in the Northeast of Europe, but fairly high Neolithic input in Western Europe. Check out this map from Haak et al. 2010, showing the similarity of modern mtDNA to that of ancient Neolithic LBK sites in Europe.
It's remarkable how MDS plots of modern populations can pick up such distant signals of ancient migrations. Obviously, I can't really prove that this is indeed what we've got here, but I can certainly see a correlation. I recommend that readers view this plot in an interactive window, so you can manipulate it with your mouse. It's easy...
- download Gnuplot
- unpack Gnuplot
- download the MDS data EU_ME.dat
- place EU_ME.dat into the "binary" Gnuplot folder
- type: splot 'EU_ME.dat' using 3:4:5:1 with labels
- spin the plot around and find some informative angles
- type: set term png size 2000, 1500
- type: set output "EU_ME.png"
- type: splot 'EU_ME.dat' using 3:4:5:1 with labels
And voila, that should give you 2000x1500 pixel png screen caps of the plot. I urge all of my project members to give it a try, because I'll be producing many more interactive plots like this. I have a feeling they'll go off like the proverbial frog in a sock.
Citation...
Haak W, Balanovsky O, Sanchez JJ, Koshel S, Zaporozhchenko V, et al. (2010) Ancient DNA from European Early Neolithic Farmers Reveals Their Near
Eastern Affinities. PLoS Biol 8(11): e1000536. doi:10.1371/journal.pbio.1000536
