A
paper published in Science today shows that three, 5,000-year-old Neolithic hunter gatherer individuals from Gotland - tested with around 10,000 genome-wide SNPs - shared most alleles with modern Polish individuals. On the other hand, a Neolithic farmer from southwestern Sweden, from about the same period, showed greatest affinity to modern Cypriots and Greeks. However, the farmer was also more similar to modern Poles than to modern Swedes. The figure below illustrates this very clearly.
http://img703.imageshack.us/img703/2241/skoalleles.png
Indeed, if we look at the STRUCTURE analysis, it shows that the farmer was genetically a lot like a modern Sardinian, or Oetzi the Iceman (see
here), albeit with more North European admixture.
http://img191.imageshack.us/img191/9971/skoadmix.jpg
So I think it's pretty clear we're dealing here with an individual of mostly deep East Mediterranean origin, who's ancestors made their way from West Asia to Europe via maritime routes (settling islands like Sardinia in the process), and then to Scandinavia via Western and Central Europe. They probably picked up their minority, although substantial, Northern European admixture in what is now Germany or Scandinavia. Of course, the other option is that the Mediterranean farmers went straight to Scandinavia by boat.
The question Swedes will be asking is, why are Poles from across the Baltic more similar to both their prehistoric hunter gatherers and farmers than they are? Firstly, it's important to realize that the differences aren't that great. Note, for instance, that Swedes are the second most similar population to the ancient hunter gatherers after Poles (see
here). However, clearly, the data suggests that there had to be other population movements into Scandinavia after the late Neolithic. These also affected Poland, but to a lesser degree.
No one yet knows exactly what these were, but if I had to take a guess, I'd say the Bell Beaker folk of the Copper Age represented one of the major waves (see figure below and
here). Also, another factor might be that the hunter gatherers tested by Skoglund et al. belonged to the Pitted Ware culture, which arrived in Scandinavia from the Eastern Baltic.
http://img51.imageshack.us/img51/5666/bbeaker.png
Anyway, on a personal level, I'm absolutely delighted with the results from this study. The reason is that it correlates very closely with the experiments I've been running with ADMIXTURE, aimed at untangling the history of the peopling of Europe using modern genomes. Note, for instance, the close correlation between the STRUCTURE plot above, and the results from my Hunter Gatherer vs. Farmer analysis (see
here). All you have to do, is to add up the blue and purple components from the STRUCTURE graph, and you'll basically get my "Baltic hunter gatherer" cluster. Also, the orange component is obviously very similar to my "Mediterranean farmer" cluster.
Obviously, if Skoglund et al. had more prehistoric samples, then these would create their own clusters. However, these clusters would be closely related to the clusters formed by modern samples. We know this by looking at the PCA results from the study, like below.
http://img812.imageshack.us/img812/3460/skopca.png
So the fact that the three hunter gatherers mostly fall into the North European/Finnish clusters (and thus show a high correlation with my Baltic hunter gatherer cluster) and the farmer mostly into the Sardinian cluster (thus showing a high correlation with my Mediterranean cluster) aren't simply artifacts of poor sampling and methodology.
On a related note, a version of my Hunter Gatherer vs. Farmer test will be available at
Gedmatch shortly. So please check it out when it's ready, which should be soon.
Reference...
Skoglund et al.,
Origins and Genetic Legacy of Neolithic Farmers and Hunter-Gatherers in Europe, Science 27 April 2012: Vol. 336 no. 6080 pp. 466-469 DOI: 10.1126/science.1216304
