Europe, 10,000 B.C.

By Razib Khan | January 8, 2012 12:31 am

The image above come from John Hawks’ weblog. I was thinking today about the resettlement of Europe since the Last Glacial Maximum. It is clear that much of northern Europe was not habitable until the Holocene, after the Ice Age. And those regions which were habitable were often marginal. But, there were zones of southern Europe which remained relatively clement. One model of how Europe was settled after the warming is that hunter-gatherers expanded north out of these southern refuges. This can explain the lower heterozygosity of northern populations (see map to left). They may have lost their genetic diversity to some extent through population bottlenecks or simply drift on the wave of demographic advance. And yet something jumped out at me on this map: the southwest portion of Portugal is reputedly the zone with the highest African admixture in continental Europe (for historical reasons). The heterozygosity may simply be a function then of the fact that southern Europe has been in greater contact with other regions of the world because of geographic proximity.

There is also a second pattern which has always elicited curiosity in me: why is it that the largest component of genetic variation in Europe separates north vs. south, as opposed to east vs. west? This does not seem to comport well with a model of expansion from southern refuges. Should not the west-east genetic variation of Ice Age Europeans who faced the tundra and ice be represented among modern populations as they expanded their range northward simultaneously? Something is wrong with the model.

First, it seems clear that a lot has changed since the Last Glacial Maximum. As recently as the late aughts authors were claiming that by ~20,000 years before the present the general shape of genetic variation we see around us had been set. I’d be willing to bet $5,000 dollars that that’s wrong. In the specific case of Europe there may be many explanations for the set of patterns we’re seeing. It may be that the original populations of the refuges were later replaced. Northern Europeans may be legitimate descendants of those groups, but the original patterns of genetic variation in southern Europe were washed away due to being overwhelmed by Neolithic populations from Anatolia. Or, it may be that modern people in the north of Europe descend from a group which moved laterally, and replaced and assimilated the original inhabitants of the continent.

There are many plausible models, and combinations of models. From what I have read people in the Reich lab are now attempting to construct a scenario for the ethnogenesis of Europeans analogous to that of South Asians. In other words, modern Europeans are a compound of the descendants of the Paleolithic hunter-gatherers with an intrusive population. The same lab seems to be positive that Indo-Europeans did have a substantial effect on genetics of South Asians. If so, then I see no reason why the same would not be so in Europe.

In any case, interesting times. We’ll know a lot more in exceedingly great detail soon enough (I’d be willing to bet money on that too!).

CATEGORIZED UNDER: Anthroplogy
  • immu

    I hate it when the French etc. cut most of the Finland out from the map. The top map is a real record – even Estonia has been cut out.

    You should read about the controversial Susiluola-findings in Finland, which suggest that there might have been Neanderthals living in the Fennoscandian plate (island) during some interglacial period. This is interesting because no one seems to think neanderthals could build boats. The findings are so controversial that further findings are needed to resolve this.

  • ackbark

    Didn’t we just read something about how people are more related on an east/west axis across continents than north/south?

    Also, when all that ice melted wouldn’t it have created substantial amounts of fog throughout Europe and excessively clammy and icy conditions in winter? I was thinking about this in connection with redheads and their different patterns of pain perception, –though more sensitive to pain generally, are they less sensitive to clamminess?

  • Grey

    I wonder about a pastoralist bow-wave. The early farmers would be restricted to suitable terrain but around the sites suitable for the full package would be more marginal land that was viable for just the pastoralist element i.e farming in the valley, shepherds in the hills. The pastoralist ring would have a lower maximum population density than the farming core but as long as it was higher than foragers then once established the pastoralist ring could expand independently and possibly much faster.

    I’m not sure how much this might effect things if at all but i’d imagine foragers being more likely to switch to herding than directly to farming.

  • dave chamberlin

    @1)extraordinary claims require extraordinary evidence. but after a pinky bone found in a Siberian cave is linked to the living residents of New Guinea I have to say anything is possible. nobody rational is completely closed minded to such possibilities anymore.

  • http://washparkprophet.blogspot.com ohwilleke

    IIRC, ancient DNA from the Upper Paleolithic is pretty similar pre- and post- LGM, but dominated in both periods by two or three mtDNA U haplogroups, rather than the broad diversity we see in Southern European ancient mtDNA starting in the Epipaleolithic ca. 14,000 years ago.

    The similarity of pre-LGM and post-LGM Upper Paloeolithic mtDNA is consistent with a refugium theory, but suggests that genetic diversity in Europe is more recent (in the last 14,000 years or so, if not necessarily so recent as the Neolithic).

    Honestly, I think we see, at least, an Upper Paleolithic, early Neolithic and Copper Age layer in most of Europe, with the UP percentage pretty small (perhaps 20% on the female side and 5%-10% on the male side with an autosomal contribution that splits the difference), and an early Neolithic contribution that is similarly larger on the maternal side than the paternal side.

  • Eurologist

    I agree that the Mediterranean diversity is clearly higher due to agriculturalists (as reflected in a higher West Asian autosomal component, but with an east-west and south-north gradient), and also due to pre-classical and classical times seafaring.

    Before LGM, travel throughout Europe was easy, and I would expect an overall fairly homogeneous population with mostly an east-west gradient (the East had more later arrivals).

    For the presently low diversity in the North we should not forget the Younger Dryas. After LGM, populations of the northernmost refugia clearly had a huge advantage at filling the void. From the cultural trail, we know that one group was Franco-Cantabrian. The Moravian/Carpathian refugium is viewed as more speculative, but IMO as real as the Ukrainian one. So, why don’t we have the highest diversity in the North, where all three mixed? IMO the easiest explanation is that the population plummeted during the Younger Dryas. We know that northern/ northeastern Europe remained populated, but very sparsely so – a huge bottle-neck, but a relatively homogeneous culture from the Netherlands almost to the Urals.

    Which group had the best chance to re-populate northern Europe when it finally warmed up? Of course, the people who already lived there.

  • Pinky B

    The oldest surviving genetic group in Europe is probably the one that Dienekes has labeled “Atlantic-Baltic” in his Dodecad research.

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This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com

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