This is an ongoing debate and a single study will not decide things one way or the other. In recent years, the evidence has been shifting towards the replacement model. In northern Europe, there seems to have been a genetic divide between late hunter-gatherers and early farmers (although the divide is just as great between the latter and present-day Europeans). In particular, European hunter-gatherers possessed genetic lineages (haplogroup U) that are rare among present-day Europeans.
Now, the pendulum is swinging back. After studying 92 Danish human remains that range in time from the Mesolithic to the Middle Ages, Melchior et al. (2010) have found evidence of genetic continuity from late hunter-gatherers to early farmers.
The extent to which early European farmers were immigrants or descendants of resident hunter-gatherers (replacement vs. cultural diffusion) has been widely debated, and new genetic elements have recently been added. A high frequency of Hg U lineages, especially U5, has been inferred for pre-Neolithic Europeans based on modern mtDNA data, with Hg U5 being fairly specific to Europe.
[…] The present findings indicate that predominantly haplogroup U lineages persist among Neolithic/Bronze Age population samples in Southern Scandinavia and it may point to regional variation in the penetrance rate of these lineages across cultural shifts in different areas of North Europe. Given our small sample sizes from these crucial time periods further studies are certainly required. However, the frequency of Hg U4 and U5 declines significantly among our more recent Iron Age and Viking Age Danish population samples to the level observed among the extant Danish population. Our study therefore would point to the Early Iron Age and not the Neolithic Funnel Beaker Culture as suggested by Malmström et al. (2009), as the time period when the mtDNA haplogroup frequency pattern, which is characteristic to the presently living population of Southern Scandinavia, emerged and remained by and large unaltered by the subsequent effects of genetic drift.
As the authors note, the sample sizes were small. But it is odd that all of the Neolithic and Early Bronze Age samples were either U4 or U5a. These lineages now account for only 1–5% and 5–7% of present-day Europeans.
Reference
Melchior, L., N. Lynnerup, H.R. Siegismund, T. Kivisild, J. Dissing. (2010). Genetic diversity among ancient Nordic populations, PLoS ONE 5(7): e11898.
doi:10.1371/journal.pone.0011898
6 comments:
But it is odd that all of the Neolithic and Early Bronze Age samples were either U4 or U5a. These lineages now account for only 1–5% and 5–7% of present-day Europeans.
There may have been increasing relaxation of selection for U4 or U5a and/or selection for other mtDNA that had become advantageous. The new cultural developments promoted some mtDNA mutations by affecting fitness somehow. The actual mechanism could be though disease, fertility, or even behaviour or IQ.
Agriculture came to Europe through the Balkans, then spread along the whole Mediterranean coast, then slowly moved into central Europe and only reached northern Europe 4 or 5 thousand years after it entered Greece.
One would imagine that as early farmers moved in to a new area, they would have mixed with the local hunter-gatherers at least somewhat. How could they have resisted appropriating some of the hunter-gatherers' women? So that the next wave of farmers looking for new lands would have been somewhat more European than the previous one. And so on and so on. By the time agriculture reached the north, the proportion of Middle Eastern ancestry among farmers would have been much diminished.
Perhaps in recent millennia new mitochondrial lineages developed that are better adapted to metabolising wheat or alcohol or something like that giving it a selective advantage.
"How long have Europeans been European?": not long because we are becomming back Africans again.
I was watching 'Human Journey' on american channel NOVA last night. Good show, very PC but good.
I miss the beginning of the show though, and I wonder who is the blond scientist involved in that jouney. Is it Bryan Sykes ?
The good: he showed San Buhsman, and it's true, they look at least as much asians than africans.
The not too bad: The inevitable interview of native people, in their assumed-by default-wisdomer than whites-who-lost-their-ancestors-memory, turns sour because the natives (amerindians, australians, siberians etc)invariably refuse to admit they come from africa and they all claim they come from 'Here'.
OK, here the blond guy could have mentioned the multiregionalist hypothesis, but nope. Well, I understand since he supports the all from africa, that's not his bussiness to mention other people's theory. The show was also probably made before the '4% neanderthal gene thing' because that would have been hard to miss.
The bad: the shows open with Sforza-the wise. He looks and speaks like Gandalf the Grey and I guess some italian accent (as compared with, say, Jean Chretien) induce the idea of ancient wisdom and universal truth.
The very bad: the inevitable female scientist explains the vitamine d story and why europeans are so pale because there is reduced light between 40-50degre latitude, just two minutes before we see siberian Chichicks with a brownish-bronze skin living in almost total darkness 200 miles within the polar circle...I guess NOVA is here to propagate PC ideology, not to ask questions.
The very very very bad: at the end of the show, the inevitable "we're all the same and single race yadayada" I guess the blond guy needs funding for his next project.
Tod, Stephen,
But isn't mtDNA largely unaffected by natural selection? I realize that natural selection must have some impact, but you would still need very strong selection pressure to go from 100% to the single digits over such a short time.
Glossy,
Your model is close to the cultural diffusion model, i.e., its primarily the memes that do the travelling, not the genes.
Ben10,
Cavalli-Sforza has paid a high price for the dolce vita. There are situations that justify saying what you don't really believe (i.e., a life or death situation), but this isn't one of them. He panicked and we're all paying the price.
It's better to be honest than to be conniving. That way, you don't have to remember so much.
isn't mtDNA largely unaffected by natural selection?
(May 11, 2010 ) Douglas C. Wallace, 'one of the world's leading geneticists'
Bioenergetics, the origins of complexity, and the ascent of man
"Consequently, the most important variables in intraspecific adaptation to local environmental changes, which are primarily energetic, should be alterations in bioenergetic genes, either genetic or epigenetic. Mutations in the mtDNA are more common than nDNA mutations and epigenomic changes can rapidly change the expression of bioenergetic genes. Efforts to explain common “complex” diseases like diabetes based exclusively on the analysis of nDNA variation in tissue-specific genes would then be expected to be relatively unproductive, as has been the case. In reality, common diseases may not be particularly “complex,” they may simply be energetic and non-Mendelian."
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