May 08, 2012

Late glacial recolonization of Europe from Near Eastern refugia

A couple of quick comments on this important new paper:

  • It is important to confirm the hypotheses put forward with ancient DNA data. For example, haplogroup V is said to be traced to Paleolithic SW Europe, and yet it is lacking in ancient DNA data. Looking at Jean Manco's ancient Eurasian DNA compendium, I only find a very late Neolithic hunter-gatherer sample from Pitted Ware in Sweden (2,800-2,000BC); if J/T subclades had entered Europe prior to the Neolithic, their almost complete absence in ancient DNA data is puzzling.
  • Both this and the recent "Copernican" paper provide age estimates for the same nodes of the tree using the mutation rate of Soares et al. (2009). The estimaets of Pala et al. (2012) appear to be older by several thousand years than those of Behar et al. (2012) for different nodes. I don't know whether this is due to a different methodology or different dataset, but, in any case, it is a warning to avoid very close correlations between archaeological-geological events and age estimates.
UPDATE: A press release on the article.

The American Journal of Human Genetics, Volume 90, Issue 5, 915-924, 4 May 2012 doi:10.1016/j.ajhg.2012.04.003

Mitochondrial DNA Signals of Late Glacial Recolonization of Europe from Near Eastern Refugia

Maria Pala et al.

Human populations, along with those of many other species, are thought to have contracted into a number of refuge areas at the height of the last Ice Age. European populations are believed to be, to a large extent, the descendants of the inhabitants of these refugia, and some extant mtDNA lineages can be traced to refugia in Franco-Cantabria (haplogroups H1, H3, V, and U5b1), the Italian Peninsula (U5b3), and the East European Plain (U4 and U5a). Parts of the Near East, such as the Levant, were also continuously inhabited throughout the Last Glacial Maximum, but unlike western and eastern Europe, no archaeological or genetic evidence for Late Glacial expansions into Europe from the Near East has hitherto been discovered. Here we report, on the basis of an enlarged whole-genome mitochondrial database, that a substantial, perhaps predominant, signal from mitochondrial haplogroups J and T, previously thought to have spread primarily from the Near East into Europe with the Neolithic population, may in fact reflect dispersals during the Late Glacial period, ∼19–12 thousand years (ka) ago.

Link

6 comments:

GailT said...

I agree that ancient DNA is needed to support their theories on an early arrival of J and in Europe, there remains too much uncertainty in analysis of current distributions. But it is a nice analysis of JT. They cite old papers on H1 and H3 being in refugia in Franco-Cantabria at the height of the last ice age, even though the most recent age estimates for those groups would seem to make this impossible. And as I read the Malyarchuck et al 2010 paper it does not seem to support a conclusion that U5a came from the East European Plain. But they are not studying H and U in this paper so I can understand that they would cite old theories on these groups.

royking said...

Fascinating! This study opens the door to the Epipaleolithic/Mesolithic migration both by land and by sea of hunter/forager/fisher populations from the Mid-East to Europe post-LGM. It may also translate into some of the anomalous Y chromosomal and autosomal interconnections between the Near East and Europe.

eurologist said...

Great paper - it should remind everyone to what high degree of resolution we must look at mtDNA (and also y-DNA) to even try making sense of migrations and diffusion. Also, as Dienekes noted, we need to remain cautious about calculated dates until properly anchored by ancient DNA. Again, I find myself being a bit skeptical when I see accumulations of nodes just at the worst climatic times around LGM. If the ages were 25% to 50% older, that would remove most nodes from the coldest and driest periods of LGM.

As I mentioned in the other thread, J1c, J2a1, T2b, T2e, and T2f may be sufficiently old to actually be present in Europe pre-LGM.

Finally, we know that during the neolithic expansion, the agriculturalists picked up all sorts of mtDNA along their way (and JT subclades are common in LBK and other neolithic ancient DNA). So, it will take very careful work to distinguish those JT subclades that are from the earliest migration into Greece and the Balkans from those that were already present there and in the remainder of Europe. Ancient mtDNA will need to be typed at the same resolution (ore whole-genome-wide) as what we see here.

Davidski said...

^ It doesn't open to door to anything.

It's just another deeply flawed study. There are many of them around, and we'll probably have to suffer a few more before scientists grow up.

Dr Rob said...

Whilst great data, the study suffers sthe same problems that the Richards/ Semino "Palaeolithic" crew propagate. Namely, (i) the mutation rates of mtDNA might be considerably quicker than they presume. (ii) the age of the clades does not mean they entered Europe at that time (iii) an (alleged) flow of post-glacial colonizers from the near east was probably genetically diverse, and not monophyletic.

All 3 factors independently and in combination could serve to blow out their time estimates.

eurologist said...

It's just another deeply flawed study. There are many of them around, and we'll probably have to suffer a few more before scientists grow up

I am not sure you know, or, better phrased, please take a look at what you post and what you know. So, I firmly state this here - do you realize that your posts have no valuable content, whatsoever?