Wednesday, June 11, 2014

Skull Shapes Differed In The Pre-LGM and Post-LGM Paleolithic Era

Modern humans arrived in Europe around 40,000 years ago (in very round numbers), replacing Neanderthals by 30,000 years ago.  Then, they were expelled from all but a few refugia in Southern Europe, by a catastrophic ice age which peaked at the Last Glacial Maximum (LGM) ca. 20,000 years ago, when most of Northern Europe was covered by glaciers because the average global temperature was about 4.5 degrees colder than it is today.  As the glaciers receded, over a period of several thousand years after the LGM, modern humans repopulated Europe from the refugia and from outside of Europe entirely.

An analysis of skull shapes shows that pre-LGM Cro-Magnon modern humans had significantly different skull shapes than post-LGM Paleolithic modern humans, than early Neolithic era modern humans, and than modern humans in approximately their modern form a few thousand years after that.

A new study of these skull shapes concludes that about two-thirds of the differences between pre-LGM and modern modern human skull shapes comes from the gap between pre-LGM modern humans and immediately post-LGM Paleolithic modern humans.  The next biggest gap was between post-LGM Paleolithic modern humans and early Neolithic modern humans.  The smallest gap was between early and late Neolithic and later era modern humans.

The study offers no opinion concerning whether this reflects a different genetic makeup or other environmental or epigenetic factors.

The study is notable, because it is the first physical anthropology evidence of which I am aware that demonstrates substantial physical anthropology differences between modern humans in Europe before and after the LGM that must have had some cause, even if the exact cause is not known.

The data from mtDNA samples, in contrast, have tended to show more continuity between pre-LGM and post-LGM hunter-gatherer populations, which is a bit surprising itself given that we known for sure that there was a total replacement of the human population of most of Europe as a result of the LGM.  Autosomal genetic data on pre-LGM modern humans in Europe is so scarce and so preliminary that it is too early to know if it differed materially from post-LGM Paleolithic populations unless you are actually in the labs doing the cutting edge work and have access to inside information as a result.

While analysis of skull shape is largely out of favor in anthropological and social scientific circles, for the very good reason that this data was grossly misapplied and misused in the 19th century hey day of this kind of scientific investigation in physical anthropology, that doesn't mean that modern studies taking this approach in the far more restrained context of modern scientific knowledge, are worthless.  They tell us something, just not as much as 19th century proto-scientists thought that they did.


About Time said...

Strange thought: maybe some CroMags found refuge in the east, outside of Europe. If any returned from "exile" after the LGM, the new mixed Europeans would think they were "foreigners." When in fact they could have been unmixed descendants of a more ancient European type---possibly affected by genetic drift and suffering from some recessive traits acquired in isolation outside of Europe.

I imagine something similar could have happened to the Tocharians. The returned exiles--- teachers and maybe even kings (Kushans) of the east--- would appear paltry to their long long European kinfolk after so many generations of separation.

andrew said...

There is nothing strange about any of those ideas. Exile and back migration are fundamental processes in human geography and population genetics over long time scales. Repopulation of Europe from refugia of former Europeans after the LGM is the prevailing paradigm. And, the mtDNA of Cro-Magnons and the mtDNA of post-LGM terrestrial hunter gatherers in Europe show surprisingly great continuity. The only problem is that the case for the repopulation of Europe coming from the East has weak support in the evidence. The Franco-Cantabrian region, parts of Italy, and the Caucasian mountains were the principal LGM refugia and the Western most Franco-Cantabrian refugium appears to have been the most influential in the repopulation of Europe after the LGM. Still, it is hardly surprising that the repopulation of Europe was by people who differed somehow or other from the original residents, since this is a paradigmatic case of total replacement.

In the case of the Tocharians there is every reason to believe that almost all of the surviving descendants of this population of admixed Uygur people. They didn't go anywhere, a position that the archaeology and genetics tend to support.

About Time said...

Hmm. Or maybe very few easterners made it back, but enough to make an impression. Aurel Stein, Sven Hedin, and Victor Mair all had strong intuitive feelings (trending a little to the mystical in some of Aurel Stein's poetic musings).

But less mystically, I wonder how all this fits with ANE. Did the ANE that made it to Europe have partial roots in CroMags or even Cucuteni people that adopted a new life and found success far from home?

It's a little romantic for me, but something I wonder about from time to time. Like prodigal sons, I suppose.