Monday, January 6, 2014

Mesolithic Western European Hunter Gatherers Partly Descended from Upper Paleolithic Reindeer Hunters

Figure 1 (From Ancient human genomes suggest three ancestral populations for present-day Europeans (Link))

This post was updated on 10/4/2015.  See blog note (10/4/2105):

The above figure is taken from the recent Lazaridis et al. paper which discusses European ancient DNA. 

Yesterday, I had a look at an addition to Figure 1(b) that Luis Aldamiz suggested (Link).  Luis had noted that a vector could be drawn through the "Scandinavian Hunter-Gatherers"  and another line through the "Western European Hunter-Gatherers".  He then pointed out that by extending these two lines, an "origin" might hypothetically be formed in order to guess at the connection between Scandanavian and Western European Hunter-Gatherers.  I think he is right.

However, thinking about Ice Age Europe, statistically speaking, the nexus of these two groups is probably further north than the Dordogne.

Based on a recent publication, we know that there were reindeer in the Catabria region of the Iberia Peninsula (Gómez‐Olivencia et al), very close to the location of the La Braña Hunter-Gatherers.

It seems apparent that the Loschbour, Luxembourg Hunter-Gatherer was related to the La Braña Hunter-Gatherers.  However, reindeer went extinct in the Northern Europe plain 11,250 years ago and in Scandanavia 10,300 years ago (Link).  Therefore, the Loschbour Man was not a reindeer hunter.  However, based on the evidence of reindeer remains during the Upper Paleolithic in the Paris Basin, the British Isles and Germany, it is very likely that many of Loschbour Man's ancestors were reindeer hunters.

Which brings us back to the curious vector relationship between the Loschbour Man and the La Braña Hunter-Gatherers.  It does suggest rather loudly that there is a reindeer hunter connection between Northern France and Northern Iberia.

In the above Figure, I have transposed the Loschbour Man-La Braña vector (shown in red) so that it is properly positioned to intersect the modern day population of Northern France.  I call this vector "Transposed Western European HGs."

I have similarly transposed the "Scandanavian Hunter-Gatherer" vector (also shown in red) two times, one for "early" and one for "late".  Given the position of glaciers in Europe during the Ice Age, this "early" vector would have been the only possible Ice Age position for "Scandanavian Hunter-Gatherers."  As the ice retreated, the "Scandinavian Hunter-Gatherers" would have pushed northward.  I show an approximate "late" transposition as "Transposed Scandinavian Hunter-Gatherers (late)."

Interestingly enough, the "Transposed Scandinavian Hunter-Gatherers (early)" and the "Transposed Western European HGs" intersect in Northern France, just where there is plenty of archaeological evidence for Palaeolithic reindeer hunters.

So I think Luis is more than onto something with these vectors.  They show a nexus for these two hunter-gatherer groups.  It is very likely that the nexus is for palaeolithic hunter-gatherer groups that hunted reindeer southward into the Iberian Peninsula, westward even as far as Iceland, and northward to the limit of the Ice Age European glaciers.

Update (Jan 7th, 2014):

Additional references showing Upper Palaeolithic Occupation of the Paris Basin, Jura and Bohemia:

Acquisition and Processing of Reindeer in the Paris Basin
James G. Enloe

Hunting practices targeting large mammal communities in the Paris Basin in the Upper Palaeolithic
Olivier Bignon-Lau

Absolute Dates for the Bohemian Middle Upper Palaeolithic
Alexander Verpoorte

Environmental context of the Magdalenian settlement in the Jura Mountains using stable isotope tracking (13C, 15N, 34S) of bone collagen from reindeer (Rangifer tarandus)
D.G. Drucker, A. Bridault, C. Cupillard
A Last Glacial Maximum pollen record from Bodmin Moor showing a possible cryptic northern refugium in southwest England
A. Kelly, D. J. Charman, R. M. Newnham

Update (January 8th, 2014):

In the interest of further understanding the relative placement of the positions of the ancient DNA discussed in this paper, I decided to sort some whole genome genetic results from the (Dodecad Ancestry Project) in terms of their major components. The following bar plots are sorted ADMIXTURE results for Europe showing component distributions roughly corresponding to the populations "Scandinavian Hunter Gatherers", "Ancient North Eurasians", and "Early European Farmers".  The raw data is taken from the Dodecad Ancestry Project blog post "Admixture Analysis with Dodecad Populations" (Link).

Scandinavian Hunter-Gatherer Distribution
(North European light orange)

Note that no "Scandinavian Hunter Gatherers [North Europeans]" reached Sardinia.  This is likely because the sea depth between Corsica and Sardinia is 100 meters.  Before the Last Glacial Maximum, the only other time that the sea level fell this low was 65,000 years ago, before modern humans reached Europe.  Therefore, Upper Palaeolithic Hunter Gatherers could only have reached Sardinia by boat, which it appears did not happen.  Instead, "Early European Farmers [South Europeans]" reached Sardinia.  A likely time was when the sea level briefly dipped to -120 meters approximately 25,000 years ago.

Also of note in this plot is that the Chuvash population has no "Early European Farmer [South European]" ancestry.   This tells us that at one point, probably before the Last Glacial Maximum, "Scandanavian Hunter Gatherers [North Europeans]" had not yet mixed with "Early European Farmers [South Europeans]".

Ancient North Eurasian Distribution (Northeast Asian dark green)
The population cluster of "Ancient North Eurasians [Northeast Asians]", shown here in dark green, is scattered across the far north of Eurasia.  Reindeer hunter gatherers from Europe, originally with mostly "Scandanavian Hunter Gatherer" ancestry, ranged eastward at least as far as Lake Baikal during the last ice age. They mixed with hunter-gatherers from Northeast Asia as indicated by the ancient DNA from MA1.  As the glaciers melted, some of these populations returned to Europe, pushing northwestward to fill a niche in what is now Finland.

[For an explanation of why some of these North Eurasian populations contain South Asia ancestry, it is simply due to bilateral migrations between the North Eurasian Steppe and South Asia. See here.]

Early European Farmers (South European light green)
The distribution of "Early European Farmers [South Europeans]" strongly indicates that this population expanded from North Africa during the Last Glacial Maximum across Gibraltar, across the Strait of Sicily, into Sardinia and possibly also from the Eastern Mediterranean. It is notable that the Chuvash, who must have left Western Europe before the last ice age, have almost no "Early European Farmer [South European]" ancestry.   [blog note (10/4/2105):  From a number of recent publications, it is clear that "Early European Farmer" or "South European" component that turns up in Admixture runs on Euroean populations is associated and descended from Southern European Epi-Gravettian populations of the Mediterranean.  It may also be associated with North Africa from the time of the Last Glacial Maximum and subsequently, when the sea level was lower.  More studies with ancient DNA from North Africa would be need to confirm this.]

Another observation is that French Basques have more than half "Early European Farmer" ancestry. Like Sardinians, they show no evidence of "West Asian" ancestry.  Looking at the composition of French Basques, and the Figure 1 position of the Loschbour Man and the La Braña samples (rotated downward from the Motala Ancient DNA), it appears that admixture between "Scandinavian Hunter Gatherers" and "Early European Farmers" occurred in the ancestors of the Loschbour Man and the La Braña hunters.

West Asian (light blue)

I've discussed the distribution of the "West Asian" component in an old post.  It is a very broadly distributed component.  However, its relative absence in French Basques, Finns and Sardinians indicates that this component spread into Western Europe sometime after the last ice age.

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