In the last week, I put up a big two-part series of posts on Substack, The wolf at history’s door and Casting out the wolf in our midst, about the spread of Indo-European (men) 5,000 years ago. By coincidence, a massive preprint on ancient DNA just came out of the Willerslev coalition of researchers, Population Genomics of Stone Age Eurasia. It really is massive, and is hard to summarize, but here’s the abstract:
The transitions from foraging to farming and later to pastoralism in Stone Age Eurasia (c. 11-3 thousand years before present, BP) represent some of the most dramatic lifestyle changes in human evolution. We sequenced 317 genomes of primarily Mesolithic and Neolithic individuals from across Eurasia combined with radiocarbon dates, stable isotope data, and pollen records. Genome imputation and co-analysis with previously published shotgun sequencing data resulted in >1600 complete ancient genome sequences offering fine-grained resolution into the Stone Age populations. We observe that: 1) Hunter-gatherer groups were more genetically diverse than previously known, and deeply divergent between western and eastern Eurasia. 2) We identify hitherto genetically undescribed hunter-gatherers from the Middle Don region that contributed ancestry to the later Yamnaya steppe pastoralists; 3) The genetic impact of the Neolithic transition was highly distinct, east and west of a boundary zone extending from the Black Sea to the Baltic. Large-scale shifts in genetic ancestry occurred to the west of this “Great Divide”, including an almost complete replacement of hunter-gatherers in Denmark, while no substantial ancestry shifts took place during the same period to the east. This difference is also reflected in genetic relatedness within the populations, decreasing substantially in the west but not in the east where it remained high until c. 4,000 BP; 4) The second major genetic transformation around 5,000 BP happened at a much faster pace with Steppe-related ancestry reaching most parts of Europe within 1,000-years. Local Neolithic farmers admixed with incoming pastoralists in eastern, western, and southern Europe whereas Scandinavia experienced another near-complete population replacement. Similar dramatic turnover-patterns are evident in western Siberia; 5) Extensive regional differences in the ancestry components involved in these early events remain visible to this day, even within countries. Neolithic farmer ancestry is highest in southern and eastern England while Steppe-related ancestry is highest in the Celtic populations of Scotland, Wales, and Cornwall (this research has been conducted using the UK Biobank resource); 6) Shifts in diet, lifestyle and environment introduced new selection pressures involving at least 21 genomic regions. Most such variants were not universally selected across populations but were only advantageous in particular ancestral backgrounds. Contrary to previous claims, we find that selection on the FADS regions, associated with fatty acid metabolism, began before the Neolithisation of Europe. Similarly, the lactase persistence allele started increasing in frequency before the expansion of Steppe-related groups into Europe and has continued to increase up to the present. Along the genetic cline separating Mesolithic hunter-gatherers from Neolithic farmers, we find significant correlations with trait associations related to skin disorders, diet and lifestyle and mental health status, suggesting marked phenotypic differences between these groups with very different lifestyles. This work provides new insights into major transformations in recent human evolution, elucidating the complex interplay between selection and admixture that shaped patterns of genetic variation in modern populations.
There’s so much, I can’t really reduce. Here are some highlights
1 – New hunter-gatherer cluster with a focus in the eastern Ukraine/Russian border region. Between the Dnieper and Don. Because I can barely read the admixture grap in extended figure 4, I’m not totally clear where this group is positioned in the graph, though it has some Causus hunter-gatherer
2 – Neolithicization was pretty slow (demic) in most of Europe, except Scandinavia. We knew this. Steppe arrival was faster everywhere, but mixed with local Neolithic substrate…except in Scandinavia, where there was straight up replacement. But Scandinavians do have Neolithic ancestry…so where’s that from?
3 – The paper claims that the Corded Ware people mixed with Globular Amphora culture. I’m pretty sure if they looked closely all the South Asians will steppe ancestry will show this too, and not any other type of European Neolithic.
4 – Scandinavia seems to have had several replacements even after the arrival of the early Battle Axe people. This is clear in Y chromosome turnover, from R1a to R1b and finally to mostly I1, the dominant lineage now. They claim that later Viking and Norse ancestry is mostly from the last pulse during the Nordic Bronze Age.
5 – They claim to detect it’s clear that Neolithic ancestry in North/Central/Eastern Europe was from Southeast Europe, while that in Western Europe was from Southwest Europe. This is expected.
6 – They confirm that in terms of polygenic prediction Yamnaya people were taller. They claim that it looks like N vs. S European differences in height aren’t selection, but stratification (Yamnaya predicts tallness).
7 – They find that dark hair and skin in Europeans seems correlated with WHG ancestry. This seems to confirm that the WHG were indeed dark of hair and eye. They find that lighter skin/hair really seems to come with Anatolian farmers and Yamnaya. Not the hunter-gatherers. Though selection does start earlier. They assert this has something to do with UV/Vitamin D, but if that, why were the HG groups dark? (if blue-eyed in the case of WHG) I think the explanation is some interaction with the agro-pastoralist lifestyle.
They also confirm that pigmentation selection went on until 3,000 years ago. This is obvious, and to me, it explains easily the heterogeneity in some CWC and post-CWC populations. Some of the early Bell Beakers in Britain look totally modern in pigmentation, but other populations are darker than they should be.
8 – Lots of selection in diet and immune system. What you’d expect. Basically a lot of illnesses might be mixture of the various populations. For example, diabetes comes from WHG.
9 – Neolithic Anatolians seem associated with some psychiatric issues. Could this be due to early dense-living? No idea. Also, they find EDU was selected for (one locus). Might be pleiotropy though.
10 – They find the African R1b around Lake Chad in some Ukrainian samples. Seems to confirm that somehow it’s from Eastern Europe? Weird.
Anyway, read it and tell me what you think.