Two important new papers appeared in
Science today. In the first one (
Brandt, Haak et al.), researchers compiled mtDNA results from 364 prehistoric central Europeans from the early Neolithic to the early Bronze Age, spanning about four millennia of history. Importantly they uncover not a smooth transition between early Neolithic farmers and modern Europeans, but a punctuated series of haplogroup frequency changes that cannot really be explained by genetic drift in a single European population evolving over time. Hopefully this kind of research can be repeated in other parts of the world, as it provides a way to see evolution and migration as it happens.
Earlier work has disproved the hypothesis that modern Europeans are simply "acculturated" hunter-gatherers, and this newer research disproves the idea that they are simply the descendants of early farmers, little modified since the beginning of the Neolithic.
I am sure that myself and others will spend some time trying to digest the wealth of information present in the paper and its supplementary materials. Yet, one conclusion can already be made, that
migrationism is alive and well.
Anyone adhering to a "pots not people" paradigm will find difficult to explain the sharp discontinuities found in the genetic record. European foragers contrast with the earliest farmers, who, in turn, contrast with and the Late Neolithic copper cultures that supplanted them a few thousand years later and spawned the Bronze Age world.
If pots aren't people, it's strange that archaeological cultures defined largely by pots (right) also appear to mark genetic contrasts.
These discontinuities are most evident in Figure 3 from the paper:
You may follow the grey line to see how central Europe, once populated exclusively by hunter-gatherers, experienced a virtual disappearance of their matrilineages for almost two thousand years after the advent of farming. Then, between the Middle to Late Neolithic, around five thousand year ago, the hunter-gatherers make their re-appearance before their lineages converge to their modern (minority) frequency. The authors present a model of migration to explain these events, illustrated in a movie in the supplementary material, and also in the figure on the left.
Of particular interest is a set of haplogroups marked by the yellow line (I, U2, T1, R) and are most strongly represented in the Unetice and Corded Ware samples before reverting to a small minority in the present-day. These may be potentially very informative to understand the c. 5,000-year old ago upheaval. I reproduce below three of the genetic distance maps from the supplement for the three latest cultures (CWC: Corded Ware; BBC: Bell Beaker; and UC: Unetice):
I note the European-ness of Bell Beaker (probably due to elevated frequencies of haplogroup H) and the eastern European-ness/west Asian-ness of Corded Ware/Unetice.
Moving on to the next shorter paper by
Bollongino et al. which produces evidence for an interesting hypothesis: that hunter-gatherers did not disappear in central Europe after the introduction of farming, but some of their descendants persisted for at least two thousand years afterwards:
In summary, the results of 14C and stable isotope analysis, together with the DNA evidence, suggest that the Blätterhöhle individuals are sampled from three distinct populations: (i) Mesolithic hunter-gatherers, (ii) Neolithic farmers, and (iii) Neolithic fisher-hunter-gatherers (special-izing in freshwater fish). The latter two notably date to the fourth mil-lennium BC, which is around 2000 years after the introduction of farming to Central Europe.
I was reminded of an
older paper about first contact between farmers and hunter-gatherers. An important consequence of the second paper is that hunter-gatherer lineages in modern Europeans may have come not only from outlying areas where foragers persisted in greater numbers, but also from within the farming realm itself.
Science 11 October 2013: Vol. 342 no. 6155 pp. 257-261 DOI: 10.1126/science.1241844
Ancient DNA Reveals Key Stages in the Formation of Central European Mitochondrial Genetic Diversity
Guido Brandt, Wolfgang Haak et al.
The processes that shaped modern European mitochondrial DNA (mtDNA) variation remain unclear. The initial peopling by Palaeolithic hunter-gatherers ~42,000 years ago and the immigration of Neolithic farmers into Europe ~8000 years ago appear to have played important roles but do not explain present-day mtDNA diversity. We generated mtDNA profiles of 364 individuals from prehistoric cultures in Central Europe to perform a chronological study, spanning the Early Neolithic to the Early Bronze Age (5500 to 1550 calibrated years before the common era). We used this transect through time to identify four marked shifts in genetic composition during the Neolithic period, revealing a key role for Late Neolithic cultures in shaping modern Central European genetic diversity.
Link
Science DOI: 10.1126/science.1245049
2000 Years of Parallel Societies in Stone Age Central Europe
Ruth Bollongino et al.
Debate on the ancestry of Europeans centers on the interplay between Mesolithic foragers and Neolithic farmers. Foragers are generally believed to have disappeared shortly after the arrival of agriculture. To investigate the relation between foragers and farmers, we examined Mesolithic and Neolithic samples from the Blätterhöhle site. Mesolithic mitochondrial DNA sequences were typical of European foragers, whereas the Neolithic sample included additional lineages that are associated with early farmers. However, isotope analyses separate the Neolithic sample into two groups: one with an agriculturalist diet and one with a forager and freshwater fish diet, the latter carrying mitochondrial DNA sequences typical of Mesolithic hunter-gatherers. This indicates that the descendants of Mesolithic people maintained a foraging lifestyle in Central Europe for more than 2000 years after the arrival of farming societies.
