The North German ancient DNA project I blogged about ages ago has finally produced a paper. It includes only eight mtDNA results, but despite the rather underwhelming harvest, I think there might be something very important here, which is the presence of mtDNA X2 but lack of X1.
Reading the quotes below, I can’t help thinking that X2 lineages in Europe might be associated with the arrival of the so called Northwest Eurasians of North/Central/East Europe and the North Caucasus, while X1 with the earlier migrations of the Sardinian-like Southwest Eurasians of Mediterranean Europe, North Africa and the Near East.
All haplogroups identified in our study, H1, H2, HV0, and X2, have been previously observed among other Neolithic populations (e.g. Deguilloux et al., 2011; Haak et al., 2010; Sampietro et al., 2007), which are also consistent with maternal lineages present among modern Europeans (Achilli et al., 2004; Reidla et al., 2003). Interestingly, we did not identify haplogroup U, which has been documented consistently in various Neolithic and earlier contexts and is thought to be one of the oldest European maternal lineages (e.g. Bramanti et al., 2009; Haak et al., 2010; Lacan et al. 2011b; Lee et al., 2012).
Interestingly, haplogroup X2 has not been identified in LBK or earlier Neolithic and Mesolithic groups despite their relatively large sample size (n = 59), but documented in late Neolithic (< 3000 cal BC) contexts in central Europe (Deguilloux et al., 2011; Haak et al., 2008; Lacan et al., 2011a).
The origin of haplogroup X2 is still unclear, but studies suggest X2 lineages were introduced into Europe during the Neolithic (Reidla et al., 2003; Richards et al., 2000). On the other hand, haplogroup X1, a subgroup more common in the Near East and North Africa, has been reported in an early Neolithic group from the Iberian peninsula (ca. 5400 cal BC, Gamba et al., 2012). The absence of X2 lineages but presence of X1 in the early farming group in Spain substantiates the scenario in which Neolithic farmers in Europe came from multiple founding populations at different time periods (Deguilloux et al., 2011; Gamba et al., 2012; Lacan et al., 2011b).
So, X2 has been located at multiple late Neolithic sites in Central Europe, including the Corded Ware burial ground at Eulau, Eastern Germany. Of course, that’s also where Y-chromosome haplogroup R1a was found (see here). I suspect this wasn’t a coincidence and it’s likely these markers entered Central Europe together from the east, probably between 4,000 and 3,000 BC.
But did they come from the Pontic-Caspian Steppe, North Caucasus, or Anatolia via the Balkans? If it was from Anatolia, then why was a Sardinian-like individual still living in the southern Balkans during the Iron Age? Keep in mind, people like that are no longer found anywhere in Europe but Sardinia.
Note also the lack of mtDNA U at the late Neolithic German sites, which is a lineage present in all Palaeolithic and Mesolithic remains from Northern, Central and Eastern Europe tested to date. This might be due to the low number of samples, but maybe it’s because these late Neolithic German groups did not absorb any significant Mesolithic admixture for a couple thousand years after arriving in Central Europe?
This would be in line with aDNA results from elsewhere in Europe, like Scandinavia, where Neolithic farmers and Mesolithic hunter-gatherers apparently lived side by side for many generations without mixing to any great extent. Indeed, perhaps this sort of strong cultural isolation is the reason why the Sardinian-like survivor was still in the Balkans thousands of years after the end of the Neolithic?
Admixture date =/= migration date (aka. modern Europeans formed in-situ during the metal ages)
Southwest Eurasians + Northwest Eurasians + Mesolithic survivors = modern Europeans
Lee, E.J., Renneberg, R., Harder, M., Krause-Kyora, B., Rinne, C., Müller, J., Nebel, A., von Wurmb-Schwark, N., Collective burials among agro-pastoral societies in later Neolithic Germany: Perspectives from ancient DNA, Journal of Archaeological Science (2012), doi: 10.1016/j.jas.2012.08.037.