Ancient mtDNA haplogroup X2 from Central Europe

Davidski reminds me of a paper by Lee et al. I had posted the abstract of, but did not comment on. He highlights the fact that mtDNA haplogroup X2 has been detected at this site (3.6-2.8ky cal BC) but not in earlier LBK Neolithic Europeans. Furthermore, he attributes the arrival of X2 in Europe to "Northwest Eurasians":

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.

Finally, phylogeography of the subclades of haplogroup X suggests that the Near East is the likely geographical source for the spread of subhaplogroup X2, and the associated population dispersal occurred around, or after, the LGM when the climate ameliorated. The presence of a daughter clade in northern Native Americans testifies to the range of this population expansion.

Moreover, it occurs at a higher frequency in Southern Europeans than Northern Europeans and is well-represented in the Caucasus, Near East, and even Africa. These twin facts are inconsistent with it being related to "Northwest Eurasians", however that hypothetical people is defined.

Of related interest, mtDNA haplogroup X2b has been detected in Iron Age "princely burials" from the same location and by the same group. Also from Reidla et al.:

The sister groups X2b and X2c (X1 and X2, respectively, in the work of Herrnstadt et al. 2002) encompass one-third of the European sequences (excluding the samples from the North Caucasus). It is of interest that some North African sequences (from Morocco and Algeria) belong to X2b as well. Subhaplogroup X2b shows a diversity that is consistent with a postglacial population expansion in both West Eurasia and North Africa.

Fernandes et al. (2012) consider X2b to be of European origin. X2 has been discovered in a Megalithic long mound from France (4.2ky cal BP), and in abundance at Treilles (c. 3,000 BC), in the latter case associated with a predominantly Y-haplogroup G2a (with some I-P37.2) population. In Jean Manco's excellent compendium, X2b is also listed as being present in Neolithic Portugal (3,400 years BC), and X2j in Neolithic Germany (4625-4250 BC); the latter is said to be "North African" by Fernandes et al. (2012).

Therefore, we can probably reject Davidski's speculation...

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 Europe together from the east, probably between 4,000 and 3,000 B.C.