Here's the latest teaser for the new David Reich et al. paper on the ethnogenesis of present-day Europeans. It's part of an abstract for a seminar to be held by Professor Reich at Jesus College, Oxford, on February 9. Interestingly, it argues that migrations from the steppe resulted in a ~50% population turnover across northern Europe from the late Neolithic onwards, which is very much in agreement with recent discussions on the topic at Eurogenes (for instance, see here).
By ~6,000-5,000 years ago, a resurgence of hunter-gatherer ancestry had occurred throughout much of Europe, but in Russia, the Yamnaya steppe herders of this time were descended not only from the preceding eastern European hunter-gatherers, but also from a population of Near Eastern ancestry. Western and Eastern Europe came into contact ~4,500 years ago, as the Late Neolithic Corded Ware people from Germany traced ~3/4 of their ancestry to the Yamnaya, documenting a massive migration into the heartland of Europe from its eastern periphery. This steppe ancestry persisted in all sampled central Europeans until at least ~3,000 years ago, and comprises about half the ancestry of today’s northern Europeans. These results support the theory of a steppe origin of at least some of the Indo-European languages of Europe, and show the power of genome-wide ancient DNA studies to document human migrations.
Source: Ancient DNA documents three ancestral populations for present-day Europeans
Update 11/02/2015: Massive migration from the steppe is a source for Indo-European languages in Europe (Haak et al. 2015 preprint).
Wolfgang Haak et al., Massive migration from the steppe is a source for Indo-European languages in Europe, bioRxiv, Posted February 10, 2015, doi: http://dx.doi.org/10.1101/013433