David Reich and Nick Patterson come down in favor of the steppe as the ur-heimat of the Indo-Europeans, at least those who migrated into Europe, in a recent abstract:
We generated genome-wide data from 65 Europeans who lived between 8,000-3,000 years ago by enriching ancient DNA libraries for a target set of about 390,000 single nucleotide polymorphisms. This strategy decreases the sequencing required to obtain genome-wide data from ancient DNA samples by around 1000-fold, allowing us to study an order of magnitude more individuals than previous studies and to obtain new insights about the past. We show that in western Europe, the farmers of both Germany and Spain >7,000 years ago were descended from a common ancestral stock. These farmers did not replace the earlier hunter-gatherers, but continued to mix with them, leading to a resurgence of hunter-gatherer ancestry in both Germany and Spain ~1,000-2,000 years later. In eastern Europe, the hunter-gatherers of Russia >7,000 years ago were distinct from those of the west, having an increased affinity to a ~24,000 year old individual from Siberia, but this affinity was reduced by ~5,000 years ago in the Yamnaya steppe pastoralists because of admixture with a population of Near Eastern ancestry. Western and Eastern Europe collided ~4,500 years ago with the appearance of the Corded Ware people in Central Europe, who derived at least two thirds of their ancestry from an eastern population closely related to the Yamnaya. The evidence for mass migration into Europe thousands of years after the arrival of agriculture, in combination with linguistic and archaeological data, makes a compelling case for the steppe as a proximate source for the spread of Indo-European languages into Europe.
This is broadly the same data which Iosif Lazaridis presented at ASHG 2014. So this itself is not new. But what I would like to draw your attention to are two posts over at Eurogenes, Ancient DNA points to the Eurasian steppe as a proximate source for Indo-European migrations into Europe, and Yamnaya genomes are a 50/50 mix of eastern Euro foragers and something else ANE-rich. Nick Patterson actually weighed in over in the comment thread for the first post. A comment in the second post was especially amusing:
Over 400 comments on an abstract? You may need to start a forum when the actual paper is released, David.
Yes, there were over 400 comments on the first post. It shows you how passionate people get about this issue. Some of the associations within this field are of a racialist nature. The Journal of Indo-European Studies was founded by Roger Pearson, though today it is edited by the respectable J. P. Mallory. This is not to say that all of those enthusiastic about this topic are quite so “out there,” but it’s quite emotional.
Until the paper itself comes out I suggest readers bone up on the archaeology, because there’s a wealth of that out there already. From what I recall the Samara samples were form David Anthony, and his The Horse, the Wheel, and Language: How Bronze-Age Riders from the Eurasian Steppes Shaped the Modern World is basically required reading in my opinion if you are interested in this issue. Also, Mallory’s older In Search of Indo-Europeans is probably worth reading as well. We live in interesting times indeed!