I've now had the chance to read and digest the following two papers in Science about the origin of Indo-European languages: Language trees with sampled ancestors support a hybrid model for the origin of Indo-European languages, Heggarty et al. The genetic history of the Southern Arc: A bridge between West Asia and Europe, Lazaridis, Alpaslan-Roodenberg et al. The Heggarty et al. paper is pure| Eurogenes Blog
In their recent paper, titled Early contact between late farming and pastoralist societies in southeastern Europe, Penske et al. make the following claim: By contrast, Yamnaya Caucasus individuals from the southern steppe can be modelled as a two-way model of around 76% Steppe Eneolithic and 26% Caucasus Eneolithic/Maykop, confirming the findings of Lazaridis and colleagues 47. This two-way mix| Eurogenes Blog