Some interesting stuff here from Allan R. Bomhard, especially in light of the ancient DNA we've seen recently from Late Neolithic/Early Bronze Age Europe.
ABSTRACT: There have been numerous attempts to find relatives of Proto-Indo-European, not the least of which is the Indo-Uralic Hypothesis. According to this hypothesis, Proto-Indo-European and Proto-Uralic are alleged to descend from a common ancestor. However, attempts to prove this hypothesis have run into numerous difficulties. One difficulty concerns the inability to econstruct the ancestral morphological system in detail, and another concerns the rather small shared vocabulary. This latter problem is further complicated by the fact that many scholars think in terms of borrowing rather than inheritance. Moreover, the lack of agreement in vocabulary affects the ability to establish viable sound correspondences and rules of combinability. This paper will attempt to show that these and other difficulties are caused, at least in large part, by the question of the origins of the Indo-European parent language. Evidence will be presented to demonstrate that Proto-Indo-European is the result of the imposition of a Eurasiatic language — to use Greenberg’s term — on a population speaking one or more primordial Northwest Caucasian languages.
Allan R. Bomhard, The Origins of Proto-Indo-European: The Caucasian Substrate Hypothesis. Paper to be presented at “The Precursors of Proto-Indo-European: the Indo-Hittite and Indo-Uralic Hypotheses”. Workshop to be held at the Leiden University Centre for Linguistics, Leiden, The Netherlands, 9—11 July 2015.
Support for linguistic macrofamilies from weighted sequence alignment
Modeling Yamnaya with qpAdm
Massive migration from the steppe is a source for Indo-European languages in Europe (Haak et al. 2015 preprint)