Quote Originally Posted by Saetrus View Post
Wang et. al:

Reply: We’re afraid that this might be a misunderstanding. There is indeed very limited gene flow between the Caucasus and the steppe groups (apart from the examples highlighted). However, we have based our PIE-related speculations on the observation that the CHG/Iranian (green) ancestry component is increasing already during the Eneolithic north of the Caucasus. This led us to propose that this might be the actual ‘tracer dye’ of an early PIE spread, which could then also accommodate the spread of PIE south of the mountain range where this ancestry component also rises in frequency resulting in a relatively homogenised dual ancestry (Anatolian + Iranian farming-related ancestry) in Chalcolithic times (see also brown arrow in Figure 2).
Problems are, though, that: CHG was already in very high proportion in the steppes as early as 4300/4200 B.C, and it only increased marginally after that, slowly accumulating an increase (that might have been an internal affair of the steppes, anyways, with more CHG-rich people prevailing over less admixed ones); and the Y-DNA makeup of the Chalcolithic and Early Bronze Age steppe does not fit that of any Caucasian population of the same period, therefore we will have to assume the language transfer involved a minor migration with tiny impact in the male lineages. A language transfer without profound sociocultural shift/rupture, without much admixture (especially in the male lineage). Possible, but not likely, particularly in a time before organized empires, writing, sophisticated political and bureaucratic apparatus for far and wide territories, and so on. PIE is a Chalcolithic language, so if it as already being spoken and evolving in the steppes by the early Chalcolithic it is hard to believe it did not start to split there, and not elsewhere, even if the language family it belonged to had come from the Caucasus.