linguistic:voice_change
Armenian hypothesis

David Reich (2018), noting the presence of some Indo-European languages (such as Hittite) in parts of ancient Anatolia, argues that "the most likely location of the population that first spoke an Indo-European language was south of the Caucasus Mountains, perhaps in present-day Iran or Armenia, because ancient DNA from people who lived there matches what we would expect for a source population both for the Yamnaya and for ancient Anatolians." Yet, Reich also notes that "...the evidence here is circumstantial as no ancient DNA from the Hittites themselves has yet been published." Kristian Kristiansen, in an interview with Der Spiegel in May 2018, stated that the Yamnaya culture may have had a predecessor at the Caucasus, where "proto-proto-Indo-European" was spoken.

Recent DNA-research has led to renewed suggestions of a Caucasian homeland for the 'proto-Indo-Europeans'. According to Kroonen et al. (2018) and Damgaard et al. (2018), ancient Anatolia "show no indication of a large-scale intrusion of a steppe population." They further note that this lends support to the Indo-Hittite hypothesis, according to which both proto-Anatolian and proto-Indo-European split-off from a common mother language "no later than the 4th millennium BCE." Haak et al. (2015) states that "the Armenian plateau hypothesis gains in plausibility" since the Yamnaya partly descended from a Near Eastern population, which resembles present-day Armenians."

Wang et al. (2018) note that the Caucasus served as a corridor for gene flow between the steppe and cultures south of the Caucasus during the Eneolithic and the Bronze Age, stating that this "opens up the possibility of a homeland of PIE south of the Caucasus." However, Wang et al. also comment that the most recent genetic evidence supports an expansion of proto-Indo-Europeans through the steppe, noting: "but the latest ancient DNA results from South Asia also lend weight to a spread of Indo-European languages "via the steppe belt. The spread of some or all of the proto-Indo-European branches would have been possible via the North Caucasus and Pontic region and from there, along with pastoralist expansions, to the heart of Europe. This scenario finds support from the well attested and now widely documented ' steppe ancestry ' in European populations, the postulate of increasingly patrilinear societies in the wake of these expansions (exemplified by R1a/R1b), as attested in the latest study on the Bell Beaker phenomenon."

David W. Anthony in a 2019 analysis, criticizes the "southern" or "Armenian" hypothesis (addressing Reich, Kristiansen, and Wang). Among his reasons being: that the Yamnaya lack evidence of genetic influence from the Bronze Age or late neolithic Caucasus (deriving instead from an earlier mixture of Eastern European hunter-gatherers and Caucasus hunter-gatherers) and have paternal lineages that seem to derive from the hunter-gatherers of the Eastern European Steppe rather than the Caucasus, as well as a scarcity in the Yamnaya of the Anatolian Farmer admixture that had become common and substantial in the Caucasus around 5,000 BC. Anthony instead suggests a genetic and linguistic origin of proto-Indo-Europeans (the Yamnaya) in the Eastern European steppe north of the Caucasus, from a mixture of these two groups (EHG and CHG). He suggests that the roots of Proto-Indo-European ("archaic" or proto-proto-Indo-European) were in the steppe rather than the south and that PIE formed mainly from a base of languages spoken by Eastern European hunter-gathers with some influences from languages of Caucasus hunter-gatherers.