CHG - pannous/hieros GitHub Wiki

The term "Caucasus hunter-gatherers" is a misnomer, because even before the time of Maykop the people surrounding the caucasus had adopted technology which originally came from Syria (Halaf, Hassuna) and from Iran, were no longer hunter-gatherers but firmly established neolithic or even chalcolithic tribes.

There were several waves, the neolithic wave contributing to deep layers of PIE: people similar to northern Caucasus and Iranian plateau cultures arrived before 6000 BCE in Pakistan and north-west India. The rather sparse elite wave of ⋍4200 BC left fewer genetic markers. Unadmixed CHG with connections to Iran reached the Volga at Khvalynsk in the 5th millennium and correlating with the arrival of agricultural settlements, cows and goats. Hunter-fisher camps that appeared on the Volga around 6200 BC might represent the vanguard of CHG which almost still deserves the name Hunter-Gatherers.

After entering the Pontic Steppes, the admixture with Eastern Hunter-Gatherers likewise continued and resulted in signature Western Steppe Herder(WSH) populations in the 5th to 4th millennium BC. The reunion between these races who separated ⋍45,000 ya was almost complete. CHG separated from the "Early Anatolian Farmers" (EAF) lineage later, at 25,000 years ago, during the Last Glacial Maximum. A reunion during the Kura Araxas culture was only partial.

So Yamnaya had two components of CHG: Unadmixed CHG with connections to Iran reaching the Volga in the 5th millennium and correlating with the arrival of agricultural settlements, cows and goats. Only later CHG admixed with Anatolian Farmers, likely via Tripolye (with signature elements of WHG). Anthony 2019

According to Narasimhan et al. (2019) Iranian farmer related people arrived before 6000 BCE in Pakistan and north-west India, before the advent of farming in northern India. They suggest the possibility that this "Iranian farmer–related ancestry [...] was [also] characteristic of northern Caucasus and Iranian plateau hunter-gatherers."[7]

Old Semitic layer in PIE and Caucasian languages:
Continued mixture of the Caucasians with Middle Eastern populations took place up to 25,000 years ago, when the coldest period in the last Ice Age started. Two individuals from Georgia dating 13.3kya and 9.7kya carried haplogroup J* and J2a.

The proto-Indo-Europeans, i.e. the Yamnaya people and the related cultures, seem to have been a mix from Eastern European Hunter-Gatherers (EHGs); and people related to the near east,[12] either Caucasus hunter-gatherers[2] or Iran Chalcolithic people, with a Caucasian hunter-gatherer component.[13][4] [note 2] Each of those two populations contributed about half the Yamnaya DNA.

Recent evidence shows that genetically the CHG cluster was the core of the PIE proto indo european phenomenon, because EHG ancestry is near absent from hittites and sardinians whereas EEF is absent from iranians. Compared to other surviving CHG languages with complex phonetics and consonant clusters, Indo european formed a radically simplified creole, presumably developed by mobile merchants to facilitate trade between northerners (EHG) westerners (EAF and maybe WHG) easterners and southerners (Semites, Sumerians, Drawidians).

Contradiction:
By the middle bronze age 2600BC individuals from the northern Aegean were considerably different: they shared half of their DNA with the Caspian Steppe

Caucasian Hunter-Gatherer (CHG) carried 36% ANE-derived admixture, while the rest of their ancestry is derived from the Dzudzuana cave individual dated ⋍26 kya, which lacked ANE-admixture.