There is very strong evidence, both from ancient samples and the distribution of living descendants, that the ancestor of all J-Y12379 who lived 8900 BC was living in the Caucasus.
The center of diversity of this mesolithic hunter-gatherer's sons' lineages appears to be the valley between the Greater and Lesser Caucasus range around Imereti. Additionally, the only ancient sample yet found comes from Kotias Klde cave within this region.
It is interesting to note that this subclade has little diversity in Kartli or Kacheti, where agriculture was subsequently introduced by the Shulaveri-Shomu culture in 6000 BC. Y12379 may once have been more widespread in these areas prior to the intrusion of this culture with ties to Mesopotamia.
The single Kakhetian sample YF02885 has TMRCA of 3400 BC with sibling Ossetian-Trabizond and Chechen lineages. This fits the pattern of the expansion of the Kura-Araxes pastoralist culture which is known from archaeology to have developed in the south Caucasus. If these lineages were spread by the Kura-Araxes culture then Y16464 either came from the core Kura Araxes zone or nearby region that adopted the culture.
Besarion Gugushvili has constructed an informative timeline showing subclade diversification dates alongside important geological events and cultural horizons.