The Insight is back with a 2-hour episode. If you unsubscribed due to a lack of new content, please resubscribe. Spencer and I devoted this episode to a “decade wrap-up,” so we had a lot to talk about (OK, ten general things to talk about, as we did a countdown), but there are already episodes in the queue on demographic transition, Levantine and Papuan genomics, and natural selection in the Americas, that will be dropping in early 2020.
Due to the constraint of time, we couldn’t really explore in full depth something that has been on our minds for a while: the likely seminal role of Southeast Asia, and Sundaland in particular, in the (re)settlement of Eurasia. Spencer has been telling me for years that Y chromosome researchers (e.g., Michael Hammer) have been noting that Southeast Asia, in particular, seems to be harbor the ancestral lineages for venerable branches such as R. These seem to derive from mutations in this area. For example, one can argue for a scenario where the ancestry of R & Q percolates up to Siberia, and shifts west, where R1 emerges among the “Ancient North Eurasians”, and eventually R1b and R1a diffuse across western and southern Eurasia. Today, R1a in Southeast Asia is an indication of migration from South Asia, closing the circle.
About ten years ago maps like the one to the right were all the rage. They are focused on uniparental haplogroups. The phylogenies are easily simply overlaid upon a map to trace out migrations. Implicit is the ‘serial bottleneck’ out of Africa framework.
But what if we have something seriously wrong? We now know there was lots of reticulation. Gene flow across populations. And it wasn’t unidirectional. Additionally, there is the weird fact that across the Middle East there seems to have a population now termed “Basal Eurasian” which split off from other non-Africans earlier, and probably had no Neanderthal ancestry at all. In contrast, Pleistocene Europeans, East Eurasians, the people of the New World and Oceanians, form a lineage.
So here is a hypothesis that I have minimal confidence in, but is not crazy as such
– “Basal Eurasians” are the primal population of the Near East
– “Eastern non-Africans” mix with Neanderthals on the way into southern and southeast Asia.
– One group of “Eastern non-Africans” moves into Oceania. Another group continues northward and eventually percolates back into the center of Eurasia, and gives rise to “West Eurasians.”
– This backflow population eventually mix with “Basal Eurasians” in the Near East.
The extremely ancient genomes from Europe, Siberia, and China are very strange in the results they present. Though the west vs. east bifurcation is evident, it looks have to occurred not much earlier than 40,000 years ago. The Goyet sample’s strange affinity to East Eurasians, as well as the fact that the first modern Europeans and Siberians seem to be not particularly more closely related to modern West and East Eurasians, also makes more sense.