We’ve been waiting for ancient DNA to answer some questions about eastern Eurasia for a while. I always thought Qiaomei Fu would spearhead it, but it doesn’t seem like it worked out that way. That’s because she’s not on a new preprint, The Genomic Formation of Human Populations in East Asia, which fills in a lot of gaps and confusing aspects of what has been reported from fragments of publications that came before (e.g., this clarifies a lot of things with Japan, see below). Since there has already been ancient DNA work on eastern Siberia and Southeast Asia, this is really focusing on the area in and around what is today the Peoples’ Republic of China. The first author has an affiliation with a university in Fujian, a province in southeast China.
Much of the analysis can be understood as organized around language families, and the demographics associated with them. In this way, it goes back to L. L. Cavalli-Sforza’s correlations between gene trees and language trees, as well as his later work on the agricultural Diasporas.
First, there isn’t something radically surprising here in their results. As I suggest above, the mass of ancient DNA in the preprint and model-building just snap together a lot of what you can see in other work, some going back decades.
Let’s start with the “Onge-like/related ancestry. ”
Below you see the strange pattern of Y chromosomal haplogroup D. It’s common in Tibet, Japan, and among the Andamanese.
In the preprint, the authors argue that there is a deep division among East Eurasian populations, going back further than 40,000 years, between a set of populations descended from groups related to Tianyuan man, and populations with affinities to the indigenous peoples of southeast Eurasia and Australia (“Ancestral Ancestral South Indians”, AASI, the Onge, the Negritos of Malaysia and the Phillippines, and Oceanians). Modern populations in East Asia can be thought of as a mix between these two groups, in various pulses and waves. The finding that some peoples in the Amazon had “Australo-Melanesian” affinity is very strange, but note that there’s no guarantee that the geographic distribution of the two clades was so skewed in the past in a north-south manner.
The Onge-related ancestry is apparently found as the deepest layer in the Tibetan plateau and contributes 45% of the ancestry to the Jomon of Japan. Among ancient proto-Austronesian peoples of Taiwan, it contributed 14% of the ancestry. Earlier work on Southeast Asia indicated that even before the expansion of Austro-Asiatic farmers out of southern China they mixed with a basal East Eurasian lineage related to the Onge.
Chinese annals record the presence of dark-skinned peoples in Yunnan nearly into historical periods. These could very well be legends or rumors, or, they could be the last relic populations that had not been fully absorbed into the Tianyuan-descended farmer expansion.
Moving more recently into the past, the preprint findings that of the Tianyuan descended populations in East Asia there is a northern and southern grouping. The northern grouping has been discussed before, it is the classic Amur-river valley population. It turns out that a sample from 5,000 years ago in northern Shaanxi, just to the north of the hearth of classical Chinese civilization in Henan, resembles these Amur-river valley populations. Though the authors don’t have samples from southern China, or even the Yangzi, they use modern samples from southern Chinese peoples, as well as ancient samples from Taiwan, to infer that it is likely that the Yangzi river valley was inhabited by a somewhat different group during prehistory than the modern Han Chinese.
In the preprint, the argument is made that Austronesian, Tai-Kadai, and Austro-Asiatic all emerged out of the Yangzi valley and its rice cultures. As noted above, other papers have already outlined the peopling of Southeast Asia using ancient DNA, so I will ignore that. But, note that for Austro-Asiatic populations, ~1/3 of the ancestry is Onge-related. Some of this was mixed in while in southern China, but some of it probably accrued later on in Southeast Asia.
Modern Austro-Asiatic populations can then be thought of as a compound of Tianyuan, and various Onge-related groups.
The modern Han Chinese seem to be a fusion of the two idealized ancestral populations described above:
No great surprise. The Han have more of an affinity for northern East Asian populations than southern ones, with those in the south having more of an affinity for southerners than those in the north. A simple model might be expansion out of Shaanxi and Henan across a landscape with many southern agriculturalists. But that makes us ask: why is there “southern” ancestry among many northern Han today?
I think the explanation is that the expansion of the Han was characterized by reversals, as well as panmixia induced by political unification. Let me outline this explicitly:
– proto-Han identity is focused around Henan and Shaanxi between 2000 BC and 300 AD. As this culture expanded into the margins of the Yangzi and into Sichuan, it absorbed “southern” ancestry (as well as elements of culture).
– During the Han dynasty, 200 BC to 200 AD, the Chinese colonized portions of the far south, and aspects of panmixia occurred, as individuals moved across China north to south and vice versa.
– The fall of the Han dynasty after 200 AD saw North China come to be ruled by “barbarians”, usually of Turkic provenance. South China maintained classical Han culture and political forms without external influence. Many northern families moved south between 200 AD and 600 AD. Many barbarians “became” Han, and mixed into the population. I believe this is when the 2-4% “West Eurasian” started to become prevalent in the north. This western ancestry was mediated through Turkic groups who were predominantly Siberian or Amur-river valley in ancestry.
R1a1a is found in North China, so I believe that this ancestry is from Iranian groups absorbed into the Turco-Mongol populations.
– The reemergence of an integrated China after 600 AD sees the shift of the center of gravity of the Chinese economy move to the center and south, in particular the Yangzi river valley (often attributed to “Champa rice”). Movement northward of South China repopulated areas that had been uninhabited moves “southern” ancestry north. Most of the population growth in the south is endogeneous, and not due to migration. There is very little to no West Eurasian ancestry in the south, as one might expect if large numbers of North Chinese moved south (the exception are probably the Hakka, who are known to be Northerners).
– There are still ethnic minorities in the South. Over the past 1,000 years, they have slowly been Sinicized and assimilated in many areas, so the proportion of “southern” ancestry in places like Guangdong has increased in part through such processes.
The Japanese are not entirely surprising. Using a two-way model with Han or Korean vs. Jomon, the Japanese are about 85% the former and 15% the latter. The proportion is a bit higher for Korean. The reason is straightforward: the Yayoi rice farmers probably derived from the Korean peninsula. Even into the edge of history Japan and the Baekje kingdom of Korea had close relations.
The interesting thing about Japan is this is an area where agriculturalists nearly overwhelmed the indigenous population, albeit absorbing them. The Jomon culture is unique because it was a sedentary hunter-gatherer society that also used pottery extensively. Previously analysis of Jomon remains produced “strange” results. In this preprint the authors give a good explanation of why: the Jomon are an even mixture of a population descended from the Onge-related clade and another one that is closer to the Amur river valley Northeast Eurasian populations, who descend from Tianyun.
Basically the Ainu are a fusion of a Siberian group, and, a population that has affinities with those indigenous to Southeast Asia before the arrival of agriculturalists. Before genetics archaeologists and anthropologists argued about the Ainu affinities. Despite sometimes looking “European” early blood group analysis quickly established an eastern affinity, but morphology and culture suggested different connections to Siberia or Australia. The Australian Aboriginals descend from one of the Onge-related groups to a great extent, so the affinities are now intelligible.
Tibetans seem to be mixed between a small proportion of Onge-related, a larger proportion of an East Asian population descended from Tianyuan and closer to the Amur river valley groups than “southern” rice farmers, and finally a population similar to the Shaanxi Han. The latter mixed with the fusion of the first two ~3-4,000 years ago. This makes intelligible the “Sino-Tibetan” language family, whose validity I’m not clear on. But the linguistic affinity might date to this period.
It also resolves confusion about the emergence of Tibetans that arose around the hypoxia papers of that period.
This is the portion that is somewhat “controversial.” In Mongolia, they find that there was the arrival of an early western group, the post-Yamnaya Afanasievo, about 5,000 years ago. They flourished in and around the Altai. They are genetically almost exactly with the Yamnaya. Then, at some point in the Bronze Age, this group was totally replaced by another much more like the Sintashta-Andronovo. These groups were similar to the Yamnaya, but ~30% of their ancestry is like “European-farmers.” The conjecture you can make here is that there was reflux from Europe that came back onto the steppe. These were almost certainly Iranian. This second wave clearly contributed much of the western ancestry into Mongols, judging by the high fraction of R1a1a-Z93 in the Altai.
But, the more intriguing aspect is south and east in Xinjiang, overlapping the zone occupied by the Indo-European Tocharians, the populations remained similar to the Afanasievo, albeit mixing with East Eurasian groups over time. The implication then is that the authors have “pegged” a separation date from the Tocharian Indo-European branch from the others, about ~5,000 years ago. Aside from Anatolian (e.g., Hittite), Tocharian is often seen to be the most basal.
Later Xinjiang also saw the arrival of Iranians. The western and southern oases of Xijiniang were Iranian, while the northern and eastern ones were Tocharian.
(the authors cite David of Eurogenes, who disagrees with their interpretation)
They find that over time genetic distance between populations in East Asia declines over time. This is analogous to what happened in Western Eurasia.
This might be a generalized process, but I think there’s a specific thing driving this: the rise of the Chinese state-polity. Not only did the Han expand and absorb, but there was gene flow to neighboring groups. It is well known that Han Chinese have been moving into Vietnam, and assimilating, for 2,000 years. Similarly, many Han in the north have been known to “go barbarian.”