Asians and Pacific Islanders: The triangle

In our youth, we read with great excitement old books on anthropology obtained from a library with considerable difficulty. The excitement was primarily from learning about the osteology of extinct apes and monkeys, including the closest sister groups of Homo sapiens. Some of those books also had a collection of plates with pictures of stone tools and various extant peoples of the world, especially hunter-gatherers who still lead a relatively archaic mode of life. Those pages too fascinated us, and we spent many an afternoon turning through them wonder-struck by how many different morpho- and eco-types of Homo sapiens were around. Of those tribes, the Melanesian in particular caught our attention with their gripping displays of headhunting, cannibalism and prion neuropathology (there was still a debate about what prions were back then). The images of Fijian tribesmen and a collection of their braining clubs left a deep impression on us (Figure 1). We had a direct experience of the same when we visited a coethnic who had been driven out of Fiji during the attack on the Hindus by the former islanders. However, in his flight back to the subcontinent, he had brought along one of those clubs of the ancestors of his Fijian enemies. We wondered about how the Melanesians and Polynesians reached their distant outposts in the Pacific. We also wondered how these Indo-Pacific peoples might be related to the tribal Indians — it did not escape our attention that some of that ancestry was visibly present in the non-tribal Indians.


Figure 1. Fijian tribal warriors with a club photographed in the late 1800s.

Answers to many of those questions have come from the genomics of extant and prehistoric peoples over the past few years. In its present form, this note is by no means a survey of all that. It is just a very brief account comprised of a few observations sparked by recent discoveries. Unfortunately, due to magazine-fever many molecular paleoanthropology papers while presenting important specimens are poorly written and illustrated. Also, due to the competing groups involved, the speed with which new specimens are piling in, differences in interpretation, and the terminological issues, these works do not afford a synthetic picture of the history of the people under consideration. So, we have had to wade through these presentations, which might ignore each other, to summarize the below points of interest regarding the evolution of the Asians and Pacific Islanders. At the broad level, the ethnogenesis of the Eurasians and Pacific islanders can be summarized by this principal component analysis of the genomic variation of extinct and extant individuals (Figure 2). Some populations are colored distinctly against the gray background of the remaining individuals and labeled. The key prehistoric genomes are indicated by big stars and labeled in the legend.

AsiansFigure 2. A plot PC1 and PC2 showing various Eurasians and Pacific Islanders. LinearBKer: Linearbandkeramik (Early European Farmers: Neolithic); Gandhara: Ancient samples from Northwestern India (what is now TSP); Aus/Papuan: Australians (squares) and Papuans (triangles); Phil/Mal Ngrt.: Aeta, Agta, Jehai and Batak peoples (Philippines/Malaysian Negritos, brown triangles); Cam: Cambodians; Twn Ausn: Taiwanese Hanben site, likely early Austronesians; Karelia HG: Eastern hunter-gatherers from Karelia (Finland-Russia border zone); Iran.Cu: Copper Age people from Hajji Firuz site; Iran.Neo: Neolithic people from Ganj Dareh site; Geoksyur Neo/Cu: Turkmenistan Neolithic and Copper Age people.

One can see that a triangle of clines describes a major fraction of Eurasians and Pacific islanders. The first is the Indian cline extending from the Andamanese populations, like the Onge, Jarawa and Great Andamanese on one end and at the other end terminating in the Sintashta steppe culture that likely corresponds to the expanding Aryans. The Paniya tribe of Kerala and Karnataka represent one of the groups from the mainland that is closer to the Andamanese end of this cline. The second notable cline is the Australasian cline, with the Papuans and Australians on one end (close to the Andamanese) and the East Asians (Hans, among others) at the other end. In between lie the Negrito tribes of the Philippines and the Malay region (brown triangles), and the Austronesians who spread into the Indo-Pacific from Taiwan in a maritime expansion, ultimately reaching New Zealand and Rapa Nui (Easter Island) of the coast of Chile. The third notable cline completing the triangle is the North Eastern Eurasian-First American cline. The Bronze Age Okunevo from Southern Siberia, the North and South American native peoples (including the prehistoric Kennewick man from the Washington state of USA), Eskimos, and Mongols are seen lying on this cline. Based on the prehistoric samples we can summarize some key events in the ethnogenesis of the Asians and Pacific Islanders thusly:

1. Before \approx 50K, there was an unknown number of archaic Homo lineages throughout Asia all the way to the Pacific islands. Of these, the Denisovans were widespread. We have direct evidence for Denisovan admixture in Tibet, Mongolia (the Salkhit woman from 34KYA shows some Denisovan admixture), the Philippines and the Indo-Pacific islands. The ancestral Asian arrived in this landscape after splitting off from the lineage leading to the Western Eurasian in the west. Then the ancestral Asian split up into several far-ranging groups, probably by around 50KYA. These early Asian lineages included:
i. The Tianyuan-like Eastern group prototyped the Tianyuan man from the Tianyuan cave near Beijing, dating to \approx 41KYBP. A recent study posits that the Tianyuan man might have had up to 3% archaic Homo admixture from a Denisovan source. The Tianyuan-like clade was probably basal to the later East Asian clades, which eventually split up into Northeast Asian and Southeast Asian clades ancestral to modern East Asians.
ii Onge-Hòabìnhian group, once extending from at least the Andamans (Onge, Jarawa, Great Andamanese) through Laos, Vietnam and Malaysia. This group has been recently registered in the ancient specimens from Hòabìnhian hunter-gatherers from East Asia from at least 8000 YBP.
iii. An early-diverging sister group of the Onge-Hòabìnhian clade were the hunter-gatherers of the Indian subcontinent from whom tribal Indians on an average get most of their ancestry (e.g., See Paniya in Figure 2). The Onge-Paniya gap in Figure 2 represents this deep divergence between the Onge-like clade proper and their mainland Indian sister group. Varying fractions of this ancestry persist in non-tribal Indians with a mostly south to north gradient (“The Ancient Ancestral South Indians” (AASI) of the Reich group). Today, other than this Indian HG clade, the broader “Onge-like” clade includes the Philippines Negritos, Papuans and Australians (Note their proximity in Figure 2).
iv. The Tibetan hunter-gatherer-Jomon group, which once stretched over Asia from at least Nepal-Tibet to Japan. These people played an important role in the ethnogenesis of the modern Japanese. The old Jomon were first invaded by a Northeast Asian population from the Amur River region, leading to the Yayoi period around 3000 YBP. This was followed by the classical Koreanic-type East Asian invasion of Japan, marking the emergence of the historical Japanese at the beginning of the Kofun period. Pure representatives of this group are extinct now, but their Y-chromosome and some autosomal genome survives in Nepal, Tibet and Japan. It seems the 2800-year-old Chokopani man from the Mustang cave in Nepal had \approx 16% of this ancestry while a 3500-year-old Jomon Japanese individual shows about 44%.

2. The Onge-Hòabìnhian clade proper lack high Denisovan ancestry but their sister group, the Papuans and Australians, show evidence for at least two introgression events with Denisovans. The Philippines Negritos, too, had 1 or 2 Denisovan admixtures. Thus, greater Onge-like clade spreading from India to South East Asia encountered Denisovan races all the way from the Philippines to Sahul (the combined Pleistocene landmass of Papua+Australia) and annihilated them across the Indo-Pacific islands while mating with them on occasion. This raises the possibility that the dwarf Homo (e.g., Homo floresiensis and the Luzon Homo) on the Philippines and Flores were races of Denisovans. The North Asian and Central Asian Denisovans seemed to have had larger body size and a characteristic huge molar.

3. A sister group of the greater Onge-like clade group or alternatively a group branching close to the stem after the Tianyuan-like and Onge-like groups somehow reached America and contributed a small amount to the ancestry of some South Americans. While initially noted by Skoglund et al. in the Amazonian tribes like Surui and Karitiana, recent work by Brazilian researchers also recovered this ancestry on the South American Pacific coast. To date, this ancestry is missing in the North and Central Americans or their Beringian predecessors. This favors the model in which this Onge-like ancestry reached the Pacific coast of South America by sea (see below).

4. Recently, Carlhoff et al. reported the genome of a pre-Neolithic young forager woman from Leang Panninge, South Sulawesi dating to 7.2-7.3 KY from the `Toalean’ archaeological complex. This is the first genome from Wallacea, the Oceanic islands between the Sunda shelf of Indonesia and the Sahul landmass of the Pleistocene. She is modeled as having \approx 50% of Onge-Papuan-like ancestry related to that seen in Sahul peoples along with the Denisovan admixture seen in them. However, the best fit models also suggest a prehistoric East Asian ancestry of \approx 50%. The authors say this can be approximated by Qihe, a Southeast Asian Neolithic individual from \approx 8.4 KYA. This suggests that not just Onge-like groups but also the Southeast Asian clade expanded into the Pacific, mixing with the former. However, this type of \approx 50-50 Qihe-Onge-like mixture is no longer present in Sulawesi or its surroundings. They seemed to have been wiped out in turn by another Southeast Asian expansion, the Austronesian expansion from Taiwan in the past 4000 years.

5. Such a see-saw contest between representatives of the greater Onge-like clade and the Austronesians of Southeast Asian roots played out repeatedly over the Philippines and the Malay archipelago. This is supported by the Southeast Asian admixture seen in the various Negritos and the remarkable the ancient DNA results from Vanuatu. This cluster of about 80 remote islands in the South Pacific is populated by people speaking an Austronesian language but having most of the ancestry from a Papuan-like group. Like Papuans, several Vanuatu tribesmen wear phallic sheaths (koteka). However, the earliest genomes from these islands suggest that they were first occupied by the Austronesians. But they were soon joined by the Papuan-like group. These Papuan-like people seemed to have wiped out the Austronesians on several islands, but the latter seemed to have held out on some of the islands. These Austronesians then appear to have made a return to mix with the former and give rise to the extant Vanuatuans.

6. If the Austronesians expanded primarily via the maritime route to span a vast swath of the globe, another Southeast Asian group, the Austroasiatics, appears to have expanded mainly by land and probably by sea. These include the speakers of Vietnamese and Khmer in continental Southeast Asia, Aslian in peninsular Malaysia and Thailand, the Nicobarese in island India, Khasi in North East India and the Munda in Eastern and North Eastern India. These Austroasiatics seem to have expanded from the Mekong river basin as a group dependent on fisher and some neolithic farming for their subsistence. One group probably arrived in the Indian mainland around 3200 YBP, where they mixed with the original Indian hunter-gatherers to give rise to the Munda-speaking tribal groups like the Santhal (Figure 2). It is likely they also resorted to a maritime route to reach Nicobar relatively early on.

Finally, we shall make a few remarks regarding the implications of these findings for the modes of spread and various language groups. There is little evidence for any clear-cut relationships between the languages of the Andamanese, Papuans and Australians despite some claims to this effect by some of the long-rangers. Nor do they show relationships to Dravidian or whatever is reconstructible of the ancient Indian substrata. This is keeping with their split in the relatively ancient past when Denisovans were still around in the Indo-Pacific region and prolonged existence as hunter-gatherer tribes. The Austronesian and Austroasiatic languages are well-defined families like Indo-European and show the hallmarks of massive, relatively recent expansions. Linguistic investigations suggest that the languages of the Kra-Dai family (e.g., Thai) might be a sister group to the Austronesian languages. The genetic evidence is not inconsistent with this proposal. The Austronesians were the masters of maritime expansion — they probably reached their Taiwanese homeland after splitting off from mainland Kra-Dai speakers. From there, they returned to the Asian mainland and Malay peninsula (Cham in Vietnam and Malay) and spread both East and west. In the East, they first moved slowly, taking the Philippines and then around 3500 YBP covered most of the Malay Archipelago. Over the next 500 years, they took Melanesia and Western Micronesia. By around 1500 YBP, they had swung west to Madagascar off the coast of Africa. Over the next 700 years, they took every remaining Micronesian and Polynesian island all the way to Easter Island and Hawaii. The Southeast Asian admixture in pre-Austronesian Leang Panninge suggests that the Austronesians were not the first to venture into the Oceanic deep East. This is also hinted by the presence of the Onge-like ancestry in South America that likely reached there directly by sea via the Pacific coast. However, Austronesians certainly seem to have been the most successful. This raises the question of whether their boats were the critical factor that allowed the Papuan-like people to reach Vanuatu after the Austronesians got there first. This might also explain why the Austronesian language rather than genetics dominated in Vanuatu by functioning as the link language between the islands. Finally, this brings us to the recent work that has provided evidence for South American admixture from a Zenu-like South American tribe among the Polynesians, supporting the much-maligned contention of Thor Heyerdahl. Here again, it is peculiar that there is no evidence for a greater South American presence in Polynesia if they managed to reach some of the islands and transmit the sweet potato (Ipomea batatas). We suspect the initiative was with the maritime Polynesians who managed to reach the South American coast and bring back some admixture to their islands along with the sweet potato. Perhaps, as Heyerdahl speculated, this contact might have also contributed to some of the iconographic convergences that he noted, like on Easter Island.

Clear monophyletic language families like Austroasiatic and Austronesian are not seen as uniting China, the Korean Peninsula and Japan, though these East Asians are genetically very close. While Japonic and Koreanic have structural similarities, evidence for their monophyly as sister groups or as part of a larger Macro-Altaic assemblage is limited. This suggests that the Yayoi probably brought the Japonic languages to Japan. This might explain the more general structural similarities with North East Asian language families like Koreanic and Tungusic but the absence of a specific relationship. The Kofun, while contributing most of the genetics of the extant Japanese, did not bring the language itself. They instead probably rose up in the Yayoi background as an elite that adopted the Yayoi language while spreading Kofun genetics.

Thus, ancient DNA is making up for the absence of recorded history. Unfortunately, this revolution has not yet touched India. Imagine if we were to know something of Jorwe culture or Ash Mound peoples — they remain archaeological black boxes along with several other slices of Indian history.

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