The people of the Andaman Islands are not genetic fossils

So this is in the news, Police: American adventurer John Allen Chau killed by isolated Sentinelese tribe on Indian island. There is some talk about whether the guy was a Christian missionary or not, but that’s not really too relevant. Whether he believes in evolution or not (he was a graduate of a very conservative Christian college), he definitely won a Darwin award before he expired.

North Sentinel is totally isolated, and the people who live there, the Sentinelese, are out of contact with the rest of the world. They are hostile to the outside world. And this is probably why the Sentinelese are still around, as the outside world does not have a good track record with hunter-gatherers. The Andamanese as a whole had a reputation for being very hostile to outsiders, as traders knew not to stop too long for water.

Because the Sentinelese are back in the news, lots of stuff is being said about them in terms of their ancestry.

First, they are not that genetically unique. A recent paper on the genetics of Southeast Asia using ancient samples makes their affinities clear.  The Onge, an Andamanese tribe, are positioned close to the two ancient samples from Laos and Malaysia. They emerge out of the same milieu as Paleolithic Southeast Asians (whose  Hoabinhian culture persisted deep into the Holocene).

The Andamanese themselves are probably from mainland Southeast Asia. The gap between the islands and the mainland was smaller ~20,000 years ago when the sea levels were lower. They could have come up from the south or the north.

Second, they are not the most “ancient” people. That doesn’t make any sense. We are all people who are equally ancient. We all descend by and large outside of Africa from a migratory wave that expanded ~60,000 years ago. Andamanese, Chinese, and Europeans. What is “ancient” about them is that they are hunter-gatherers who have continued to practice that mode of production down to the present. But that’s a matter of culture and not genetics.

Third, in alignment with the above two points, they are not uniquely and distinctly isolated from all other human populations. They are not descendants of an early wave out of Africa preserved on these islands. They are not distinct from all other non-Africans. Rather, they seem to be closer to the peoples of Oceania, Papuans, and Australian Aboriginals, than Northeast Asians. And closer to Northeast Asians than they are to West Eurasians. The latest evidence is that the Andamanese were part of a broader diversification of lineages ~40-50,000 years ago to the east of India that gave rise to the peoples of the western Pacific Rim. Within this broader set of groups, some form a distinct clade that is not with Northeast Asians (often these are like “Australasian”).

Finally, the census size for the Sentinelese is in the range of 100 individuals. This seems on the edge of viability over the long term.

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7 thoughts on “The people of the Andaman Islands are not genetic fossils

  1. They may not be “genetic fossils” but they have been isolated from almost all of the rest of humanity since before the Neolithic Revolution, something that can only also be said for some hunter-gatherer tribes deep in the Amazon jungle and some Papuan tribes deep in the interior of that island. There are very few mostly “uncontacted” people left in the world and they are among them.

    While we probably know almost everything useful about them that we ever will genetically (and could fill in any important gaps with one or two samples), and have some sense of their material culture and attitude towards outsiders, their language, religious ideas, and understanding of their environment are very valuable “cultural fossils” which are also, unfortunately, very hard to study without irrevocably damaging these distinct cultural features.

    It is been hypothesized that their language may be part of a mostly extinct language family shared with one or two other isolates in India and island Southeast Asia, that Greenberg called the Indo-Pacific family, that might also include the Australian aboriginal languages. Their language could be a critical clue to piecing this together in an effort to understand the deep roots of the human presence in Asia that has largely been swept away by later farmers and herders and fishermen. Their language could also be a critical data point regarding theories of how languages evolve in isolated populations over long periods of time.

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  2. Yes, they may not be unique genetically, but they have been isolated for tens of thousands (nearly 30,000?) of years with no intermixing with outside groups. I feel that is quite interesting.

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  3. Interestingly the andamanese have y haplogroup D mostly. If that is the case with the sentinelese too their isolation may be only 16000 years. In case the sentinelese have y haplogroup C then probably diverged 40000 years ago.

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  4. The relationship of the Hoabinhian groups and Onge is a great subject. First, I agree basically with the post and that’s what the evidence shows us.

    In more detail, though, there’s a bit more we can sign that they’re not exactly a clade together to all Asian populations.

    From the prehistoric peopling of Southeast Asia: We also find a distinctive relationship between the group 1 samples and the Ikawazu Jōmon of Japan (IK002). Outgroup f3 statistics (11, 16) show that group 1 shares the most genetic drift with all ancient mainland samples and Jōmon (fig. S12 and table S4). All other ancient genomes share more drift with present-day East Asian and Southeast Asian populations than with Jōmon (figs. S13 to S19 and tables S4 to S11).

    This is apparent in the fastNGSadmix analysis when assuming six ancestral components (K = 6) (fig. S11), where the Jōmon sample contains East Asian components and components found in group 1. To detect populations with genetic affinities to Jōmon, relative to present-day Japanese, we computed D statistics of the form D(Japanese, Jōmon; X, Mbuti), setting X to be different presentday and ancient Southeast Asian individuals (table S22). The strongest signal is seen when X = Ma911 and La368 (group 1 individuals), showing a marginally nonsignificant affinity to Jōmon (11). This signal is not observed with X = Papuans or Önge, suggesting that the Jōmon and Hòabìnhians may share group 1 ancestry (11). (e.g. East Asians and Jomon both relate to Onge and Papuans the same, but differently to Hoabinhians).

    In the trees in that paper, the Hoabinhians also have very little additional shared drift with Onge after their separation of Onge+Hoabinhian from the main ancestry in East Asians (which itself happens after the separation of the pre-Onge+Hoabinhian+main_East_Asian from Papuan). The Hoabinhian and Onge are closest, but the Hoabinhian are not really a whole lot closer than the majority ancestry in East Asians (rest is Tianyuan related minority). I’d guess they’re together on that PCA on the post above because they’re both in a similar position relative to sharing the East Asian specific drift that dominates, but they don’t actually share a lot with each other.

    I don’t think any of this is incompatible with an approx 20000 YBP migration to the Andamans though.

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  5. Looking at “prehistoric peopling of Southeast Asia” (Fig. S
    12), suggest that Group 1 (Hoabinhian/Onge like) share more drift with East Asians(Including Japanese) than South Asians. This is a bit counter intuitive since South Eurasian type ancestry tops out at 80% in South Asian and 20% in East Asians respectively. Can someone give a good scientific explanation for this pattern so that it makes sense.

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