Sentinelese – Gene Expression

The sad story of John Allen Chau, the young self-styled missionary who was killed on North Sentinel Island, has some really strange elements that are coming to the surface. The New York Times has published a piece which reports on extracts of a letter he wrote to his parents describing his motivations and observations when it came to proselytizing among the Sentinelese.

The people Mr. Chau chose for his mission are among the most impenetrable communities in the world, known for their intense hostility to outsiders. They have killed or tried to kill many outsiders who attempted to step on their rugged island 700 miles off India’s mainland, where they are one of the last undiluted hunter and gatherer societies.
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The man yelled, and Mr. Chau tried to respond, singing some worship songs and yelling back something in Xhosa, a language he apparently knew a few words of from when he coached soccer in South Africa a few years ago.
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In one passage, he asked God if North Sentinel was “Satan’s last stronghold.” In another: “What makes them become this defensive and hostile?”

The article mentions that “Anthropologists say the islanders’ ancestors possibly migrated from Africa more than a thousand years ago.” This really doesn’t make any sense, but it jumped out at me because of the weird fact that Chau tried to speak to them in Xhosa, a Bantu language with influences from Khoesan dialects. Perhaps the reason he did this inexplicable thing is he’s read too much the pap that the people of North Sentinel are some pristine population descended from early Africans?

A more interesting aspect of the article is the questioning of why these last isolated island hunter-gatherers are so hostile. The fact is if they weren’t so hostile, they would almost certainly be extinct by now. The record of hunter-gatherer populations interacting with agriculturalists is one of absorption, assimilation, extermination or subordination.

The hostility of the peoples of the Andaman Islanders to outsiders has long been attested:

Situated in the bay of Bengal, the Andaman islands have been known to outsiders since ancient times. Andaman islanders respond with intense hostility at any attempt of outside contact, hurling arrows and stones at any unlucky visitor approaching their shores.
Early Arab and Persian documents report that Andaman islands were inhabited by cannibals – an exaggeration probably originating from the ferocity of attacks with which these travelers were greeted. Later Indian and European explorers steered clear off these islands to avoid the hostile inhabitants.

And this is why the Andaman Islanders remained relatively distinct ethnographically down to the early modern period. The Negrito people of Malaysia and the Philippines no longer speak their ancestral languages, while the Andamanese did until recently.

This incident reminds me of a dark passage from Jared Diamond’s The Third Chimpanzee. Contrary to the optimism of Carl Sagan, Diamond asserted that if there were aliens out there, we should work very hard not to have them know we exist. His reasoning was that less culturally advanced peoples never had a good interaction more culturally advanced people.

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.