Thursday, 17 February 2005

The Sentineli

This one's an article I promised back in January.

The recent massive earthquake in the Indian Ocean - now thought to have registered 9.3 on the open-ended richter scale - briefly brought a very isolated people into the limelight.

The people are the Sentineli, who voluntarily cut themselves off from the mainstream of humanity a long time ago. Most likely about 40,000 years ago, in fact.
From :
They are the quintessential Andamanese: to this day they live their primitive but comfortable and unhurried lives in complete isolation on a small island, they are hostile to all outsiders and they do not wish to change this state of affairs. Violence is the traditional way to ensure the undisturbed enjoyment of their way of life: even today, give the chance, they would kill strangers outright and they still hide from landing parties that look too strong to fight.
The island and its inhabitants have enjoyed a peculiarly charmed existence. Apart from a few brief visits during their 90-year rule, the British took very little interest in the island and for decades at a time seemed to forget its existence altogether. The Japanese were not long enough in the Andamans to meddle, especially since the island had no strategic importance. The Indians, too, took some years before noticing their forgotten island. The first official census after independence 1949 in 1951 failed to mention the Sentineli altogether.
Their charmed existence continues: the earthquake significantly enlarged their rather crowded island - it was on the landmass that rose rather than fell - and the sea turtles are coming back.

The Sentineli are Negritos - or, in somewhat un-PC terms, Pygmies. Dark skinned, curley haired, and short. Except that these people are tall pygmies. Again, from :
Even if we take the higest estimate of 500, how do they manage without all sorts of inbreeeding problems? And manage they do! Observations from off-shore Indian boat throwing gift coconuts into the water for the Sentineli to pick up have revealed them to be an extremely healthy, alert, wide-awake and cheerful people. They just do not like visitors. Quite a number of children have also been observed on such occasions and their average body size seems to be so tall ("seems to" because nobody has yet been close enough to lay a measuring tape on a Sentineli or stand next to one for comparison) that "pygmy" is probably a mis-nomer in their case. They all seem extremely healthy indeed.
[A Geneticist comments] Human evolution is fascinating and nothing that you say is a simple question of medical genetics. On the other hand, it is well known that reduction in genetic diversity (for example in the Pacific) led to a reduction in immunity against certain infectious diseases, and in the increased prevalence of diseases such as diabetes. It is well known, that the Polynesians went through a very tough genetic bottleneck, possibly stricter than the Sentineli. But the numbers recovered after their initial bottleneck and they were able to settle the whole of the Pacific.
The Sentineli are particularly enigmatic. We know a bit more about the other Andamanese islanders, and they are a peculiar bunch in their own right.
Inhabitants of the Andaman Islands, a remote archipelago east of India, are direct descendants of the first modern humans to have inhabited Asia, geneticists conclude in a new study.

But the islanders lack a distinctive genetic feature found among Australian aborigines, another early group to leave Africa, suggesting they were part of a separate exodus.

The Andaman Islanders are "arguably the most enigmatic people on our planet," a team of geneticists led by Dr. Erika Hagelberg of the University of Oslo write in the journal Current Biology.

Their physical features - short stature, dark skin, peppercorn hair and large buttocks - are characteristic of African Pygmies. "They look like they belong in Africa, but here they are sitting in this island chain in the middle of the Indian Ocean," said Dr. Peter Underhill of Stanford University, a co-author of the new report.

Adding to the puzzle is that their language, according to Joseph Greenberg, who, before his death in 2001, classified the world's languages, belongs to a family that includes those of Tasmania, Papua New Guinea and Melanesia.
Examination of DNA also reveals an interesting (pre)History :
Genetic analysis of mitochondrial DNA, a genetic element passed down only through women, shows that the Onge and Jarawa people belong to a lineage, known as M, that is common throughout Asia, the geneticists say. This establishes them as Asians, not Africans, among whom a different mitochondrial lineage, called L, is dominant.

The geneticists then looked at the Y chromosome, which is passed down only through men and often gives a more detailed picture of genetic history than the mitochondrial DNA. The Onge and Jarawa men turned out to carry a special change or mutation in the DNA of their Y chromosome that is thought to be indicative of the Paleolithic population of Asia, the hunters and gatherers who preceded the first human settlements.

The mutation, known as Marker 174, occurs among ethnic groups at the periphery of Asia who avoided being swamped by the populations that spread after the agricultural revolution that occurred about 8,000 years ago. It is found in many Japanese, in the Tibetans of the Himalayas and among isolated people of Southeast Asia, like the Hmong.

The discovery of Marker 174 among the Andamanese suggests that they too are part of this relict Paleolithic population, descended from the first modern humans to leave Africa.

Dr. Underhill, an expert on the genetic history of the Y chromosome, said the Paleolithic population of Asia might well have looked as African as the Onge and Jarawa do now, and that people with the appearance of present-day Asians might have emerged only later. It is also possible, he said, that their resemblance to African Pygmies is a human adaptation to living in forests that the two populations developed independently.

A finding of particular interest is that the Andamanese do not carry another Y chromosome signature, known as Marker RPS4Y, that is common among Australian aborigines.

This suggests that there were at least two separate emigrations of modern humans from Africa, Dr. Underhill said. Both probably left northeast Africa by boat 40,000 or 50,000 years ago and pushed slowly along the coastlines of the Arabian Peninsula and India. No archaeological record of these epic journeys has been found, perhaps because the world's oceans were 120 meters lower during the last ice age and the evidence of early human passage is under water.

One group of emigrants that acquired the Marker 174 mutation reached Southeast Asia, including the Andaman islands, and then moved inland and north to Japan, in Dr. Underhill's reconstruction. A second group, carrying the Marker RPS4Y, took a different fork in Southeast Asia, continuing south toward Australia.
Other pieces of the puzzle can be found in a previous article, and over at Dissecting Leftism (of all places).

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