Luke
Harding in New Delhi
The Guardian
 | | Andaman
islands study says tribes from Africa may have come 60,000 years ago |
Stone
Age tribes living on the Andaman islands at the eastern edge of the Bay of Bengal
migrated from Africa far earlier than previously thought, according to a study
which says they may have been living in isolation from the rest of the world for
more than 60,000 years.
The study, based on genetic samples from the dwindling
Onge and Jarawa tribes on the islands, sheds new light on human evolution. It
suggests patterns of prehistoric migration are extremely complex and raises the
possibility that modern man emerged simultaneously on several continents.
The
four tribes on the lush archipelago of 200 islands, lying south of Burma but governed
by India, resemble African pygmies.
After the arrival of the British,
and more recently Indian settlers, their number has fallen to about 400.
Three
of the four tribes have come into contact with modern civilisation. The Onge,
who live on Little Andaman, have been resettled by the Indian government. The
Jarawa, who inhabit the main islands, emerged when a trunk road was built through
their forest land in 1989. Only 36 Great Andamanese survive. The rest were wiped
out in colonial times by modern disease.
But the war-like Sentinelese
of the tiny North Sentinel Island have fiercely resisted any contact with the
outside world.
An attempt to meet them in April 1974 ended when the Sentinelese
showered an approaching boat with arrows and butchered a pig left behind by scientists.
Lalji Singh, director of India's Centre for Cellular and Molecular Biology, said
yesterday: "The Sentinelese are the only pre-Neolithic tribe left in the world
where no contact has been made. You have to reach them by boat but it is risky
because you can't run away by boat. And you can't take other tribespeople to explain
to them because they speak an entirely different language."
This year,
Dr Singh gained permission to take DNA samples from 46 Onge men who now live in
a reserve, and blood samples from a handful of Jarawa. The results initially appeared
to support the established theory that the original islanders came from Africa
tens of thousands of years ago.
Analysis of the Y-chromosome revealed
an ancient genetic mutation characteristic of African races. The discovery suggested
the Onge migrated to the Andamans - probably by foot when sea levels were lower.
When the glaciers melted at the end of the last Ice Age, the Onge found themselves
cut off as a series of islands formed.
But when Dr Singh examined the
Jarawa samples, he found they were different. The distinctive insertion in Y-chromosome
was missing. This raised the possibility the Jarawa had migrated before the Onge
who arrived 50,000 to 60,000 years ago. Orthey had come from elsewhere.
"It
is a mystery," Dr Singh said. "We can't say whether the Jarawa migrated from Africa.
The results are very different from the Onge. And the Jarawa are not related to
any group on mainland India.
"If we could get some samples from the Sentinelese
that might help, but they are very hostile and the government does not allow you
to go there."
The findings appear to show that the Andaman tribes evolved
not only in profound isolation from the outside world but also from each other.
They also lend credence to the multi-regional theory of human evolution. It argues
humans evolved separately in different parts of the world.
"I tend to
believe humans didn't originate in one place," Dr Singh said. A study two years
ago by Dr Erika Hagelberg, a Cambridge scientist, had appeared to confirm the
African link. She analysed hair samples brought from the Andamans in 1907 by Alfred
Radcliffe-Brown, a British anthropologist, which had been stored in Cambridge
in dusty glass cabinets ever since.
Dr Hagelberg found that clusters of
DNA fragments from the hair were similar to those in African populations, especially
southern pygmies. Proponents of the Out of Africa theory believe the first humans
left Africa 100,000 years ago, reaching Asia 60,000 years ago. Later settlers
wiped out most tribes. But a few, marooned in isolated pockets such as the Andamans,
survived.
New Delhi has allowed Dr Singh to return next month to collect
more samples from the Jarawa, whose fragile environment is rapidly being wiped
out by logging and tourism. He and others believe their DNA may hold the key to
wiping out diseases such as malaria.
"These people have been able to survive
by natural selection without any interference from modern medicine for thousands
of years," he said. "Their genes are living proof of the survival of the fittest."
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