HYDERABAD - Two primitive tribes in India's Andaman and Nicobar islands are believed to be direct descendants of the first humans who migrated from Africa at least 50,000 years ago, according to a study by Indian biologists.

A team of biologists at the Centre for Cellular and Molecular Biology in the southern Indian city of Hyderabad studied the DNA of 10 Onge and Great Andamanese people in the Indian Ocean archipelago who lived for tens of thousands of years in "genetic isolation" from other human contact.

The findings suggest the tribes are descended from the "oldest population of the world and were among the first batch of modern humans to migrate from Africa," said director of the centre, professor Lalji Singh.

The tribals have similar physical features to Africans and their DNA suggests that they have close links with Africa.

Mitochondrial DNA, which is passed maternally and found in every human cell, can be traced to a single female ancestor who lived about 150,000 to 200,000 years ago. It is believed the descendants of this "Eve" that all humans claim as their ancestor began migrating out of Africa in batches some 70,000 years ago.

The tribals' DNA is extremely close to the so-called African root gene of the single female ancestor, Singh said this week.

This made it likely that they migrated from Africa via a sea route 50,000 to 70,000 years ago and have lived "in genetic isolation" since in the Andaman Islands, said Singh. "These islanders could hold the key to the mystery of our origins. They are windows to look into the past and hence need to be preserved," Singh said.

The two other "Stone Age" tribes living in the islands - the Jarawas and the Sentinelese - were not studied because they are resistant to contact with outsiders, the scientists said.

The Indian government has discouraged outside contact with the tribals in an effort to preserve their traditions and protect them from falling victim to illnesses to which they might have no resistance.

The Nicabarese, another tribal group in the islands who were tested, showed they had a closer DNA affinity with people from Asia, suggesting a more recent arrival from the east in the past 18,000 years, Singh said.

There were fears some of the tribes living in the chain of islands might have been wiped out in the devastating tsunamis of December 26 that were triggered by a powerful underground earthquake nearby off the coast of Indonesia.

But the four Stone Age tribes - the 99-member Onge, 250 Sentinelese, the 39 almost extinct Andamanese and 350 Jarawas - have been accounted for in a post-tsunami headcount, tribal and government officials say.

There were many casualties, however, among the far more numerous Nicobarese tribals who are farmers and live along the coast. Some 1,899 people died in the tsunamis that hit the islands and some 5,554 people are listed as missing, according to government figures.

Source: Suntimes.co.za/AFP