Two tribes living on India's Andaman islands may be direct descendents of the earliest modern humans who moved out of Africa 70,000 years ago, scientists reported last week.
Scientists at the Centre for Cellular and Molecular Biology (CCMB) in the southern Indian city of Hyderabad said these two tribes could be the oldest surviving human stock in Asia, and their research may overturn the reigning theory on early human migration.
Most scientists believe that all populations today are descendants of modern humans who migrated out of East Africa about 70,000 years ago to replace early humans elsewhere.
According to the reigning theory, modern humans first migrated from Africa, north along the Nile River, across the Sinai Peninsula, into central Asia before moving east towards India.
"Our findings suggest they also traced a coastal route along east Africa and the Arabian Peninsula into South Asia," said Kumarasami Thangaraj, a senior scientist at CCMB.
CCMB director Lalji Singh, along with Thangaraj and a team of scientists have reported their work in the latest issue of the American journal Science in association with an Estonian team.
An independent investigation by Malaysian and British scientists corroborated the CCMB findings.
The Great Andamanese and Onge tribes have remained isolated in the Andaman and Nicobar islands for tens of thousands of years. This helped the scientists to search for signs of origin that erase quickly when populations intermix.
Scientists at CCMB studied the genetic mutations of five members each of these two tribes to construct a human family tree spanning 70,000 years.
They found the Onge and Great Andamanese -- both Negrito tribes -- resembled the African population more closely than east Asians or the mainland Indian population of today.
"This could have happened only if the two tribes were almost direct descendents of the first human beings believed to have been born in Africa 150,000 years ago," said Lalji Singh.
The CCMB's findings suggest that a group of early humans from Africa used the coastal route to reach the Andaman islands 65,000 to 70,000 years ago. "Their journey could have predated the land journey by 10,000 years," said Singh.
The scientists at CCMB claim the new evidence could make these two tribes the oldest surviving human stock in Asia.
"They are absolutely unique and of great value to humanity," said Singh. Rapid modernization is, however, taking its toll on the native lifestyle of these tribes despite their resistance.
Their populations have also decreased steadily with about 20 Great Andamanese and 98 Onge surviving today. It is believed that before British colonizers reached the islands in the mid-18th century, the Great Andamanese population numbered over 5,000.
These tribes still survive as hunter-gatherer communities using primitive tools and living in the jungle.
"It is the last Eden and it is disappearing fast," said Singh of the island archipelago and its existing native populations.
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