indian scientists have uncovered a missing link in the prehistoric human migration jigsaw puzzle by revealing that two reclusive tribes in the Andaman and Nicobar Islands are among the world's oldest surviving indigenous groups.

The researchers from the Centre for Cellular and Molecular Biology (ccmb), in Hyderabad, have gathered enough genetic clues to prove that the Great Andamanese and the Onge, whose numbers are shrinking day by day, are the direct descendants of modern humans who evolved in east Africa some 150,000 years ago (Science, May 13, Vol 308, No 5724). "Ancient genetic mutations found in these groups make them closer to Africans than any other populations that survive today,' Lalji Singh, ccmb director and a co-author of the study, told Down To Earth.

The study looked at the mitochondrial dna (mdna), which is ideal to trace maternal lineage. Led by K Thangaraj, the scientists analysed m dna of three tribes living in the Andaman and Nicobar Islands