They have survived for thousands of years in one of the world's most isolated areas. But at least two of the Stone Age aboriginal tribes that live on the remote Andaman and Nicobar Islands have been gravely affected by Sunday's giant tsunami, which ripped through the sprawling archipelago in the Bay of Bengal, killing at least 3,000 people.
Wednesday the Indian authorities here admitted they were dealing with a disaster -- and said they had been unable to make contact with the Shompens, a reclusive tribe who live on the island of Great Nicobar.
Officials said they were sending messengers to some of the most remote islands, more than 16 hours away by boat, to ascertain who was left alive.
The relief operation has been made more complicated by the fact that many of the worse affected areas are also home to reclusive communities, whose ancestors migrated to the islands more than 30,000 years ago.
Yesterday the islands' governor, Ram Kapse, said he was sending a boat to Sentinel Island, home to the world's last truly Stone Age tribe. The 100-strong Sentinalese, who originated from Africa, have resisted all contact with the outside world. They have opened fire on friendly visiting anthropologists with poison arrows.
The boat being sent there would not land on the island but would have a look at their situation from a safe "outer circle," Professor Kapse said.
The fate of the Shompens, meanwhile, a Mongoloid tribe who live on the southern tip of Great Nicobar Island, was not known, he added.
The Indian authorities have so far failed to reach them. They have also not managed to land on two tiny but inhabited nearby islands, Konsul and Pilomilo.
"We are doing our best. But many villagers are simply not yet reachable," said the administration's chief secretary, VV Bhat. He added: "There has been a massive dislocation. Whole villages have disappeared. Jetties in many of the islands have gone, too, making it impossible to land by boat. Coconut and forest trees have been ripped down flat."
So far, it is thought the worst affected island in the group is Car Nicobar, a small, low-lying island where entire villages inhabited by tribal Nicobarese were washed away.
Yesterday one tribal survivor, Casper James, described how he was about to go to church when the first tremors struck early on Sunday.
He dragged his wife and daughter out of their house and started racing up into the jungle. Three minutes later a giant wave tore into his village, Malacca, demolishing it.
"There was a tremendous sound. We shouted to all our neighbors to run. We ran 200m up the hill. Behind us, trees and cylinders floated past. The village disappeared. There was nothing left," James said. He added: "When I went back, I saw many hands sticking out of the sand."
James is one of the survivors from the small, flat and lush island of Car Nicobar, part of the remote and sprawling Andaman and Nicobar archipelago that bore the full brunt of Sunday's tsunami.
Five days after the disaster there was still confusion as to how many people have died here. Indian officials said that 3,000 had gone missing and were presumed dead, although only 306 bodies have actually been recovered.
The final death toll will only be known when terrified villagers finally emerge from the dense forests of coconut palms and casuarina trees where they have been hiding.