The last surviving member of one of the tribes inhabiting the Andaman and Nicobar Islands in the Bay of Bengal has died, according to the United Kingdom-based human rights organization Survival International, an ominous signal for the handful who remain.

Boa Sr, who died last week, was the last speaker of ‘Bo', one of the 10 Great Andamanese languages, Survival International reported. She was believed to be around 85 years old. The Bo are thought to have lived in the Andaman Islands for as much as 65,000 years, making them the descendants of one of the oldest human cultures on Earth. Boa Sr was the oldest of the Great Andamanese, who now number just 52. Originally 10 distinct tribes, the Great Andamanese were 5,000 strong when the British colonized the Andaman Islands in 1858.

Survival International runs worldwide campaigns to fight to keep tribal peoples alive and unexploited through mass letter-writing campaigns in several different countries including Malaysia, Kenya, Canada and others.

The remote tribes in the past were some of the most socially isolated people on earth and some are noted for vigorously resisting attempts of contact by outsiders. Almost nothing was recorded of them or their languages until about 1860, when the British established a penal colony on one of the islands. During rescue attempts following the 2004 Boxing Day tsunami, which killed an estimated 230,000 people across 14 countries, some were photographed shooting arrows at rescue helicopters.

Despite the fact that they inhabit an island paradise, the tribes are under threat from a wide variety of sources. Most were killed or died of diseases brought by the British many decades ago. Only about 600-700 local tribal people remain on the islands. As many as 300,000 Hindi, Bengali, Tamil and Punjabis from the mainland have immigrated there.

The islands are also under potential threat from global warming, which is expected to raise the sea levels and wipe out low-lying areas. However, despite the 2004 tsunami, which generated waves in some places as high as 100 meters, the tribes survived largely intact despite its heavy impact on their islands. When the sea receded prior to the waves, they said, they knew to race uphill.

The Sentinelese tribe, photographed shooting at the helicopter, resist all contact with outsiders approaching their tiny island. But the forest reserve of another group, the 320-strong Jawara tribe, were overrun by settlers from the Indian mainland, stealing the animals they hunt, plying them with alcohol and tobacco and sexually abusing Jarawa women. In the past, local police were often complicit in this abuse, according to Survival international.

Indian activists and Survival International fear that the Jarawa may soon follow Boa Sr into extinction unless their lands are protected. The islands administration has ignored an Indian Supreme Court order to close a road cutting through the Jarawas' land, and some years ago, Survival International reported, no effort was being been made to curb abuse by police.

"It is a tragic irony that these unique tribes, whose sophisticated knowledge of their environment has allowed them to survive on the Andamans for 60,000 years, are under threat from their fellow man," said Survival's director Stephen Corry, at the time. "The Indian government must act to protect them before it is too late.'

Boa Sr survived the Asian tsunami of December 2004, and told linguists, ‘We were all there when the earthquake came. The eldest told us ‘the Earth would part, don't run away or move.' The elders told us, that's how we know.'

Survival International quoted linguist Anvita Abbi, who knew Boa Sr for many years, as saying: "Since she was the only speaker of [Bo] she was very lonely as she had no one to converse with. Boa Sr. had a very good sense of humor and her smile and full-throated laughter were infectious. You cannot imagine the pain and anguish that I spend each day in being a mute witness to the loss of a remarkable culture and unique language.'

Boa Sr told Abbi she felt the neighboring Jarawa were lucky to live in their forest away from the settlers who now occupy much of the islands.

"The Great Andamanese were first massacred, then all but wiped out by paternalistic policies which left them ravaged by epidemics of disease, and robbed of their land and independence," Corry said. "With the death of Boa Sr and the extinction of the Bo language, a unique part of human society is now just a memory. Boa's loss is a bleak reminder that we must not allow this to happen to the other tribes of the Andaman Islands."