(Image source from: Sky News)

The body of American John Allen, who fell in a volley of arrows fired by reclusive tribes, may never be recovered from the lost island, according to experts.

The threat to the Sentinelese from Chau's one-man invasion is such that tribal rights specialists say no murder charges will ever be laid and Chau's body will have to stay out of sight to protect what is probably the world's last pre-neolithic tribe.

The authorities - who do not dare implement their rule over North Sentinel island - have not even tried to send police ashore to query the tribe who have been greeting outsiders with ill will for centuries.

Related content: Sentinelese Tribe: Indian Tribe Detached from Outside World

Police on Friday sent a boat near North Sentinel for the second time since the killing.

"Due precautions were taken by the team to ensure that this particularly vulnerable tribal group are not disturbed and distressed during this exercise," said a police statement.

Fears that 21st-century diseases as mild as the common cold could kill off the tribe, or that experiencing electricity and the internet would devastate their lifestyle, has left them in a restrained bubble that Chau sought to burst with his "Jesus loves you" message.

The American died earlier this week after making several attempts to reach the Sentinelese to preach Christianity - knowing it was illegal to go within three miles (five kilometers) of the island.

Pankaj Sekhsaria, a tribal rights expert and author on the Andaman and Nicobar islands, said it would be "a futile exercise" to try to recover Chau's body.

"I don't think it is a good idea to go anywhere near (North Sentinel) because it will create conflict with the community there," he told AFP.

"I don't believe there is any safe way to retrieve the body without putting both the Sentinelese and those attempting it at risk," added Sophie Grig, senior researcher for Survival International which campaigns for such isolated groups.

Anup Kapoor, an anthropology professor at the University of Delhi, said that anyone wanting to open a dialogue with the Sentinelese had to show they were "on the same level."

"Don't wear anything," he recommended. "Only then you can hope to have some sort of interaction."

Kapoor once had contacts with the Onge, another Andamans tribe, adding: "It was only after I took off my clothes, except my underwear."

The lack of knowledge of the Sentinelese believed to be the last surviving descendants of the first humans to arrive in Asia - and who 13th-century adventurer Marco Polo called "brutish and savage" is the main handicap.

"We have no clue about their communication systems, their history and, culture, how can we go anywhere near them," said Kapoor.

"What we know is that they have been killed and persecuted historically by the British and the Japanese. They hate anyone in uniform. If they see someone in uniform, they will kill him on the spot.

"Let them be the way they are. Leave them in peace in the ecosystem they are in. Do not disturb them because that will only make them more aggressive."

Police are now struggling with a double dilemma: how to answer the prayers of Chau's family and maintain the privacy around North Sentinel that is essential for the tribe's survival.

Andamans police chief Dependra Pathak has said no timeline can be given for finding a body.

And Sekhsaria warned the authorities may now have to strengthen surveillance around North Sentinel to prevent a Chau copycat.

"The administration is seized of the matter, they are already thinking about the surveillance," he said without giving detail.

Outsiders have had an unsmooth reception when going to North Sentinel. Arrows were fired at a helicopter that checked on the tribe after the devastating 2004 Indian Ocean tsunami. Two fishermen who strayed too close in 2006 were killed.

-Sowmya Sangam