But there were other tribes, he learned, that had hardly changed since the days of Radcliffe-Brown. One group lived alone on a 20-square-mile island called North Sentinel and had barely been seen at all. The other group, known as the Jarawa, were fearsome archers, known for hiding in the treetops and neatly impaling with arrows outsiders who encroached on their territory. Government policy toward the Jarawa fell to the Bush Police, who were armed with rifles and kept careful records of casualties on both sides.

Mr. Pandit was openly contemptuous of this martial approach, which dated back to the British Raj. In 1967, he managed to join a “gift-dropping” expedition to North Sentinel Island, where the police dropped off coconuts and bananas while the members of the tribe, known as the Sentinelese, hid in the forest.

“They were watching us carefully, and they must not have been happy, because they picked up their bows and arrows,” he said. “This whole encounter was so amazing, because here is civilized man facing primitive man in its extreme state, living very simply.”

In 1968, Mr. Pandit had a stroke of luck. Three Jarawa teenagers, captured raiding a village, were kept in prison for a month, so Mr. Pandit had a chance to study them at close range. He showed them airplanes and cars. He scribbled down words in their language. After a month, the three young men, loaded down with gifts, were released back to the forest.

There was a silence. Then, six years later, for reasons Mr. Pandit could never explain, a group of Jarawa greeted him on the beach with song and dance. He visited, after that, every two weeks or so. They would strip off his clothes, poke fingers in his eyes, pocket his spectacles.

He recalls these days, even now, with a kind of reverence and delight.

“I have seen a Jarawa girl,” he said. “I can never forget her face, though it was many years back. She sat in the boat watching us as if she was Queen Victoria, with such dignity and such poise. You see, then I realized one doesn’t need clothes and ornaments and crown to make you dignified. What comes spontaneously, your inner self, you can project your personality that way.”