In 1961 the brothers established Brazil's first Indian reserve, the Parque Nacional do Xingu. Covering 26,000 square miles of rainforest, it now has a population four times what it was when it started.
Cláudio and Orlando Villas Bôas talking to a Xingu Indian. circa 1960
Others have followed its example, and Brazil's 350,000 Indians now control 11 per cent of the country, an area equivalent to France, Germany and Benelux combined. Their parks are islands of good environmental practice in the midst of desolation.
The Villas Bôas philosophy was to protect land and health, and restrict the entry only of items that would damage native society: for example, guns, alcohol and manufactured items that competed with tribal crafts. Missionaries were also excluded, along with tourists. The aim was to "allow them to change at the speed Indians want, rather than at a speed imposed on them".
A gregarious bear of a man, whom one friend described as looking like a Turkish bath attendant, Orlando Villas Bôas had a tremendous rapport with the Indians, who warmed to his uproarious sense of humour. The brothers - whom the Indians called their "Great White Fathers" - lived for weeks when necessary on wild honey and locusts.
Orlando survived more than 200 attacks of malaria. After retiring from the Xingu reserve he wrote nine books about his work with his brother, the retiring Claudio. They complemented each other well. "Claudio is into more serious literature," Orlando explained. "I prefer to read Donald Duck."
Orlando Villas Bôas was born on January 12 1914 on his father's coffee plantation near the city of Botucatu, 150 miles north-west of Sao Paulo. As boys, he and his brothers, Claudio and Leonardo, would listen wide-eyed to their father's tales of venturing into Brazil's backlands and his encounters with Indians.
In 1942 the brothers got themselves chosen for the Roncador-Xingu expedition, sent by the government to open up the unmapped region near the Araguaia river and the River of the Dead. The leader deemed the brothers too callow, so they grew beards, put on grubby clothes and followed the expedition into the bush. They were taken on as camp secretary, warehouse manager and personnel chief.
Orlando Villas Bôas with three Caiapó Indians. Circa 1956
Lasting until 1960, this was to be Brazil's last major expedition to open up the interior of the country for settlement; it resulted in 1,000 miles of road through the jungle, charted six unknown rivers and discovered at least 18 villages.
"The Indians were fantastic road builders," Orlando Villas Bôas recalled. "They could see better, resist the fevers, tolerate the mosquitoes and feed themselves. When the food rations disappeared our workers threw up their hands in despair. The Indians thought this hilarious.
They disappeared into the forest and 20 minutes later returned with a monkey and armadillo meat, various roots and a splendid selection of fruit. They didn't want to be paid. They wanted solidarity."
The Villas Bôas brothers were admirers of Candido Rondon, the Brazilian Army officer who hunted big game with Theodore Roosevelt and founded Brazil's first Indian protection agency.
They adhered to Rondon's motto for outsiders coming into contact with indigenous tribes: "Die maybe, kill never." The brothers were instrumental in establishing the first contact with the Xavantes in 1948, the Jurunas in 1949, the Kayabis in 1951, the Txucarramaes in 1953 and the Suyas in 1959.
After contacting the Kalapalo, Orlando Villas Bôas appeared to solve the riddle of the Amazon explorer Colonel Percy Fawcett, who disappeared while canoeing through the steaming forests of the Upper Xingu in 1925.
Villas Bôas announced that chief Sarari had confessed that the Kalapalos had killed Fawcett after he had upset them by not sharing a duck he had shot - an outrage to the communally-minded Indians - and then slapping a child.
"All the Kalapalos came to the top of the cliff by the lake and sat in a semi circle," Villas Bôas recalled. "They made me promise that no aeroplanes would come [to take revenge], and after that they told me how the killing was done."
Villas Bôas brought back what were supposedly Fawcett's bones as evidence, but Fawcett's son Brian later insisted they belonged to a shorter man. Moreover, a duplicate set of dentures, kept by Fawcett's widow, did not fit the skull.
Orlando Villas Bôas with the bones he said were those of Colonel Percy Fawcett
Leonardo Villas Bôas died in the 1960s, but the surviving brothers stayed with the Indians until the 1980s. They were awarded the Gold Medal of the Royal Geographical Society.
When Claudio died in 1998, the tribes of the Xingu held a rare ceremony in his honour. John Hemming, the former director of the Royal Geographical Society, described it:
"Muscular warriors from a dozen tribes painted their bodies in a dazzling array of black and red designs, and donned their finery of brilliant head-dresses, fluffy feather arm-bands and bead belts. There were pounding dances and powerful wrestling matches in the dust of the village square.
"Then came the solemn funerary ceremony. Orlando Villas Bôas flew in to a welcome of deep emotion. Every elderly Indian man and woman embraced him, and there were tears in the eyes of the 84-year-old Orlando. His face and clothes were covered in red urucum body dye.
A log representing the dead Claudio was erected at the centre of the village, painted in geometric designs and adorned with the feathers befitting a great chief. Throughout the moonlit night, a small fire burned in front of this pole and pairs of shamans chanted quietly and melodiously in honour of their departed champion."
Orlando Villas Bôas is survived by his wife and their two sons.
Leonardo, Orlando and Cláudio Villas Boas