The Ultimate Undiscovered People Quiz

Though newspapers announced the "discovery" of a previously unknown group of humans in the Brazilian Amazon rainforest in 2008, the Brazilian government had known of their existence for almost a hundred years.

A whopping 70 percent of the Brazilian state of Amapa consists of unexplored forests.

Indian expert Jose Carlos dos Reis Meirelles led Brazilian government officials to the undiscovered tribe, and later admitted that he had been observing them for 20 years.

Early European explorers imagined inhabitants of far-off places to be mutants and half-men-half-beasts. They, of course, eventually realized that the native inhabitants of the Americas were very similar anatomically to themselves.

A people or a tribe describes a group of human beings who share a common territory, language, history and culture.

Though we don't know the exact number, of course, Survival International -- a London-based organization formed to protect aboriginal peoples -- estimates that there are about 100 uncontacted tribes around the world.

Uncontacted or isolated peoples can probably still be found in the Indian Ocean islands, in areas of the Pacific and in South America.

The Sentinelese, believed to be the most isolated group in the world, live in a remote corner of the Andaman Islands in the Indian Ocean.

When outsiders make contact with formerly isolated peoples, they often treat them badly or infect them with microbes from which they have no immunity.

Famous explorer Christopher Columbus encountered the friendly Arawak people during his travels to the West Indies.

In the 1980s, members of the Zo'é tribe in Brazil fell ill after exposure to Christian missionaries who carried germs from which they had no immunity. Forty-five of their members died of flu, malaria and respiratory diseases.

In 1990, outsiders massacred the entire Akunzu tribe, hunters and corn-growers from a remote region of western Brazil. Homesteaders who wanted their land were responsible for the massacre of several hundred people.

Today, the Brazilian government uses specially equipped aircraft with heat sensors to track isolated tribes from above, even if they can't be seen.

Though the Sentinelese Islanders are so isolated even from other Andaman Islanders that they speak a different language, they do know how to make tools and weapons from metal.

The Sentinelese Islanders are believed to be directly descended from the first human beings to emerge from Africa about 60,000 years ago.