The first inhabitants of Papua New Guinea, probably migrants from the Indonesian archipelago, arrived about 50,000 years ago. These migrants arrived in several waves, and the land that they encountered had a remarkable effect on cultural development. Because New Guinea's terrain is marked by imposing mountains and extremely rugged territory, different population groups developed in virtual isolation. Each group developed its own language and its own tribal culture, a development that gives Papua New Guinea one of the world's most diverse and fascinating cultural landscapes.
The first contact with the island by Europeans occurred in the early 16th century, when the Portuguese explorer Jorge de Meneses sighted the country and named it Ilhas dos Papuas (Land of the Fuzzy-Haired People). However, it wasn't until the mid-1800's that European missionaries and traders began to settle on the island, and even those few settlers limited their presence mostly to the accessible coastal areas. Over the next several decades Papua New Guinea was claimed by the Germans, the British, and the Dutch, but it came under the control of Australia after World War One. The inland Highland region, thought to be too inhospitable for habitation, wasn't even explored until the 1930s. Astoundingly, European explorers in search of gold instead discovered over one million people, living in fertile mountain valleys and in cultures that hadn't changed since the Stone Age. By the 1960s there had emerged a significant independence movement in the country, and in 1975, after a brief period of internal autonomy, Papua New Guinea declared its full independence.
The people can be divided into four ethnic groups: New Guineans (from the north of the main island), Papuans (from the south), Highlanders, and Islanders. There is, however, considerable cultural variation within each of these groups. The peoples of the south coast were notorious for headhunting and cannibalism before the arrival of the Europeans. Many people still live in small villages and follow traditional tribal customs. Although English is the official language in schools and government, almost 800 distinct languages are spoken in the islands.
Source: http://www.geographia.com