Many of the other islands within PNG territory, including New Britain, New Ireland, Bougainville, the Admiralty Islands, the Trobriand Islands, and the Louisiade Archipelago, were never linked to New Guinea by land bridges, and they lack many of the land mammals and flightless birds that are common to New Guinea and Australia.
Australia and New Guinea are portions of the ancient supercontinent of Gondwana, which started to break into smaller continents in the Cretaceous era, 130–65 million years ago. Australia finally broke free from Antarctica about 45 million years ago. All the Australasian lands are home to the Antarctic flora, descended from the flora of southern Gondwana, including the coniferous podocarps and Araucaria pines, and the broadleafed southern beech (Nothofagus). These plant families are still present in Papua New Guinea.
As the Indo-Australian Plate (which includes landmasses of India, Australia, and the Indian Ocean floor in-between) drifts north, it collides with the Eurasian Plate, and the collision of the two plates pushed up the Himalayas, the Indonesian islands, and New Guinea's Central Range. The Central Range is much younger and higher than the mountains of Australia, so high that it is home to rare equatorial glaciers. New Guinea is part of the humid tropics, and many Indomalayan rainforest plants spread across the narrow straits from Asia, mixing together with the old Australian and Antarctic floras.
History of Papua New Guinea
Human remains have been found on New Guinea which have been dated to about 50,000 years ago. These ancient inhabitants probably had their origins in Southeast Asia. Agriculture was independently developed in the New Guinea highlands around 9,000 years ago, making it one of the few areas of original plant domestication in the world. A major migration of Austronesian speaking peoples came to coastal regions roughly 2,500 years ago, and this is correlated with the introduction of pottery, pigs, and certain fishing techniques. More recently, some 300 years ago, the sweet potato entered New Guinea having been introduced to the Moluccas from South America by the then-locally dominant colonial power, Portugal. The far higher crop yields from sweet potato gardens radically transformed traditional agriculture; sweet potato largely supplanted the previous staple, taro, and gave rise to a significant increase in population in the highlands.
Little was known in the West about the island until the nineteenth century, although traders from Southeast Asia had been visiting New Guinea as long as 5,000 years ago collecting bird of paradise plumes, and European explorers had encountered it as early as the sixteenth century. The country was named in the nineteenth century: the word papua is derived from a Malay word describing the frizzy Melanesian hair, and "New Guinea" (Nueva Guinea) was the name coined by the Spanish explorer Yñigo Ortiz de Retez, who in 1545 noted the resemblance of the people to those he had earlier seen along the Guinea coast of Africa.
The northern half of the country came into German hands in 1884 as German New Guinea. During World War I, it was occupied by Australia, which had begun administering the southern part as Papua (from 1884, British New Guinea) in 1915. After World War I, Australia was given a mandate to administer the former German New Guinea by the League of Nations. Papua, by contrast, was deemed to be an External Territory of the Australian Commonwealth, though as a matter of law it remained a British possession, an issue which had significance for the country's post-Independence legal system after 1975. This difference in legal status meant that Papua and New Guinea had entirely separate administrations, both controlled by Australia.
The two territories were combined into the Territory of Papua and New Guinea after World War II, which later was simply referred to as "Papua New Guinea". The Administration of Papua was now also open to United Nations oversight. However, certain statutes continued (and continue) to have application only in one of the two territories, a matter considerably complicated today by the adjustment of the former boundary among contiguous provinces with respect to road access and language groups, so that such statutes apply on one side only of a boundary which no longer exists.
Peaceful independence from Australia occurred on September 16, 1975, and close ties remain (Australia remains the largest bilateral aid donor to Papua New Guinea). A secessionist revolt which claimed 20,000 lives raged on the island of Bougainville from 1988 until it was resolved in 1997. Autonomous Bougainville recently elected Joseph Kabui as president.