agreement was reached in 2001, by which it was agreed that an autonomous region would be established and an independence referendum would be held; the latter was held in 2019. Prehistory The earliest known site of human occupation in Bougainville is Kilu Cave, located on Buka Island. The bottom-most archaeological deposits in the cave were radiocarbon-dated to between 28,700 and 20,100 years ago. During the Last Glacial Maximum, until approximately 10,000 years ago, present-day Bougainville Island was part of a single landmass known as "Greater Bougainville", which spanned from the northern tip of Buka Island to the Nggela Islands north of Guadalcanal. The "obvious immediate origin for its first colonists" of Bougainville is the Bismarck Archipelago to the north, where sites have been identified dating back 35,000 to 40,000 years. The first settlers of Bougainville were Melanesians, likely related to present-day Papuans and Aboriginal Australians. Approximately 3,000 years ago, a wave of Austronesian peoples arrived in Bougainville, bringing with them the Lapita culture. The Austronesians brought with them a fully agricultural lifestyle, also introducing distinctive pottery and domesticated pigs, dogs and chickens to Bougainville. The advent of the Lapita culture resulted in "a pattern of apparent extinctions of birds and endemic mammals". Both Austronesian and non-Austronesian languages (historically called "East Papuan") continue to be spoken on Bougainville today. There has been substantial genetic and cultural mixing between the Austronesian and non-Austronesian populations, "such that language is no longer correlated with either genetics or culture in any direct or simplistic way". Douglas Oliver in his 1991 book discussed one of the unique aspects of the people of Bougainville: [A] trait shared by the present-day descendants of both northerners and southerners is their skin-colour, which is very black. Indeed, it is darker than that of any population of present-day Pacific islanders, including the present-day indigenes of New Ireland, the larger homeland of the first Bougainvilleans. The presence of Bougainville as a 'black spot' in an island world of brownskins (later called redskins) raises a question that cannot now be answered. Were the genes producing that darker pigmentation carried by the first Bougainvilleans when they arrived? Or did they evolve by natural or 'social' selection, during the millennia in which the descendants of those pioneers remained isolated, reproductively, from neighbouring islanders? Nothing now known about Bougainville’s physical environment can support an argument for the natural selection of its peoples' distinctively black pigmentation; therefore