The history of Human habitation within the Australian continent begins with the first arrival of peoples ancestral to the present indigenous inhabitants. Whether these first migrations involved one or several successive waves and distinct peoples is still a matter for some academic debate, as is its timing. The minimum widely-accepted timeframe places this at 40,000 to 43,000 years Before Present (BP); the upper range supported by others is 60,000 years BP to 70,000 years BP.
In any event, this migration was achieved during the closing stages of the Pleistocene epoch, when sea levels were typically much lower than they are today. Repeated episodes of extended glaciations resulted in decreases of sea levels by some 100–150 m. The continental coastline therefore extended much further out into the Timor Sea than it does today, and Australia and New Guinea formed a single landmass (known as Saul), connected by an extensive land bridge across the Arafura Sea, Gulf of Carpentaria and Torres Strait.
It is theorised that these original peoples first navigated the shorter distances from and between the Sunda Islands to reach Sahul; then via the land bridge to spread out through the continent. Archaeological evidence indicates human habitation at the upper Swan River, Western Australia by about 40,000 years ago; Tasmania (also at that time connected via a land bridge) was reached at least 30,000 years ago.
The ancestral Australian Aboriginal peoples were thus long established and continued to develop, diversify and settle through much of the continent. As the sea levels again rose at the terminus of the most recent glacial period some 10,000 years ago the Australian continent once more became a separated landmass. However, the newly-formed 150 km wide Torres Strait with its chain of islands still provided the means for cultural contact and trade between New Guinea and the northern Cape York Peninsula.
Several thousand years ago the Melanesian Torres Strait Islander peoples were established in the Torres Strait Islands, and commerce and contact was continued via this route although there is little evidence to suggest immediate influences extended much further south. A more sporadic contact along the northern Australian coast was maintained by seafarers across the Timor and Arafura Seas, with substantial evidence of Makassar contact with Australia in the centuries prior to European arrival, and also evidence of earlier contacts and exchanges by other groups. However, these exchanges do not appear to have involved any extended settlement or migrations of non-Aboriginal peoples to the region

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