The immigration history of Australia began with the initial human migration to the continent around 80,000 years ago when the ancestors of Aboriginal Australians arrived on the continent via the islands of Maritime Southeast Asia and New Guinea. From the early 17th century onwards, the continent experienced the first coastal landings and exploration by European explorers. Permanent European settlement began in 1788 with the establishment of a British penal colony in New South Wales. From early federation in 1901, Australia maintained the White Australia Policy, which was abolished after World War II, heralding the modern era of multiculturalism in Australia. From the late 1970s there was a significant increase in immigration from Asian and other non-European countries. Australia is also a signatory to the Convention Relating to the Status of Refugees and recognises the right of asylum. Original inhabitants The first inhabitants in Australia were the ancestors of the present indigenous people. Whether these first migrations involved one or several successive waves and distinct peoples is still subject to academic debate, as is its timing. The minimum widely accepted time frame places presence of humans in Australia at 40,000 to 43,000 years Before Present (BP), while the upper range supported by others is 60,000 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 glaciation 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 Sahul), 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