Archaeological evidence shows that modern humans had reached South-east Asia by 70,000 years ago and that they had spread to Australia by at least 50,000 years ago.
The viewpoints about the origins of these peoples are entangled with the wider debate regarding the origins of all modern humans.
, Australia and New Guinea were connected as a single landmass (termed Sahul) that remained contiguous until separated by rising sea levels around 9 ka (ref. Despite this, the initial Sahul colonists appear to have rapidly diverged into distinct New Guinean and Australian populations, with limited signs of subsequent gene flow—although genetic data remains sparse.
Little is known about the post-colonization diversification of Australian lineages or the effects of major environmental and cultural changes over the last 50 thousand years (kyr).
The continental coastline extended much further out into the Timor Sea, 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.
Nevertheless, the sea still presented a major obstacle so it is theorised that these ancestral people reached Australia by island hopping.
These people belonged to a single genetic lineage and were the descendants of a population that originated in Africa.
After continent-wide colonization, strong regional patterns developed and these have survived despite substantial climatic and cultural change during the late Pleistocene and Holocene epochs.
Remarkably, we find evidence for the continuous presence of populations in discrete geographic areas dating back to around 50 ka, in agreement with the notable Aboriginal Australian cultural attachment to their country.
Scott Cane wrote in 2013 that the first wave may have been prompted by the eruption of Mount Toba and if they arrived around 70,000 years ago could have crossed the water from Timor, when the sea level was low - but if they came later, around 50,000 years ago, a more likely route would be through the Moluccas to New Guinea.
Given that the likely landfall regions have been under around 50 metres of water for the last 15,000 years, it is unlikely that the timing will ever be established with certainty.
Palaeoclimatically, these include continental-scale aridification and cooling of Australia during the Last Glacial Maximum (21 ± 3 ka), warming in the early Holocene (9–6 ka), and intensification of the El Niño/Southern Oscillation during the mid-to-late Holocene (4–2 ka).