A new genetic analysis indicates that ancient humans reached the continent of Sahul, encompassing modern Australia and New Guinea, around 60,000 years ago via two distinct routes. The study supports the earlier timeline over a more recent one and highlights the northern path as predominant. Researchers analyzed nearly 2,500 genome sequences to draw these conclusions.
The arrival of humans in what is now Australia and New Guinea has long puzzled scientists, given the need for significant ocean crossings even during periods of lower sea levels. Sahul, the ancient landmass uniting mainland Australia, Tasmania, and New Guinea, formed during glacial maximums. Archaeologists have debated the timing, with estimates ranging from at least 60,000 years ago to around 45,000 years ago, and the routes taken.
Two primary migration paths have been proposed: a southern route from Southeast Asia through the Sunda region, including Malaysia, Indonesia, and Timor, leading to Australia; and a northern route via the Philippines and Sulawesi to New Guinea, bolstered by evidence such as million-year-old stone tools found there.
In a study published in Science Advances, Martin Richards at the University of Huddersfield in the UK and colleagues examined almost 2,500 genome sequences from Indigenous Australians, Papua New Guineans, and populations across the western Pacific and Southeast Asia. By assessing mutation rates and genetic links, they determined that humans settled Sahul through both routes, though the northern one was most common.
"We dated both dispersals to about the same time – roughly 60,000 years ago," Richards said. This finding endorses the 'long chronology' of settlement, countering the 'short chronology' of 45,000 to 50,000 years ago.
The research also shows bidirectional movement, including an ancient New Guinean genetic lineage in a 1,700-year-old Iron Age burial on Sulawesi, and early voyages to the Solomon Islands post-arrival.
Adam Brumm at Griffith University in Brisbane noted the study's reinforcement of the northern route, linking it to ancient cave art in Sulawesi dating to at least 51,200 years ago, possibly older. Peter Veth at the University of Western Australia in Perth added that evidence from the Madjedbebe site in Australia's Northern Territory supports activity over 60,000 years ago, aligning with this genetic evidence.