In the distant past, groups of people undertook one of the boldest journeys in human history—they crossed turbulent ocean currents in primitive watercraft to reach the ancient continent of Sahul, which today is divided into Australia, New Guinea, and Tasmania. For a long time, scientists debated when and by what route these courageous seafarers arrived in these new lands. Recently, an international team of geneticists has shed new light on this question.

Ancient Continents and Maritime Barriers

Tens of thousands of years ago, global sea levels were much lower, and many areas now submerged were once part of vast landmasses. At that time, Southeast Asia formed the region known as Sundaland, while Australia, New Guinea, and Tasmania made up the massive southern continent of Sahul. However, even with lower sea levels, a chain of islands surrounded by deep waters remained between Sundaland and Sahul. This biogeographical region, known as Wallacea, posed a significant obstacle for ancient humans: wide and deep straits separated the islands, making land crossings impossible.

Brave Ocean Crossings

To reach Sahul, people had to traverse dangerous stretches of open ocean, at least 100 kilometers across. Such journeys required not only courage but also advanced seafaring skills.

When and How Was Sahul Settled?

Archaeologists have long tried to determine when the first humans arrived in Sahul. Some experts believe settlement occurred around 65,000 years ago, based on excavations at the Madjedbebe site in northern Australia. Geneticists analyzing the DNA of modern populations tend to favor a later date—about 45,000 to 50,000 years ago.

There was also debate about the migration route. One hypothesis suggested settlement via the present-day islands of Timor and Roti—the so-called "southern route." Another theory proposed movement along the "northern route" through the Philippines and Sulawesi to New Guinea. Archaeological finds, such as ancient stone tools on Sulawesi dating back over a million years, support the idea of an early hominid presence in this region.

Genetic Analysis: Two Routes at Once

To clarify how people reached Sahul, an international team of geneticists led by Martin Richards from the University of Huddersfield (UK) conducted a large-scale genetic study. The researchers analyzed 2,456 mitochondrial genomes from Indigenous peoples of Australia, New Guinea, populations of the western Pacific, and Southeast Asia. Mitochondrial DNA allows scientists to reconstruct maternal lineages and date key events in population history.

By building a detailed genealogical tree and using the "molecular clock" method, the team determined that the ancestral lines of Indigenous Australians, New Guineans, and groups from Southeast Asia split about 60,000 years ago. This matches archaeological estimates for the settlement of Australia.

The most intriguing discovery concerns the migration routes: the analysis showed that people reached Sahul not by a single path, but by two different routes simultaneously—via both the northern and southern corridors. The main flow moved through northern Indonesia and the Philippines, reaching Sulawesi and then New Guinea. Far fewer people traveled the southern route, passing through southern Indonesia (including Timor and Roti) and Sundaland. Thus, settlement occurred through two streams at once, highlighting the scale of the migration and the advanced seafaring abilities of ancient humans.

Return Contacts and Further Expansion

The study also revealed that migration was not one-way. Scientists discovered an ancient New Guinean genetic lineage in a 1,700-year-old burial on the island of Sulawesi. This indicates that descendants of Sahul’s first settlers maintained contact with the islands of Southeast Asia for millennia, making return journeys and leaving their genetic mark along the way.

Genetic analysis also showed that soon after arriving in Sahul, these seafarers quickly moved further east, settling new lands including the modern Solomon Islands. People did not remain in one place but actively explored coastlines and islands.

The scientific study was published in the journal Science Advances.