A study of the most likely way for the first people to arrive in Australia has concluded that it was a deliberate expedition, by people who knew where they were going with the organizational skills to plan it. The findings draw together research on genetics, archaeology, and palaeogeography.

Settlement of Australia dates back at least 65,000 years, but we know little about the journey. One theory, dubbed the southern route, involves a boat voyage from either Timor or Roti. The other involves island-hopping to what is now New Guinea, which was then connected to Australia as part of the supercontinent Sahul.

Professors Sean Ulm and Michael Bird of James Cook University have modeled the southern route, in Quarternary Science Reviews, using the fact that sea levels were 75 meters (250 feet) lower than today. Although it is now 640 kilometers (400 miles) from Darwin to Dili (the capital of East Timor), at the time the Australian coastline extended much of this way, with a series of barrier islands 130 kilometers (81 miles) from Timor and 87 kilometers (54 miles) from Roti.

Timor has coastal mountains so high, Ulm told IFLScience, people standing on their summits could have seen the row of islands in the distance. Nevertheless, getting there would have been no casual day outing. Calculating the prevailing winds and ocean currents of the day, the researchers concluded the voyage would have taken 4-7 days even with active paddling. Such a trip would only be possible in boats stocked with plenty of food, confirming the much-debated technological development of the day. “Accidental drifting was unlikely to lead to successful crossings,” Bird said in a statement. 

Once these now-drowned islands were reached, the Australian mainland was less than 10 kilometers (16 miles) beyond.

Genetic analysis of Indigenous Australians has refuted the idea (occasionally revived for racist purposes) that they arrived in several waves, each largely displacing the previous populations. Instead, the founders were 100-200 people who arrived either as a single migration, or a series of smaller events closely packed in time. By at least 35,000 years ago Australians were largely genetically isolated from the rest of the world – whatever drove the original voyages apparently ceased.

This isolation is part of what makes Ulm favor the southern route. He pointed out to IFLScience that Australia was connected to New Guinea by land until around 10,000 years ago, yet there was little genetic intermingling. The reason for this is unknown, and the topic of much speculation by anthropologists, but it suggests that anyone coming via New Guinea would have needed to make not one but two difficult crossings, making it more likely that people standing on those Timorese mountains looked south and said, “That looks nice, let's go there.” Remarkably, they had the organization and technology to do it.