A new study suggests that the first humans to move into Australia and New Guinea came in larger numbers—and perhaps with more of a plan—than some researchers previously thought.

People have lived in Australia and New Guinea since at least 60,000 years ago, when sea levels were about 100 meters (300 feet) lower than today. Due to lower sea levels, a land bridge across the Torres Strait linked Australia and New Guinea into a single landmass (termed Sahul). The first humans to set foot on Sahul probably arrived via closely spaced islands that stretched like stepping-stones across the 1,800km (1,100 miles) of ocean from the exposed continental shelf of Southeast Asia. And a new study suggests that it would have taken at least 1,300 people crossing these islands to give us a lasting foothold.

Playing on hard mode

Trying to colonize a new, uninhabited land is a challenge. If you bring too many people at once, the sudden influx could put too much strain on local resources, and everyone would die. But if you don’t bring enough people to reproduce and maintain genetic diversity, each generation gets smaller until the group eventually runs out of people and everyone dies. Flinders University ecologist Corey Bradshaw and his colleagues wanted to figure out how many people needed to settle in Sahul to make sure humans didn’t end up going locally extinct.