How do you count people nobody counted? For nearly a century, the answer in Australia was: badly. In the 1930s, the anthropologist Alfred Radcliffe-Brown put the Indigenous population before colonization at about 250,000. That figure shaped textbooks, museum labels and political arguments for generations.

Now a national research team says it was far too low. Their new estimate is 2.22 million people living on the continent when the First Fleet arrived in 1788, in some comparisons up to seven times earlier calculations. Professor Corey Bradshaw of Flinders University, who contributed to the work, is part of a centre that collaborates with Indigenous partners on the project.

The method is a little like detective work. The researchers did not rely on a single clue. They combined ethnographic observations, archaeological findings, genetic reconstructions and computer models. They also asked a simple but clever question: how many people could each environment, from tropical coast to desert edge, realistically have supported?

When several independent lines of evidence point to the same range, the answer becomes harder to dismiss.