CANBERRA, AUSTRALIA—As many as 3,000 people may have made up the founding population of Australia, according to a controversial new study Alan Williams of Australian National University. He used a database of radiocarbon dates obtained from Australian cooking pits, human burials, shell mounds, and charcoal deposits, thinking that the growth of the human population would be reflected in the number of surviving archaeological sites. By calculating the rate of change in the population over time, and then using the population estimate in 1788, when Europeans arrived, he estimates that the population 45,000 years ago must have been between 1,000 and 3,000 people. Estimates based on the genetic diversity of modern aboriginal Australians have suggested a considerably smaller founding population. “It’s not just a family that got stuck on a raft and washed away. It’s people with the intention to move, to explore,” he said.