Elspeth Hayes with Mark Djandjomerr and traditional owner May Nango extracting comparative samples Photo: David Vadiveloo / Gundjeihmi Aboriginal Corporation

Humans first arrived by sea to Australia around 65,000 years ago, according to a new archaeological study published in Nature Wednesday. The finding pushes the date of human arrival to the continent — a debated subject — back 5,000 to 20,000 years.

"This age increases the age of occupation of Australia by many thousands of years. This is extremely important as there has been an endless debate about the initial occupation of the continent, with some arguing it was late[r], only within the last 45,000 years, and others [arguing it was] earlier," said Michael Petraglia, an anthropologist from the Max Planck Institute for the Science of Human History. Petraglia, who was not part of this study, told Axios that the dating of the artifacts from the Madjedbebe site looks "rock solid."

Why this matters: This study indicates humans left Africa and had the ability and aspiration to traverse the ocean for weeks to an unseen land at a much earlier period than previously thought. It also means humans arrived in Australia when megafauna lived on the continent, which may influence the debate over what led to the extinction of the large animals like the 1000-pound kangaroos and Volkswagen-sized tortoises.

What they did: The research team first re-analyzed material in museums from excavations at the aboriginal rock shelter Madjedbebe in northern Australia in 1972 and 1989. They then completed their own expanded excavations in 2012 and 2015, allowing them to see the structure and intact details of the site. They collected charcoal from a fireplace and sand grains from the walls and analyzed them with single-grain optically stimulated luminescence (OSL) dating, which can be used to tell the last time the sand was exposed to sunlight. To confirm the findings, they did a blind test with some of their samples at an independent lab.

"The most significant finding in my opinion is that Aboriginal people arrived here 65,000 years ago, much earlier than previous thought, with a rich and sophisticated cultural repertoire, including complex stone tools and artistic behavior," study author Chris Clarkson, who is an archaeologist from the University of Queensland, told Axios.

Near the campfire, they found pigments that may have been used for painting walls and coloring their bodies. Peter Hiscock, an archaeologist from the University of Sydney who was not part of the study, told Axios: "Clarkson has found a remarkable scene...These artifacts include what are now the earliest known polished (ground) axes, a known marker of elaborate hafted tools - 20,000 years older than axes anywhere else in the world."

Debate on the demise of the megafauna: Clarkson told Axios the findings show humans coexisted with megafauna for a long time. He argues that this puts to rest the Blitzkreig theory (that humans quickly wiped out some species), and possibly disputes the belief that humans, not climate, were the main factor in their demise. "The extinction of the megafauna now seems to have been gradual and may not have directly involved humans at all," Clarkson said.

However, Petraglia said the "overlap between early human occupation and the extinction of megafauna suggests that humans may have played an important role in contributing to the demise of these great creatures...by [the] sophisticated hunting and gathering communities."

Further research needed: Curtis Marean, who wrote a view on this study, said this reiterates the need for archaeologists to not only discover new sites but retest old ones with new technology. "The latest work in Australia shows us the pay-off, and provides a reminder that this massive continent could reveal many other secrets during future fieldwork," Marean wrote.

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