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Why do some researchers disagree about the earliest dates for human arrival in Australia?

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Aboriginal people of Galiwnku Island in Australia — Australian Aboriginal peoples Aboriginal people from Galiwnku Island gathering to watch the proceedings at which Prime Minister Kevin Rudd formally apologized to the Aboriginal peoples of Australia for their mistreatment under earlier Australian governments, February 2008.

While it is generally accepted that Australian Aboriginal peoples have inhabited the continent for at least 45,000 to 50,000 years, some researchers propose an earlier arrival, potentially between 65,000 and 80,000 years ago.1

This disagreement stems primarily from the interpretation of data collected at archaeological sites such as Madjedbebe and Nauwalabila I in the Northern Territory. Researchers supporting the earlier dates rely on optically stimulated luminescence (OSL) dating, which measures when sand grains were last exposed to sunlight.123

However, other scholars remain skeptical of these findings. They argue that because these sites are located in areas with significant termite activity, the insects' tunneling can cause artifacts—such as stone tools—to be displaced downward into older soil layers. Critics contend that this vertical movement invalidates the association between the artifacts and the age of the surrounding sand, making the earlier chronological estimates unreliable.123