Researchers at La Trobe University, Australia, and the University of Utah, U.S., report that recent DNA findings challenge claims of a 65,000-year-old human arrival in Sahul—the ancient paleocontinent that existed during the Pleistocene ice age, made up of present-day Australia, Tasmania, and New Guinea.

Science tends to be irreverent of preexisting beliefs. Overturning the Earth-centric universe with one that centers around the sun upset thousands of years of well-reasoned observations and mythical contemplations.

Later discoveries showed that the sun itself moves along a rural stretch of a spiral arm amidst hundreds of billions of stars in the Milky Way, in a universe brimming with trillions of galaxies, firmly upending any concept of humanity being at or even near the center of anything.

Archaeological anthropology has gained an especially irreverent reputation, as there is scarcely an origin story of any culture on Earth that has not been amended or refuted by its findings. That irreverence also applies to the field itself when evidence emerges to question long-accepted interpretations, including those once presented as prevailing frameworks.

Human migration into Sahul is a pivotal event in understanding the global dispersal of current modern humans. Earlier archaeological work proposed dates as far back as 65 kya, and with good supporting evidence. Mololo Cave on Waigeo Island, immediately west of New Guinea, holds a resin artifact dated to 51.1 ± 2.7 kya.

Sulawesi cave art on an Indonesian island dates to approximately 51.2 kya, supporting human presence along a possible northern migration route. At the Madjedbebe site in Northern Australia, multiple dating techniques present evidence of 65 kya stone tools and other human activity.

With such convincing evidence of early human population presence in ancient Oceania, it is easy to see how an over 50 kya timeline for arrival in Australia was reached—but there is a problem.

Two studies recently published in Nature and Science both find that Neanderthal interbreeding with anatomically modern humans occurred only once, in Europe, between approximately 43.5 kya and 51.5 kya.

Previous evidence shows that all current modern humans outside of Africa carry approximately 2% Neanderthal DNA in their genomes. If the Neanderthal DNA in indigenous Sahul populations matches that of other populations, it could place a hard limit on when their ancestors made the journey.

In the study, "Recent DNA Studies Question a 65 kya Arrival of Humans in Sahul," published in Archaeology in Oceania, researchers conducted a comparative analysis of Neanderthal and Denisovan genetic signatures in living Sahul populations to determine whether they align with other non-African populations.

Evidence shows that living Sahul populations carry approximately 2% Neanderthal DNA in their genomes, with no dilution of Neanderthal ancestry in Sahulians compared to other non-African populations has been observed.

Denisovan ancestry in Sahul ranges between 2% and 5%. No substantial admixture is detected from Homo erectus, Homo floresiensis, or Homo luzonensis.

Edited by Sadie Harley, reviewed by Andrew Zinin