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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鈥攖he 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 卤 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鈥攂ut 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," 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.

Researchers conclude that genetic evidence does not support a timeline earlier than approximately 50 kya for human settlement in Sahul. Findings suggest a scenario in which modern humans dispersed rapidly eastward after Neanderthal interbreeding, later acquiring Denisovan genetic signatures during movement through Asia.

While genomic evidence supports this less than 50 kya scenario, it leaves looming large questions about the evidence showing much older occupation. It could be evidence of an earlier expansion of current modern humans who either died out, avoided Neanderthal admixture out of Africa, or only minimally contributed to current population genetics.

Not covered in the current study is the possibility of a non-current modern human presence. The recent genomic identification of a Homo longi skull from the 146k-year-old "Dragon Man" from Harbin, northeastern China, along with even older evidence from Tibet show that Denisovans have a long history across East Asia, inhabiting a wide range of habitats.

If there were Denisovan populations in Sahul or in the greater Oceania island region, it might explain some of the earliest site evidence.

Some previous research has already found that the indigenous Ayta Magbukon people in the Philippines, who retain the highest levels of Denisovan gene admixture in the world at up to 9%, were found to have experienced an independent Denisovan admixture event than the next highest group, Australians and Papuans (at up to 6% Denisovan admixture).

Regardless of the next prevailing framework that emerges from the inclusion of new genome-based tools and improved site-dating methods, the history that people write for themselves based on science or myth will likely be overturned a few more times by the irreverent research of archaeological anthropologists.

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