40,000 Year Old Australian Archaeology Site Reignites Debate On Origins

An Aboriginal leader in Australia claims archaeologists have discovered the world’s southernmost site of early human life. The site is reported to be 40,000 years old.  Is this the earliest human site here, and what does it mean in terms of the origins of human settlement?

Michael Mansell of the Tasmanian Aboriginal Centre states, “When the archaeological report came out it showed that (life there) had gone back longer than any other recorded place anywhere else in Tasmania, dating back to 40,000 years.”

The projects head archaeologist Rob Paton added, “We haven’t even done a reading on the bottom sample yet, I was expecting 17,000 (years) for the base of the trench and about 4 or 5,000 (years) for the top. That suggests to me that they’re probably correct, giving us a top reading of 28,000 (years old) and certainly seeming to go back another 10,000 (years) at least beyond that. We do have the oldest, most southern site anywhere in the world, an important site for anyone and quite exciting for us.”

The date was achieved using a process called thermoluminescence or TL in archaeological terms, which is in essence ‘heat glow’. When certain materials are last heated or exposed to sunlight, the lattice structure traps some radioactivity. Since there is a known and constant decay rate for this radioactivity, it can consequently be measured giving an accurate time frame. TL fills an important gap between the accuracy range of radiocarbon (C14) dating which generally is accurate only to around 40-60,000 years BP (Before Present) and Potassium Argon (K-Ar) dating which does not begin to be accurate until at least 100,000 BP. TL is also a valuable tool for measuring sediments and ceramics where carbon samples cannot be taken.

The site was located during a survey work that took place prior to transportation construction in Tasmania near the Derwent River, and yielded around three million artifacts.

There is some debate as to the earliest arrival of our species in Australia. The Genographic Project estimates that Aboriginal Australians branched off approximately 60,000 BP.

There is also some evidence of occupation earlier than the 40,000 BP range. The oldest rock art found in Australia dates from between 45,000 to 65,000 BP. Rock art can take 2 forms: petroglyphs (rock engravings) and pictographs (rock paintings). Rock art can be dated using traditional C14 methods, although optically stimulated luminescence (OSL) and accelerator mass spectrometry (AMS) are also option.

Petroglyph in Australia

Pictograph: Lascaux Cave, France

There are also human remains called Mungo Man that were found almost 1000 km west of Sydney in New South Wales by Lake Mungo that were dated between 56,000 and 68,000 BP.

The New York Times reports:
Geneticists re-examining the first settlement of Australia and Papua-New Guinea by modern humans have concluded that the two islands were reached some 50,000 years ago by a single group of people who remained in substantial or total isolation until recent times. The finding, if upheld, would undermine assumptions that there have been subsequent waves of migration into Australia.

The oldest human remains from Australia, about 45,000 years in age, have quite thin or gracile bones, whereas fossils from 20,000 years ago are robust. The new findings suggest that the difference must stem from some internal process like adaptation to climatic change, and not to interbreeding with the archaic species Homo erectus, as some have suggested.

Regardless, the first ones took a land bridge from southern/southeastern Asia down the Sunda Shelf in modern day Indonesia. Considering the sea levels were up to 150 meters lower at the time because much of the water on the planet was locked up in ice shelves and continental glaciers, this would have meant an connected isthmus nearly reaching the Sahal Shelf (Australia and Papua New Guinea itself). There is an open water gap between the two that would have stretched at least 90 km, meaning that the Aboriginal Australians would have had to have the world’s earliest definite use of navigable rafts or canoes, although to date there is no archaeological remains of either found.

Although the actual arrival time may never be known, the earliest physical evidence of habitation by modern homo sapiens outside Africa is in Australia, and this recent archaeological site in Tasmania is one of the oldest.

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