A team of archaeologists and geoscientists recently revealed the secrets of the ancient topography of Sahul, an Ice Age landmass that included Australia and New Guinea. Their research, published in Quaternary Science Reviews, reveals intriguing details about a little-known period in human history.
For much of Australia's past 65,000 years of human history, lower sea levels revealed a large dry landmass in the northwest of the Australian continent, connecting the Kimberley and Arnhem lands into one continuous area. Through careful analysis of high-resolution bathymetric data (seafloor topography), the researchers found that during marine isotope stage 4 (71,000-59,000 years ago), this now-submerged area was once a vast archipelago and was stable for about 9,000 years.
During the second marine isotope phase (29,000-14,000 years ago), it became a completely exposed shelf characterized by an inland sea adjacent to a sizable freshwater lake and surrounded by high steep walls cut by deep canyons.
The team's population model shows that during marine isotope phase 4-2, the now-submerged continental shelf experienced fluctuations in potential carrying capacity and could have supported a population ranging from 50,000 to 500,000 people at different times.
However, between 14,500 and 14,100 years ago (during Meltwater Pulse 1A) and 12,000-9,000 years ago, global sea levels rose rapidly, causing about 50% of the northwest continental shelf to be rapidly submerged, causing profound changes in human life span.
These events likely triggered the retreat of humans before coastline erosion, as reflected in the peak of occupational intensity at the archaeological sites of Kimberley and Arnhem and the sudden appearance of distinctive new rock art styles in both areas.
Lead researcher Kasih Norman said: "The existence of this vast archipelago likely facilitated the successful dispersal of the first maritime explorers from Varasei Island (in present-day Indonesia), providing a familiar environment for them to adapt to the vast continent of Sahul."
Additionally, the study highlights the critical role that now-submerged continental margins played in early human expansion. Norman added: "The temptation to ignore the late Pleistocene Sahul shelf edge in discussions of early human reproduction and expansion risks oversimplifying and misunderstanding this critical historical period."
The implications of these findings highlight the need to reassess narratives of early human migrations and the impact of climate change on ancient populations.
"Our population models show that populations peaked during the last Ice Age, about 20,000 years ago, when the entire extent of the North West Shelf was dry land," Norman said. "Now, new genetic research supports this finding, showing that the Tiwi Islander population was very large at the peak of the last Ice Age, just east of the study area."
The rise of undersea archeology in Australia is contributing to global understanding of late Pleistocene human migrations, as underwater landscapes continue to yield valuable archaeological finds.
This study is an important milestone in understanding the complex interactions between ancient landscapes, humans and environmental change. Dr. Norman said that as the exploration and analysis of underwater sites expands, it is expected that more secrets of humankind's shared history will be revealed.
Compiled from /scitechdaily