Archaeologists are generating a 65,000-year-old rainfall record from ancient food scraps found at Australia's earliest-known site of human occupation.
University of Queensland researcher Dr Anna Florin said the research was giving a glimpse into the Kakadu region's environment from the time when people first entered the continent from the north.
"Using the scraps from meals eaten tens of thousands of years ago, we can tell a localised story of climate change and explore its effects on communities living in the Kakadu region through time," said Dr Florin, who also works with ARC Centre of Excellence for Australian Biodiversity and Heritage.
Using the nutshell of anyakngarra - also known as pandanus - a team of researchers led by Dr Florin worked alongside Mirarr Traditional Owners to develop a new method to investigate past rainfall at the site called Madjedbebe.
"The nutshells hold evidence in their composition for the amount of water available to them when they were growing and can be used to understand past rainfall," Dr Florin said.
Excavation director Professor Chris Clarkson from UQ's School of Social Science said the research was a huge leap forward.
"We're now able to read the changing rainfall record through time and match this to the amazing strategies that were developed by Aboriginal people to cope with a dramatically changing landscape," Professor Clarkson said.
The nutshells - discovered during excavations at Madjedbebe on Mirarr Country in the Alligator Rivers region in 2012 - are the leftovers of meals eaten up to 65,000 years ago.
Coupled with other archaeological evidence from Madjedbebe, the research showed the region was likely a good place to be even during glacial periods, Dr Florin said.
"It allowed people to thrive during the driest spells in Australia's history.
"This included during the Last Glacial Maximum - a period of global aridity occurring between about 25,000 and 18,000 years ago - in which Australia's arid zone dramatically expanded.
"We can now see the region would have allowed early Australians to thrive during long dry spells, perhaps also attracting communities from surrounding areas," Dr Florin said.
Another significant finding of the study was that the driest time in this long record of human use of the site was not during the Last Glacial Maximum, she said, but today.
"Kakadu is experiencing the driest time since humans first arrived in the country," Dr Florin said.
"The region's plants and animals are experiencing extreme hardships.
"Feral animals, loss of biodiversity and disruptions to cultural landscape management, including vegetation burning, all pose increased threats to the health and wellbeing of the landscape and its Traditional Owners."
Gundjeihmi Aboriginal Corporation chief executive officer Justin O'Brien said an "extraordinary depth of knowledge" was being gained at the Madjedbebe site.
"This research reaffirms the importance of its long-term protection," Mr O'Brien said.
Contributors to the joint study include the Max Planck Institute for the Science of Human History, University of Washington, University of Canterbury, Australian Nuclear Science and Technology Organisation, University of Wollongong and Griffith University.
The study was funded by the Australian Institute of Nuclear Science and Engineering, the Australian Research Council, the Wenner Gren Foundation, the Dan David Foundation, CABAH, and the Max Planck Institute for the Science of Human History.
The research was published today in Nature Ecology and Evolution (DOI: 10.1038/s41559-020-01379-8).
Contact: Dr Anna Florin, +61 (0)432 689 226, [email protected]; Professor Chris Clarkson, +61 (0)429 992 491, [email protected]; Ms Kirsten Blair, Gundjeihmi Aboriginal Corporation, +61 (0) 412 853 641, [email protected]
Images, from top: 1) Fruit of the Anyakngarra, also known as pandanus. The soft base is made into a drink and their nuts are an excellent source of fat and protein.
2) Anyakngarra (Pandanus spiralis) growing on the Magela Creek floodplain, Mirarr Country, northern Australia.
3) Fruit of an anyakgnarra, broken open to expose the delicious nuts. When burnt, the tough shell can survive for thousands of years and includes information about the water available to the plant when it was growing.
4) Anyakngarra (Pandanus spiralis) preserved for 65,000 years.
5) Anna Florin collecting anyakngarra fruits on Mirarr Country in the Kakadu region of northern Australia.
6) Madjedbebe rock shelter (Mirarr Country, northern Australia) the continent's earliest known site of human occupation.
