“People have been eating the same nut at the same place for 65,000 years, which is fantastic for scientists, because you can make direct comparisons,” Dr Florin said.
The scientists used carbon dating to determine the amount of water in the environment when the pandanus plants were growing, giving an indication of overall rainfall.
Dr Florin said they discovered the current period was the driest the Kakadu region had ever been, including at the height of the last ice age, between about 25,000 and 18,000 years ago.
“It’s not so much that there’s less rainfall today, but the rainfall is coupled with more evaporation because we have warmer overall temperatures now,” she said.
“During the last glacial stage we know northern Australia got very dry but there were also cold periods which meant there wasn’t as much evaporation.
“So the current environment [of Kakadu] is the most arid it’s been in human history.”
Despite the periodic dry spells, the consumption of pandanus nuts continued at the site almost entirely unbroken, which researchers believe shows it was a hub for trading and migration.
“In those drier periods we see spikes in the number of artifacts we’re finding, which indicated that more people were travelling to the area,” Dr Florin said.
“And that coincides with spikes in the number of artifacts made of ‘exotic’ material, that is material that is not from the region, that comes from a long way away.
“It suggests people were moving further for food because it was drier, and were coming together at places where they knew they could get food and water.”
The samples were taken from the site, in the Alligator River area, in 2012, and have been progressively analysed in the years since.
The researchers initially did tests on modern pandanus plants to get baseline readings on the plant’s make-up under specific rainfall conditions before analysing the ancient samples.
Excavation director 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 research has been published in the journal Nature Ecology and Evolution.
Stuart Layt covers health, science and technology for the Brisbane Times. He was formerly the Queensland political reporter for AAP.