Researchers uncover lives of ancient humans in ‘handful of dirt’
Australian archaeologists used DNA technology to trace modern day humans’ ancient roots using more than 700 sediment samples dating back 300,000 years.
Australian archaeologists have used DNA technology to trace the ancient roots of modern day humans at the Denisova Cave in Siberia using more than 700 sediment samples dating back 300,000 years.
The archeologically rich cave in the foothills of Russia’s Altai Mountains has long been known as the first place where fossil remains of a mysterious group of archaic humans dubbed the Denisovans were discovered, with Neanderthal fossils also being found there.
An international team of scientists including geochronologists from the University of Wollongong, as well as experts from Russia and Germany, using sediment dating and DNA analysis have now revealed a fuller picture of the sequence of human occupation of the cave.
The study, which uncovered 175 sediment samples from modern humans providing the first evidence of their occupation of the site as well as shedding light on Denisovans and Neanderthals, is the largest analysis ever made of sediment DNA from a single site.
The University of Wollongong team used luminescence or optical dating technology to date small DNA samples hidden in the sediment, through measuring the brightness of the light through the samples to date the samples.
Professor Richard “Bert” Roberts, who along with Professor Zenobia Jacobs, Associate Professor Bo Li and PhD candidate Kieran O’Gorman collected the samples in 2017, said the findings revealed a “comprehensive set of samples spanning more than 300,000 years of Siberian history”.
“I really do think it does represent a breakthrough in the way we can look at archaeological sites,” he said.
“The big advantage is that we only have a dozen human fossils and based on this one study we have 175 hits for human DNA.
“It’s like ten times more even if we can’t find fossils, as it’s very rare to find when you’re looking for something large as you don‘t often get something large preserved in the ground because it gets nibbled away on and rainwater degrades bone. And that’s where we get the DNA from.”
Along with DNA analysis from the Max Planck Institute for Evolutionary Anthropology in Germany the study showed that Denisovans were the most ancient dwellers in the cave spanning from 250,000 years ago until 60,000 years ago, and were responsible for the earliest stone tools.
Neanderthals first appeared 200,000 years ago before disappearing 40,000 years ago, just as they vanished across Eurasia, with a new variety of DNA that was previously unknown also being uncovered.
Meanwhile, modern humans were late arrivals to the cave, with their DNA first appearing in sediments dating back 60,000 and 45,000 years.
Professor Roberts said the study, which will be published in scientific journal Nature this week, was significant because it also uncovered evidence of the ancient animals that also inhabited the cave.
“It’s not only about the DNA you get from the human side of the story, we also talk about the hyenas, mammoths, bears that are no longer there and all sorts of animals that have come and gone,” he said.
“You can get a lot out of the ground - just a handful of dirt can give you a huge amount of history around the animals and humans alive at the time.”
The research also uncovered new details around the climactic changes at work in ancient times, the first around 190,000 years ago coinciding with a shift from warm to colder conditions which caused a change in hyena and bear populations and Neanderthals first appearing.
The second major change from cold to warn which occurred between 130,000 and 100,000 years ago coincides with the Denisovans vanishing.
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