Early human DNA could actually serve as a sign of an ancient civilization having resided in a certain part of the world, even without any bones as tangible proof. That was the discovery made by a group of researchers who found the DNA of Neanderthals and Denisovans in sediment samples across seven separate archaeological sites.
It can often be challenging to determine if people had existed in certain caves, archaeological digs, or other points of interest related to our ancestors. But with the new discovery, this could make it easier for researchers to determine which group of early humans lived in these areas where skeletal remains are often elusive, and tools and other artifacts are usually the only clues of a previous civilization having lived there.
“This work represents an enormous scientific breakthrough,” said Natural Science Museum (Spain) scientist Antonio Rosas, who was quoted by BBC in a report on the discovery.
“We can now tell which species of hominid occupied a cave and on which particular stratigraphic level, even when no bone or skeletal remains are present.”
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A detailed report from Ars Technica looked at how the researchers were able to track down early human DNA through extraction from sediment samples taken from European caves. The team that included Max Planck Institute for Evolutionary Anthropology researcher Viviane Slon had centered their efforts on mitochondrial DNA, or genetic material distinct from a cell’s primary DNA. This type of DNA evolves faster, and can be found in more copies per cell.
“That would allow us more chances to retrieve it from the sediment and also a better way to distinguish between different [species],” Slon told Ars Technica.
Explaining the extraction process to Ars, Slon said that she and her colleagues had taken about half a teaspoon of soil from the archaeological sites, and used chemical reagents to isolate the early human DNA and place it into solution. This allowed her team to extract the DNA and feed it to a sequencing machine for analysis.
Ars added that Slon’s team was the first to extract mitochondrial DNA by “synthesizing one half of the zip,” assuming DNA’s mechanics allow it to work like a cross between a zipper and a jigsaw puzzle. In this model, each of the zipper’s teeth can only mesh together with a specific tooth, and the fact that scientists have enough DNA data on several extinct species of animals is also taken into account. Once the aforementioned half of the “zip” is synthesized, that results in a “genetic bait for DNA sequences” which is then placed in the solution, allowing it to match with the other half and get extracted.
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Based on the findings, the researchers were able to find the DNA of early human species such as Neanderthals and Denisovans, along with DNA belonging to woolly mammoths, wooly rhinos, and other extinct species from the same time. After cross-checking the new information with existing data, it was determined that the team found Neanderthal DNA in areas where bones of these ancient humans were found in the past. Likewise, BBC noted that sediment taken from Denisova Cave in Russia had yielded Denisovan DNA, just as one would expect.
Reactions to the study have been overwhelmingly positive, as several scientists who were not involved in the study spoke to Ars to sing its praises. One of these scientists, Aarhus University archaeologist Christian Hoggard, told the publication that the new research could inspire scientists to focus more on sediments rather than artifacts when trying to look for signs of previous civilizations at archaeological sites.
With the technique proven to be reliable, the researchers now hope to extract early human DNA from sites which were once lived in by still-unidentified ancestors of ours. And it could lead to even more exciting discoveries going forward, while helping scientists further understand the evolution of man from our early human ancestors to today’s modern humans.
“The technique could increase the sample size of the Neanderthal and Denisovan mitochondrial genomes, which until now were limited by the number of preserved remains,” said study co-author Carles Lalueza-Fox of the Spanish National Research Council.
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