The dirt on the floor of an ancient, isolated cave in Mexico provided scientists with a source of valuable ancient DNA.
The discovery marked the first time scientists managed to sequence ancient DNA from just soil samples, and it is all thanks to the Upper Paleolithic bears that actively used the cave as a toilet some sixteen thousand years ago.
The scientists described their finding as to the “Moon landing of genomics,” Sciencealert reported.
The breakthrough suggests that fossilized remains are no longer the only way to uncover ancient DNA.
Additionally, it shows ancient DNA can now be analyzed in the context of populations instead of being scattered, fragmentary instances.
Geneticist Eske Willerslev of the University of Copenhagen explained:
“When an animal or a human urinates or defecates, cells from the organism are also excreted. And the DNA fragments from these cells are what we can detect in the soil samples.”
He also added that they used powerful sequencing techniques and reconstructed genomes according to the fragments for the first time.
They proved that hair, urine, and faeces provide solid genetic material, which, inadequate conditions, can survive for over 10,000 years.
The cave where the samples were found is famous thanks to its historical significance.
Multiple stone tools and fragments, dating back to between 25,000 and 30,000 years ago, are a trace of human occupations, though they weren’t the only occupants of the cave.
Bones and signs of DNA also showed the presence of numerous animals like bats, voles, bears, rodents, and kangaroo rats.
Thanks to the sample, Willerslev and his team have sequenced and recreated completely the genomes of two Upper Paleolithic bears.