“This is the moon landing of genomics because fossils will no longer be needed”
Chiquihuite Cave, where the samples were taken from, is a high-altitude site, 2,750 metres above sea level. Nearly 2,000 stone tools and small tool fragments, known as flakes, were discovered.
The same group of scientists revealed last year that DNA analysis of the plant and animal remains from the sediment packed around the tools in the cave dates the tools and the human occupation of the site to 25,000-30,000 years ago – 15,000 years earlier than people were previously thought to have reached the Americas. Human DNA has not yet been found.
DNA of mice, black bears, rodents, bats, voles and kangaroo rats was found and the genome of the two species of bear has now been sequenced. The huge predatory short-faced bear, which also lived in North America, stood at nearly two metres just on all fours and could weigh up to 1,000 kilos.
Assistant Professor Mikkel Winther Pedersen, first author of the paper, said: “The short-faced bears that lived in northern Mexico were distinctly different from the population of black bears living in north-western Canada. This is an excellent example of the new knowledge that suddenly becomes available when you reconstruct genomes based on DNA fragments extracted from soil.”
Professor Pedersen described the new sequencing as ‘the dawn of an entirely new era’ of population genomics.
He said: “Studies of ancient environmental DNA have been very limited until now. Fragmented DNA from a soil sample could only tell us whether a specific species lived in a certain locality at a certain time, but it gave us no concrete details about the individual in question.
“So, we couldn’t compare this individual with present-day individuals of the same species. But we can now. We have published for the first time a DNA profile of an American black bear that lived in a mountain cave in northern Mexico in the Stone Age. I’m not exaggerating when I say that the potential to extract this type of information from a soil sample of a mere few grams will revolutionise our field.”
Fragments in sediment will be able to be tested in many former Stone Age settlements around the world.
Professor Willerslev added: “Imagine the stories those traces could tell. It’s a little insane – but also fascinating – to think that, back in the Stone Age, these bears urinated and defecated in the Chiquihuite Cave and left us the traces we’re able to analyse today.”
Published: 19/4/21