In search of traces of the past, researchers venture into remote caves: Here archaeologists are on their way to the Chiquihuite cave in Mexico, where prehistoric stone tools were found
The Chiquihuite Cave is located 2,650 meters above sea level in the highlands of the Mexican state of Zacateras. Your entrance overlooks the valley, which is around a thousand meters below, and offers protection and a view at the same time. In fact, archaeologists have made some groundbreaking discoveries in this cave. As early as 2012, during a test excavation, they found the first indications of an Ice Age settlement of this cave by animals and plants.
During more extensive excavations four years later, scientists found even clearer traces: At a depth of up to three meters they discovered around 2,000 man-made stone tools that were probably used for cutting and chopping. The special feature: Over 200 of these stone tools were embedded in layers of gravel, which were dated from 25,000 to 32,000 years ago. According to this, humans must have been in America before the height of the last ice age and penetrated as far as Mexico – 15,000 years earlier than previously assumed.
Who these people were, however, remains open. Because the design of the tools does not resemble any previous find and no bones of the former cave dwellers could be found. The archaeologists conclude that these people were probably hunters and gatherers who only visited the site occasionally. When and where they came to America is still a mystery.
In order to get more information about the prehistoric toolmakers, researchers led by Eske Willerslev from the University of Copenhagen have searched for the DNA of the former cave visitors. “When a living being urinates or defecates, for example, some of its cells are also excreted. We can then detect the DNA fragments from these cells in soil samples, ”explains Willerslev.
Instead of traces of the human inhabitants, the researchers in the Chiquihuite cave have so far only encountered animal DNA: In addition to the genetic make-up of mice, voles, kangaroo rats and bats, they were also able to reconstruct the genome of two black bear species that lived in the cave 16,000 years ago to have. They include an ancestor of the American black bear (Ursus americanus) and a short-faced bear (Arctodus simus) that became extinct 12,000 years ago.