Forensic findings of the Stone Age kind: Using an innovative method, researchers have elicited DNA traces from a 20,000-year-old deer tooth pendant, which probably came from the former wearer. Genetic comparisons show that the denisova cave dweller in southern Siberia was related to northern Eurasian people of the era known from sites further east. The scientists say that the new possibility for non-destructive isolation of genetic traces could hold great potential for anthropology and archaeology.
Ancient utensils or ornaments: who made, used or wore them? Up to now it has been difficult to assign Stone Age finds to specific persons, because burials and grave goods were rare in this era. In order to nevertheless gain clues, an international research team led by the Max Planck Institute for Evolutionary Anthropology (MPI EVA) in Leipzig has now sounded out the potential of a method known from criminal forensics: by detecting genetic material it can sometimes be proven that a perpetrator used a certain object. However, the genetic traces are comparatively recent. However, the idea is that user DNA could have been preserved in certain materials for thousands of years and be suitable for isolation.
Forensic investigations into ancient objects
The researchers focused on objects made of bone and teeth. As they explain, the chances of success were greater because these organic materials are more porous than stone objects. This enables them to better bind genetic material from skin cells, sweat and other body fluids. As the team points out, an important consideration in developing their method was that the sampling strategy would not damage the valuable artifacts. Therefore, the team first tested which chemicals are suitable for non-destructive DNA extraction from archaeological bone and tooth materials.
A phosphate-based solution turned out to be the most suitable. "When we wash the artifacts at temperatures of up to 90 degrees Celsius, we are able to extract DNA from the wash water while the objects remain fully intact. You could say that we have set up a washing machine for ancient artifacts in our clean room laboratory,” says lead author Elena Essel from the MPI EVA. To circumvent the problem of contamination of finds by modern humans, after initial failures, scientists focused on newly excavated objects. Consistent hygiene measures meanwhile prevent them from being contaminated by modern DNA. The new analytical method was finally used successfully in the investigation of a find from the famous Denisova Cave in southern Siberia. It is a pendant discovered in 2019 that was made from a deer tooth in the Neolithic period.
The pendant of a Stone Age woman
As the researchers report, they were able to successfully isolate not only the animal's genome but also human DNA from this find. "The amount we were able to extract from the surface of the trailer was really extraordinary - almost as if we had sampled a human tooth," says Essel. The researchers first analyzed the proportion of mitochondrial DNA from the material obtained. Based on certain genetic characteristics in the human and animal sequences, it was possible to draw conclusions about the age of the find. This enabled the researchers to estimate the period between 19,000 and 25,000 years ago without even having to sacrifice material for radiocarbon dating.
Analysis of human mitochondrial DNA also suggested that it came from a single human. But the team was also able to reconstruct part of the nuclear genome of the person who appears to have worn or made the pendant at the time. Based on the number of X chromosomes, the researchers were able to document that it was obviously a woman. In addition, genetic comparisons showed that this Denizova Cave resident was related to people living in more eastern parts of Siberia at the same time, whose skeletal remains had been analyzed in previous studies.
According to the scientists, the results now show considerable potential for research. They hope to now be able to apply the method to other Stone Age objects made from bones and teeth. It is possible that they can also be assigned to specific people and thus provide new insights into the mysterious communities of the Stone Age.
Source: Max Planck Institute for Evolutionary Anthropology, Article: Nature, doi: 10.1038/s41586-023-06035-2