About a decade ago, the theory that Neanderthals had bred with Homo sapiens outside of Africa rocked the anthropological, archeological, and genetics worlds. Some scientists looked down on these now extinct human cousins, but quickly learned that they themselves could share as much as four percent of their DNA with Neanderthals. The question of how long ago and where this interbreeding occurred is still being debated. Now, some new analysis is further filling in the timeline of Neanderthal and modern human interactions and the two may have intermingled for quite some time.
[Related: Neanderthals were likely creating art 57,000 years ago.]
A new genetic analysis of bone fragments from an archaeological site in central Germany shows that modern humans had reached northern Europe 45,000 years ago. This means that their arrival overlapped with the Neanderthals who had been living there for several thousand years before going extinct. The evidence also adds to the suspicion that the movement of modern humans into Europe and Asia about 50,000 years ago helped drive Neanderthals into extinction. The findings are described in three new papers published January 31 in journals Nature and Nature Ecology and Evolution.
Neanderthals were living in northern Europe for more than 500,000 years by the time that modern humans began to arrive. A multidisciplinary team of researchers studied bone fragments and stone tool blades from a site near Ranis, Germany. It was first explored in the 1930s, but a team from institutions in Austria, China, Denmark, France, Germany, Italy, Spain, Sweden, Switzerland, the United Kingdom, and the United States re-excavated the area from 2016 to 2022.
This site is best known for some finely flaked, leaf-shaped stone tool blades called leaf points. The leaf points found there were dated to the final years of the Middle Paleolithic period— between 300,000 and 30,000 years ago—or the beginning of the Upper Paleolithic, which starts around 50,000 years ago. The tools are among the oldest confirmed sites of modern human Stone Age culture in north central and northwestern Europe.
The leaf points are similar to stone tools that have been uncovered at several sites in the United Kingdom, Poland, Moravia, and elsewhere in Germany. Archaeologists believe that they were all produced by the same culture known as the Lincombian–Ranisian–Jerzmanowician (LRJ) culture.
Previous dating of the Ranis site estimated that it was 40,000 years old or older. However, without recognizable bones to indicate who crafted the tools found there, it was not clear if Neanderthals or Homo sapiens made them. In order to know if a Neanderthal or Homo sapien crafted the tools, it would take some DNA.
The DNA evidence
During the re-excavation, the team was able to get to some rocks that 20th Century scientists couldn’t get to, to look for LRJ culture bones or more tools.
“After removing that rock by hand, we finally uncovered the LRJ layers and even found human fossils. This came as a huge surprise, as no human fossils were known from the LRJ before, and was a reward for the hard work at the site,” Marcel Weiss, a study co-author neurophysicist at Friedrich-Alexander-Universität Erlangen-Nürnberg and the Max Planck Institute for Evolutionary Anthropology in Germany, said in a statement.
[Related: Neanderthals may have been early risers.]
These human remains meant that they could perform genetic analysis to see who could have made the stone tools. The extracted DNA in the ancient bones was highly fragmented. Study co-author and University of California, Berkeley research fellow Elena Zavala isolated and sequenced the basic DNA and all of the mitochondrial DNA that was inherited from the mother.
“We confirmed that the skeletal fragments belonged to Homo sapiens. Interestingly, several fragments shared the same mitochondrial DNA sequences—even fragments from different excavations,” Zavala said in a statement. “This indicates that the fragments belonged to the same individual or their maternal relatives, linking these new finds with the ones from decades ago.”
These bone fragments were initially identified as human through analysis of bone proteins by study co-author Dorothea Mylopotamitaki, a doctoral student at the Collège de France. The team compared the Ranis mitochondrial DNA sequences with other mitochondrial DNA sequences from human remains at other paleolithic sites in Europe.
They used this data to construct a family tree of early Homo sapiens across Europe. They found that all but 13 fragments from the Ranis cave were similar to one another. They also resembled mitochondrial DNA from a 43,000-year-old skull of a woman found in a cave in the Czech Republic. The only standout in the sample was an individual from Italy.
“That raises some questions: Was this a single population? What could be the relationship here?” Zavala said. “But with mitochondrial DNA, that’s only one side of the history. It’s only the maternal side. We would need to have nuclear DNA to be able to start looking into this.”
The DNA revealed that Homo sapiens were present at least in this part of Germany, not just Neanderthals.
Insights into human diet
The cave excavation also found traces of DNA from multiple mammals. There were traces of horses, cave bears, woolly rhinoceroses, and reindeer, which indicates that the area had a colder climate similar to the tundra of Siberia and northern Scandinavia today.
It also indicates that the human diet at the time was based on these large land animals.
[Related: Neanderthals caught and cooked crabs 90,000 years ago.]
“Zooarchaeological analysis shows that the Ranis cave was used intermittently by denning hyaenas, hibernating cave bears, and small groups of humans,” Geoff Smith, a study co-author and zooarchaeologist from the University of Kent and the Max Planck Institute for Evolutionary Anthropology, said in a statement. “While these humans only used the cave for short periods of time, they consumed meat from a range of animals. Although the bones were broken into smaller pieces, they were exceptionally well preserved and allowed us to apply the latest cutting-edge methods from archaeological science, proteomics and genetics.”
It also indicates that earlier groups of Homo sapiens dispersing across Eurasia could adapt to harsh changes in climate conditions.
“Until recently, it was thought that resilience to cold-climate conditions did not appear until several thousand years later, so this is a fascinating and surprising result,” study co-author and University of La Laguna in Spain paleoclimatologist Sarah Pederzani said in a statement.
Revising the timeline
Radiocarbon dating of human and animal bones from different layers of the site was used to build a timeline of the cave. Many of the bones had traces of human modifications on their surfaces, which links their dates to the presence of humans from the LRJ culture in the area.
“We found very good agreement between the radiocarbon dates from the Homo sapiens bones from both excavation collections and with modified animal bones from the LRJ layers of the new excavation, making a very strong link between the human remains and LRJ,” study co-author and Postdoctoral Fellow at the Francis Crick Institute Helen Fewlass said in a statement. “The evidence suggests that Homo sapiens were sporadically occupying the site from as early as 47,500 years ago.”