The Cave with Bones
In February 2002, a team of Romanian speleologists exploring a karst system in the southwestern Carpathian Mountains discovered a hidden chamber. The cave, named Peștera cu Oase ("The Cave with Bones"), was littered with the skeletal remains of Late Pleistocene cave bears (Ursus spelaeus). On the cave's surface, they found a complete lower jawbone, a human mandible. Designated "Oase 1," this fossil was directly dated by accelerator mass spectrometry to be between 37,000 and 42,000 years old. This age places it among the oldest known remains of early modern humans in Europe.
The physical form of the mandible presented a puzzle. It belonged to a modern human—it has a projecting chin, a feature absent in Neanderthals. Yet, it also possessed archaic characteristics. The jawbone has an exceptionally wide ramus (the vertical portion at the back) and its molars get progressively larger towards the back, with an unusually large third molar. These features are outside the typical range for modern humans and closer to those seen in Neanderthals and other archaic hominins. This mosaic of traits immediately suggested a complex ancestry and provided the first anatomical hints of interbreeding between modern humans and Neanderthals in Europe. Further discoveries in the cave, including a cranium from a second individual ("Oase 2"), confirmed this pattern of mixed modern and archaic features.
A recent family secret
The anatomical clues in the Oase 1 jawbone were compelling, but the definitive evidence came from its DNA. In 2015, a team led by paleogeneticist Svante Pääbo at the Max Planck Institute for Evolutionary Anthropology successfully sequenced its genome. The results were stunning. The genome of the Oase individual contains between 6% and 9% Neanderthal DNA. This is the highest percentage of Neanderthal ancestry ever found in a modern human, far exceeding the 1-3% found in present-day non-African populations.
The genetic data revealed the percentage. The segments of Neanderthal DNA in the Oase 1 genome were exceptionally long. Because DNA gets broken up and recombined with each passing generation, long, continuous segments indicate a very recent ancestor. The analysis showed that the Oase individual had a Neanderthal ancestor just four to six generations back in their family tree. This means the interbreeding event happened less than 200 years before the Oase individual lived. This finding provides direct evidence of modern humans and Neanderthals mixing in Europe during the Upper Paleolithic. The Oase population does not appear to have contributed substantially to the gene pool of later Europeans. Their lineage represents an early, pioneering group of modern humans in Europe that eventually died out.