Peștera cu Oase (pronounced "PEH-shte-ra koo OAH-se") is a group of 12 cave passages and rooms near the city of Anina in Caraș-Severin County, southwestern Romania. This cave is famous for containing some of the oldest remains of early modern humans in Europe, dating back between 42,000 and 37,000 years.

The "Oase 1" lower jaw is fully grown, but the facial bones belong to a person who was about 14 to 16 years old. This suggests the bones came from two different individuals, named "Oase 1" and "Oase 2." Later studies showed that a bone from the side of the head, called the temporal bone, belonged to a third person, named "Oase 3." However, further research found that this bone came from the same skull as the facial and head bones of "Oase 2."

There are no signs of tools, fire, or other human activity in the cave, which may mean the bones were carried into the cave by water through cracks in the rock. The remains of "Oase 2" and "Oase 3" show a mix of features seen in early modern humans and Neanderthals. For example, the bones have a forward-pointing chin, no prominent brow ridge, and a large, rounded skull. However, they also have older traits, such as a large face, a bony ridge behind the ear, and large teeth that grow even larger toward the back of the mouth. These mixed features are similar to those found in a 25,000-year-old child fossil from Abrigo do Lagar Velho and a 31,000-year-old site called Mladeč, as described by Cidália Duarte and others in 1999.

In 2015, genetic testing of the "Oase 1" fossil showed that it had Neanderthal ancestors. The fossil had 5 to 11% Neanderthal DNA in its overall genetic makeup, and one of its 12th chromosomes was 50% Neanderthal.

The cave

In February 2002, a group of cave researchers exploring a limestone cave system in the Miniș Valley, located in the southwestern Carpathian Mountains near Anina, found a new chamber filled with many animal bones. The cave appeared to have been used mainly as a place where cave bears from the Late Pleistocene era (Ursus spelaeus) hibernated. Some bones were placed on raised rocks, which suggests that humans might have played a role in how the remains were arranged. During the exploration, researchers Ștefan Milota, Adrian Bîlgăr, and Laurențiu Sarcina discovered a complete human lower jaw on the cave floor. The chamber was named Peștera cu Oase (The Cave with Bones), and the human jaw was called "Oase 1" (also known as "Ion din Anina" or "John of Anina").

Recent radiocarbon dating of the Oase fossils shows they are 37,800 years old. Located near the Iron Gates in the Danubian corridor, these fossils may represent one of the earliest groups of modern humans to have entered Europe.

Oase 1

In June 2003, a research team led by Ștefan Milota, Ricardo Rodrigo, and Mircea Gherase found more human remains on the surface of the cave. These remains belonged to an adult male and included a full set of bones from the front part of the skull, a mostly complete left temporal bone, and several pieces from the frontal, parietal, and occipital bones.

The age of the remains, called "Oase 1," was determined using a scientific method called radiocarbon dating. The results show the remains are about 40,450 years old, with a possible range of 1,020 years.

The bones of Oase 1 show physical features from both early modern humans and older human groups, such as Neanderthals.

Since 2015, DNA studies of Oase 1 have uncovered several important discoveries.

Oase 2

Scientists mapped out the complete DNA of "Oase 2," which is between 41,500 and 39,500 years old, using a part of the skull called the petrous bone. The DNA information was very detailed, with 20 copies of the genome analyzed.

About 6% of "Oase 2"'s DNA comes from Neanderthals, which is less than what was found in "Oase 1." However, this percentage is still much higher than scientists expected based on its age and compared to other ancient DNA from the Upper Palaeolithic period.

"Oase 2" shares the same basic group of mitochondrial DNA, called haplogroup N, as "Oase 1." When compared to all known DNA samples, "Oase 2" and "Oase 1" are genetically most similar to each other. These two individuals likely belonged to closely related groups, but not exactly the same population.

"Oase 1" is genetically closer to ancient people from Ice Age Europe than "Oase 2," while "Oase 2" is more similar to ancient people from Asia and Native Americans. "Oase 1" also shows a genetic link to another ancient individual called "Peştera Muierii 2," which is not seen in "Oase 2." Among ancient DNA samples, the next closest genetic match to "Oase 2" is a person from Northern China who lived about 40,000 years ago. Neither "Oase 1" nor "Oase 2" is closely related to any modern human populations.

Current research

Peștera cu Oase is still being studied by scientists. Results from the 2005 research are being carefully examined by several institutions, including the Romanian "Emil Racoviță" Institute of Speleology, Australian National University (electron spin resonance and uranium-series dating on 21 bone/tooth samples and 29 sediment samples), University of Bristol (uranium-series analysis on 22 bone samples), University of Bergen (uranium-series dating on 7 samples), University of Oxford (AMS radiocarbon dating on 8 bone/tooth samples), Max Planck Institute (stable isotope analysis and ancient DNA on 37 bone/tooth samples), and University of Vienna (AMS radiocarbon dating on 25 bone/tooth samples).

A skull discovered in Peștera cu Oase between 2004 and 2005 shows characteristics of both modern humans and Neanderthals. Radiocarbon dating shows the skull is 37,800 years old, making it one of the oldest modern human fossils found in Europe. Erik Trinkaus (2007) concluded that modern humans and Neanderthals interbred thousands of years ago.

Implications for research

The physical differences between early modern humans and late Neanderthals, along with differences in DNA from mitochondria, suggest a major change in human populations during the transition from the Middle to Upper Paleolithic periods. This led to the idea of a "Out of Africa with Complete Replacement" model, which suggests that modern humans completely replaced Neanderthals in Europe.

However, recent studies using direct dating of fossils show that some early modern human remains are much younger than previously thought, dating to the mid or late Holocene period, which is much later than earlier estimates.

The "Peștera cu Oase" findings are important because they show a mix of modern human and Neanderthal traits. These fossils are well-preserved and can be clearly identified as a specific type. They overlap in time with late Neanderthals, such as those found in Vindija Cave (Croatia), dated to about 32,000 years ago, and in Arcy-sur-Cure (France), dated to about 34,000 years ago. The presence of Neanderthal-like traits in the Oase fossils supports the idea that these people lived around the same time as Neanderthals, which matches patterns of where and when Neanderthals were found.

Genetic evidence does not rule out the possibility that Neanderthals and modern humans interbred. Physical and archaeological evidence also suggest that Neanderthal traits continued in later human populations. The "Peștera cu Oase" findings support the idea that early modern humans in Europe mixed with Neanderthals.

This model suggests that when modern humans arrived in Europe, they met Neanderthals who had similar cognitive abilities and cultural achievements. At the local and regional levels, interactions between these groups could have included conflict, avoidance, or full mixing. Over time, however, the larger population of modern humans led to the gradual loss of Neanderthal DNA in later human populations, resulting in a blending of biological and cultural traits.