Peștera cu Oase (pronounced "PEH-shteh-rah koo OAH-seh") is a group of 12 cave passages and rooms near the city of Anina in Caraș-Severin County, southwestern Romania. This location 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 teenager in their mid-20s, suggesting this is a second individual, called "Oase 2." Further study showed that a bone from the left side of the skull comes from a third person, who was either a teenager or an adult woman, named "Oase 3." However, later research found that this bone is part of the same skull as the facial and head bones of "Oase 2." There are no signs of tools, fire, or torches in the area, 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. These remains have traits common to modern humans, such as a protruding chin, no brow ridge, and a large, rounded braincase. However, they also have older traits, like 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 in Abrigo do Lagar Velho and a 31,000-year-old site called Mladeč, as noted by Cidália Duarte and others in 1999.

In 2015, genetic research showed that the "Oase 1" fossil had a recent Neanderthal ancestor, with about 5-11% of its DNA from Neanderthals. The 12th chromosome of this fossil was 50% Neanderthal.

The cave

In February 2002, a cave exploring team discovered a new chamber in the limestone area of Miniș Valley, located in the southwestern Carpathian Mountains near Anina. The chamber contained many mammal bones. The cave appears to have been used mainly as a place for hibernation by the Late Pleistocene cave bear (Ursus spelaeus). Some bones were found on raised rocks, which suggests possible human activity in the area. The team found a complete human jawbone on the ancient ground. The chamber was named Peștera cu Oase (The Cave with Bones), and the jawbone was called "Oase 1" (also known as "Ion din Anina" or "John of Anina").

Carbon 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 some of the earliest modern human groups to have arrived in Europe.

Oase 1

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

The calibrated radiocarbon date for "Oase 1" is 40,450±1020 BP.

Oase 1 shows physical characteristics from both early modern humans and archaic humans, including traits similar to Neanderthals.

DNA analysis of Oase 1 since 2015 has revealed several important discoveries.

Oase 2

Scientists mapped out the genome of "Oase 2" (41,500–39,500 years old) with high accuracy (20 times) using a part of the skull called the petrous bone.

About 6% of "Oase 2"'s genome 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 Upper Palaeolithic genomes.

"Oase 2" shares the same specific group of mitochondrial DNA haplogroup N as "Oase 1." When compared to all known DNA samples, "Oase 2" and "Oase 1" have the closest genetic similarity. "Oase 1" and "Oase 2" likely came from related but not identical populations.

"Oase 1" has a genetic connection to Ice Age Europeans that "Oase 2" does not share. Instead, "Oase 2" is more closely related to people from Asia and Native Americans. "Oase 1" also has a genetic link to "Peştera Muierii 2" that "Oase 2" does not have. Among ancient DNA samples, the next closest genetic match to "Oase 2" is the Tianyuan man from Northern China, who lived about 40,000 years ago. Neither "Oase 1" nor "Oase 2" is closely related genetically to any modern human populations.

Current research

Peștera cu Oase is still being studied by scientists. Results from the 2005 research are being analyzed by several institutions, including the Romanian "Emil Racoviță" Institute of Speleology, Australian National University, University of Bristol, University of Bergen, University of Oxford, Max Planck Institute, and University of Vienna. These groups are using methods such as electron spin resonance, uranium-series dating, and radiocarbon dating to examine 21 bone/tooth samples, 29 sediment samples, 22 bone samples, 7 samples, 8 bone/tooth samples, and 25 bone/tooth samples. They are also studying stable isotopes and ancient DNA from 37 bone/tooth samples.

A skull discovered in Peștera cu Oase in 2004 or 2005 shows traits 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. In 2007, Erik Trinkaus 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 genetic differences in their DNA, have led scientists to believe that modern humans completely replaced Neanderthals when they arrived in Europe during the Middle-to-Upper Palaeolithic transition. This idea is called the "Out of Africa with Complete Replacement" model.

However, recent studies have shown that some early modern human fossils previously thought to be from the Middle Palaeolithic are actually much younger, dating to the mid/late Holocene period. This means they are not as old as earlier estimates suggested.

The "Peștera cu Oase" fossils are especially important because they show a mix of modern human and Neanderthal traits. These fossils are also well-preserved, allowing scientists to determine their age directly. They overlap in time with late Neanderthals, such as those found in Vindija Cave (Croatia) and Arcy-sur-Cure (France), which are dated to about 32,000 and 34,000 years ago, respectively. The presence of Neanderthal-like features in the Oase fossils supports the idea that early modern humans lived at the same time as Neanderthals and may have interacted with them.

Genetic evidence does not rule out the possibility that modern humans and Neanderthals interbred. Additionally, physical and archaeological findings suggest that Neanderthals may have survived alongside modern humans for a time. The Oase fossils provide strong support for a model in which early modern humans and Neanderthals intermixed when modern humans first arrived in Europe.

This model suggests that when modern humans entered Europe, they met Neanderthals who had similar cognitive abilities and cultural achievements. This led to a wide range of interactions, including conflict, avoidance, and interbreeding. Over time, the larger population of modern humans led to the gradual disappearance of Neanderthal genetic traits in later human populations.