Using the uranium series method, scientists refined the dating of an ancient skull from the Petralona Cave in Greece. They concluded that the remains belonged to Homo heidelbergensis, who lived at least 277,000 years ago. The results of the study were published in the Journal of Human Evolution.
Petralona Cave is a Paleolithic site located in northern Greece, approximately 55 kilometers from Thessaloniki. In 1960, local residents discovered a well-preserved skull of an archaic human, which resembles neither the remains of modern humans (Homo sapiens) nor those of Neanderthals (H. neanderthalensis). The skull belonged to a man with a strong brow ridge, a massive braincase, and a large facial skeleton. Among other ancient skulls, it most closely resembles the remains of the so-called Rhodesian Man (H. rhodesiensis), discovered over a century ago in what is now Zambia.
The skull from Petralona Cave was discovered not by archaeologists, but by local residents. Because of this, the exact stratigraphic position of these remains within the site remains unknown, although it is noted that they were found near the cave wall. For this reason, among other reasons, the age of the remains has remained a subject of debate among scientists. Using various methods, they have obtained dates ranging from approximately 700,000 to 150,000 years ago. In particular, using electron paramagnetic resonance, researchers estimated the age of the find at approximately 150,000 to 250,000 years.
Christophe Falguères of the Institute of Paleoanthropology in Paris and his colleagues from the UK, Greece, China, and France refined the find's age. This time, they used the uranium series method, which they used to date the calcite deposits preserved directly on the skull, as well as samples of deposits from Petralona Cave.
The data obtained indicated that the skull is older than expected based on electron paramagnetic resonance. According to the scientists, calcite deposits began to form on the remains of this individual at least 286,000 ± 9,000 years ago, meaning it may have lived around the same time as the aforementioned Rhodesian man, whose skull is estimated to be approximately 299,000 ± 25,000 years old.
However, determining how long ago the remains were deposited in Petralona Cave before the calcite studied formed on them is extremely difficult. Scientists have discovered that dripstones on the cave wall, where the skull was presumably originally found, likely predate the life of this individual. They are approximately 539,000 years old. Therefore, the results of this study indicate that this archaic individual lived between 539,000 and 277,000 years ago. The new dating is consistent with the conclusion that the skull belonged to Homo heidelbergensis (H. heidelbergensis), in the broad sense of the term (sensu lato).
The skull in Petralona Cave was found missing its lower jaw. However, this did not stop researchers from recently reconstructing the appearance of an archaic man. In place of the missing part, they used a model of the lower jaw of Homo heidelbergensis, who lived significantly earlier—approximately 609,000 ± 40,000 years ago.
