Scientists Intrigued by Non-Human Skull Embedded in Cave Wall

Scientists believe they're close to solving an ancient mystery involving a strange hominin skull, neither Neanderthal nor human, that was found fused to a cave wall — with a stalagmite sticking out of the top, to complete the eerie scene — in Macedonia, Greece.

In a new study published in the Journal of Human Evolution, researchers from France's Institut de Paléontologie Humaine (or Human Paleontology Institute in English) claim they've been able to place an age on the "Petralona cranium," which was named after the cave system where the mysterious, almost-horned skull, as seen below, was discovered some 65 years ago. 

As Archaeology Magazine explains, this bizarre, non-human noggin has fascinated and frustrated scientists ever since it was discovered in 1960, sans lower jaw and encrusted with the mineral calcite, by a villager in the nearby port city of Thessaloniki.

For decades, researchers fiercely debated the age of the skull in hopes of determining what Homo genus it came from — because, as shown below, it doesn't resemble any other known hominin cranium.

With researchers over the years claiming the skull was anywhere between 170,000 and 700,000 years old based on various dating techniques, scientists have had to rely on the best technology and hypotheses of the era when attempting to figure out when the skull dates from — and more importantly, who or what creature it came from.

In this new study, the Human Paleontology Institute team, led by archaeologist Christophe Falguères, used a remarkably simple technique to offer a more concise time frame for the Petralona skull. Using calcite samples directly from the skull itself and from the deposits surrounding it, the researchers used a technique known as uranium-series dating that measures the decay rate of uranium isotopes as they morph into thorium over time.

In typical outdoor environments, as Archaeology Mag explains, uranium is abundant, making the dating technique a non-starter for most materials. Caves, however, are different: as a closed system, water moves through rocks before evaporating, leaving behind uranium-rich calcite deposits whose thorium byproducts can ultimately be aged using this highly accurate radiometric dating technique.

Using that methodology, Falguères and his team determined that calcite deposits on the skull started forming at least 286,000 years ago, with a margin of error of about 9,000 years. Ultimately, the French paleontologists determined it could be as young as 277,000 years and as old 539,000, placing it smack-dab in the Middle Pleistocene epoch that took place between 773,000 to 126,000 years ago.

In an interview with Live Science about the research, paper co-writer Chris Stringer of the Museum of Natural History in London said that the new age range for the Petralona skull suggest a "persistence and coexistence of this population alongside the evolving Neanderthal lineage in the later Middle Pleistocene of Europe."

While it certainly wouldn't be the first time we've seen evidence of modern humans and other hominins, including Neanderthals, coexisting (and interbreeding), these new dates for the Petralona skull offer a more detailed reckoning of our prehistoric past.

More on bones: A Dinosaur Appears to Have Died on the Exact Spot They Later Built a Dinosaur Museum, Burying Its Fossil Underneath It