A strange fossilised skull found in a Greek cave more than 60 years ago may finally be giving up some of its secrets. New analysis suggests it’s at least 300,000 years old, placing it alongside early Homo sapiens in Africa and the first Neanderthals in Europe.
The Petralona skull, discovered in northern Greece in 1960, has long caused headaches for paleoanthropologists, who struggle to decide where it fits into our human family tree.
The fossil lacked distinct features of well-known human species like Neanderthal and Homo erectus, and was found in complete isolation, sticking out from a cave wall with no surrounding artefacts or animal bones that could be dated.
“As soon as I saw it and measured it, I knew that it wasn’t Neanderthal and it wasn’t Homo erectus either,” Prof Chris Stringer, a palaeoanthropologist at the Natural History Museum in London and one of the study’s co-authors, told BBC Science Focus. “It was something different.”
Stringer long suspected that the specimen belonged to another of our cousins: Homo heidelbergensis, a robust human species that lived hundreds of thousands of years ago across Africa, Europe and possibly Asia.
Without a firm date for the skull, however, it was difficult to know where it fit into the human story, or even to be certain of its identity at all.
The new study applied uranium-series dating to the calcite coating on the fossil.
Calcite is one of the most common mineral forms of calcium carbonate, and forms on fossils when water gets into their pores and cavities, creating new mineral structures. Uranium-series dating uses this calcite to its advantage, and by detecting the level of uranium breakdown that has occurred in the mineral, it was used to calculate the fossil's age.
The results of this new test point to an age of around 286,000 years. But the nature of the tests has still left questions around the skull's age.
“If the calcite on the fossil developed very quickly after the fossil was deposited in the cave, then our age of about 288,000 to 290,000 is a good age for the fossil,” Stringer said.
“But if the fossil actually had lain around in the cave before the calcite got on it, then that age is only a minimum age.”
Even with that caveat, the results place Petralona close in time to another famous Homo heidelbergensis skull from Kabwe, Zambia, dated to around 300,000 years ago.
“Morphologically, they belong together and dating-wise they seem to be close too,” Stringer said.
The finding strengthens the view that Homo heidelbergensis was widespread and long-lived, overlapping with other human species rather than directly giving rise to them.
In other words, rather than being the common ancestor of modern humans and Neanderthals as once thought, Homo heidelbergensis were almost certainly our contemporaries – at least for a time.
That diversity, Stringer added, makes our story even richer: “We’ve known for a while that human evolution was complex… But it’s even more diverse than we thought, with many different experiments in how to be human. We’re just the only survivors, of course.”
Read more:
- An ancient tooth is reshaping what we know about Stonehenge
- This tiny stone tool may have just rewritten human history
- Archaeologists have unlocked new secrets of life in Pompeii