Ancient jawbone ‘a revolution’ in understanding of human evolution

The discovery of a prehistoric jawbone in a cave in Israel forces scientists to rethink theories of how the earliest humans came to populate the planet and is a “welcome surprise”, according to an Irish palaeontologist.

The fossil, dated to nearly 200,000 years ago, suggests our ancestors left Africa, where they originated, far earlier than previously thought, said Dr John Murray of NUIG School of Earth and Ocean Sciences. "The timing is what makes this [finding] special," he added.

Until recently, several converging lines of evidence – from fossils, genetics and archaeology – suggested modern humans (Homo sapiens) first dispersed from Africa into Eurasia about 60,000 years ago, quickly supplanting other early human species, such as Neanderthals, that they may have encountered along the way.

Narrative clouded

The finding suggests that movement actually occurred 180,000 years ago. Recent discoveries including a trove of 100,000-year-old human teeth found in a cave in China, however, had clouded this narrative.

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The jawbone found at the Misliya cave site in northern Israel – part of what’s known as The Levant, and always regarded as a migratory corridor – has added a new and unexpected twist, Dr Murray said.

The discovery, details of which were published in the journal Science, suggests there were multiple waves of migration across Europe and Asia, and could also mean that modern humans in the Middle East were mingling, and possibly mating, with other human species for tens of thousands of years.

‘A revolution’

This possibility was also suggested in ancient DNA studies. "This fossil find begins to open up that possibility," Dr Murray told The Irish Times.

"This is a revolution in the way we understand the evolution of our own species," explained Prof Israel Hershkovitz, who led the work at Tel Aviv University.

Prof Hershkovitz said the record now indicates that humans probably ventured beyond the African continent whenever the climate allowed it. “I don’t believe there was one big exodus out of Africa,” he said. “I think that throughout hundreds of thousands of years [humans] were coming in and out of Africa all the time.

“While you might have the best archaeologists and the best excavators, there is always an element of chance and luck” in such discoveries, said Dr Murray. He is involved in excavations in the southern Caucasus, on the border between Europe and Asia, where significant Neanderthal finds have been made.

New questions

Misliya “answers some questions but also throw ups new questions – the hallmark of all good science”, he added.

With a range of improved dating technologies now available, a lot more discoveries in coming years on the timing issue were likely, Dr Murray said.

Dr Maria McNamara, senior lecturer in palaeontology at UCC, said: “This discovery is very exciting, as the fossil is almost twice as old as what were previously the oldest fossils of anatomically modern humans outside of Africa, and is consistent with other recently published evidence that there were multiple waves of migration of modern humans out of Africa; not just a single pulse around 60,000 years ago.” – Additional reporting: Guardian