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By reanalysing human skull fragments discovered four decades ago in Greece, an international team of researchers now believe that an early modern human migration out of Africa may have reached Europe by at least 210,000 years ago.
This pushes back the known date of Homo sapiens in the region by more than 150,000 years.
The new analysis involved two partial skulls discovered in Apidima Cave, southern Greece, in 1978.
Both fossils, named Apidima 1 and Apidima 2, were initially dated to at least 160,000 years old, but there has always been doubt about this figure. The two fragments were first discovered wedged high up between two cave walls, meaning that they lacked any associated context that would have made the dating more accurate.
By looking at the shapes of the skulls, it was clear that there were some significant differences between them, which cast further doubt on them being the same age.
The Apidima 2 cranium was more complete and showed similarities to the skulls of Neanderthals discovered in both Gibraltar and Italy. Apidima 1 was more reminiscent of modern human fossils that date to around 100,000 years old.
'When we submitted the first draft of our paper for possible publication, the reviewers were naturally sceptical that there was a modern human fossil from Greece found alongside an early Neanderthal fossil, with both of them dating from at least 160,000 years ago,' says Chris.
'So we conducted further analyses and dating work, which produced even more surprises.'
The team used a technique known as Uranium series to date not only the sediments still surrounding the fossils, but also the bone itself.
When it came to the more Neanderthal-like skull of Apidima 2, the new dating fell in line with the previous estimates, yielding an age of 170,000 years old. It was when the researchers dated Apidima 1 that the surprises came.
If they are correct, this skull fragment dates to at least 210,000 years ago, far earlier than expected.
There have been suggestions that the fossil's lack of Neanderthal-like features could indicate that it belonged to an early Neanderthal that had yet to develop the associated morphological traits. But the team's detailed analysis suggests that this is not the case, and that it does indeed belong to Homo sapiens.
This implies that when modern humans made early migrations out of Africa, they may have travelled far wider than initially thought, even making it to the eastern edges of Europe.
'Our scenario suggests that there was an early modern group of humans in Greece by 210,000 years ago, perhaps related to comparable populations in the Near East, but that this group was then subsequently replaced by a Neanderthal population - represented by Apidima 2 - by about 170,000 years ago,' says Chris.
We know modern humans had made multiple early forays out of Africa before the major dispersal event that led to H. sapiens successfully colonising the rest of the world around 60,000 years ago. Early H. sapiens fossils from Israel are known at about 170,000 and 120,000 years old.
These early dispersal events are not thought to have been particularly successful. Researchers believe that H. sapiens only truly became a global species during a later migration, spreading out across much of Asia and down into Australia after about 60,000 years ago.
Even then, the earliest dates for the arrival of modern humans in Europe come in at roughly 42,000 years ago. This may now have to change.
'If these latest analyses are correct, H. sapiens entered Europe over 150,000 years earlier than we thought, raising a whole new range of questions and possibilities including where they came from and what happened to them,' explains Chris.
'The most likely route from Africa would have been through the Near East, and the existence of such early sapiens groups outside Africa has already been suspected from enigmatic signs of early DNA exchanges between Neanderthal and H. sapiens populations.'
The dating suggests that there may be further evidence for these modern human populations in Europe and the surrounding regions, and it could be just that researchers have not been looking for them.
'Unfortunately, there are no stone tools directly associated with either of the Apidima crania to help in establishing connections elsewhere,' says Chris. 'But if we have interpreted the Apidima evidence correctly then the handiwork of these early H. sapiens must be present elsewhere in the European record.'