Archaeologists have been digging in a quarry on the island of Naxos since 2013
The Aegean Sea had traditionally been thought impassable for early hominins
Yet the dig has unearthed 12,000 stone tools of a type used by Neanderthals
They must have developed boats or reached Naxos when sea levels were lower
Either way the results will shake up our understanding of early human migrations
Early humans reached the Greek islands tens of thousands of years earlier than was previously thought, evidence from an archaeological dig on Naxos suggests.
Archaeologists digging in a quarry on the island have uncovered around 12,000 stone tools and weapons consistent with those used by Neanderthals.
The findings overturn existing theories on early hominin migrations — with the Greek islands originally thought to have been uninhabited until around 9,000 years ago.
Instead, researchers propose that either Neanderthals were sophisticated enough to make boats — or they walked to the island when sea levels were lower in the Ice Age.
Either way, the results show that Neanderthals could adapt to new environmental challenges, and may have taken previously unknown routes in their migrations.
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Archaeologist Tristan Carter of Canada's McMaster University and colleagues have been working on Naxos since 2013, excavating in a quarry called Stelida on the northwest coast of the island.
The team has unearthed thousands of tools and hunting weapons, fashioned from the local stone — chert — which they have dated back to between around 13,000–200,000 years ago.
Among the tools are so-called Mode III — or Mouseterian — technologies in which small and sharp stone tools are struck from prepared cores and then retouched.
Mode III technologies are commonly associated with Neanderthals, suggesting that they were active around Naxos at this time.
'Until recently, this part of the world was seen as irrelevant to early human studies,' said Professor Carter.
'But the results force us to completely rethink the history of the Mediterranean islands.'
While mainland Europe was known to be occupied by Stone Age hunters as far back as 1 million years ago, experts had thought that the islands of the Mediterranean were first settled only some 9,000 years ago, by farmers.
The rationale behind this assumption had been the notion that only modern humans — or Homo sapiens — would have been sophisticated enough to build seafaring vessels and reach the isolated landmasses.
Given this, archaeologists believed that the Aegean Sea that separates modern Turkey from continental Greece would have proved an impassable obstacle to Neanderthals and other early hominins.
This would have made the only obvious route in and out of Europe the land bridge of Thrace, in what is today the southeast Balkans.
The discovery of Mode III stone tools on the island of Naxos, however, suggests that these assumptions may need to be revisited.
One possible explanation could be that Neanderthals were able to fashion crude, seafaring boats capable of crossing short spans of water.
Alternatively, the researchers propose that the Aegean may have been more accessible at the time — and the Neanderthals simply walked there.
This may have been possible at various times during the last Ice Age, when ice locked up at the poles would have lowered sea levels, potentially exposing a land bridge between Africa and Europe — one that incorporated Naxos.
According to the team, the area would have proven attractive to early humans thanks to its supplies of fresh water and abundance of raw materials that would have been ideally suited to the construction of tools.
Nevertheless, Professor Carter added, 'in entering this region the pre-Neanderthal populations would have been faced with a new and challenging environment, with different animals, plants and diseases, all requiring new adaptive strategies.'
The full findings of the study were published in the journal Science Advances.