Researchers have uncovered evidence on the Greek island of Naxos in the Aegean Sea that Neanderthals and early humans traveled there at least 200,000 years ago, tens of thousands of years earlier than scientists previously believed.

The findings call into question the widely held notion that Europe’s first hominins arrived exclusively via overland routes through Anatolia into the Balkans. The study also suggests that early humans were more cognitively advanced than previously believed.

Scholars had previously believed that the Aegean Sea had been an impassable barrier to early humans.

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The team unearthed the evidence at a prehistoric quarry site called Stelida on the island of Naxos, located in the Aegean basin between southern mainland Greece and western Turkey. Hominins, likely including Neanderthals, used chert stone found at the site to make tools and weapons, although no bones were found at the site.

The Stelida site is a hill 152 meters above sea level first excavated in 1981, and was initially believed to be 20,000-4,500 years old.

A Canadian-led research team in recent years uncovered some 12,000 artifacts from the site, including tools for cutting, scraping and piercing, representing some 200,000 years of history. The team has been excavating the site since 2013 as part of an international collaboration dubbed the Stelida Naxos Archaeological Project.

The age and type of the artifacts, as well as Neanderthal remains found in southern Greece alongside similar artifacts, point to the species’ presence on the island, the researchers said. Earlier human species may have also been on the island.

“Until recently, this part of the world was seen as irrelevant to early human studies but the results force us to completely rethink the history of the Mediterranean islands,” Tristan Carter, the lead author of the study, said in a statement.

The team from McMaster University in Ontario published its findings in the peer-reviewed journal ScienceAdvances last week.

Looking at the bigger picture, the team suggests that scholars rethink the dispersal of hominins during the Pleistocene epoch, which stretched from 2.58 million years ago until around 11,700 years ago.

Stone Age hunters were known to have inhabited Europe up to one million years ago.

During the Ice Age, at certain points the receding sea level in the Mediterranean may have exposed a land route connecting Europe and Africa, allowing the early humans to cross marshy plains in the Aegean to get to the island and elsewhere.

The researchers also raise the possibility that Neanderthals could have crossed short distances of water with crude boats.

Scholars previously argued that only anatomically modern humans had been able to voyage over water and colonize islands, as well as other remote or extreme environments, including deserts and mountain ranges.

Other recent findings, such as evidence of Denisovans, another early species of human, living at high altitudes in Asia, and the “hobbits” found on the island of Flores in Indonesia, suggest that early hominins were more widespread than previously believed, the researchers said.

The researchers stressed that there is no direct evidence that Neanderthals sailed to the island, since they could have accessed it solely when sea levels were low enough to form a land bridge, but if pre-sapien humans had indeed visited or lived on islands, it would have significant implications for our understanding of their capabilities and cognition. Early seafaring would have been cognitively challenging, and would imply that the early hominins had language and technical capabilities to create vessels and navigate.

The presence of the valuable chert on the island would have encouraged the hominins to visit, even if water levels rose. They first would have had to wade across shallow water to reach the island, but would have needed rudimentary boats to cross to the island later.

The fluctuating conditions in the region would have provided the hominins with what the researchers described as “nursery” conditions to start seafaring — they could have made voyages to known locations, staying within sight of land.

Evidence of Neanderthals has previously been found in mainland Greece and Turkey, and indirect evidence in Greece suggested they may have been able to undertake short trips across water.

The Aegean basin would also have been a novel environment for the early humans, which would have required them to adapt and innovate, even if they didn’t need to use boats to get there.

“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,” Carter said.

Throughout the Pleistocene epoch early humans at least sporadically traversed the area. Early Homo sapiens were there around 40,000-30,000 years ago, and may have arrived by boat, the researchers said.

When sea levels were lower, the Aegean basin would have been an attractive wetland environment for early humans, with rich coastal lowlands, raw materials for tools, freshwater sources and lakes that would have attracted prey.

The area could have therefore been an attraction to early humans, instead of an obstacle, and they could have arrived in Europe more haphazardly than directly. The Marmara-Thrace corridor, from modern Turkey into northern Greece, is the easiest way from Asia into Europe, but early humans did not have a set destination, the researchers note.