An archaeological find in Russia has shed light on the migration of modern humans into Europe.
The researchers looked bone and ivory artefacts found at Kostenki
Artefacts uncovered at the Kostenki site, south of Moscow, suggest modern humans were at this spot about 45,000 years ago.
The first moderns may have entered Europe through a different route than was previously thought, the international team reports.
The research is published in the journal Science.
"Until now, it appeared as though the earliest presence of modern humans in Europe was in south central Europe, in places like Bulgaria and Greece," explained John Hoffecker, author on the paper and a research scientist at the University of Colorado at Boulder, US.
"This reflects an entry from the Levant (eastern shores of the Mediterranean) just before 44,000 years ago."
But the team believes it has now found an alternative and possibly earlier entry route into the continent.
The researchers examined tools, personal ornaments and carved ivory discovered under a layer of ancient volcanic ash at the site, which lies along the Don River.
The artefacts most likely belonged to modern humans and dated to about as early as 45,000 years ago, said Professor Hoffecker. However they were dissimilar to artefacts found at the other European sites, he added.
"This suggests we have a not very closely related group of people at Kostenki, suggesting at the very least that we have an alternate route for modern humans into Europe - perhaps this being the earliest one," he told the BBC News website.
Professor Hoffecker said he was surprised to have found such early evidence of modern humans at Kostenki.
"It is arguably the coolest and driest part of mid-latitude Europe. It is the last place we would expect to see them first," he added.
A possible reason to migrate to these harsher conditions may have been the lack of Neanderthals present in this area at this time.
"The absence of Neanderthals meant there were no competitors to deal with for resources," Professor Hoffecker said.
Fossil records suggest modern humans emerged in sub-Saharan Africa about 200,000 years ago, but their dispersal is thought to have begun between 60,000 and 50,000 years ago.
Evidence of modern humans has been found in Australia, dating to about 50,000 to 45,000 years ago.
Professor Hoffecker said it was difficult to say exactly where the modern humans found in Kostenki would have come from.
One possible route, some researchers believe, is from western Asia via the Caucasus Mountains, which lie between the Caspian and Black Seas.
A skull found in South Africa has been linked to modern humans
He added that modern humans might have migrated into central Asia, but then turned back on themselves to make the move into Europe.
Another paper, published in the same journal, reveals that a skull found in South Africa appears to represent an ancestor of the modern humans that eventually migrated to Europe and Asia.
Professor Chris Stringer of the department of palaeontology at the Natural History Museum, London, said: "These papers are interesting from an anthropological and archaeological point of view, and confirm some of the things we have thought on this subject.
"I think we will see increasing evidence of these ancestral modern people and their behaviour in western Asia, and at an even earlier date, in Africa."