Sept. 28 (UPI) -- Modern humans were occupying parts of Western Europe at least 38,000 to 41,000 years ago, 5,000 years earlier than previously thought.
The discovery and analysis of ancient stone tools in a Portuguese cave -- detailed Monday in the journal PNAS -- suggests modern humans were along Europe's Atlantic Coast at the same time that Neanderthals occupied the region.
Paleontologists have been excavating the Portuguese cave known as Lapa do Picareiro for more than 25 years, but until now, researchers had failed to turn up evidence that modern humans might have arrived prior to the disappearance of local Neanderthals.
During recent digs, researchers unearthed stone tools similar to those associated with early human populations at the other end of the continent, where Europe becomes Asia.
"The technology used to make the tools is found in sites all across Europe from northern Spain to Russia," Jonathan Haws, professor and chair of the anthropology department at the University of Louisville, told UPI in an email.
"They are part of the Aurignacian technocomplex that has several phases over time. The early phases do not have associated human remains but the later ones have a few modern human remains," Haws said. "Since these phases are technologically almost identical, we extrapolate back in time the association with modern humans to the early phases."
By radiocarbon dating several butchered animal bones found in close proximity to the tools, researchers were able to confirm the presence of modern humans in Western Europe during the early stages of the Late Stone Age.
Researchers have uncovered ample evidence that modern humans populated Europe from east to west, but the timing and trajectory of the earliest dispersals of modern humans have remained unclear.
The latest findings lend support to the theory that the earliest groups of anatomically modern humans moved from east to west across Europe, in addition to offering a bit of clarity on the timing of early pan-European dispersals.
Researchers remain in the dark, however, on whether early groups from Eurasia moved mostly across inland Europe, following the continent's major rivers, or preferred to migrate along the southern coast.
"We need more field work," Haws said. "Archaeological surveys are needed along potential routes. There are ongoing projects that may soon yield this evidence."
The new findings also lend support to the results of genomic surveys that have shown limited interbreeding between modern humans and Neanderthals.
"The findings agree with the latest genetic evidence for the assimilation of Neanderthals into modern human populations," Haws said. "The Neanderthal input into the modern human genome is very slight suggesting limited contact and interbreeding."
"Our findings suggest that modern humans moved so rapidly across Eurasia and into what is now Portugal because Neanderthal populations were very sparse," Haws said. "The lack of evidence of technology transfers from incoming modern humans to Neanderthals also supports the conclusion that interactions were rare."
Though researchers have yet to turn up evidence of concurrent Neanderthal stone technology at Lapa do Picareiro, excavations at a nearby Portuguese cave suggest Neanderthals were still in the area by the time modern humans showed up. Still, paleontologists estimate Neanderthals were likely in decline.
"The fact that [human tools] exist in this cave at roughly 40,000 years ago really upset our previously held ideas that Neanderthals survived longer and were able to resist modern human colonization," Haws said. "It really shows that modern humans had moved rapidly and largely unimpeded across Eurasia."
Researchers are continuing to excavate Late Paleolithic cave sites in the region to get a better sense of the occupational overlap of modern humans and Neanderthals in Western Europe.
"We're already working on extracting ancient DNA from the cave sediments to reconstruct the genomes of both groups," Haws. "The question of late Neanderthal survival is still open and we hope to definitely answer that because it's directly linked to the question of possible interaction and assimilation."