Scientists dispute time of Neanderthals' demise
Researchers believe 'grunting cave men' likely interbred with modern humans
WASHINGTON (Reuters) Bones found in a Croatian cave show that Neanderthals, once portrayed as grunting, primitive cave men, lived as recently as 28,000 years ago, and probably interbred with modern humans, researchers said Monday.
Previous evidence suggested Neanderthals died out about 34,000 years ago and were replaced by modern Homo sapiens. But an international team of scientists did more tests on the Neanderthal bones found in the 1970s and determined they were much younger than that.
"The new radiocarbon dates suggest Neanderthals would have coexisted with early modern humans in Central Europe for several millennia," Fred Smith, chairman of the anthropology department at Northern Illinois University, said in a statement.
Writing in the Proceedings of the National Academy of Sciences, Smith and colleagues argued their findings dispute theories that when modern humans appeared, they were so superior to primitive Neanderthals that they either "out-competed" them or actively wiped them out.
"I think what is most likely is that early modern humans dispersed into Europe, in some places competed with and replaced (Neanderthals), in other places assimilated (with) them," said Erik Trinkaus, an anthropologist at Washington University in St. Louis, who led the study.
"The differences between the two groups in basic behavior and abilities must have been small and rather subtle," he said.
Neanderthal bones named after the valley in Germany where they were first found are heavier and more robust than those of modern humans. They suggest a squatter, stronger type of human, with a more "primitive" face and head.
"They would have basically looked like modern humans who were quite stocky. They would have had rather large faces. They would have been dirty and scarred and ugly, but the modern humans wouldn't have looked any better," Trinkaus said.
Neanderthals have always been classified as a separate species from humans, and one way to define species involves the inability to interbreed.
But Trinkaus and Smith, as well as some others, have been putting forward the controversial idea that Neanderthals and early modern humans did interbreed.
This year, Trinkaus reported finding the 24,500-year-old bones of a child in Portugal that he said showed characteristics of Neanderthals and modern humans.
Smith said he also thought the Croatian bones had some "modern" characteristics. "For example, (they) do tend to show features that are a bit more like modern humans than other Neanderthals show," he said.
"And most early modern Europeans exhibit some features that are hard to explain, if Neanderthals are totally excluded from their ancestry. Trinkaus' Lagar Vehlo (in Portugal) child is one example of this, but there are others," Smith added.
"Thus, I think, as do many of my colleagues, that Neanderthals are being assimilated to some extent into early modern human populations."
Trinkaus said the new evidence shows the two populations would have had plenty of time to mix in the thousands of years they lived alongside one another.
But another team of scientists extracted DNA from Neanderthal bones and said it showed they could not have been ancestors of modern humans. But Trinkaus and Smith dispute that study, which did not examine all of the Neanderthals' DNA.
"I question how much it tells us," Trinkaus said.
Archaeologists also found stone tools at the Vindija cave site, which is about 55 km north of the Croatian capital of Zagreb.
Usually, crude stone tools are associated with Neanderthals, while modern humans are credited with making more sophisticated stone and bone tools.
Both kinds of tools were found at the Vindija site.
"It's possible Neanderthals developed all these tools or got the bone tools through trade with moderns," Smith said.
So what did happen to the Neanderthals?
Smith and Trinkaus said if modern humans had even a small advantage in producing children who survived, they would have quickly outnumbered Neanderthals.
"Another factor is disease. Probably these early modern populations had bugs that Neanderthals were not immune to," he added.
He said most experts doubt modern humans killed off the Neanderthals.