Sophisticated leather-working tools found in a cave in France offer the first evidence that Neanderthals had more advanced bone tools than early modern humans, researchers said Monday.

The four fragments of hide-softening bone tools known as lissoirs, or smoothers, were found at two neighboring sites in southern France, according to the study published in the Proceedings of the National Academy of Sciences.

Radiocarbon dating shows that the tools are about 50,000 years old, said scientists.

That would make the bone tools the oldest known in Europe, having been made and used well before modern humans replaced the Neanderthals some 40,000 years ago, researchers said.

Neanderthals are better known for using stone tools, and many archeologists have believed that more advanced bone tool use was introduced to Neanderthals by modern humans.

While the latest findings are far from conclusive, they may lead to different ways of thinking about which groups were using bone tools for leather-working, and when.

Perhaps the Neanderthals came up with the idea on their own, said lead author Shannon McPherron of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

"For now the bone tools from these two sites are one of the better pieces of evidence we have for Neanderthals developing on their own a technology previously associated only with modern humans," he said.

Researchers cannot rule out the possibility that modern humans entered Europe earlier than thought and passed on this technology to Neanderthals.

Still, the artifacts were uncovered in places that show no evidence of any other cultures.

"If Neanderthals developed this type of bone tool on their own, it is possible that modern humans then acquired this technology from Neanderthals," said co-author Marie Soressi of Leiden University in The Netherlands.

"Modern humans seem to have entered Europe with pointed bone tools only, and soon after started to make lissoirs. This is the first possible evidence for transmission from Neanderthals to our direct ancestors."

Other bone tools have been found from Neanderthal sites, but those have been scrapers, notched tools or handaxes.

"But here we have an example of Neandertals taking advantage of the pliability and flexibility of bone to shape it in new ways to do things stone could not do," said McPherron.

The bone lissoir, shaped from deer ribs, is run back and forth against a hide to render it more supple, shiny and water-resistant.

In fact, the researchers said similar instruments are still being used by leather workers today.