Scientists have recovered a fossil fragment of a human lower jaw from a cave in Serbia.

The jawbone, which may have belonged to an ancient Homo erectus, is the oldest hominin fossil found in the southeastern region of Europe.

In 2000, a team of international researchers from Serbia and Canada began excavating a cave in Balanica, Serbia, which had ancient archaeological remains. They found a jawbone fragment with three molars still intact, in a pit dug within the cave.

Using three independent dating techniques, scientists determined that the fossil could be at least 397,000 years old and possibly older than 525,000 years old. During this time, humans in Western Europe started to develop Neanderthal traits. But the newly-found specimen lacked several Neanderthal features; instead it resembled the more primitive Homo erectus, reports LiveScience.

Researchers believe this discovery might change the view that Neanderthals evolved throughout Europe during this time. Archaeologists have earlier unearthed several Neanderthal fossils, exclusively found in Western Europe. They assumed that Neanderthals were widespread throughout Europe during this time.

But the new findings suggest that Neanderthals might not have evolved in this southeastern region of Europe at that time, said the researchers. They believe the evolution of Neanderthals in Western Europe was influenced by periodic isolation caused by rising glaciers that cut off Western Europe from the rest of the continent.

This paved the way for humans to evolve into Neanderthals - the closest extinct relatives of humans - with distinctive features. On the other hand, ancient humans in southeastern Europe were never geographically isolated from Asia and Africa due to rising glaciers. "So there is no pressure on them to develop into something different," study co-author Mirjana Roksandic, a bioarchaeologist from the University of Winnipeg in Canada, told LiveScience.

The details of the study are published in the journal PLOS ONE.