A fossil find in a cave in Serbia suggests Eastern Europe was an important pathway in human evolution as mankind spread out of Africa, scientists say.

Canadian researchers, with partners from France, England and Serbia, have dated a partial lower human jaw as being almost 400,000 years old, and said it could be even a half-million years old.

That makes the jawbone the easternmost European fossil of its age so far discovered, sharing far more in common with African and Asian fossils than with contemporary examples from Western Europe, the researchers said.

"During this time, humans in western Europe started to develop Neanderthal traits, which are lacking in this specimen," paleoanthropologist Mirjana Roksandic from the University of Winnipeg said. "Humans in southeastern Europe were never geographically isolated from Asia and Africa by glaciers and accordingly, this resulted in different evolutionary forces acting on early human populations in this region."

The fossil lends weight to the possibility the Balkan Peninsula could have been a gateway in the movement of populations from Asia to Europe, the researchers said.

"This is opening up the window to study Eastern Europe as an important place in human evolution. It's important to all the modern European evolution that comes after that," Jack Rink of McMaster University in Ontario said. "This fossil being so old and coming from that place links it to fossils that came out of Africa not long before that, in the context of human development."

The researched has been published in the open-access journal PLoS ONE.