Fragments of a partial skull unearthed in a cave in northern Spain have revealed a previously unknown population of ancient humans, according to new research.

The research team at the Atapuerca archaeological sites in Burgos, Spain, has just broken its own record by discovering, for the third time, the oldest human in Western Europe.

The prehistoric facial bones were found buried in 50 feet of mud and silt, and are believed to be 1.1 to 1.4 million years old, researchers said.