An ancient skull turned out to have belonged to the most ancient baboon known to science.

The new findings back up past suspicious that the Papio angusticeps fossil represents the earliest known member of the modern baboon species Papio hamadryas, the University of Witwatersrand reported. The skull was discovered at the Malapa fossil site, and is believed to date back to two million years ago.

"Baboons are known to have co-existed with hominins at several fossil localities in East Africa and South Africa and they are sometimes even used as comparative models in human evolution," said Christopher Gilbert, of Hunter College, CUNY.

Modern baboons are generally divided into populations recognized as either species or subspecies that live across sub-Saharan Africa and spread into the Arabian Peninsula. The origin of these well-known species has remained poorly understood, and these new findings could provide some insight.

"According to molecular clock studies, baboons are estimated to have diverged from their closest relatives by 1.8 to 2.2 million years ago; however, until now, most fossil specimens known within this time range have been either too fragmentary to be definitive or too primitive to be confirmed as members of the living species Papio hamadryas," Gilbert said. "The specimen from Malapa and our current analyses help to confirm the suggestion of previous researchers that P. angusticeps may, in fact, be an early population of P. hamadryas."

The estimated age of the specimen from Malapa almost completely lines up with the previous molecular clock analyses of baboons, and is anatomy is in close agreement with what is seen in baboons today.

"If you placed a number of P. angusticeps specimens into a modern osteology collection, I don't think you'd be able pick them out as any different from those of modern baboons from East and South Africa," Gilbert said.

The findings were published in a recent edition of the journal PLOS One.