Fossilised cranium bones of Saadanius hijazensis.
Credit: I. S. Zalmout, W.J. Sanders et al for Nature
PARIS: The last ancestor shared by monkeys and humans probably lived between 28 and 24 million years ago, several million later than previously thought, fossils have revealed.
A partial skull of the unknown species, found in western Saudi Arabia, rewrites the timeline of primate evolution and fills in a yawning gap in the fossil record, the researchers said.
Up to now, genome-based analysis put the split between hominoids - which includes apes and humans - and cercopithecoids, or so-called Old World monkeys, at 35 to 30 million years ago.
New species sheds light on split
But the new species, dubbed Saadanius hijazensis, has been accurately dated to about 28 million years ago, and may have persisted even longer before the split occurred.
Its distinctive features show that the last common ancestor of monkeys, apes and humans - called catarrhines - existed further up the evolutionary tree than the genetic approach suggested.
The discovery also makes it possible for the first time to identify the mysterious fossil of another primate that lived some four million years later as clearly belonging to a post-split ape.
Pinpointing human origins
"The shift in age does not change how we think of human origins," said lead scientist William Sanders, a professor at the University of Michigan.
"But it does help us to narrow down the time period in which the group that ultimately produced humans and their direct ancestors arose. We can now search in this 28-to-24 million year time frame," he said in an email exchange.
