Newly discovered fossil could be apes' common ancestor

BARCELONA, Spain, Oct. 29 (UPI) -- An ancient skeleton discovered in a landfill in Spain is forcing scientists to rethink the evolution of apes.

Scientists described the new genus and species, Pliobates cataloniae, in a new paper published in the journal Science -- a species researchers believe is a descendant of the common ancestor of all apes. To the surprise of paleontologists, the early ape looks more like today's gibbons than expected.

Gibbons are a "lesser" ape, more monkey-like in appearance, separate from the great apes, which today include gorillas, chimpanzees, bonobos and humans.

Somewhere around 25 to 30 million years ago, the evolutionary path of Old World monkeys and apes diverged. Not long after, the ape lineage split into lesser and greater apes. Researchers have had a difficult time finding remains of the earliest ape species, prior to the split.

Pliobates cataloniae lived roughly 11.6 million years ago, after the split of apes and monkey, as well as the big and small ape split. But researchers say its features resemble those of an ancestor of gibbons and great apes, and have thus placed it at the base of the ape family tree.

Scientists expected apes' common ancestor to have mostly great-ape features, but that appears not to be the case.

"Pliobates indicates that gibbons must not necessarily be a dwarfed lineage, and suggests instead that the last common ancestor of both lesser and great apes was, at least in several respects -- such as skull shape and body size -- more gibbon-like than previously thought," lead study author David Alba, a researcher at the Miquel Crusafont Catalan Institute of Paleontology (ICP) in Spain, told the Washington Post.

"This thus has implications for the origin of gibbons, which is quite important if we take into account that there is no known fossil record of gibbons for at least their first ten million years of evolutionary history," Alba added.

Alba and his colleagues analyzed the many characteristic of the newly name species, finding enough primitive monkey-like features to suggest Pliobates cataloniae was not far removed from the monkey-ape split. Yet, the species also boasts all the features one might expect from the common ancestor of all apes: lack of external tail, an upright posture and several cranial characteristics.

But as with most studies of this nature, the findings aren't entirely clear. The new species could also be a close relative of ancient gibbons, its great ape features simply a coincidence of evolution.

"Pliobates might be the sister group of extant gibbons only," admitted study co-author Salvador Moya-Sola, director of the ICP. "We hope that future discoveries in the landfill of Can Mata will help us to clarify the role played by small-bodied catarrhines in hominoid evolution and, finally, to solve the enigma of extant gibbons' origins."

In other words, there's more work (and digging) to be done.