A partial skeleton of an ancient ape adds a new twig to the family tree that includes man and gives strong evidence of when primates first left their treetop homes and began walking on land.
Researcher Steve Ward said the 15-million-year-old fossilized bones found in East Africa are distinctly different from other ancient apes, prompting him and his colleagues to identify them as the only member of a new genus they call Equatorius.
Ward, a primate anatomy expert at Northeastern Ohio Universities College of Medicine in Rootstown, Ohio, is senior author of a study to be published Friday in the journal Science.
Equatorius is not thought to be a direct ancestor of humans or of modern apes, said Ward. The animal probably was an evolutionary dead end, a species that disappeared after about 1 1/2 million years. But it provides important evidence of a poorly understood era that Ward calls "the golden age of ape evolution."
"There was a large group of primitive apes that appeared in East Africa sometime before 23 million years ago," said Ward. "They exploded in an evolutionary sense into many, many genera and species."
Ape species around 10 million to 14 million years ago spread out from Africa and moved into Europe and Asia where they thrived initially, but eventually most became extinct.
Equatorius, said Ward, was a late representative of that era and was probably among the first to abandon the tree top home of earlier apes species.
Fossilized hand, finger, arm and shoulder bones show strong evidence that Equatorius "spent a lot of time on the ground," said Ward. "This is the first time that we see evidence of that in the fossil record of apes."
He called this "a very important finding" in understanding the evolutionary steps leading eventually to modern primates that spend almost no time in trees and are able to walk upright.