Foot find shows prehuman Lucy wasn't alone

LOS ANGELES -- Lucy, it turns out, had company -- another prehuman that also walked but spent more of its time in trees.

Until now, there was no proof of another human relative living around the same time as the species made famous by the Lucy skeleton. But a fossil discovery reveals there was another creature around 3 million years ago and it gives new insight into the evolution of a key human trait -- walking on two legs.

The creature came to light when an international team of researchers unearthed a partial foot in eastern Africa. Like Lucy, it walked upright, but had a grasping foot that it used to climb tree branches. Scientists said it's now clear that various human relatives experimented with upright walking.

"This is just another window into solving the problem of how we got from a primitive foot to the modern human foot," said Bruce Latimer of Case Western Reserve University, Cleveland, who helped discover the fossil remains.

Various hominoid species have coexisted throughout human evolutionary history, but this is the first sign of another during Lucy's time.

So what was this tree-climbing and ground-dwelling creature? Scientists don't yet know, but it's clear the foot did not come from Lucy's species, Australopithecus afarensis.

It's rare to find prehuman feet because bones are fragile and don't preserve well. So American and Ethiopian scientists led by the Cleveland Museum of Natural History were excited when they excavated eight foot and toe bones in 2009 in the remote Afar region of Ethiopia, 30 miles north of where Lucy was discovered in 1974.

The discovery is detailed in today's issue of the journal Nature. The authors did not name the new species.