As a specialist in fossil feet, Dartmouth anthropologist Jeremy DeSilva has scrutinized Homo naledi, the latest addition to the human ancestral lineage, which was announced Sept. 10.

Of the 1,600 fossil fragments of this creature recovered from the Rising Star Cave in South Africa, 107 are the remains of feet. The 107 include one nearly complete adult foot and assorted parts provisionally assigned to two other adults and a juvenile.

DeSilva, who co-led the analysis of the creature's feet, is senior author of a study to be published Oct. 6 in the journal Nature Communications. A PDF is available on request.

DeSilva, an associate professor of anthropology, previously described the foot and leg of Australopithecus sediba, a human precursor nearly two million years old found in another cave a few miles from Rising Star. DeSilva welcomed the opportunity to analyze H. naledi, whose foot and ankle are very much like those of modern humans in form, structure and probable function, he says.

"It was a striding long-distance traveler with an arched foot and a non-grasping big toe with subtle differences from humans today in having somewhat more curved toes and a reduced arch. It looks like what the foot of Homo erectus might look like. H. erectus is the earliest human with body proportions similar to our own, with long legs, short arms. It might be closely related to H. erectus, but the brain is smaller and it has a Lucy-like shoulder with curved fingers. This is a new combination that we haven't seen before."

The pelvis is more outward flaring, like that of Lucy - the famous Australopithecus afarensis. "This configuration moved the hip muscles away from the hip joints and gave them more leverage in walking, perhaps more of an advantage than humans have today. Over time, the architecture of the pelvis evolved and expanded to allow the birth of larger-brained babies."

DeSilva says that throughout Africa there were probably all these creatures living in microhabitats, evolving different kinds of adaptations to survive in their environments. "Humans are like every other animal on the planet. Our evolutionary history is mixed. It's a mosaic, lots of different experiments, and we just happen to be the only one left, for whatever reason."