Cool Human Stuff

Human ancestor couldn’t climb much better than modern humans, study says.

by National Geographic:

An unprecedented fossil foot bone appears to confirm that Australopithecus afarensis—the early human ancestors made famous by the “Lucy” skeleton—walked like modern humans, a new study says.

Unearthed at a known A. afarensis fossil trove in Hadar, Ethiopia, the 3.2-million-year-old fossil is a metatarsal, one of five long bones that connect the large bones in the back of the foot to those of the toes.

The fossil’s size and shape allowed scientists to determine that the foot it had belonged to was stiff and had a well-defined arch—two features that help modern humans spring forward and that cushion the shocks of bipedal walking.

A newfound Australopithecus afarensis foot bone (top left) compared to a human foot. Diagram courtesy Kimberly A. Congdon, Carol Ward, and Elizabeth Harman

Scientists had already known, from pelvis fossils and other remains, that A. afarensis could walk on two legs and no longer had the apelike “foot thumbs” used by other human ancestral species for grasping and climbing.

While ape feet flex in the middle to enable better climbing, arched feet like humans’—and, it appears, like Lucy’s—are stiff, allowing bipedal steps to propel us forward more efficiently, said lead study author Carol Ward, an anthropologist at the University of Missouri.

A. afarensis’s feet now appear to have been well adapted to deal with such side effects of bipedalism, to the detriment of their tree-climbing abilities, according to the study, which will be published tomorrow in the journal Science.

National Geographic

Pretty cool human stuff.