We already knew that our direct ancestors were by no means a bunch of knuckle-draggers. Now fossil analysis suggests they walked permanently rather than swinging from trees.

The findings come from a fossilised footbone from an Australopithecus afarensis, which was a hominid. That’s the family which eventually developed into humans, chimpanzees, gorillas and gibbons.

The bone came from the same area in Ethiopia where researchers discovered “Lucy” in 1974, a 40%-complete skeleton that helped us discover that in the ancestry development of humans, the ability to walk upright came before an increase in brain size.

The bone is the fourth (one along from the little toe side) metatarsal, which is the long bone that joins a toe to the “body” of a foot. In apes, this area is relatively flat and the foot is designed to be more flexible to allow for easier gripping of trees or branches. In humans, the foot has two arches (one along, one across), which act as a shock absorber, as well as making it easier to walk by pushing off from one foot.

It’s now clear that Australopithecus afarensis also had arched feet, which likely means the creature had evolved to always move via upright walking. This would have meant it was able to move over long distances even when trees weren’t available, which would have increased its range for food gathering.

The discovery follows the unearthing last year of animal bones featuring cut marks made with crude tools rather than teethmarks. Given the location and age of the bones, credit went to Australopithecus afarensis that had previously been assumed to be vegetarians; the new theory is that they fashioned the tools to make it easier for removing meat from carcasses.

At the time, researchers noted that the creatures would have had to travel several miles to the nearest source of rocks suitable for the tools. The new discovery suggests that they were indeed physically equipped for such a journey.

(Picture credit: Kimberly A. Congdon/Carol Ward/Elizabeth Harman/Science)