Scientists believe they have discovered the fossilized remains of humankind's oldest walking ancestor.

The U.S. and Ethiopian team discovered the bones last month at a site in the northeastern Afar region of Ethiopia. They estimate the bones to be close to 4 million years old.

An ankle bone found at the site proves the creature walked upright, according co-leader of the team, Scientist Bruce Latimer, director of the Cleveland Museum of Natural History.

The fossils discovered include a pelvis, ribs, shoulder blade, vertebrae, a complete tibia and parts of a thighbone.

Prior to this discovery, the oldest known hominid skeleton was unearthed in 1974, an Australopithecus afarensis proto-human, better known as "Lucy," which is 3.2 million years old.