Ancient Ape Walked Upright: Fossil Discovery Hints at Human Ancestry
The discovery of a never-before-seen bump on the leg bone of a 7 million-year-old fossil ape shows it walked upright on two legs while it was on the ground, a new study finds.
Only members of the human lineage have this lump, called the femoral tubercle. That makes the species, Sahelanthropus tchadensis, the earliest known hominin, according to the study, published Jan. 2 in the journal science Advances. (hominins are the group of species, including humans, that existed after the split from chimpanzees and bonobos. Walking upright on two legs is a defining characteristic of hominins.)
“That [bump] really sold it to us,” study lead author Scott A. Williams, an associate professor of paleoanthropology at New York University, told Live Science. “That really convinced me that, OK, we think it’s a biped, and therefore, we think it’s a member of the hominin lineage.”
The reanalysis of S. tchadensis‘ femur also confirmed two more human-like anatomical features. First, the bone twisted inward, placing the knees closer together than the hips, as in modern humans. Second, there was a distinct lump on the side of the fossil where the
Twenty years later, two forearm bones, or ulnae, and a femur fragment belonging to S. tchadensis were revealed.the authors argued that the femur belonged to an ape that walked on two legs. But other scientists disagreed with this assessment, stating that the thigh bone shape did not indicate frequent bipedality.
Williams said he was on the fence about S. tchadensis being bipedal – and, therefore, a hominin – because it is “really old.” the ape lived around the time scientists believe the last common ancestor of humans and chimpanzees lived, approximately 6 million to 7 million years