In the study, published in Science Advances, researchers in the United States, led by paleoanthropologist Scott Williams at New York University, examined the remains of the primitive species Sahelanthropus tchadensis that were discovered in the desert of northern Chad in Central Africa just over 20 years ago.
Ever since its discovery, researchers have debated whether Sahelanthropus was bipedal or not, and consequently whether it was a hominin, that is, a species within our own evolutionary line, and if so, the oldest known ancestor.
Bipedal gait
The skull, which is well preserved, as well as the shape of the femur and the attachments of the gluteal muscles, have long suggested that this was the case, but hard evidence has been lacking. Given the extremely old age of the find – seven million years – most researchers have considered such evidence to be necessary. After all, Sahelanthropus is far older than the famous Lucy and other better-known hominins.
Now, such clear evidence seems to have come to light. Using three-dimensional geometric morphometry, Scott Williams and his colleagues have identified a bony protrusion, a tubercle, on the femur. The protrusion is the attachment point for the largest and most powerful muscle in the human body, the gluteus maximus. It is located at the front of the hip joint and is absolutely crucial for us to be able to stand upright and walk on two legs.
Early development
The researchers also point out that Sahelanthropus had relatively long femurs, compared with its ulna. Consequently, the species had relatively long legs and short arms, in contrast to modern great apes, which have long arms and short legs.
That doesn't mean Sahelanthropus was particularly human-like. Scott Williams says the species was essentially a great ape, with a brain the size of a chimpanzee, and likely spent a lot of time climbing trees. But it was also adapted to walking on two legs. In other words, bipedalism evolved very early in our ancestors, long before we began to assume more human-like proportions.
Facts: Sahelanthropus
TT
Sahelanthropus tchadensis is the name of a pre-human that lived in what is now Chad in Central Africa about seven million years ago.
It apparently walked upright on two legs, despite its very primitive appearance.
The species is our oldest known ancestor.
