Scott Williams, the associate professor of New York University’s anthropology department, said: “Sahelanthropus tchadensis was essentially a bipedal ape that possessed a chimpanzee-sized brain and likely spent a significant portion of its time in trees, foraging and seeking safety.
“Despite its appearance, Sahelanthropus was adapted to using bipedal posture and movement on the ground.”
Sahelanthropus was first discovered in Chad’s Djurab desert and its skull was so well preserved it was given a nickname – Toumai, meaning “hope of life” in the Dazaga language.
The skull showed the ape had small canine teeth and a relatively flat face, suggesting it was closer to the human lineage than chimpanzees, but experts were still unsure where it sat in the evolutionary timeline.
It is believed that the earliest human ancestors evolved around 5 to 10 million years ago in East Africa, following climatic and environmental upheaval, but the exact date and species remain a mystery.
Analysis indicates bipedalism
Previous studies had suggested that Toumai might have been bipedal because the occipital hole, where the spinal column connects with the skull, has a centred position indicating perpendicular inclination in relation to the ground – a characteristic of humans.
The position of the eye socket also appears to suggest the creature walked upright.
However, more recent research has suggested that the femurs are too curved for a bipedal gate, indicating that Sahelanthropus was probably a knuckle walker, similar to modern gorillas.
For the new study, scientists used 3D geometric morphometrics – a technique which places co-ordinate points on a fossil and then compares them to other specimens.
The analysis revealed three features that indicated bipedalism in Sahelanthropus: the presence of a femoral tubercle, a natural twist in the femur that helps the leg point forward, aiding bipedalism; and the presence of gluteal muscles similar to those found in early hominids, which facilitated standing and walking.
