A recent study has provided compelling evidence that the fossil known as Sahelanthropus tchadensis, dating back approximately seven million years, was capable of bipedal locomotion. Conducted by a team of anthropologists, the research indicates that this ancient species may be one of the earliest known human ancestors, challenging long-standing assumptions about the evolution of upright walking.
The study, published on January 3, 2026, in the journal Science Advances, reveals significant anatomical features that suggest Sahelanthropus walked on two legs. Researchers utilized advanced 3D imaging techniques to identify a crucial skeletal feature, the femoral tubercle, which is linked to the iliofemoral ligament. This ligament, known as the strongest in the human body, plays an essential role in maintaining an upright posture during movement.
Scott Williams, an associate professor at New York University and the study’s lead author, noted, “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.” This statement underscores the unique blend of characteristics that define Sahelanthropus, highlighting its adaptation to both arboreal and terrestrial environments.
The fossil was first discovered in the Djurab Desert in Chad by paleontologists from the University of Poitiers in the early 2000s. Initial studies primarily focused on the skull, limiting insights into its locomotion. However, subsequent analyses of additional skeletal remains, including ulnae and femora, reignited debates regarding the species’ ability to walk upright.
In this latest study, the research team reexamined these bones, employing two main analytical approaches. They compared the skeletal traits with those of both modern species and other fossil specimens. Additionally, they applied 3D geometric morphometrics, a technique that allows for intricate analysis of bone shapes, to uncover meaningful differences.
The findings identified three key features in Sahelanthropus that support the hypothesis of bipedalism. The presence of femoral antetorsion and a specialized gluteal complex corroborated previous suggestions of upright walking capabilities. Moreover, the limb proportions revealed that Sahelanthropus had a relatively long femur compared to its ulna, a characteristic associated with bipedal behavior, contrasting with the shorter-legged structure typical of modern apes.
The study’s collaborative effort included scientists from the University of Washington, Chaffey College, and the University of Chicago. In addition to Williams, the authors included doctoral students Xue Wang and Jordan Guerra, as well as Isabella Araiza, now a doctoral candidate at the University of Washington, and professors Marc Meyer and Jeffery Spear.
Williams concluded, “Our analysis of these fossils offers direct evidence that Sahelanthropus tchadensis could walk on two legs, demonstrating that bipedalism evolved early in our lineage from an ancestor resembling today’s chimpanzees and bonobos.” This assertion not only reshapes the understanding of human evolutionary history but also emphasizes the importance of continued research into ancient species.
The funding for this significant study was provided by the National Science Foundation. As the investigation into human origins progresses, the implications of these findings will undoubtedly spark further research and discussion within the scientific community.
