Seven-Million-Year-Old Fossils Reveal Earliest Upright Walking in Human Ancestors

A groundbreaking study has shed new light on one of humanity's earliest ancestors. Sahelanthropus tchadensis, a hominin that lived seven million years ago, may have walked upright long before other known pre-humans. This discovery challenges previous assumptions about when bipedalism first emerged in human evolution.

The story began in 2002, when researchers uncovered a fossilised skull of Sahelanthropus tchadensis in Chad's Djurab Desert. For years, this remained the only known specimen of the species, with no additional fossils reported since. Initially, scientists believed Ardipithecus ramidus—dating back 4.4 million years—was the first primate to walk partially upright.

Recent reexamination of the Sahelanthropus fossils revealed three key skeletal features found only in true pre-humans. The femur displayed a prominent bump, known as the femoral tubercle, indicating a strong Y-shaped ligament that stabilised the hip during standing. Additionally, the bone was slightly twisted along its length, a trait linked to upright movement.

The leg bones also showed attachment points for powerful gluteal muscles, crucial for both climbing and walking on two legs. Unlike modern apes, the limb proportions of Sahelanthropus closely matched those of Australopithecus, another early human relative. These adaptations suggest the species may have walked upright at times, marking a crucial step in human evolution.

The findings push back the timeline for bipedalism by millions of years. Sahelanthropus now stands as the earliest known hominin with traits linked to upright walking. This discovery reshapes our understanding of how and when key human characteristics first developed.