The world's oldest known humans started walking on two feet approximately seven million years ago, as a broken and blackened leg bone and two forearm bones belonging to a species known as Sahelanthropus tchadensis imply that they had also walked on two legs during that time.
The bones were initially discovered in Chad’s Djurab desert nearly two decades ago, but the peer-reviewed study was published in the scientific journal Nature last Wednesday.
The study included an analysis of a femur fossil that directs to a possibility that the ancient species could have moved similarly to modern-day humans. The two forearm bones weren't initially thought to be part of the Sahelanthropus fossil but were discovered near the skull.
The analysis was reportedly difficult to conduct as the bones were missing joints on each end. The joints would have proved a strong indication that the species in question was bipedal.
Humans vs. Chimps and Apes
The discovery may contribute to how early humans split apart from apes to start their own evolutionary line. However, the species' forearms indicate that they had spent a lot of their time in the trees.
The Sahelanthropus tchadensis existed during a period when chimps and apes were diverted from the human lineage. The species may possibly be the oldest known hominin — a taxonomic tribe that consists of modern humans, extinct human species, and their ancestors, as well as chimpanzees and bonobos.