Are Humans Descended from a Knuckle‐Walking Ancestor?

Abstract

Abstract A central topic in human evolution pertains to the emergence of habitual bipedalism [i.e., upright walking (UW)], a behavioural characteristic that defines the human lineage and is unique among primates. To pinpoint the factors that led to the appearance of UW, one has to reconstruct the locomotor behaviour of the last common ancestor of humans and their closest living relatives, the chimpanzees. Chimpanzees and gorillas adopt a peculiar mode of locomotion when travelling on the ground, knuckle‐walking (KW). This article evaluates the evidence for and against the hypothesis that humans have descended from a KW ancestor. The conflicting nature of this evidence does not allow firm conclusions, but future avenues of research are proposed. Key Concepts The context for the emergence of habitual bipedalism/upright walking is a key topic in human evolutionary studies. Bipedalism/upright walking is a characteristic that defines the human lineage. Some evidence suggests that the ancestor of the earliest hominins was a knuckle‐walker. However, other evidence appears to contradict this possibility. The role of knuckle‐walking in human evolution will be better understood as more data about the functional anatomy of knuckle‐walking is gathered and as more fossils are described that shed light on the morphology of the last common ancestor of humans and chimpanzees.