Human ancestors used their hands just as modern humans 3 million years ago, according to anthropologists from the University of Kent, working with researchers from University College London, the Max Planck Institute for Evolutionary Anthropology in Leipzig (Germany) and the Vienna University of Technology (Austria).
The research shows that Australopithecus africanus, a 3-2 million-year-old species from South Africa traditionally considered not to have engaged in habitual tool manufacture, has a human-like trabecular bone pattern in the bones of the thumb and palm (the metacarpals) consistent with forceful opposition of the thumb and fingers typically adopted during tool use.
Researchers used new techniques to reveal how fossil species were using their hands by examining the internal spongey structure of the trabecular bone. This bone remodels quickly during life and can reflect the actual behavior of individuals in their lifetime. Researchers first examined the trabeculae of hand bones of humans and chimpanzees. They found clear differences between humans, who have a unique ability for forceful precision gripping between thumb and fingers (e.g. when turning a key), and chimpanzees, who cannot adopt human-like postures. This unique pattern was present in known non-arboreal and stone tool-making fossil human species, such as Neanderthals.
The human ability for forceful precision and power squeeze gripping (e.g. when using a hammer) was linked to two key evolutionary transitions in hand use- a reduction in arboreal climbing and the manufacture and use of stone tools. However, it was not clear when these locomotory and manipulative transitions occurred.