New research suggests that our ancestors used human-like hand postures much earlier than was previously thought.
Anthropologists have produced first results to support archaeological evidence for stone tool use among australopiths - one of the longest-lived and best-known early human species - two-three million years ago.
To reach this conclusion, Matthew Skinner and Tracy Kivell from University of Kent examined the internal spongey structure of bone called trabeculae.
Trabecular bone remodels quickly during life and can reflect the actual behaviour of individuals in their lifetime.
They first examined the trabeculae of hand bones of humans and chimpanzees.
The team found clear differences between humans, who have a unique ability for forceful precision gripping between thumb and fingers, and chimpanzees, who cannot adopt human-like postures.
This unique human pattern is present in known non-arboreal and stone tool-making fossil human species such as the Neanderthals.
The findings show that Australopithecus africanus from South Africa had a human-like trabecular bone pattern in the bones of the thumb and palm consistent with forceful opposition of the thumb and fingers typically adopted during tool use.
"The results support previously published archaeological evidence for stone tool use in australopiths and provide skeletal evidence that our early ancestors used human-like hand postures much earlier and more frequently than previously considered," the authors noted.
Skinner and Kivell worked with researchers from University College London, the Max Planck Institute for Evolutionary Anthropology in Leipzig (Germany) and the Vienna University of Technology (Austria).