Early Human Ancestors Had the Upper Hand with Tool Use

It turns out that our ancient human ancestors used their hands like we do. Scientists have discovered that pre-Homo human ancestral species, such as Australopithecus africanus used human-like hand postures far earlier than expected.

The findings come after the discovery that australopiths used stone tools between two to three million years ago. The stone tools seemed to indicate that they had the distinctly human ability for forceful precision (such as when turning a key in a lock) and power "squeeze" gripping (like when using a hammer). These particular abilities are links to two evolutionary transitions in hand use: a reduction in arboreal climbing and the manufacture and use of stone tools.

In order to learn a bit more about when these changes occurred, scientists used new techniques to reveal how fossil species used their hands. They examined the internal, spongy structure of bone called trabeculae. Trabecular bone remodels quickly during life and can reflect the actual behavior of individuals in their lifetime.

The scientists first examined the trabeculae of hand bones of humans and chimps. Not surprisingly, they found clear differences between humans, who have a unique ability for forceful precision gripping between thumb and fingers, and chimps. Then, the scientists examined fossils.

The scientists looked at two to three million-year-old species from South Africa that have traditionally been considered to not have engaged in habitual tool manufacture. Surprisingly, though, the scientists found human-like trabecular bone pattern in the bones of the thumb and the palm of these species.

The findings support recently discovered archaeological evidence for tool use in australopiths. In other words, it appears that our ancient human ancestors were using tools and human-like hand postures far earlier than anyone expected.

The findings are published in the journal Science.

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