jueves, 17 de diciembre de 2015

How Hands Made Humans Human


The Homo naledi hand’s curved fingers mean it was regularly climbing trees, but its wrist, thumb, and palm suggest it was also using tools.  Photo by Peter Schmid and William Harcourt-Smith/Wits University
 
New insights from the strange species Homo naledi.

It’s easy to forget the marvel of human hands. Musicians’ hands play masterful compositions on the piano; artists’ hands paint timeless works; surgeons’ hands save lives. The rest of us use our miraculous hands to get dressed, pour coffee, and type messages—sometimes entirely with our opposable thumbs.

Like our big brains, our agile hands are part of what makes us human. The construction of nerves, tendons, and bones is a result of millions of years of evolution. But how exactly did they get that way? And when did they emerge on our evolutionary timeline?

The fossilized hand bones of our human ancestors, including those of the recently discovered species Homo naledi, give us some clues. Homo naledi has a strange mix of modern human and not-so-modern features. Among them is a puzzling pair of hands: The wrist, palm, and thumb look like ours, but the long, curved fingers are more apelike. We’ve never seen anything like it.

This mix of features “gives us that smoking gun for how the hand was being used,” Matt Tocheri, a hand expert and paleoanthropologist with the Smithsonian’s Human Origins Program, told me. Tocheri co-authored a study published in Nature that analyzed a nearly complete right hand of an adult Homo naledi specimen. Its curved fingers mean it was regularly climbing trees, but its wrist, thumb, and palm suggest it was using tools. [...] slate.com

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