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Stop Twiddling Your Nubs: How left hands helped thumb evolution

A team of anthropologists from the University of Kent have published a paper suggesting that our non-dominant hands may have helped along the evolution of our thumbs.

Knapping/University of Kent

Knapping/University of Kent

Opposable thumbs are integral to most things we do; we’d be stuffed without them. Try drinking a glass of water without these awesome appendages and you might feel like a Velociraptor. Thumbs are one of those things that make us human – check out the thumbs of chimps for instance.

Our substantial human thumbs appear in the fossil record at the same time as do our substantial human tools, coincidence? Maybe.

For this study, the researchers measured the frequency and intensity of thumb and finger usage during stone tool making – the same stone tool making which would have occupied plenty of proto-human time. The researchers found that the thumb of the non-dominant hand was used more often and for more high intensity work than the non-dominant fingers.

If this doesn’t seem like a selection pressure, a force to sculpt the long and powerful thumbs we have today, then I suggest you read up on your hand axe history. Human beings made hand axes for 2,000,000 years. Hand axes were fundamental throughout human evolution. Could you imagine if we continued to use iPhones for 200 years, let alone two million?

A hand axe. Photograph from Birmingham Museum and Art Gallery/CC BY 2.0

A hand axe. Photograph from Birmingham Museum and Art Gallery/CC BY 2.0

The non-dominant thumb was integral for holding on to the hand axe while the dominant hand chiselled its shape with high intensity blows. Hand axes were then used for every purpose: carving meat off the bone, digging up delicious roots, and smashing up the heads of rival tribes-people. Having a well-made hand axe would have most certainly meant the difference between life and death, the difference between feeding your family or not.

With the strong-thumbed genes of the supreme tool carver passed on, constraints of genetics would impose symmetry on these marvellous appendages – thus leaving us with our modern day, extremely handy thumbs.

Originally published on Think Inc.

Story source: Science Daily

Research paper: Alastair J.M. Key, Christopher J. Dunmore. The evolution of the hominin thumb and the influence exerted by the non-dominant hand during stone tool productionJournal of Human Evolution, 2014; DOI: 10.1016/j.jhevol.2014.08.006