Only ~10% of Homo sapiens are left-handed. This is true in both modern populations and fossils. The dominant hand of more than 50 European fossils has been identified. 47 are right-handed (92%). This stands in stark contrast to our chimpanzee cousins; for whom hand preference is closer to 50:50. Why we developed such a strong preference is unknown.
However, there's growing evidence that this shift happened relatively early in human evolution. Scientists have recently identified the fourth left-handed Neanderthal. This places right-handed Neanderthals in a similar majority (88%) to modern humans. This would suggest that whatever caused this preference developed before our species split. This would make a left-handed minority at least half a million years old.
Vergisson: A left-handed tooth
Identifying which hand a fossil preferred can be tricky at the best of times. Typically, researchers look for signs of asymmetry in the skeleton. After all, your bones are alive. They grow and develop in response to the forces they're subjected to. If one arm is favoured, it will experience more forces; driving asymmetric. However, these differences are typically quite small. In fact, they can be so small that other lifestyle factors can mask them.
All of this makes the discovery of the fourth left-handed Neanderthal impressive. Researchers were able to identify which hand the Neanderthal from Vergisson 4 preferred from a single tooth. Because that's all that's left of the poor thing.
Vergi - as I like to call this fossil - lived in France ~40,000 years ago. At least, Vergi lived there for around 10 years until they met their untimely demise. All that's left is some of their group's technology, food-waste (they liked reindeer) and one of Vergi's incisors. Whilst Vergi might have had a short life, they still did something significant. At least, from an archaeological perspective.
Vergi, like many Neanderthals, used their teeth to make tools. Many Neanderthal teeth show a unique pattern of damage. It's consistent with holding a material in the teeth. One hand then pulls it tight, whilst the other scrapes it with a stone tool. Maybe Vergi did this to pull the bark of a branch or scrape animal hide clean, we can't say. What did happen was sometimes they would scrape too high and accidentally clang their teeth. This produces damage, the direction of which is determined by the hand being used when the mistake was made. The damage to Vergi's teeth indicates they were left-handed. This makes Vergi the fourth known left-handed Neanderthal, joining two fossils from Croatia and one from France.
And the fact that they were making stuff with their mouth might make Vergi the first case of Neanderthal child-labour.
Reference
Condemi, S., Monge, J., Quertelet, S., Frayer, D.W. and Combier, J., 2016. Vergisson 4: a left‐handed Neandertal. American Journal of Physical Anthropology.
Stephens, N.B., Kivell, T.L., Gross, T., Pahr, D.H., Lazenby, R.A., Hublin, J.J., Hershkovitz, I. and Skinner, M.M., 2016. Trabecular architecture in the thumb of Pan and Homo: implications for investigating hand use, loading, and hand preference in the fossil record. American Journal of Physical Anthropology.
