This tells us when that shift occurred, but not why. Some have argued that it all comes down to language. Just as most people are right-handed – a trait, remember, controlled by the left side of the brain – so do most people do the bulk of their linguistic processing in their brain’s left hemisphere. Indeed, this left-brained specialisation for language is even more common than right-handedness – which might suggest that as the left hemisphere evolved for language, the preference for the right hand may have intensified simply as a side effect. This is called the Homo loquens hypothesis: lateralisation in general was driven by the evolution of an upright, bipedal stance, while the rightward preference was driven, some time later, by the evolution of language.

Right-handedness, then, may simply be an accidental by-product of the way most of our brains are wired up. But proving the hypothesis is difficult, or even impossible, since it would ideally involve running neurological tests on our long-dead ancestors. The truth is we'll probably never quite know what the sequence of events was that led our species to lean so overwhelmingly on the right sides of our bodies and the left sides of our brains.

As for the left-handers out there? Take heart! According to a 1977 paper in the journal Psychological Bulletin, "there is remarkably little evidence for any association of left-handedness with deficit, as has often been suggested". In fact, some research shows that left-handed folks might even have an easier time recovering from brain damage. And their left hand seems to have the advantage of surprise in a fight, which means they can be better at combat sports. All of which suggests there are advantages to breaking from the norm.

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