Pick up a pen, throw a stone or thread a needle: most people instinctively favor their right hand. Why should evolution produce such an uneven split when our hands look almost identical?
A 2020 meta-analysis estimated that approximately 10.6% of people are left-handed. The imbalance is real, although its size varies with how handedness is measured and with cultural pressures. PubMed
Other primates also favor one hand. What distinguishes humans is the strength of our shared rightward preference. A 2022 comparison of 1,786 individuals across 38 primate species confirmed that human right-handedness is exceptional in the sampled task. eLife
Well supported: handedness reflects development, experience and many genetic influences. A genetic study involving more than 1.7 million people identified 48 associated variants, contradicting the idea of a single “right-handed gene.” Nature Human Behaviour
Plausible but debated: specializing one hand improved skilled tool use, while a common direction helped people learn from one another. Links between hand control and language-related brain organization may also have contributed. These explanations remain difficult to separate.
The evolutionary puzzle has two parts: why individuals specialize, and why so many specialize on the same side. Evidence for the first is clearer than the explanation for humanity’s collective lean to the right.
