An in-depth feature published on 2 August 2026 in the Ideas section of EL PAÍS looks at one of the most stable and puzzling figures in human biology. Roughly nine in ten people prefer to use their right hand, regardless of culture, historical period or region. Many animals, from cats to parrots, prefer one paw or foot. What makes humans unusual is that almost the whole species prefers the same side. The feature was written by science journalist Patricia Fernández de Lis and also features geneticist Silvia Paracchini (University of St Andrews).

Dr. Miquel Llorente (Comparative Minds Research Group) was invited to explain the problem from a comparative and evolutionary point of view. He pointed to the difference between us and our closest relatives: "In chimpanzees, for every left-hander there are two right-handers; in humans, there are eight or nine. That jump is what needs explaining, and we still don't have a clear answer."

The feature covers the main evidence available so far. Brain asymmetries can already be seen in the fossil skulls of australopiths. The oldest stone tools suggest that most early hominins struck with the right hand. Genome-wide studies have found more than forty genes linked to handedness, but none of them explains it on its own. Llorente discussed the hypothesis that connects right-handedness with the gestural origins of language. Communicative gestures are mostly made with the right hand, which is controlled by the left hemisphere, the same side of the brain that handles language in most people. He described the process as a snowball. It started with a mild right-hand bias, similar to what we see in great apes today. Bipedal walking, tool-making, gestures, language and culture then strengthened it over millions of years.

Llorente also added a point that often gets lost in popular accounts. The gestural hypothesis does not claim that speech replaced gesture. It claims that human language has used several channels at once (voice, hands and body) since its origins, and still does. This idea is the basis of the group's recent paper in Acta Psychologica, which argues that language itself acted as an evolutionary pressure that made most humans right-handed.

🔗 Read the full article:

• EL PAÍS: ¿Por qué somos (casi todos) diestros? Dos millones de años de misterio evolutivo

📝 Related scientific publication from our group:

Gázquez, J. M. M., Castelain, T., & Llorente, M. (2026). Language as an evolutionary pressure of human handedness. Acta Psychologica, 264, 106489. https://doi.org/10.1016/j.actpsy.2026.106489