Most People Are Right Handed, But Why?
- Editor OGN Daily
- 2 hours ago
- 2 min read
Roughly 85 to 90 percent of people are right-handed, while just 10 to 15 percent are left-handed, and a small percentage are ambidextrous. Why is that?
The predominant theory is that right-handedness is (or has become) the default outcome of early brain development as encoded by the genome - and that bias happens before birth. “This preference is already visible in the movements of unborn fetuses,” says Clyde Francks, a professor of brain imaging genomics at Max Planck Institute and Radboud University Medical Center in The Netherlands. Ultrasound scans have shown that by the 10th week of gestation, most fetuses move the right arm more than the left, and from the 15th week most suck the right thumb rather than the left."
Research suggests that dozens of genes - perhaps up to 40 - play a role in shaping handedness. Rather than determining it outright, these genes build the brain in a way that typically favours the right hand as the dominant one, Francks explains.
But if right-handedness is the brain’s default setting, what makes some people left-handed? “We think that most instances of left-handedness occur simply due to random variation during development of the embryonic brain, without specific genetic or environmental influences,” says Francks. “For example, random fluctuations in the concentrations of certain molecules during key stages of brain formation” could influence which hand you write and throw with.
Sometimes the culture you grow up in plays a role in whether you’re right or left handed. In some Asian, Arab, and African countries, the left hand is considered “unclean” and children with a dominant left hand are forced to become right-handed.
Another theory for humans bing predominantly right handed is because of a perceived evolutionary advantage. Some scientists think most people are right-handed because it gave our ancestors an edge. This theory links handedness to tool use and the passing down of skilled movements across generations, says Paul Rodway, a psychologist at the University of Chester. Archaeological evidence backs that up: A 2011 study found that humans have strongly favoured their right hand for tool use for at least half a million years.
So, the prevailing conclusion is that cultural pressure can influence which hand people use, but the preference likely begins before birth. Genes involved in brain development create a natural bias toward the right hand, and over time, evolutionary forces such as tool use may have strengthened that tendency.
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