The Washington PostDemocracy Dies in Darkness

The Big Number: Lefties make up about 10 percent of the world

Placeholder while article actions load

When you sign your name, odds are good that you will do so with your right hand. Only about 10 percent of people worldwide are left-handed, experts say. They’re more comfortable writing, throwing a ball and doing other manual tasks with their left hand. Most of the others prefer to use their right hand — although a few people are ambidextrous, able to use the right and left hands equally well, and a scattering use different hands for different tasks, known as mixed-handedness.

Left-handers were rarer years ago, according to some estimates, consisting of only 2 percent of the population in about 1860 and 4 percent in 1920. Some attribute the growth to today’s 10 percent to a decline in the once-common efforts to force youngsters to use their right hand when learning to write or use cutlery and to an increase in the variety of available left-handed gadgets and tools — scissors, can openers and oven mitts, for instance — as well as musical instruments and sports equipment. But why are some people lefties? Research has suggested a variety of factors, including specific genes, birth weight, mother’s age, preterm births, multiple births, ultrasounds during pregnancy and more. Still, “the biological basis of hand preference . . . remains largely unexplained,” wrote the authors of research published this year in Scientific Reports. Preferring one hand over the other could be simply random variation. Studies have shown, however, that males are more likely than females to be left-handed. This Tuesday, International Lefthanders Day celebrates all who choose sinistrality, the medical term for left-handedness.

— Linda Searing

How fast do I need to walk to be healthy?

Sexting among teems is not that rare