Published online 4 September 2003 | Nature | doi:10.1038/news030901-7

News

Handedness equals hairstyle

One gene might control both - and explain the divided brain.

Lefties' hair is less predictable than right-handers.Lefties' hair is less predictable than right-handers.© Corbis

Right-handed people tend to have hair that swirls clockwise, a US researcher has discovered1.

Amar Klar of the National Cancer Institute in Frederick, Maryland, surreptitiously inspected people's pates by spying on them in airports and shopping malls - ignoring the long-haired and the bald.

More than 95% of right-handers' hair whorls clockwise on the scalp, he found. The locks of lefties and the ambidextrous are equally likely to coil either way.

A single gene with either 'right' or 'random' forms might underlie the trend, says Klar. People with one or two copies of the right version would be right-handed, with clockwise hair; those with two random versions would split 50/50 for handedness and hair whorls. He is now seeking such a gene.

"It's one of the most exciting things [I've seen] in a while," says geneticist Ralph Greenspan of the Neurosciences Institute in San Diego, California. A gene causing asymmetric cell division in the young embryo might set up asymmetry throughout the body, he suggests.

But many genes might influence handedness, counters Clyde Francks of the University of Oxford, UK, who is hunting for such genes. Only finding these molecules will reveal the answer, he argues.

Right, left

Around 90% of people favour their right hand for writing and throwing. Researchers argue about whether genes or learning create this preference.

Most people assume that there is no single 'handedness' gene because it is not simply inherited. Two left-handed parents, for example, will often have right-handed children.

Klar believes his hypothesis accounts for these puzzles. If children of left-handers inherit the 'random' gene, they could be left- or right-handed. This would also explain why identical twins can be right- and left-handed.

The genes underlying handedness might also explain why our brains are asymmetrical. And left-handed or ambidextrous people are more likely to store language in the right side of the brain, are more prone to schizophrenia and, anecdotally, are more often creative or even geniuses. 

  • References

    1. Klar, A.J.S. Human handedness and scalp hair whorl direction develop from a common genetic mechanism. Genetics, in the press, (2003).