According to Peter Frost, an anthropologist at Laval University in Quebec City, since most people have dark hair, blondes stand out.
Blonde hair evolved between 10,000 and 15,000 years ago. For our Ice Age ancestors, light hair may have helped women attract mates, who had become scarce.
Today, the benefits of blondeness may be mostly psychological.
Teen actress and singer Miley Cyrus wowed fans this week by chopping off most of her hair and dying it platinum blonde. Afterwards, she tweeted, “LOVE my hair ? feel so happy, pretty, and free.”
The urge to be blonde may also be driven by deep evolutionary history beginning many millennia ago when light shades first appeared on women’s manes, allowing them to turn the heads of potential mates.
“The more common a hair colour becomes, the less often it is preferred,” Discovery News quoted Frost as saying.
“It’s a kind of novelty effect. The moment you become ordinary, you no longer have the same appeal. There’s selection for being a bit different and eye-catching,” he said.
Modern humans evolved in Africa. Even after migrating to Europe about 35,000 years ago, scientists think that all people had black hair.
Then, sometime between 10,000 and 15,000 years ago in northern and eastern Europe, studies suggest, the hair-colour gene MC1R developed variations that produced a diversity of hues, including red, brown and blonde.
Eye colour, which is controlled by several genes, including one called OCA2, diversified at the same time. Some researchers have speculated that lighter hair and eyes helped people better acquire vitamin D in a high-latitude environment.
However, Frost has a different theory.
During the last Ice Age, he proposes, men had to travel longer distances through Arctic tundra to find animals to hunt. That led to higher death rates for men as well as a decreased chance for polygamy because it would have been nearly impossible to support more than one family with such scarcity of food.
As women came to outnumber the supply of monogamous men, they had to become more competitive for male attention.
In evolutionary terms, this produced strong sexual selection for novel hair and eye colours. Women with unusually bright looks were eye-catching and appealing.
Men didn’t experience the same pressure, which might explain why it is still more common for women to be born blonde, and why it takes longer for blonde hair to darken on girls than it does on boys.
Even today, Frost said, the market for blonde hair dye is greater among women in places like Latin America, where naturally light locks are particularly unusual.
In Sweden, where a large proportion of people are blonde, women often darken their hair. Purple, magenta and other unusual hues have also become popular.
In addition to the desire to stand out, going blonde might represent a subconscious attempt to look young and cute.
That’s because, along with broad foreheads and little noses, blonde hair is also more common in young children than in adults.