How women evolved blond hair to win cavemen's hearts

For those who are still considering the debate on whether men prefer blondes, a study may have provided proof in favour of the flaxen-haired, if only because they appeal to the "caveman" within.

Academic researchers have discovered that women in northern Europe evolved with light hair and blue eyes at the end of the Ice Age to stand out from the crowd and lure men away from the far more common brunette.

Blond hair originated through genetic necessity at a time when there was a shortage of both food and males, leading to a high ratio of women competing for smaller numbers of potential partners, according to the study published this week in the academic journal, Evolution and Human Behaviour.

Until these shortages about 10,000 to 11,000 years ago, humans had uniformly dark hair and eyes.

The physical ardour required with hunting bison, reindeer and mammoths in some regions meant many male hunters died and left women with a shrinking pool of breeders.

Flaxen-haired women arose out of a rare mutation but increased in numbers because their chances of breeding turned out to be better.

Peter Frost, a Canadian anthropologist and author of the study, published under the aegis of St Andrews University in Fife, said hair colour became popular as a result of the "pressures of sexual selection on early European women".

Human hair and eye colour is unusually diverse in northern and eastern Europe ... [and their] origin over a short span of evolutionary time indicate some kind of selection. Sexual selection is particularly indicated because it is known to favour colour traits," he said.

He added that the environment skewed the sex ratio in favour of men "to leave more women than men unmated at any one time".

Such an imbalance, he said, would have increased the pressures of sexual selection on early European women, one possible outcome being an unusual complex of colour traits: hair and eye colour diversity and, possibly, extreme skin de-pigmentation.

There are at least seven different shades of blond hair in Europe and the question of how such a large variation developed in a relatively short period of time in a geographical region has always remained a mystery. Dr Frost concluded that the lighter shades of blond hair evolved as a response to food shortages in areas where women could not collect food for themselves and were utterly reliant on the male hunters, as they were in some parts of northern Europe.

But while blondes may have had more fun at the dawn of time, researchers at City University in London last year found that modern men responded more positively to pictures of brunettes and redheaded women than to their blonde counterparts.

Experts said that as relations between men and women have evolved, men may have become more attracted by brains, represented in their psyche by brunettes, than the more physical charms of blond hair.

Peter Ayton, professor of psychology at City University, who led the research, said dark hair could now be more a potent symbol than blond.

"As the role of women has evolved, men's expectations of women have changed," Professor Ayton said. "They are looking for more intense, equal partnerships and appearance has a large role to play. It is even possible that certain hair colours can indicate wealth and experience."