According to the study, north European women evolved blonde hair and blue eyes at the end of the Ice Age to make them stand out from their rivals at a time of fierce competition for scarce males.

The study argues that blond hair originated in the region because of food shortages 10,000-11,000 years ago. Until then, humans had the dark brown hair and dark eyes that still dominate in the rest of the world. Almost the only sustenance in northern Europe came from roaming herds of mammoths, reindeer, bison and horses. Finding them required long, arduous hunting trips in which numerous males died, leading to a high ratio of surviving women to men.

Lighter hair colours, which started as rare mutations, became popular for breeding and numbers increased dramatically, according to the research, published under the aegis of the University of St Andrews.

“Human hair and eye colour are unusually diverse in northern and eastern Europe (and their) origin over a short span of evolutionary time indicates some kind of selection,” says the study by Peter Frost, a Canadian anthropologist. Frost adds that the high death rate among male hunters “increased the pressures of sexual selection on early European women, one possible outcome being an unusual complex of colour traits.”

Frost’s theory, to be published this week in Evolution and Human Behavior, the academic journal, was supported by Professor John Manning, a specialist in evolutionary psychology at the University of Central Lancashire. “Hair and eye colour tend to be uniform in many parts of the world, but in Europe there is a welter of variants,” he said. “The mate choice explanation now being put forward is, in my mind, close to being correct.”

Frost’s theory is also backed up by a separate scientific analysis of north European genes carried out at three Japanese universities, which has isolated the date of the genetic mutation that resulted in blond hair to about 11,000 years ago.

The hair colour gene MC1R has at least seven variants in Europe and the continent has an unusually wide range of hair and eye shades. In the rest of the world, dark hair and eyes are overwhelmingly dominant.

Just how such variety emerged over such a short period of time in one part of the world has long been a mystery. According to the new research, if the changes had occurred by the usual processes of evolution, they would have taken about 850,000 years. But modern humans, emigrating from Africa, reached Europe only 35,000-40,000 years ago.

Instead, Frost attributes the rapid evolution to how they gathered food. In Africa there was less dependence on animals and women were able to collect fruit for themselves. In Europe, by contrast, food gathering was almost exclusively a male hunter’s preserve. The retreating ice sheets left behind a landscape of fertile soil with plenty of grass and moss for herbivorous animals to eat, but few plants edible for humans. Women therefore took on jobs such as building shelters and making clothes while the men went on hunting trips, where the death rate was high.

The increase in competition for males led to rapid change as women struggled to evolve the most alluring qualities. Frost believes his theory is supported by studies which show blonde hair is an indicator for high oestrogen levels in women.

Jilly Cooper, 69, the author, described how in her blonde youth she had “certainly got more glances. I remember when I went to Majorca when I was 20, my bum was sore from getting pinched”.

However, Jodie Kidd, 27, the blonde model, disagrees with the theory: “I don’t think being blonde makes you more ripe for sexual activity. It’s much more to do with personality than what you look like. Beauty is much deeper than the colour of your hair.”

Film star blondes such as Marilyn Monroe, Brigitte Bardot, Sharon Stone and Scarlett Johansson are held up as ideals of feminine allure. However, the future of the blonde is uncertain.

Correction: The World Health Organisation has asked us to remove an earlier erroneous reference suggesting it had conducted a study which forecast natural blonds were likely to be extinct within 200 years. The WHO issued a formal denial of such a study in 2002. Click here for the WHO statement.

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