AFTER centuries of jokes and cruel remarks, redheads may have the last laugh. Natural selection will turn those with ginger hair into an exotic and desirable rarity in the next 100 years.

Scientists are warning that racial mingling will reduce the number of people with red hair, consigning the likes of Nicole Kidman, Chris Evans and Charlie Dimmock to history. Blondes are also likely to disappear — although they will linger for slightly longer because there are more of them, according to researchers.

The reason, they say, is that people of different races are mixing and inter-marrying at a rate never seen before because of globalisation and migration. Natural blondes and redheads will be prized as never before.

Such striking hair colours are already becoming exceptional when seen as part of the global population, said Dr Desmond Tobin, who researches hair cell biology at Bradford University.

“As the amount of migration, inter-marriage and mixing increases we will see them all but disappear,” he explained.

He was speaking at a conference — organised by the Oxford Hair Foundation, a research centre — which also heard that although about a third of British women sport blonde hair, most get their colour straight from a bottle. “Only about 3% are naturally blonde,” said Tobin.

The proportion of redheads is even smaller at about 1%-2% — except in Ireland and Scotland where it is estimated at up to 8%.

The proportions of both hair colours are already thought to have declined, particularly over the past 50 years.

However, Nicky Clarke, a hair stylist whose clients include red-headed Sarah Ferguson, the Duchess of York, and blonde Denise van Outen, said natural blondes and redheads inspired thousands of his customers to seek similar colours for their own hair. “It would be sad to lose that diversity,” he said.

Scientists see such changes as evolution at work — but others see the loss of redheads and blondes as a step backwards.

Quite why humans evolved red or blonde hair is considered one of the mysteries of human evolution. Although humans probably evolved in Africa 1m-2m years ago, red and blonde hair appeared only once humans had settled in Europe — possibly as recently as 20,000 years ago.

The genetics of red and blonde hair are also complex. For example, one of the main genes for hair colour has 40 variants — but only about six cause red hair.

People must inherit two of these six genes — one from each parent — to have red hair.The chances of this are always small — which is why there are so few redheads. The best chance occurs in stable rural communities with a common ancestry — where people carrying the genes are likely to meet and have children.

This is probably how redheads took hold in Scotland and blondes became common in Scandinavia.

However, such communities are now rare and face influxes of newcomers — reducing the chance that any two parents will each have the genes needed to produce red or blonde hair in their children. In cities the chances are far smaller.

Jonathan Rees, the professor of dermatology at Edinburgh University who discovered the gene for red hair, said: “Blondeness appears to follow similar patterns of inheritance.”

In the past, redheads and blondes in concentrated communities have thrived. Some researchers suggest that many ancient societies, including the Romans, prized redheads and blondes as mates — meaning that they could choose the fittest partners.

However, while blondeness is still prized in western Europe and America, the global trend appears to be moving in a different direction.

Earlier this month Newsweek magazine featured the Canadian-born model Saira Mohan on its cover, declaring her coffee-coloured skin and dark hair to be the new “global face” of beauty. Mohan, the magazine reported, owed her fusion of western and eastern beauty to an ancestry that could be traced back to India, Ireland and France.

Tobin said: “The genes for red and blonde hair could spread in sparsely populated areas like ancient Scandinavia or Britain but now they are simply being swamped.”

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