Nicole's hair secrets
What do Cleopatra, Napoleon Bonaparte and Nicole Kidman have in common? David Derbyshire investigates the genetics of red hair
General Custer was one. So was Napoleon Bonaparte. Underneath Oliver Cromwell's severe helmet was a mass of red hair. Cleopatra used henna to enhance her auburn tresses, while Christopher Columbus took ginger hair to America.
But while fiery-headed leaders, artists, poets and disc jockeys crop up with alarming regularity, evidence is emerging that red hair may be a relatively new phenomenon for mankind.
|Not Neanderthal: red hair is now thought to be a relatively recent development for mankind|
According to the most recent estimates, the first red hair sprouted just 20,000 years ago, long after the advent of modern homo sapiens and towards the end of the last great ice age.
Some have even argued that redheads such as Nicole Kidman, Charlie Dimmock, Chris Evans and Neil Kinnock could have inherited a trait originally passed on to modern man by the Neanderthals.
The secret history of redheads is one of the topics explored at the Hair Affair, a half day of talks and workshops exploring the science of hair, organised by the Royal Institution and L'Oréal and supported by The Daily Telegraph on October 25.
The redhead roll call makes for impressive reading. It includes Vincent Van Gogh, Henri Matisse, William Blake, Lord Byron, James Joyce, J K Rowling, Jean Paul Sartre, George Bernard Shaw, Bette Davis, Katharine Hepburn, Marilyn Monroe, Elizabeth I, Queen Victoria and William the Conqueror.
Despite the old folk tale that redheads are the result of interbreeding between brunettes and blonds, hair colour is actually determined by a more subtle genetic influence.
Like skin colour, hair colour comes from the pigment melanin and, in particular, two types: eumelanin, the most common form, ranges in colour from brown to black, while pheomelanin is red or yellow.
Hair and skin colour arise from the balance of these two types and the total amount of melanin produced. White skins produce less melanin than dark skins. Japanese black hair is almost entirely made of eumelanin, while Irish red hair has almost only pheomelanin.
Melanin is a good sun block, preventing damage from ultraviolet rays. The pigment is unlikely to have evolved as a protection against skin cancer (which threatens life long after reproductive age and so would be unlikely to be selected against in evolution) but might protect against burns, secondary infection and loss of fluids.
Several years ago Jonathan Rees, professor of dermatology at Edinburgh University, and colleagues discovered a gene responsible for melanin production, the melanocortin 1 receptor (MC1R).
If someone has one of about four of five variations of this gene, and if the variation is inherited from both parents, then they are likely to be red haired. If the variation has been inherited from just one parent, they have an increased chance of being red haired. What was surprising was how recently this genetic trait first appeared.
"We don't know with certainty when the first redheads walked the earth," says Prof Rees. "But we believe these changes arose in less time than we thought, maybe 20,000 to 40,000 years ago."
The red-headed gene mutation is rarely found in people of African descent. Evolutionary experts have argued that it cropped up after ancestors of white Europeans left the continent and moved northwards around 70,000 to 100,000 years ago.
"The explanations generally fall into two groups," says Prof Rees. "The first is that there may have been some advantage to having red hair and pale skin. One reason for this is that you make vitamin D in your skin and therefore you're less likely to get rickets if you have pale skin and there is not much sunlight around."
The team's analysis of the red-headed gene, however, found little evidence that red hair and pale skin were a positive trait added to mankind's genetic heritage by natural selection outside Africa.
The clue came from an analysis of codons - the sequences of DNA or RNA that provide the recipe for any one of the 20 amino acids that form the building blocks of proteins. The sequences consist of three base pairs of DNA - three "letters" of the genetic code. Two of these letters are crucial to the make-up of the amino acid. But some changes in the third base pair make little difference to the end result - the equivalent of spelling tic with a K instead of a C.
By studying the ratio of changes in this third base with the changes in the other two base pairs, it is possible to identify genetic traits that are the result of natural selection and those that have just cropped up by chance.
"With the redhead gene, you don't see any evidence for selection. The changes we see are compatible with just random change," said Prof Rees. "The gene is more important in Africa than it is in Europe. You mustn't have pale skin and bright red hair in Africa. That would make sense."
Of course, red hair is not exclusively found in pale-skinned people. In Jamaica, there are families with deep brown skin and bright red hair. On the island, the red-hair gene was brought from Europe a few hundred years ago, possibly by white sailors who fathered children there.
If the Edinburgh team are right, and the redhead gene originated only 20,000 to 40,000 years ago, it may kill off a theory that emerged last year - that the red-hair gene originated in the Neanderthals.
The idea was based on a claim that the gene was at least 100,000 years old and so may have been present before modern man left Africa. To pass into our DNA, our ancestors would have had to have interbred with Neanderthals - an unfashionable theory among the experts in human origins.
"There's not much evidence for it," said Prof Rees. While the Edinburgh team are investigating the purpose of colour, a team in Paris are helping to explain the purpose of hair.
Researchers at L'Oréal believe the common perception that hair is purely about keeping warm - and is therefore expendable - is wrong. They believe hair might play a vital role in repairing wounds.
Hair grows in a continuous cycle. During the growth period (anagen phase), hair grows 0.3-0.5mm a day. This phase lasts about three years, but can vary from just a few months to up to 10 years. It is followed by a three-week period of self-destruction (catagen phase).
The hair follicle does not produce hair, and the cells in its base die. Finally comes the hair loss or telogen phase. The hair falls or is brushed, washed and combed out. This resting periods lasts for three months, before the follicle starts growing again.
At any one time, up to 90 per cent of the hair is in the growth phase, while around 10 per cent is in the loss phase. Typically, the head loses between 50 and 100 hairs every day.
This pattern of destruction and regrowth has long suggested the presence of stem-cell reservoirs - banks of "parent" cells from which the new follicles can be regenerated.
In the early 1990s, scientists reported the discovery of the hair bulge, the area they believed contained the stem cells, just below the skin surface. For 10 years this discovery was unchallenged.
However, a team led by Dr Bruno Bernard at L'Oréal's research centre in Paris discovered the bulge was just half the story. Another reservoir of stem cells was also found 4mm below the skin.
During the catagen phase, the stem cells in the lower part climb up to reach the reservoir. They fuse until the hair starts growing again, and then separate into their distinct reservoirs. The process resembles a yo-yo.
Dr Bernard believes the two reservoirs are not just important in hair growth, they may also act as the skin's emergency services in the event of an injury. "It has been observed that when you have a wound, the epidermis [the thin, protective outer layer of the skin] is rebuilt from the follicle," he said. "These stem cells play a role.
"We believe our recent discovery feeds off this observation. The epidermis is an essential component of the body because it separates the inside from the outside. If there is a wound, it has to be closed as quickly as possible. I believe the existence of these two reservoirs is a survival tool.
"The presence of a stem-cell reservoir deep in the dermis [the deep, inner layer of the skin] might ensure a proper renewal of the follicle, especially when the upper part is destroyed by wounding.
"As a matter of fact, we had shown in the late Eighties that one could regenerate an epidermis from both the upper and lower parts of human hair follicle. This has been recently confirmed.
"This is of key importance for people since the epidermis wound-healing process starts from hair follicles. The lower reservoir may help maintaining this organ. In an emergency, it helps to close the wound quickly."
The discovery of stem-cell reservoirs in the hair follicle could have implications for some cosmetic treatments that burn away follicles.
"When people say they want to get rid of all their hair, they should be careful," said Dr Bernard. "If you get rid of it, you might get in trouble if you get a wound. I would question whether laser treatment to permanently remove hair is such a good thing."
The Hair Affair, an afternoon of workshops and lectures organised by the Royal Institution and L'Oréal, explores the science of hair. The event, which is supported by The Daily Telegraph, takes place on October 25.
Research scientists from L'Oréal in Paris will join British researchers to reveal what makes hair curly, why hair is red, how hairspray and shampoo work and why hair falls out. There is also a chance to make shampoo and create hair gel.
Hair Affair is free, and is aimed at families and school parties. We have 100 children's and 100 adults' tickets reserved for the first readers to book places by phone. The first 10 callers will receive a free copy of L'Oréal's guide to the science of hair, while the first two will be offered a tour of the Royal Institution. To claim a place, call 020 7670 2969.
For more information, see www.rigb.org/insideout