No, freckles will not disappear

Whether on screen or on the street, there is one hair color that never stops capturing our attention, from the lightest to the deepest of its shades, it’s freckles. If red hair has this effect on us, it’s because it’s rare: 1 or 2% of the world’s population. Although the genetic variants responsible for these fiery glimpses are rare, freckles are not destined to disappear, contrary to what some claim.

“Redheads are not going to go extinct,” says Katrina Zorina Lichtenwalter, a postdoctoral fellow at the Institute for Behavioral Genetics at the University of Colorado at Boulder.

To understand this phenomenon, it is first necessary to go back to the origins of freckles. It turns out that fiery hair fascinates not only the tabloids, but also science, which is conducting an unexpected number of studies on the color variations of human hair. If there’s one thing that stands out from this work, it’s the certainty that redheads still have a bright future ahead of them.

This is a prehistoric trait. According to a DNA analysis conducted on a 50,000-year-old specimen, some Neanderthals had fair skin and red hair. Beautiful Mummy Loulan, a famous 3,800-year-old Bronze Age mummy, was discovered in a desert in northwest China with dark brown hair intact. From the 5th century on in the area that became southeastern Europe and Turkey, King Rhesus of Thrace was depicted with a carrot-colored beard and hair on Greek pottery.

Since the genes involved are recessive, two copies are required for her to give birth to a baby Ginger, one from the father and one from the mother. As Zorina-Lichtenwalter explains, only red-haired parents can be sure of their children’s hair color.

in his book Red: the history of the redheadAuthor Jacky Coliss Harvey explains the possibility of having a red-headed baby as follows: “If genetics were a card game, the freckles would be the two sticks, cut out by all the other cards in the deck.”

On the origins of modeling

Whether it is in humans, horses, dogs, pigs, or any other mammal, freckles are the result of a few genetic mutations that both parents must carry. The “freckle gene” was discovered in 1995 by a team that included Ian Jackson, who is now Professor Emeritus at the University of Edinburgh in Scotland.

melanocortin 1 receptor, or MC1RIt plays a major role in the production of melanin, the dark pigment that protects the skin from ultraviolet radiation, especially sunlight, and gives the eyes and skin their color. For example, eumelanin results in brown or black hair. Pheomelanin is the cause of red or blonde hair, but it also causes pale skin and freckles.

In red-skinned individuals, the skin cells responsible for pigmentation, the melanocytes, have different receptors on their surface. When exposed to ultraviolet light, this receptor fails to trigger the conversion of the yellow/red pigments of melanin into brown/black protective pigments. ” MC1R It is one of the genes that contribute to the production of dark melanin and in the absence of this element, the skin will become pale,” says Zorina-Lichtenwalter, and be particularly susceptible to sunburn.

In their 1995 study, Jackson and his colleagues compared 30 Irish and British red-haired people with the same number of dark-skinned people. More than 80% of people with red hair and/or light skin carry mutations in the gene MC1R. In brown-haired people, that percentage dropped to 20%.

“This is the first time that a genetic coding for a common visual characteristic has been identified in humans,” geneticist Richard Spritz told the press when the study was published.

Benefits and risks

Pale skin was a major feature of people who experienced the gray skies and short winter days of northern Europe after migrating from sunny regions. “There was selection pressure to lose pigmentation,” says Zorina-Lichtenwalter, because lighter skin absorbs more UV radiation, allowing more vitamin D to be produced from the limited sunlight that characterizes northern regions. Vitamin D promotes calcium absorption and retention, helps build stronger bones and protects against infections.

These health benefits increased a woman’s chances of surviving pregnancy and childbirth, and of passing genes for fair skin and blonde or red hair to her offspring. This trait is very common in the United Kingdom and Ireland, where there are more fair-skinned redheads than anywhere else on Earth. Some unofficial estimates put the percentage at around 10%.

Most of the work on freckle genes is focused on increasing the risk of skin cancer. under the influence of genetic mutations MC1R Associated with red hair, pale skin, and freckles, more ultraviolet light can reach DNA and cause damage. A study showed that the incidence of one of the most aggressive forms of cancer, melanoma, increased by 42% in people with the R variant of the gene. MC1R. In the United States, there are 20 times more melanomas in the white population than in the black population.

However, the average age at which skin cancer is diagnosed is 65 years. Thus, Zorina-Lichtenwalter continues, “The phenomenon does not threaten reproductive health. At this age, women have already passed their genes on to the next generation. This is why freckles are unlikely to disappear from genes.

Gene history

Working in 1995, Jackson knew there was a lot to understand about the factors that give hair its red color. “It seemed logical that other genes were involved,” he says, but at the time it was impossible for him to explore further: genetic research was too slow and expensive. While rapid advances in genomic technology and computing have already enabled the launch of the Human Genome Project, it will take until 2001 to lay eyes on the first draft of the genetic map.

Almost a quarter of a century later, the trend is toward rapid and inexpensive genetic research. Jackson and his colleagues recently replicated their investigation using Unimaginable Resources in 1995. They analyzed DNA provided by the UK Biobank, a biobank containing genetic data for more than half a million UK residents. They discovered eight new genetic variants that affect red hair and skin pigmentation. “It was really cool to find all this data in the biobank,” says Jackson. This study, published in 2022, identified most of the genetic variations that code for different hair colors.

According to Jackson, the majority of redheads have two different types. MC1R, one from each parent. However, many other genes can also cause red hair. “Freckles are the result of a certain combination,” he explains. The researchers assigned each involved gene a “genetic risk score”: some variants increase the likelihood of freckles, while others have a much smaller effect, without being completely dismissed. You don’t have to have them all to have red hair, says Jackson.

” MC1R “King when it comes to freckles,” says Zorina-Lichtenwalter. “It has a large share of the responsibility for pigmentation. More than four-fifths of redheads carry the gene MC1RAnd the remaining part is the fruit of other genes.

Geography and genealogy

A recent genetic study in the United Kingdom linked freckles to birthplace, with the largest number of redheads in the north and west of the country. “The biobank determines the latitude and longitude of each individual’s hometown,” Jackson adds. “The farther north the place of birth is, the more likely it is to be a gingerbread man.”

The gene pool associated with freckles and fair skin thrives in isolated areas, gated communities, and islands. In Scotland, estimates place the percentage of redheads between 6%, according to Jackson’s work, and 12 or 14%; About 10% in Ireland and 6% in Great Britain. Although these regions are no longer isolated from the rest of the world, “when you encounter an island population whose reproduction is isolated, and whatever alleles are studied, their frequency increases from one generation to the next,” explains Zorina-Lichtenwalter. .

However, freckles are not only for Celts or Caucasians. The distribution of personality testifies to the global movement of DNA across regions and societies. Despite the high frequency in Northern Europe, in certain regions of Russia and among the descendants of Europeans in Australia, no ethnic group escapes this lustrous hair. For example, higher-than-average frequencies have been observed in Morocco and Jamaica.

Indeed, if several genes are able to trigger the production of the skin-protecting dark pigment eumelanin, as Zorina-Lichtenwalter points out, then it appears that MC1R It is the dominant gene for hair color, which is why it has variants MC1R It can result in red hair in Jamaicans or other dark-skinned people. »

Extinction myth

Claims that redheads are an endangered species are not recent, Jackson said, and some of them were clearly greedy.

“Redheads Join Polar Bears as Victims of Climate Change,” reads a sensational article headline. This is an affirmation that speaks for itself. It is true that extreme weather events are increasing under the influence of climate change, but from there to amplify UV radiation enough to alter the genetic heritage of the northern hemisphere in the space of a few hundred years as is assumed, there is a gap, says Zorina-Lichtenwalter. The author of that statement was Alistair Moffat, CEO of genetic testing company ScotlandsDNA, which has since closed shop.

Prior to this, the now-dissolved Oxford Hair Foundation was betting on the extinction of freckles by the year 2100, justifying its assertions of the gradual disappearance of the genetic variant at the origin of radiant hair. “The foundation in question was a cosmetics and hair dye company-funded front to generate interest in hair dyes,” Jackson said.

It happens that recessive genes become rare, but to completely disappear from the genetic landscape, every carrier of the gene in question must die or stop reproducing, which is not about to happen.

No matter where they live, redheads are a subject of special concern, from stigma to admiration. To celebrate longevity around the world, they hold events in the UK, France, Italy and the US every year. And the most important thing happens in August, when thousands of actors from all over the world gather in Holland for the Redhead Days festival.