The genetics of red
Ginger coloring in people—as well as horses, dogs, pigs, and other mammals—is conferred by just a handful of genetic mutations that both parents must carry. The “redhead gene” was discovered in 1995 by a team including Ian Jackson, now a professor emeritus at Scotland’s University of Edinburgh. This melanocortin 1
receptor gene, or
MC1R, plays a key role in producing melanin, the tan pigment that protects skin from ultraviolet radiation (sunlight) and also colors eyes and skin. One type, eumelanin, endows brown or black hair. Pheomelanin creates red or blonde locks and confers light skin and freckles. In people who have red hair, the skin cells (melanocytes) that produce pigment have a variant receptor on the cell surface. When exposed to UV light, this variant fails to trigger a switch that changes melanin pigment from yellow/red to the protective brown/black. “
MC1R is one of several genes that work together to produce dark melanin, and without that switch, you’re going to have light skin,” says Zorina-Lichtenwalter—and easily burn when out in the sun. In their 1995 research, Jackson and his colleagues compared 30 Irish and British redheads with the same number of brunettes. More than 80 percent of rosy-haired and/or fair-skinned people carried variations in the
MC1R gene; but just 20 percent of the brown-haired individuals did. When they published the study, geneticist Richard Spritz
told the media “this is the first time in humans that a specific gene for any common visible characteristic has been identified.”
Genetic advantage—and peril
Pale coloration bestowed a key advantage to cultures migrating from sunnier regions into northern Europe with its gray skies and short winter days. “There was evolutionary pressure to lose skin pigmentation,” Zorina-Lichtenwalter explains, because lighter skin absorbs more UV, which produces more vitamin D from the limited amount of sunlight in northern regions. Vitamin D helps the body absorb and retain calcium, build stronger bones, and protect against inflammation.
These health benefits increased the likelihood that women would survive pregnancy and birth, successfully passing on genes for light skin and red or blonde hair to their offspring. The trait flourished in the United Kingdom and Ireland, where there are, by far, more fair-skinned redheads than anywhere else on Earth. Some unofficial estimates peg the number at around 10 percent. Much of the research into redhead genetics stems from their elevated skin cancer risk. The
MC1R gene mutations linked to crimson hair, light skin, and freckles also allows more UV to reach DNA and damage it. One study found that people carrying a so-called R variant of the
MC1R gene had
a 42 percent higher incidence of melanoma, one of the most aggressive forms of cancer. Melanoma is
20 times more prevalent in Caucasians than in African Americans. However, the
average age for melanoma diagnosis is 65. Therefore, Zorina-Lichtenwalter says, “it doesn’t threaten reproductive fitness.” At that age, women have already passed their genes to the next generation. This is why, she says, redheads are unlikely to disappear from the gene pool.
More ginger genes
When he was working on that 1995 genetic analysis, Jackson knew there was more to understand about the factors conferring red hair. “It seemed logical that there were other genes involved,” he says, but deeper exploration was not yet possible: Genetic research was extremely slow and costly. While rapid advances in genetic technologies and computing had launched the Human Genome Project, the first draft of the genetic map would not be complete until 2001. Now, a quarter-century later, quick, inexpensive genetic research is the norm. Jackson and his colleagues recently revisited their inquiry with resources unthinkable in 1995. They analyzed DNA from the
UK Biobank, which contains genetic and health information on a half million residents of the United Kingdom. They discovered
eight previously unknown genetic variants that affect red hair and skin pigmentation. “To go through and find those genes using the Biobank was very, very satisfying,” Jackson says. This research, published in 2022, identified most of the genetic variation contributing to differences in hair color.
Most redheads have two
MC1R variants, according to Jackson, one from each parent. But several other genes also affect whether your hair will be red. “It's a particular combination that gives rise to red hair,” he says. Researchers assigned each of the implicated genes a “genetic risk score”: with some variants exerting higher probability of red locks. Others had much less clout but were still associated. You don’t need all of them to have red hair, Jackson says. “
MC1R is king when it comes to red headedness,” Zorina-Lichtenwalter says. “It has a tremendous amount of say in whether we'll have dark pigmentation or light pigmentation.” More than four-fifths of redheads carry
MC1R; whereas the remaining reds are caused by other genes.
Geography and ancestry
A recent
U.K. genetic study correlated the incidence of burnished tresses with place of birth, with more redheads in the country’s north and west. “In the Biobank, you've got the latitude and longitude of birthplace of every individual.” Jackson says. “The further north you were born, the higher the likelihood of having red hair.” Red-haired, light-skinned genetics thrived in remote regions, closed communities, and islands––such as Scotland (estimates of redheads there range from Jackson’s 6 percent up to 12 or 14 percent); Ireland (10 percent); and Britain (6 percent). While the populations of these countries are no longer cut off from the rest of the world, “when you have an insular population, isolated from others reproductively, then whatever alleles, they rise in frequency from generation to generation,” Zorina-Lichtenwalter says. However, redheads are not only Celts or Caucasians. Their distribution is a testament to the global movement of DNA across societies and landscapes. Although
most common in Northern Europe, parts of Russia, and among European descendants in Australia, there are redheads from all ethnicities and races. For example, both Morocco and Jamaica have higher-than-average numbers.
The reason, Zorina-Lichtenwalter says, is that several genes are responsible for triggering dark eumelanin production to protect skin. But for hair color, she says “
MC1R does appear to dominate, which is why variants in
MC1R can still produce red hair in Jamaicans and other dark-skinned people.”
We are not amidst a redhead extinction event
Claims that redheads are a dying breed are not new, and some of them were clearly linked to financial gain, Jackson says. One headline that started an uproar blared, “
Redheads May Soon Join Polar Bears As Casualties Of Climate Change,” which is a serious stretch. Climate change is creating more extreme temperature, drought, and flood; but the possibility that it will impact UV radiation enough to alter Northern Hemisphere genetics––within the predicted few hundred years––is slim, says Zorina-Lichtenwalter. The source of this claim was Alistair Moffat, CEO of the now-defunct genetic testing company
ScotlandsDNA. Prior to that, the
Oxford Hair Foundation (also dissolved) predicted that
redheads would be extinct by 2100, with the gene variant that confers flaming hair slowly disappearing. “[The institute] was a front, funded by a hair dye and cosmetics company to generate interest in hair color,” Jackson says. While recessive genes can become rare, they don't utterly disappear unless every person who carries that gene either perishes—or does not bear children. And clearly that’s not going to happen.
Wherever they live, redheads garner outsized attention, sometimes stigmatized, sometimes admired. As testament to their continued presence in the world, they
celebrate themselves in yearly “red pride” events in the U.K., France, and Italy, as well as the U.S. The largest may be an event in August, when thousands of gingers from across the world convene in the Netherlands for “
Redhead Days.”
