Red hair may be increasing as study points to surprising evolution trend

A study from Harvard Medical School indicates natural selection has favored the red hair gene, resulting in a potential increase in the number of redheaded people as humanity continues to evolve.

By analyzing nearly 16,000 ancient genomes spanning 10,000 years, researchers identified a list of traits that nature is actively pushing forward. Among the most prominent were the genetic variants for red hair.

"Perhaps having red hair was beneficial 4,000 years ago, or perhaps it came along for the ride with a more important trait," the authors noted.

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The study, published in the journal Nature, relied on a large database of ancient DNA from West Eurasia. Using new computing methods, the team was able to filter out random fluctuations in DNA to identify what it called "directional selection."

Directional selection happens when a particular version of a gene gives an organism a strong survival or reproductive advantage, causing it to become more common in a population faster than it would by chance, according to experts.

Prior to this study, scientists only knew of about 21 such instances in human history, one of which was lactose tolerance. This new research uncovered hundreds more.

"With these new techniques and a large amount of ancient genomic data, we can now watch how selection shaped biology in real time," Ali Akbari, first author of the study and senior staff scientist in the lab of Harvard geneticist David Reich, said in a press release.

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The data showed that genetic markers for red hair are among 479 gene variants that have been strongly favored over the past 10,000 years. One likely explanation, the researchers said, is a major shift in human history: the transition to farming.

As humans moved away from hunting and gathering and settled into agricultural societies, their environment and behavior changed radically, triggering an evolutionary "acceleration."

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While the Harvard study provides the first definitive statistical proof that red hair was actively selected during the rise of farming, the researchers noted that the exact prehistoric benefit still requires more study.

However, scientists have long pointed to vitamin D synthesis as a likely driver for the rise of these light-pigmented traits in northern climates.

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While redheads remain a minority of the global population today, the Harvard study’s analysis suggests that they may not be an evolutionary accident.

Instead, the red hair trait was "boosted" by natural selection as humans adapted to the challenges of a modern world, according to the researchers.

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The researchers urged caution in how these findings are interpreted.

"What a variant is associated with now is not necessarily why an allele propagated," the authors noted.