Red hair gene appears to have been favored by natural selection

Harvard researchers analyzing ancient genomes found red-hair gene variants among hundreds of traits that appear to have been favored over 10,000 years.

Genetic variants linked to red hair appear to have been favored by natural selection over thousands of years, according to a Harvard Medical School study that analyzed nearly 16,000 ancient genomes.

The research, published in the journal Nature , examined ancient DNA from West Eurasia spanning about 10,000 years of human evolution. Researchers identified hundreds of gene variants that appear to have increased in frequency faster than random chance would explain, including markers associated with red hair.

The finding does not mean scientists have settled why red hair became more common in some populations. The study points to a signal of selection, not a confirmed prehistoric cause. Researchers noted that a trait’s present-day association may not explain why it spread in the past.

“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 wrote.

The team used newer computing methods to distinguish random genetic drift from what scientists call directional selection — the process in which a version of a gene provides a survival or reproductive advantage and becomes more common in a population. Before this work, scientists had identified only about 21 such cases in human history, including lactose tolerance, according to the report. The new analysis found hundreds more.

Ali Akbari, first author of the study and a senior staff scientist in the lab of Harvard geneticist David Reich, said the larger ancient DNA record and updated methods allow researchers to track selection more directly. “With these new techniques and a large amount of ancient genomic data, we can now watch how selection shaped biology in real time,” Akbari said in a press release.

Researchers tied the broader burst of evolutionary change to the shift from hunting and gathering to farming, when human diets, settlements and environments changed significantly. The report also notes that scientists have long considered vitamin D synthesis a possible factor in the rise of lighter pigmentation traits in northern climates.

Redheads remain a small share of the global population. The study’s significance is narrower but notable: it suggests red hair was not merely a random genetic holdover, but part of a wider pattern of human adaptation still being reconstructed from ancient DNA.