Ancient DNA Reveals Millennia-Long Natural Selection for Red‑Hair Gene Across Europe

New research indicates that individuals carrying the red‑hair allele have been evolutionary winners in Europe for more than 10,000 years. The study, led by Harvard scientists, examined DNA from nearly 16,000 ancient remains and over 6,000 living Europeans, providing robust proof that human biology continues to evolve long after farming began.

Researchers identified 479 genetic variants that show clear signs of positive selection. Among these are genes linked to red hair and fair skin, as well as variants that affect susceptibility to coeliac disease, diabetes risk, baldness and rheumatoid arthritis.

The authors suggest that the advantage of red hair may stem from its association with lighter skin, which enhances vitamin D synthesis in low‑sunlight environments—a crucial benefit for early European farmers.

Prior to this work, only about 21 traits had been documented as having risen through natural selection, such as lactase persistence. The scarcity of earlier examples had led some to argue that directional selection was rare after modern humans left Africa.

By leveraging an unprecedented volume of ancient genomic data and advanced computational methods, the team demonstrated that selection pressures intensified during the transition from hunter‑gatherer societies to agricultural ones, reshaping hundreds of genes across West Eurasia.

"With these new techniques and the sheer scale of ancient DNA, we can now observe how selection sculpted our biology in near real‑time," said Dr. Ali Akbari, the study’s first author.

Beyond vitamin D, the rise of certain disease‑related alleles poses intriguing puzzles. A mutation that heightens the risk of coeliac disease emerged around 4,000 years ago and has steadily increased, implying that carriers may have enjoyed other survival advantages despite the autoimmune threat.

Similarly, the immune‑regulating gene TYK2, which markedly raises tuberculosis susceptibility, grew in frequency between 9,000 and 3,000 years ago before declining, hinting at a complex balance between pathogen defense and disease risk.

The analysis also uncovered negative selection against genetic profiles that promote a high body‑fat percentage, supporting the classic “thrifty genes” hypothesis: traits advantageous for storing energy during scarce hunter‑gatherer periods became detrimental once agriculture ensured a steadier food supply.

"This work lets us assign both place and time to the forces that have shaped us," noted Prof. David Reich, senior author and Harvard Medical School geneticist.

While the findings are confined to West Eurasian populations, they raise broader questions about whether similar evolutionary dynamics occurred elsewhere. The full study appears in Nature.