Red Hair Gene Continues to Thrive in Europe
People with red hair, who have faced their share of teasing and various stereotypes, might find some solace in recent findings: it seems, from an evolutionary standpoint, they’re doing pretty well. A significant genetic study has shown that the gene responsible for red hair has been positively selected in Europe for over 10,000 years.
This research wasn’t specifically geared toward uncovering why red hair is so persistent, but it did tackle a broader inquiry about whether human evolution has come to a standstill since agriculture began. By studying DNA from nearly 16,000 ancient human remains along with over 6,000 modern individuals, the researchers presented strong evidence that biological evolution is still very much in motion.
Throughout the study, scientists pinpointed 479 genetic variations that seemed to have been favored by natural selection. Interestingly, genes associated with red hair and fair skin, along with those linked to coeliac disease and reduced risks for conditions like diabetes, baldness, and rheumatoid arthritis, have all seen a rise in frequency in more recent history.
One of the researchers speculated, “Maybe having red hair offered some advantages 4,000 years ago, or it could be that it just came along with another more significant trait.” For example, previous studies suggest that individuals with red hair and light skin might be able to produce vitamin D more effectively, which could have provided survival advantages in areas with less sunlight.
Historically, only about 21 genetic traits were known to have increased through natural selection, such as those allowing for milk digestion in adulthood. The limited evidence previously suggested that directional selection had been relatively rare since modern humans emerged in Africa around 300,000 years ago, followed by dispersal into different global populations.
This new study utilized an unprecedented collection of ancient DNA samples, combined with advanced computational methods, to demonstrate that evolutionary selection has influenced the rise or decline of hundreds of genes in West Eurasia, particularly accelerating after the shift from hunter-gatherer lifestyles to farming.
Dr. Ali Akbari, the first author of the report from Harvard University, noted, “With these new techniques and the large dataset of ancient genomic information, we can now observe how selection has influenced biology in real time.”
Some of the genetic traits identified seem relatively intuitive. For instance, the genes associated with red hair and fair skin likely correlate with a higher synthesis of vitamin D in sun-deprived farming regions, the scientists speculated.
However, other trends were less straightforward. A mutation strongly linked to coeliac disease first appeared around 4,000 years ago and has become increasingly prevalent. Interestingly, individuals carrying this gene variant managed to survive and reproduce despite the heightened risk of an autoimmune disorder.
Similarly, a gene called TYK2, which significantly increases tuberculosis risk, rose in frequency between 9,000 and 3,000 years ago before later dropping off. This inconsistency raises the possibility that such disease-risk genes might have provided protection against certain pathogens that were more widespread during specific periods.
The research also uncovered negative selection against certain gene combinations that lead to high body fat percentages—an observation aligned with the “thrifty genes” hypothesis. This suggests that while genetic traits allowing fat storage were advantageous for hunter-gatherers during times of scarcity, they became less beneficial once agriculture provided a more stable food supply.
“This work lets us pinpoint the time and place of the forces that have shaped our biology,” said Prof. David Reich, a genetics professor at Harvard Medical School and the senior author of the study.
While the study primarily examined evolutionary trends in West Eurasia, it didn’t explore whether these patterns are unique to those populations or if similar processes are happening on a global scale. The findings have been published in Nature.
