Ancient DNA Reveals Immune Genes That May Lower Allergy Risk, Not Increase It

A new analysis of ancient DNA challenges the long-held idea that modern allergies are simply the evolutionary cost of immune systems adapted to fight infections in the past. Instead, researchers found that some genetic variants shaped by natural selection over the last 10,000 years actually reduce the risk of allergic conditions such as asthma and dermatitis, not increase it.

The findings come from a study published as a preprint on bioRxiv on April 14, 2026, which analyzed immune-related genetic variants in thousands of ancient human genomes spanning from the late Pleistocene to recent centuries. By tracking how these variants changed in frequency over time, particularly after the advent of agriculture, scientists were able to assess their impact on both infectious disease resistance and immune-mediated disorders.

Contrary to expectations, alleles that showed signs of positive selection—meaning they became more common because they provided a survival advantage—were associated with lower risk of allergic diseases. At the same time, other variants under selection were linked to higher risk of conditions like intestinal inflammatory disease and autoimmune hypothyroidism, suggesting a complex trade-off in immune evolution.

As one evolutionary geneticist not involved in the study noted, the idea that allergies are an unavoidable side effect of past adaptations to pathogens is “too simplistic.” The research indicates that evolution has not only shaped immune defenses to combat infections but has also, in some cases, fine-tuned them to avoid overreacting to harmless substances like pollen or food proteins.

The study leveraged newly available ancient DNA datasets that allow scientists to trace genetic changes across major transitions in human history, including the shift from hunter-gatherer lifestyles to farming. These datasets now include genomes from over 15,000 individuals who lived between 18,000 and 200 years ago, providing unprecedented resolution for detecting natural selection.

While the results do not rule out that some immune adaptations increased susceptibility to autoimmune or inflammatory conditions, they highlight that the relationship between past pathogen pressures and modern immune disorders is not uniformly one of increasing risk. Instead, natural selection has acted in multiple directions—sometimes enhancing protection against infection while reducing allergy risk and in other cases increasing vulnerability to immune dysregulation.

Researchers caution that the findings come from a preprint and have not yet undergone peer review. They also emphasize that genetic risk is only one factor in complex diseases like allergies, which are influenced by environment, lifestyle, and immune development. Still, the work represents a significant step in using evolutionary genetics to understand the origins of modern immune-related disorders.