Study Reveals Ongoing Natural Selection in Modern Humans

Researchers at National Yang Ming Chiao Tung University have published a study in The American Journal of Human Genetics that highlights how humans are still undergoing natural selection. By examining genomic data from over 72,000 Han Taiwanese individuals in the Taiwan Biobank, the team tracked how specific genetic variants change in frequency across different adult age groups.

The study identified 168 variants under active selection. About 90 percent of these are rare, which means conventional genome-wide scans often miss them. Of these, 71 are classified as pathogenic or likely pathogenic in the ClinVar database. These variants are associated with a range of health issues, including cancer, cardiovascular disease, and neurological disorders. The method demonstrates that biobanks serve as more than just disease research tools; they function as a window into contemporary human evolution.

One significant finding involves the BRCA1 gene. The researchers found a rare haplotype with 16 protein-altering variants that appear to be under purifying selection, meaning the population is naturally filtering them out. Interestingly, areas near BRCA1, BRCA2, and MLH1 showed signs of positive selection. This indicates that the same DNA repair genes can face different evolutionary pressures simultaneously, reflecting the complex trade-offs inherent in human genetics.

The study also linked genetic variants to red blood cell traits, potentially reflecting historical adaptation to malaria. By observing how these genes, such as ATG9A and FADS2, influence multiple physiological systems, the team mapped out how selection shapes human health. This approach offers a way to identify medically relevant variants in diverse populations, especially since current genomic datasets often skew toward European ancestry. This framework provides a new pathway to improve precision medicine and understand how evolution continues to shape health outcomes.