Taipei: A study by researchers at National Yang Ming Chiao Tung University (NYCU) has documented ongoing natural selection shaping disease susceptibility among Taiwan's contemporary population. According to Focus Taiwan, the study analyzed genetic data from 72,635 Han Taiwanese individuals using the Taiwan Biobank, a national biomedical research database. By comparing frequencies of genetic variants, known as allele frequency, across different age groups, the team identified 168 variants that appeared to be undergoing natural selection, including 159 variants showing a gradual decline or disappearance across generations. Researchers noted a "consistent signal" involving red blood cell traits, with 149 variants decreasing in frequency among younger age groups associated with larger red blood cell volume and lower hemoglobin concentration. This consistent pattern suggests natural selection is progressively reducing the prevalence of genetic variants linked to larger red blood cell volume. The team hypothesiz ed that this trend relates to historical adaptation to infectious diseases like malaria, which was prevalent in Taiwan until about 60 years ago. This type of natural selection, where genetic variations detrimental to survival are gradually removed over successive generations, is known as "purifying selection." Meanwhile, the team also identified traces of natural selection in genes related to DNA repair and cancer. One of these, a BRCA1 haplotype carrying multiple pathogenic variants, was found to be decreasing in frequency among younger generations. Knowledge of such rare and population-specific pathogenic variants could provide benefits in areas such as disease risk assessment and precision medicine. The study was led by Ko Wen-ya, associate professor in NYCU's Department of Life Sciences and Institute of Genome Sciences, in collaboration with Yoko Satta of the Graduate University of Advanced Studies in Japan. It was published in the American Journal of Human Genetics in July.