Understanding why some populations metabolize carbohydrates more efficiently than others has long puzzled nutritional geneticists. New high-coverage ancient genomic data from Japan now offers a rare window into when and why starch-digestion genes began diverging — findings with direct relevance to modern metabolic health research and the ongoing debate over dietary adaptation across human populations.
Published in PNAS, the study leveraged high-coverage ancient genomes from prehistoric Japanese populations to reconstruct both migration histories and the evolutionary trajectory of starch-related genetic variants. The researchers identified divergent population histories among early Japanese groups and tracked genetic variation in genes associated with starch metabolism — likely including amylase copy-number variants (AMY1) and related loci — correlating these shifts with the archaeological and dietary transitions of the period. The high genome coverage allowed finer resolution than most prior ancient DNA work from East Eurasia, enabling statistical confidence in detecting selection signals tied to carbohydrate processing.
This work fits into an accelerating area of research examining how agricultural transitions drove rapid genomic adaptation in human digestive systems. The well-established link between AMY1 copy number and salivary amylase production — and by extension starch tolerance — has been studied in modern populations, but pinpointing when selection intensified has been methodologically constrained. High-coverage ancient genomes, rather than the low-pass sequencing typical of older paleogenomic studies, make it possible to call structural variants and rare alleles with much greater reliability. The Japan setting is particularly valuable because the archipelago experienced distinct waves of migration and a relatively late but intensive shift toward rice agriculture, creating a natural experiment in dietary-driven selection. Key limitations include the geographic and temporal scope of the sampled individuals; broader East Asian ancient genome coverage will be necessary to confirm whether the patterns observed are Japan-specific or reflect wider regional dynamics. Overall, this is an incrementally significant but methodologically strong contribution to nutritional genomics.
