Rice, one of the world's most important crops, originates from eastern Asia. Here in a newly published Genome Research paper, we show that major dietory change due to rice domestication may lead to the rapid increase of allele frequency of a mutation in an incretin gene in humans. We report that the human GIP locus was differentially selected among human populations based on the analysis of a nonsynonymous SNP (rs2291725). Haplotype structure analysis suggests that, owing to positive selection, the derived allele at 2291725 arose to dominance in East Asians ~8.1 thousand years ago. In addition, cComparative and functional analyses showed that the human GIP gene encodes a cryptic glucose-dependent insulinotropic polypeptide (GIP) isoform (GIP55S or GIP55G) that encompasses the SNP and is resistant to serum degradation relative to the known mature GIP peptide. Importantly, we found that GIP55G, which is encoded by the derived allele, exhibits a higher bioactivity as compared to GIP55S, which is derived from the ancestral allele. Haplotype structure analysis suggested that the derived allele of the SNP arose to dominance in East Asians ~8kya (This is the exact time when rice was domesticated!). The combined results suggested that SNP rs2291725 represents a functional mutation and may contribute to the population genetics observation. Given that GIP signaling plays a critical role in homeostasis regulation at both enteroinsular and enteroadipocyte axes, our study highlights the importance of understanding adaptations in energy-balance regulation in the face of the emerging diabetes and obesity epidemics.