A rare feat in evolutionary biology A PNAS commentary that was published 2 days ago: * K. Naruse, & H. Takeda, Plasticity-led evolution of the gut length in wild medaka, _Proc. Natl. Acad. Sci. U.S.A_. 123 (18) e2609145123, https://doi.org/10.1073/pnas.2609145123 (2026). I've taken the title above from the concluding remarks: > Katsumura et al. have achieved a rare feat in evolutionary biology by mapping the complete molecular trajectory of an adaptive trait. The abstract: > The molecular mechanisms by which environmentally induced traits become genetically fixed are not well understood. A recent PNAS study by Katsumura et al. (1) addresses this long-standing issue in wild medaka fish. The authors demonstrate that seasonal gut length plasticity is controlled by DNA methylation at a specific CpG island and that sequential loss of these methylation sites during evolution dismantles this epigenetic switch. This exposes cryptic standing genetic variation to natural selection.…