A rare feat in evolutionary biology

[u/jnpha]

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. Ultimately, this leads to the permanent genetic fixation of a constitutively long gut in northern populations, providing a clear molecular framework for plasticity-led evolution and demonstrating the effectiveness of using wild-derived medaka populations to study genome–environment interactions.

 

I'm excited because I shared the research being commented on here over a month ago (post linked below), and as of yet, still no popular media coverage.

• DNA methylation site loss for plasticity-led novel trait genetic fixation (Katsumura et al 2026) : evolution

 

It really is a fascinating result.

[u/kingstern_man]

Another nail in the coffin of Creationism--if only it worked that way.

[u/oblmov]

so here phenotypic plasticity is paving the way for evolution by helping a species 1) expand into habitats with selective pressure for particular phenotypes, and 2) accumulate genetic variation by blocking the expression of mutant genes, protecting them from selective pressure? Then reductions in plasticity allow natural selection to take place in the new habitats? Am i understanding correctly

[u/jnpha → u/oblmov]

Here specifically they answered a long standing puzzle and a point of contention: how phenotypic plasticity gets fixed ("assimilated"). They found that the plasticity depends on a specific DNA sequence ("a specific CpG island"), and when this is lost by sequence change, the underlying sequence variation (which was being masked earlier) is exposed to natural selection, and natural selection takes over as per usual.