Editorial NexoScience
Could something your great-grandmother lived through actually be shaping your health today, without a single mutation in your DNA? That question sits behind a growing body of research on epigenetic inheritance, the idea that experiences imprinted on the environment, not just the genetic code itself, can be passed down from parents to children and even grandchildren.
The theory of evolution as most people learned it in school leaves epigenetics out almost entirely. Charles Darwin’s model of natural selection and the “modern synthesis” that formalized it in the mid-1900s were built before anyone understood DNA methylation, histone modification or non-coding RNA, the molecular switches that turn genes on and off without altering the sequence underneath. A new review published in the journal Epigenetics argues that leaving those mechanisms out of the evolutionary model is no longer defensible, given how much evidence has piled up showing environmental exposures reshaping traits across generations.
A famine from eighty years ago still shows up in blood tests today. One of the clearest human examples comes from the Dutch Hunger Winter of 1944 and 1945, when a German blockade cut off food supplies to the Netherlands and left much of the population surviving on daily rations of under 800 calories. Researchers who later studied the children of women who were pregnant during the famine found higher rates of glucose intolerance, obesity and coronary heart disease decades afterward. The timing mattered as much as the exposure itself: women who were in early pregnancy during the famine had daughters with a higher risk of breast cancer, while those exposed in mid pregnancy had children with more kidney damage and airway disease.
Chemical exposure can echo for generations after it ends. Animal studies make the pattern easier to isolate from confounding factors. When pregnant rats were exposed to the agricultural fungicide vinclozolin, their direct offspring showed relatively few problems, but by the third generation, descendants who were never directly exposed to the chemical had significantly reduced sperm counts linked to inherited DNA methylation changes. A similar delayed pattern showed up with DDT, once sprayed worldwide to fight malaria: effects on body fat and metabolism did not appear in the first generation, only surfacing once researchers tracked lineages three generations removed from the original exposure.
Wild animals show the same pattern without any lab intervention. Darwin’s finches in the Galápagos, the same birds that helped inspire the theory of natural selection, offer an unexpected twist on their own legacy. Comparing finches from rural and urban parts of the islands, researchers found almost no genetic differences between the two populations, yet significant epigenetic variation and distinct physical traits. House sparrows showed the same disconnect, with more epigenetic variation than genetic variation across individuals. In both cases, the environment appears to be reshaping how genes are expressed well before, or even instead of, the DNA sequence itself changing.
None of this replaces DNA, and the review is careful to say so. The correlation between environmental exposure and inherited traits does not mean genetics stops mattering, and most of the human evidence, including the Dutch famine data, comes from natural experiments rather than controlled trials, which makes it harder to fully separate epigenetic inheritance from other factors like shared environment or culture across generations. The strongest causal evidence for transgenerational effects still comes from controlled animal studies, where researchers can rule out confounders that are impossible to control for in people.
What the review argues, ultimately, is not that Darwin was wrong, but that the textbook picture of evolution is incomplete. Adding epigenetic inheritance to the model does not overturn natural selection, it adds a second, faster channel through which environments can shape which traits get passed on, running in parallel with the slower churn of genetic mutation.
Source: Korolenko A, Skinner MK. “Generational stability of epigenetic transgenerational inheritance facilitates adaptation and evolution.” Epigenetics, 2024. DOI: 10.1080/15592294.2024.2380929.
