Why no individual is like another when epigenetics come into play

Epigenetic modifications—chemical changes to DNA that do not alter its sequence—regulate gene expression and contribute to individual behavioural differences among animals. These modifications can result from both environmental influences and intrinsic factors, creating a dynamic interplay where behaviour and environment reciprocally shape the epigenome. This process enhances individual ecological niches and maintains diversity within populations, influencing adaptation and evolution.

Why do animals behave differently, and what are the consequences of this? A research team now provides a new explanation: epigenetic processes—chemical markings on DNA—may play a key role. The study, published in the journal Trends in Ecology & Evolution, links individuality, environmental adaptation, genetics, ecology, and evolution in a novel way.
The researchers propose that individuality and epigenetic variation influence each other. This bidirectionality—this mutual interaction—helps us to better understand ecological and evolutionary processes, they say.
At the center of the study is epigenetics. This refers to chemical modifications of DNA in which small molecules attach to the genetic material. These modifications do not alter the genetic sequence itself, but they regulate how frequently a gene is translated into proteins. Proteins, in turn, shape the observable traits and characteristics of an organism.

Thus, the same genetic blueprint—the same genotype—can give rise to different appearances, known as phenotypes. The researchers propose that epigenetic mechanisms contribute to how animals develop their individual ecological niche.

An individual niche is the range of environmental conditions under which a specific individual with a given set of traits could possibly live and reproduce. It is a subset of the species' niche that arises from the interaction of the individual with its environment.
The researchers distinguish between epigenetic changes triggered by environmental factors and those that arise independently, such as genetically determined or spontaneously occurring modifications. All forms play different roles in shaping individual differences.

What is particularly noteworthy is the idea that it is not only epigenetic processes that influence an individual's behaviour and, consequently, their environment, but that, conversely, the environment altered by individual decisions can also give rise to new epigenetic patterns.

For example, individuals may seek out a new living environment or alter their surroundings by building a nest, which in turn affects the epigenome—the totality of all epigenetic marks. Even without direct inheritance via the germline, the epigenome can thus be altered in offspring.

This has far-reaching consequences: such processes could buffer natural selection and thereby generate and maintain epigenetic diversity within populations.
For understanding ecological and evolutionary processes, this represents a shift in perspective. Rather than examining genetic or phenotypic differences in isolation, researchers should analyze genetic, epigenetic and observable traits of the same individuals together.

This concept helps explain how environmental change is linked to individualization. In times of climate change and biodiversity loss, it provides an important foundation for better assessing the adaptive capacity and resilience of natural populations.

Denis Meuthen et al, Exploring the interplay of epigenetics and individualization, Trends in Ecology & Evolution (2026). DOI: 10.1016/j.tree.2025.12.010