Frozen Evolution. Or, that’s not the way it is, Mr. Darwin. A Farewell to Selfish Gene.

In the broad sense, any deterministic, i.e. repeated under the same conditions, affecting of the phenotype by the local conditions of the environment, can be considered to be phenotype plasticity.  However, it is more correct to consider this phenomenon to be a manifestation of the low ability of the developmental canalization of the given organism, i.e. its inability to balance (buffer) the effects of random external and internal factors on the process of ontogenesis (see XII.7.2). In the narrow sense, phenotype plasticity is considered to constitute affecting of phenotype characteristics by the environment that is useful from the standpoint of the individual in the given environment. The ability to usefully adapt to the conditions of the environment is an adaptive characteristic that, like any other adaptive trait of living systems, was formed in the given species by natural selection during evolution.

Where the local conditions are relatively constant and where the offspring of the given individual will most probably be exposed to them, it is advantageous if the particular phenotype adaptation is inherited directly from the parents. The mechanisms of epigenetic inheritance are very frequently active when these traits are passed on. These mechanisms are far more plastic than that genetic inheritance and not only permit evolutionary programming of the formation of the relevant modification as a consequence of the action of a certain external stimulus, but simultaneously also allow for the disappearance of the particular modification if the particular external stimulus does not act for a longer time, for example, for several generations. The greatest numbers of examples of epigenetically inherited phenotype modifications are known for plants. For example, the morphology of individual flax plants differs very substantially according to the amount of nutrients in the soil, where the particular trait, gained during a single generation, is passed on through the seeds to the next generation (Cullis 1984). However, examples of similar phenotype modifications, which can be inherited even after a number of generations, are also encountered in some animals, especially those that reproduce asexually (Agrawal, Laforsch, & Tollrian 1999). Methylation and suppression of the cycloidea gene in the flax Linaria vulgaris, which demonstrably occurred at least 250 years ago and has been maintained by artificial selection to the present day, is probably the longest transferred (known) epigenetic modification (Cubas, Vincent, & Coen 1999). It is quite possible that many other known mutations actually correspond to epimutation – epigenetic changes inherited for a long time (see Dennis 2003).