XII.7.4 Organisms whose individual development is based on epigenetic processes have greater evolutionary potential than organisms whose constitution is purely genetically-determined
Organisms with “hard”, i.e. only genetic programming, of their body structure would apparently have much worse potential for further evolutionary development than organisms in whose ontogenesis epigenetic processes play a more important role (Kirschner & Gerhart 1998).It is hard to imagine the evolution (anagenesis) of an organism that would have special genes for the lengths of nerves, veins, muscles and bones in a certain limb.The limbs of such an organism could change in evolution only if all the participating genes were to mutate simultaneously in a suitable manner.In real organisms, the lengths of the nerves, veins, muscles and bones of the limbs are determined epigenetically so that, when a mutation occurs changing the parameters of any of these components, the other components adapt to this and, during ontogenesis, a functional, although somewhat altered, limb is formed.Participation of epigenetic processes in the regulation of ontogenesis ensures that, even if a random mutation somehow affects the progress of the ontogenetic processes, ontogenesis as a whole will most probably once again lead to the formation of a functional and viable organism.Experience gained in study of developmental malformations, such as two-headed calves, drosophila with legs instead of antennae or with eyes formed on the surface of various organs, six-legged frogs, frogs with eyes inside their mouths instead of on top of their heads, etc., shows that these are not unfounded theoretical considerations(Rollo 1994). Whether the malformations occur as a consequence of genetic mutations or as a result of a nongenetic defect during ontogenesis, at least partly functional organism is usually formed.If there were sufficiently effective reproductive isolation, it would apparently be only a question of suitable selection pressures for the functioning of these monsters to be evolutionarily “tuned” so that they could compete with the original form of the organism in utilizing a suitable niche.