Assimiliating an Associative Trait: from Eco-Physiology to Epigenetics

The possible evolutionary significance of epigenetic memory and codes is a key problem for extended evolutionary synthesis and biosemiotics. In this paper, some less known original works are reviewed which highlight theoretical parallels between current evolutionary epigenetics, on the one hand, and its predecessors in the eco-physiology of higher nervous activity, on the other. Recently, these areas have begun to converge, with first evidence now indicating the possibility of transgenerational epigenetic inheritance of conditional associations in the mammalian nervous system, and related findings in other taxa. This can serve as an interesting example of evolutionary code-making, where the molecular mechanisms underlying arbitrary associations between stimuli involve lasting changes in gene expression that may be transmitted epigenetically across generations, and which in some cases could be further assimilated into the genome over subsequent evolution. Although preliminary, such epigenetic scenarios would also offer an interesting, if so far overlooked parallel to earlier research carried out by one of I.P. Pavlov’s leading students, acad. P.K. Anokhin, and his colleagues, but also by eminent eco-physiologists of the time, several of whom offered arguments for the possibility of unconditional reflexes representing evolutionarily later, specialized, and reduced forms of associative reflexes, from which they may be derived. Although discarded under the growing dominance of modern synthesis, these early epigenetic investigations may deserve renewed attention in the modern context, and if further confirmed, could open essentially new perspectives on the morphofunctional evolution of the nervous system.