Epigenetic inheritance in evolution

Abstract

We discuss the role of cell memory in heredity and evolution. We describe the properties of the epigenetic inheritance systems (EISs) that underlie cell memory and enable environmentally and developmentally induced cell phenotypes to be transmitted in cell lineages, and argue that transgenerational epigenetic inheritance is an important and neglected part of heredity. By looking at the part EISs have played in the evolution of multicellularity, ontogeny, chromosome organization, and the origin of some post-mating isolating mechanisms, we show how considering the role of epigenetic inheritance can sometimes shed light on major evolutionary processes.Most biologists, including ourselves, accept that the theory of evolution developed by Darwin is basically correct: adaptive changes occur through the selection of heritable differences between individuals. What is not generally accepted is Darwin's idea that some of the heritable differences on which selection acts are generated by environmental changes. After all, geneticists have shown how ample new variation can be provided by rare mutations and the shuffling of genes during sexual processes. The ultimate source of variation is the random changes in the sequences of DNA bases that constitute the genes. Since, according to orthodox views, genes pass from generation to generation unaffected by external factors, there is little room in modern evolutionary theory for the idea that the environment can induce heritable changes. Such 'Lamarckian' beliefs are wrong, it is argued, because we know that 'acquired characters' are not inherited. The role of the environment is in the selection, not the generation, of heritable variation. 159

Emotion: The self-regulatory sense

“…410 He also endorsed Alexander Bain's "fundamental law of pleasure and pain," which states that pleasure is connected with an increase and pain a decrease in vital power (the tit-fortat self-regulatory code), a law founded upon "the principle of self-conservation, the self-regulating, selfacting impulse of the animal system" 411 (emphasis mine). Had Darwin been privy to modern understandings of the chemical networks, computational, and regulatory dynamics involved in genetics, epigenetic inheritance, 42,186 social genomics, 193 and neuroplasticity, 412 it seems likely he would have noted the importance of here-and-now environmental interactions and behavioral responses, and perhaps more pointedly given emotion its functional due. Still, despite his laudable parsimony, Darwin concluded that "the 'language of emotion' is certainly of importance for the welfare of mankind."…”

“…Upon the mapping of the genome, however, the subsequent revelations about epigenetic control processes have forever altered the central dogma by elucidating the crucial role of environmental cues, intrinsic signals, and cellular memory in evolution. [186][187][188] Revelations of how supposedly "junk DNA" and noncoding RNA are actually providing ongoing regulatory switching 189,190 ; with relational ifthen rules of engagement that ensure specific gene products are brought into action when and only when appropriate, 191 and mediating the very developmental morphology of an organism 192 as well as its behavior. Revelations of how epigenetic switching yields critical modifications during cellular stress responses, 100,[193][194][195][196] plays a key role in immune functioning, 197 and serves as modulators of neuronal responses, 198 of neural development and neuroplasticity.…”

The Topology of Evolutionary Biology

“…The phenotype, on the other hand, is therefore not modified directly, but indirectly through the modification of the genome from which it arises (We simplify here by disregarding e.g. epigenetic inheritance [46]). The accessibility relation at phenotypic level therefore has to be understood as a consequence of the interplay of genotypic accessibility and the GP-map.…”

Genesis of phenotypic and genotypic diversity in land plants: The present as the key to the past

“…A good example is the presence or absence of wings in genetically identical ants according to caste, which simply reflects differential environmental cues (polyphenism: Abouheif & Wray, 2002). Thus, evo-devo studies need to consider not only functional linkages with other genes but also epigenetic constraints on expression (see papers in Jablonka & Lamb, 1995) and environmental cues, potentially spawning yet another discipline that has playfully been titled 'eco-devo'.…”