Epigenetics: a heuristic model…
September 26, 2013 | James Kohl
A heuristic model
Heuristic: refers to experience-based techniques for problem solving, learning, and discovery that give a solution which is not guaranteed to be optimal. Examples of this method include using a rule of thumb, an educated guess, an intuitive judgment, stereotyping, or common sense. What we have below might could therefore be described as a common sense model of nutrient-dependent pheromone-controlled adaptive evolution.
A heuristic model on the role of plasticity in adaptive evolution: plasticity increases adaptation, population viability and genetic variation [see abstract below; subscription required]
Article excerpt: “…incorporating plasticity is conceptually as simple as acknowledging the fact that genotypes may have the potential to use environmental information to express better fit phenotypes. Other central tenets of mainstream evolutionary thought (i.e. random mutation and selection of phenotypes according to environmental conditions) evidently remain unchanged. The simple addition of environmentally sensitive adaptive gene regulation, however, provides a demonstrated mechanism for swift adaptation to rapidly changing environments that may have often lead to lineage diversification and evolutionary innovations.”
My comment: We have consistently seen the failure to acknowledge that genetic predispositions clearly enable epigenetic effects of olfactory/pheromonal input, which results in “better fit phenotypes” sans mutations. This means other central tenets of mainstream evolutonary thought must change. Indeed, the central tenets must change because there is no experimental evidence that suggests random mutation and selection of phenotypes is possible.
Instead, there is only evidence that mutations are not fixed in the DNA of the organized genomes of any species that has adaptively evolved. That evidence can be compared to across-species examples that show the de novo creation of olfactory receptor genes enables the fixation of new alleles, which is nutrient-dependent and pheromone-controlled in species from microbes to man. See, for example: Nutrient-dependent/pheromone-controlled adaptive evolution: a model; Human pheromones and food odors: epigenetic influences on the socioaffective nature of evolved behaviors,
Abstract: An ongoing new synthesis in evolutionary theory is expanding our view of the sources of heritable variation beyond point mutations of fixed phenotypic effects to include environmentally sensitive changes in gene regulation. This expansion of the paradigm is necessary given ample evidence for a heritable ability to alter gene expression in response to environmental cues. In consequence, single genotypes are often capable of adaptively expressing different phenotypes in different environments, i.e. are adaptively plastic. We present an individual-based heuristic model to compare the adaptive dynamics of populations composed of plastic or non-plastic genotypes under a wide range of scenarios where we modify environmental variation, mutation rate and costs of plasticity. The model shows that adaptive plasticity contributes to the maintenance of genetic variation within populations, reduces bottlenecks when facing rapid environmental changes and confers an overall faster rate of adaptation. In fluctuating environments, plasticity is favoured by selection and maintained in the population. However, if the environment stabilizes and costs of plasticity are high, plasticity is reduced by selection, leading to genetic assimilation, which could result in species diversification. More broadly, our model shows that adaptive plasticity is a common consequence of selection under environmental heterogeneity, and hence a potentially common phenomenon in nature. Thus, taking adaptive plasticity into account substantially extends our view of adaptive evolution. — Source: The Royal Society