A mathematical model of phenotypic cause, effects on genes, and affects on behavior

Phenotypic and Evolutionary Consequences of Social Behaviours: Interactions among Individuals Affect Direct Genetic Effects

Published November 30, 2012

Open Access (Abstract excerpts):

1. “When expression of genes in social partners affects trait expression in a focal individual, indirect genetic effects occur.”

2. “We show that social interactions may not only cause indirect genetic effects but can also modify direct genetic effects.”

3. “Our model reveals that both direct and indirect genetic effects can depend to a large extent on both group size and interaction strength, altering group mean phenotype and variance.”

4. ” Our analysis highlights key properties of indirect genetic effects with important consequences for trait evolution, the level of selection and potentially speciation.”

My comment:

1. The authors acknowledge that social selection occurs when a phenotypic trait of one or more conspecifics affects the fitness of others.  In their mathematical model it becomes obvious that social interactions depend on the number of interacting individuals in a non-linear way.

2. The authors acknowledge that behavior in primitive organisms, such as bacteria and amoeba, also is affected by genes expressed in other individuals.

3. The author’s do not acknowledge that the metabolism of nutrient chemicals to species-specific pheromones is responsible for the affects of fitness on conspecifics in all species.

There is no need for them to incorporate biologically based cause and effect into their mathematical model of how individual interactions effect genes and affect behavior in other individuals. In microbes, however, the affect on behavior occurs in the context of quorum-sensing, which exemplifies the nutrient chemical-dependent pheromone-controlled reproductive fitness of microbes and every other species across an evolutionary continuum of adaptively evolved behavior. In all species, what organisms eat is metabolized to pheromones that modulate social selection for reproductive fitness of individuals and of groups.

This epigenetic effect of nutrient chemicals and pheromones  is exemplified in the honeybee model organism.  The diet of the queen determines her pheromone production, which affects the behavior of every other colony member. This epigenetic effect was recently also exemplified in a mouse model.  Genetically predisposed, diet-dependent, and sex-dependent production of an odor causes  species-specific behaviors.

Equations are not used in my model for epigenetic effects of nutrient chemical-dependent hormone-organized and hormone-activated invertebrate and vertebrate behavior. I simply extended what is known about the behavioral affects of nutrient chemical-dependent pheromone-controlled reproduction in microbes to every other species. That is what is required for adaptive evolution to occur in species from microbes to man.

Clearly, the only thing wrong with mathematical models of cause and effect is that they attribute indirect genetic effects, direct genetic effects, and affects on behavior to something unknown at a time when olfaction and odor receptors provide a clear evolutionary trail that can be followed from unicellular organisms to insects to humans.  Simply put, the common molecular mechanisms of cause and effect are known to involve nutrient chemical-dependent pheromone production that affects behavior in all species whether or not you can do the math (or understand it).




Author: James Kohl

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