New alleles: The BIG BUT vs nutrient-dependent pheromone-controlled fixation
September 13, 2013 | James Kohl
In a typical discussion of the recent work: Rates of Phenotypic and Genomic Evolution during the Cambrian Explosion, I wrote for the benefit of my antagonists:
“Any allele that is not fixed is more likely to represent potential for change, not something related to mutation-driven evolution…. A model organism does show, however, that “Feeding plasticity in the nematode Pristionchus pacificus is influenced by sex and social context and is linked to developmental speed.” Within the next hour I added a link, a quote, and a comment on another report:
Quote: “In conclusion, classical theory in population genetics is confirmed, but natural selection might not be of invariable magnitude and sign. Our findings thus set the stage for the development of more general theoretical models explaining the fate of new alleles across long evolutionary timescales.
Comment: My model is not theoretical, it integrates biological facts across species from microbes to man. Species incompatibilities in nematodes are associated with cysteine-to-alanine substitutions (Wilson et al., 2011), which may alter nutrient-dependent pheromone production and fixation.
Addendum: I was alerted to the latest report about genetic variants and the BIG BUT about their natural selection, by mention of it here: Fate of New Genes Cannot Be Predicted. The problem with prediction is that alleles initially are not fixed. And there is no way to predict which alleles are nutrient-dependent and pheromone-controlled until after they are fixed. After new alleles are fixed, it becomes clear that their benefit to species survival was directly linked from nutrient uptake to the metabolism of novel nutrients to pheromones that control reproduction , which is how pheromones control fixation of “bottom-up” nutrient-dependent ” alleles from the top down.
However, fixation obviously must incorporate the degree of plasticity that enables adaptations to changes in the availability of nutrients, or changes in the amount of nutrients required to maintain behavioral development across life cycles in different organisms. This is where the examples from model organisms become essential to establishing a model that can be compared to misrepresentations of mutation-driven evolution, which have never explained mutation fixation or anything else about fixation and are still unable to do so. The BIG BUT of theory is “…natural selection might not be of invariable magnitude and sign.”
That’s one reason why I included examples of fixation directly linked to ecological niche construction, and to social niche construction, and to neurogenic niche construction, and to socio-cognitive niche construction in my model. Variable alleles obviously become fixed. However, in the latest article, which does not explain fixation in nematodes, we have clear insight into why fixation cannot be explained in any species except via a model of nutrient-dependent pheromone-controlled adaptive evolution.
For example, I wrote: Clearly, however, the epigenetic effects of food odors and pheromones are involved in neurogenic niche construction as exemplified in nematodes (Bumbarger, Riebesell, Rödelsperger, & Sommer, 2013), and in flies (Swarup et al., 2013). I added this example, later: Differences in the behavior of nematodes are determined by nutrient-dependent rewiring of their primitive nervous system (Bumbarger et al., 2013). Species incompatibilities in nematodes are associated with cysteine-to-alanine substitutions (Wilson et al., 2011), which may alter nutrient-dependent pheromone production.
But all the examples from the different animal species I used attest to the role of nutrient-dependent pheromone-controlled adaptive evolution. Thus, we now have the BIG BUT of evolutionary theory that can be examined in the context of a model of biologically based cause and effect. It may be that evolutionary theorists will continue to attempt to deal with the problem of their BIG BUT: natural selection for something of “invariable magnitude and sign”, but natural selection is clearly not a problem for biologists who understand the concept of nutrient-dependent pheromone-controlled adaptive evolution, which is the only type of evolution that occurs. Picture evolutionary theorists who continue to look for the “needle in the haystack,” which is something of “invariable magnitude and sign.” Meanwhile, biologists must know that natural selection is for nutrients (e.g., the food that sustains life). And there are no BUTs about that.