Pheromones, epigenetics, and our sense of smell
March 7, 2013 | James Kohl
In discussion of Darwinian Natural Selection, I was asked: “…do you now agree that ‘genes of large effect’ are not currently useful concepts for contradicting Darwinism?”
Note: “Such genes were written out of the mid-20th-century Darwinian synthesis based on statistical arguments of R.A. Fisher, which were contrived to make natural selection compatible with a gradualist version of Mendel’s genetics.”
My response: ‘Genes of large effect’ clearly contradict Darwinian Natural Selection. In my model, nutrients epigenetically “tweak” the “genes of large effect.” This nutrient-dependent epigenetic tweaking effects immense gene networks. The nutrients metabolize to species-specific pheromones, which signal nutrient-dependent reproductive fitness.
The metabolism of the nutrients to species-specific pheromones controls the epigenetic effects of the nutrients on the immense gene networks. The control of species survival by pheromones extends from microbial natural selection of nutrients that metabolize to pheromones to adaptively evolved nutrient-dependent pheromone-controlled sexual selection. Organisms that sexually reproduce select for sex differences in pheromones that signal nutrient-dependent reproductive fitness.
Pheromones signal nutrient-dependent reproductive fitness, which is how the metabolism of nutrients to pheromones controls reproduction in species from microbes to man. Compared to statistical representations of Darwinian Natural Selection that have no explanatory power in the context of how selection occurs, or what is selected, we can now answer this question: Do we owe our sense of smell to epigenetics?
Excerpt: “Olfactory sensory neurons – nerve cells in the nose – directly sense molecules that convey scent, then send the signals to the brain.”
It is now clear that natural selection for odors associated with nutrients in an epigenetic landscape of competition among individuals depends on de novo creation of a odor receptor. Odor receptors allow nutrients to enter the cell. When a nutrient enters the cell it alters the thermodynamic control of the molecular mechanisms that enable or prevent its metabolism. The result is an alteration of the microRNA / messenger RNA balance When a nutrient is successfully metabolized, messenger RNA degradation helps to stabilize the microRNA / messenger RNA balance.
The degradation of messenger RNA results in a nutrient-derived chemical signal that is incorporated into the blend of pheromones the cell uses to signal other cells. The pheromones indicate that genetically similar cells may also create de novo olfactory receptors for odors associated with nutrients that enable them to increase their fitness via nutrient uptake. This enables the molecular mechanisms common to all species to control nutrient-dependent reproductive fitness.
See also: Smell of Genes Packed Away Science 7 December 2012 (3 months ago)
“Forced expression of the lamin b receptor reversed the morphological sequestration of the olfactory receptor genes and also decreased the expression of the chosen active allele, probably because the thousands of transcription factor binding sites of the normally sequestered olfactory receptor genes were now competing for binding of activating factors.”
My comment: Forced expression of a receptor can now be compared to the genetically predisposed ability of nutrients to induce de novo receptor expression in the cell wall. Metabolism of the nutrients to pheromones controls natural selection for nutrients. No evidence suggests that the molecular mechanisms for nutrient-dependent pheromone-controlled reproduction vary across species. The lack of evidence strongly suggests conservation of nutrient-dependent pheromone-controlled adaptive evolution via reproduction in species from microbes to man. YES, is the answer to the question Do we owe our sense of smell to epigenetics?
That answer is clear in Human pheromones and food odors: epigenetic influences on the socioaffective nature of evolved behaviors. I concluded: “Olfaction and odor receptors provide a clear evolutionary trail that can be followed from unicellular organisms to insects to humans.” We now know how our sense of smell allows odors to epigenetically effects hormones that affect our behavior. There is also evidence for similar molecular mechanisms in plants, which suggests that plants and animals use microRNA-directed DNA methylation and heterochromatin formation for maintenance of the germ line epigenome and transgenerational epigenetic inheritance via Piwi-interacting RNAs.
Evidence that plants and animals use the same molecular mechanisms suggests to me it is time to abandon the Darwinian synthesis based on statistical arguments. Enough is known about molecular epigenetics to link natural selection to biological facts.