Kara C. Hoover: Smell with inspiration: The evolutionary significance of olfaction

Excerpt from 2010:

Human pheromones, a controversial subject, seem to be a natural phenomenon, with a small number identified in clinical studies.

Researchers show how our sense of smell evolved, including in cave men


People with different DNA sequences in the gene producing the OR7D4 receptor respond differently to this smell…. People’s responses to androstenone can be predicted by their OR7D4 DNA sequence, and vice versa.

Journal article excerpt:

The underlying adaptive context of possible selective pressures acting on olfactory receptor genes is not known but may be linked to food… and health….

My comment: DNA sequences do not evolve. The epigenetic landscape is linked to the physical landscape of DNA via nutrient-dependent RNA-directed DNA methylation and RNA-mediated amino acid substitutions. The substitutions are fixed in organized genomes via the physiology of nutrient-dependent reproduction in all genera. No experimental evidence of biologically-based cause and effect suggests there is any way to link mutations, which perturb protein folding, to the evolution of increasingly complex biodiversity.

Anyone who looks at the comments linked to the articles below will see that no amount of experimental evidence that links the physics and the chemistry of nutrient-dependent RNA-mediated amino acid substitutions to protein folding will convince theorists that mutation-driven evolution cannot occur in the context of what is known to serious scientists. Thus, Hoover et al., (2015) have restated the obvious in the context of mutations and evolution: “The underlying adaptive context of possible selective pressures acting on olfactory receptor genes is not known…”

Theorists who attribute evolution to mutations ignore the obvious link from ecological variation to ecological adaptations via olfaction and pheromones. That means they must also ignore all evidence that links food odor and pheromones to receptor-mediated changes in the morphological phenotypes and behavioral phenotypes of species from microbes to man via their RNA-mediated metabolic networks and genetic networks.

Thus, the high frequency of variants that impair receptor function, high fixation values for deleterious alleles, and selection test results all suggest the interpretation of the Ka/Ks ratio as maintenance of the ancestral state via purifying selection is not likely.

My comment: Fixation of the deleterious alleles eliminates the associated olfactory receptor genes in the context of selection for the de novo creation of nutrient-dependent olfactory receptor genes, which are fixed in organized genomes via links from nutrient uptake to the physiology of reproduction.

Conclusion: (excerpt)

Olfaction is a primary sense involved in the detection of environmental and conspecific cues…. Mutations often accumulate on redundant genes, including olfactory receptor genes, rendering them nonfunctional over time. This pattern is evident in humans but we also see new functional variants emerge (Mainland et al. 2014). An example… exhibits geographically patterned variation linked to adaptation.

They try to place their study results into the context of how our olfactory genome evolved, but acknowledge the fact that “a range of anthropological, genetic, and neurobiological skills will be necessary…”

My comments on the following articles attest to that fact.

Brain folding related to surface area and thickness, not number of neurons

My comment: From a purely physical perspective they link the probable mechanisms involved “…that control the rate of neurogenesis and increases in cell size relative to the rate of progenitor and intermediate progenitor cell proliferation in early cortical development.”

From any perspective that involves the biophysically constrained nutrient-dependent RNA-mediated cell type differentiation of all genera via their physiology of reproduction, they inadvertently link the nutrient-energy dependent fixation of amino acid substitutions to cortical development in different mammals via their nutrient-dependent pheromone-controlled physiology of reproduction.

These researchers appear to be like the serious scientists who reported that “Feedback loops link odor and pheromone signaling with reproduction

They do not appear to be like evolutionary theorists who do not understand biologically-based cause and effect.

Heaven scent: Finding may help restore fragrance to roses

Excerpt: This gene, which produces an enzyme, revealed the odor-producing process.

My comment: This exemplifies how quickly traits are removed that are linked from nutrient-uptake to metabolic networks and genetic networks via RNA-mediated amino acid substitutions and scent production in plants.

‘Map of life’ predicts ET. (So where is he?)


The book claims that evolution is therefore far from random, but a predictable process that operates according to a fairly rigid set of rules.

My comment: No one seems willing to place the difference in the bacteria that re-evolved their flagella in 4 days and the difference in the roses (3 generations) into the context of mutations and evolution.

The book by Simon Conway-Morris about a predictable process and rigid set of rules can be compare to the conclusion in the 2013 book by Masatoshi Nei: Mutation-Driven Evolution


…genomic conservation and constraint-breaking mutation is the ultimate source of all biological innovations and the enormous amount of biodiversity in this world.

My comment: Nei’s claims have been the subject of a month-long discussion at Evolution is unpredictable and irreversible, biologists show.

The claims by Conway-Morris have been exemplified in the context of nutrient-dependent RNA-mediated amino acid substitutions that determine the cell types of all genera via fixation of the substitutions in the context of their physiology of reproduction. The rules that Conway-Morris may be referring to may be strict, but they also seem to predict that likelihood that ecological variation in the food supply leads to ecological adaptations via the physiology of nutrient-dependent reproduction in all genera.  The rules probably fit Darwin’s claims about the need to place “conditions of life” before natural selection. If the rules are that all organisms must eat and reproduce for biodiversity to arise, the rules also make more sense than claims about contraint-breaking mutations, since mutations perturb protein folding. RNA-mediated amino acid substitutions, for comparison, stabilize the organized genomes of all genera.

See also:

Discovery of nanotubes offers new clues about cell-to-cell communication

Single-celled predator evolves tiny, human-like ‘eye’

Sniff tests used to create olfactory fingerprint

Can autism be measured in a sniff?  

Epigenetic Mechanism Tunes Brain Cells

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