… it is the molecular biology common to all species that assures us olfaction and odor receptors provide a clear evolutionary trail, which can be followed from unicellular organisms to insects to humans.
I’m not sure where researchers first strayed from the gene, cell, tissue, organ, organ-system pathway, but I am happy to see evidence that research may get back on the path that directly links sensory input to brain function and behavior.
The gene-cell-tissue-organ-organ system pathway is required to link sensory input from the social environment to behavior. Pheromones, but not what we see, directly activate this pathway.
Olfactory primacy is central to my model for the development of sexual preferences across species (e.g, including birds).