Understanding evolution, adaptation, and phenotype
The differential transmission of genes depends on the availability of nutrients. The metabolism of nutrients to species-specific pheromones enables natural selection.
nutrients
Pre-existing genetic variability or random mutations: a matter of priorities and choices
This fact can be explained to a general audience by saying that food odors cause us to eat what causes us to produce pheromones that cause us to associate, or not associate, with other people. In this context, pheromones are social odors.