Epigenetics
As life evolves, the adaptive tricks of the past are stored genetically. This toolkit provides the means for variations and new combinations.
Tiny tweaks can work wonders. A single gene regulates the complex wing patterns, structures, and colors for mimicry in butterflies. Epigenetic controls are applied to achieve the desired result.
A great number of traits are managed by expression of gene complexes which are often regulated by environmental conditions, and even by state of mind.
Animal development is rife with thresholds. The expression of complex morphological and behavioral phenotypes may be sensitive to many environmental or circumstantial stimuli at multiple periods during development. ~ American biologist Mark Rowland & Douglas Emlen
The caste that eusocial ants and bees have for life are epigenetically determined from the same set of genes, based upon their diet early on. The size and shape of dung beetle horns are sensitive to nutritional history.
The vast array of coloration that animals display varies via regulation of a sparse set of genes. In some species, colors, and other visible features signal social status.
Lusty Birds
The tiny red-backed fairy-wren, averaging 8 grams, is endemic to the rivers and coastal areas of Australia. Sexual dimorphism comes with coloration. Females and juveniles are a drab brown.
Males are either drab or wear a fiery red collar, depending on how hot their sex life is. Hormones regulate which path a male fairy-wren is on, based upon social interactions prior to the breeding season.
A male feeling empowered by success in flirting develops into a bright guy, flush with testosterone. Conversely, those who get negative social feedback – receiving scant interest from females or picked upon by other males – dulls a bird as testosterone drops. While the drab males do breed, the reds sire more offspring that year.
The plumage change is not permanent. In a year or 2, a fairy-wren male may be better placed to put on a bright red collar and go further in fathering.
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Such status badges as fairy-wrens wear are found in numerous social animals, most prolifically birds. Relative success in sociality regulates hormones which reversibly alter genetic expression.
Male house sparrows have black bibs which distinguish dominant birds from subordinates by size. Harris’ sparrows with the blackest head feathers are the top birds.
Male African red-shouldered widowbirds wear epaulets. Territory holders have larger and redder shoulder patches than those that float between territories.
Whether a male orangutan is flanged or not is a simple hormonal change, activated by the ape’s recognition of social circumstance.
The above examples illustrate how easily, and dynamically, phenotypic changes can be accomplished in animals via psychology.
