Breakage may be advantageous. An individual with an intramaxillary joint suddenly appeared and was favored. Early stage in the evolution of the eye. Small changes in developmental process can have major effects on phenotype. Ontogeny may recapitulate phylogeny.
Descendant has more fully developed features than ancestor.
Goldschmidt's 'hopeful monsters' , ie major evolutionary changes occurring through macromutation or systemic mutation. Very unusual phenotype highly unlikely to be more fit. Homeotic mutations . Typically transpose part of the body from one region to another. The fruit flies have gained and lost pairs of wings.