Theoretically, purifying selection is evolution

Excerpt: “The study focuses exclusively on the type of evolution known as purifying selection…”
Excerpt: “Using a computational model…”
Theorists are forced to think about evolution in the context of mathematical models.
Darwin’s theory put his “conditions of life” first. What should that tell biologically uninformed science idiots about the pseudoscientific nonsense integrated into computational models?
[W]hat Haldane, Fisher, Sewell Wright, Hardy, Weinberg et al. did was invent…. Evolution was defined as “changes in gene frequencies in natural populations.” The accumulation of genetic mutations was touted to be enough to change one species to another…. Assumptions, made but not verified, were taught as fact. http://www.huffingtonpost.com/suzan-mazur/replace-the-modern-sythes_b_5284211.html
Plotkin and others are still trying to tell others that their assumptions about mutations make sense — if only in the context of purifying selection.

Addendum:

If purifying selection is all that’s required to show serious scientists that evolution is unpredictable and irreversible, those who claim to be serious scientists are biologically uninformed.
See also: Research highlights the importance of a balanced diet for mental health
A single nutrient-dependent amino acid substitution has been linked to life history transitions in behavior. See: Oppositional COMT Val158Met effects on resting state functional connectivity in adolescents and adults
That fact links the nutrient-dependent pheromone-controlled ecological adaptations exemplified in the honeybee model organism of RNA-mediated cell type differentiation to nutrient-dependent cell type differentiation in all genera via the physiology of reproduction, which enables fixation of the amino acid substitutions.