Allen MacNeill has posted his long promised overview of evolutionary mechanisms of variation in RM & NS: The Creationist and ID Strawman
Creationists and supporters of Intelligent Design Theory (“IDers”) are fond of erecting a strawman in place of evolutionary theory, one that they can then dismantle and point to as “proof” that their “theories” are superior. Perhaps the most egregious such strawman is encapsulated in the phrase “RM & NS”. Short for “random mutation and natural selection”, RM & NS is held up by creationists and IDers as the core of evolutionary biology, and are then attacked as insufficient to explain the diversity of life and (in the case of some IDers) its origin and evolution as well.
Evolutionary biologists know that this is a classical “strawman” argument, because we know that evolution is not simply reducible to “random mutation and natural selection” alone. Indeed, Darwin himself proposed that natural selection was the best explanation for the origin of adaptations, and that natural selection itself was an outcome that necessarily arises from three prerequisites:
• variation (between individuals in populations),
• inheritance (of traits from parents to offspring), and
• fecundity (reproduction resulting in more offspring than necessary for replacement).
Given these prerequisites, some individuals survive and reproduce more often than others, and hence their characteristics become more common in their populations over time.
Allen lists 43 sources of variation (as a minimum) and “at least three different processes that result from them: natural selection, sexual selection, and random genetic drift.”