Here's an excerpt from a post by Bob O'Hara about how wrong anti-evolutionists can get the theory wrong, even if they aren't all-out creationists:
We can see their confusion even where they are trying to agree with evolutionary biologists: they are even ignorant of what fitness means. This is how they define it:... co-varies with the probability that it will contribute its phenotypic traits to its offspring... Hilarious!we’ll follow the current consensus according to which an individual’s relative fitness co-varies with the probability that it will contribute its phenotypic traits to its offspring.This is not just wrong. To see why, imagine an individual that passes on its phenotype to every one of its offspring. According to Fodor & Piattelli-Palmarini, it has maximal fitness: transmission is 100%. But imagine that the trait is for only having two offspring. Compare that to an individual who half the time passes on the trait of having 10 offspring, and the rest of the time the offspring are sterile. Fodor & Piattelli-Palmarini may think that these individuals are less fit, but if these are the only two phenotypes in the population, the “fitter” phenotype will be lost. For the rest of us fitness is defined in relation to the population (and the environment!), not transmission within a family.