 Thus, the Hagedoorns endorse points 1–5 above, while describing two additional processes besides #4 (the founding of a new population), namely the splitting of a population and the random sampling of parents. They further explain the relevance of #3 (small populations): “the smaller the group, the more limited its potential variability, the sooner it will be pure altogether” (p. 123). And finally, they maintain that drift can produce fixation (“purity”), or the complete loss of variation within a population, even in the absence of selection. Fisher (1922b) reads the Hagedoorns as claiming that “random survival is a more important factor in limiting the variability of species than preferential survival” (p. 321), a claim that he challenged by attempting to show that such a process would be too slow to overcome the rate of mutation (and thus the introduction of new variability—but he seems to say otherwise in 1922a).