grad·u·al·ism / ˈgrajoōəˌlizəm/ • n. a policy of gradual reform rather than sudden change or revolution. ∎ Biol. the hypothesis that evolution proceeds chiefly by the accumulation of gradual changes (in contrast to the punctuationist model).DERIVATIVES: grad·u·al·ist n.grad·u·al·is·tic / ˌgrajəwəˈlistik/ adj.
Gradualism, also called phyletic gradualism, is the view that the course of evolution is gradual with small changes accumulating through time. Gradualism is opposed to punctualism, where evolutionary change is thought to happen in short episodes of rapid evolution followed by long periods of stasis when little or no evolutionary change occurs. The latter view is based on the interpretation of the fossil record and is common among palaeontologists, whereas the former view builds on a version of population genetics theory. However, most evolutionary biologists hold the view that the two concepts are not necessarily contradictory because gradual changes in genotype may occasionally lead to major changes in phenotype.
See also Catastrophism; Evolution; Punctuated Equilibrium