Gradualism - Geology and Biology

Geology and Biology

In the natural sciences, gradualism is a theory which holds that profound change is the cumulative product of slow but continuous processes, often contrasted with catastrophism. The theory was proposed in 1795 by James Hutton, a Scottish physician and gentleman farmer, and was later incorporated into Charles Lyell's theory of uniformitarianism. Tenets from both theories were applied to biology and formed the basis of early evolutionary theory.

Charles Darwin was influenced by Lyell's Principles of Geology, which explained both uniformitarian methodology and theory. Using uniformitarianism, which states that one cannot make an appeal to any force or phenomenon which cannot presently be observed (see catastrophism), Darwin theorized that the evolutionary process must occur gradually, not in saltations, since saltations are not presently observed, and extreme deviations from the usual phenotypic variation would be more likely to be selected against.

Gradualism is often confused with the concept of phyletic gradualism. It is a term coined by Stephen Jay Gould and Niles Eldredge to contrast with their model of punctuated equilibrium, which is gradualist itself, but argues that most evolution is marked by long periods of evolutionary stability (called stasis), which is punctuated by rare instances of branching evolution.