Gradualism

Gradualism holds that evolution occurs through the accumulation of slight modifications over long periods of time. Charles Darwin believed that biological evolution progressed through small, gradual changes within populations through a succession of generations.

Gradualism is related to, but should not be confused with, the concept of geological uniformitarianism which was popularized by Charles Lyell.

Fossils and Gradualism
Darwin predicted, in his book, that if his theory of evolution were true, there should be innumerable fossil creatures in the ground showing the change from one form of organism to another.

This concept, which is also known as phyletic gradualism, is in sharp contrast to the punctuated equilibrium theory later proposed by Niles Eldredge and Stephen Jay Gould to explain the absence of the intermediate fossils that Darwin predicted should exist if the theory of evolution were true.

Firstly, why, if species have descended from other species by insensibly fine gradations, do we not everywhere see innumerable transitional forms?'' (The Origin of Species: The Preservation of Favored Races in the Struggle for Life, first edition reprint (and in further editions) Avenel Books, p. 205)

To Darwin the fossil record should be full of smooth transitions, essentially categorized as transitional forms. This should be seen even from the most primitive of single-celled organisms changing, becoming more complex and eventually leading to multicellular organisms. But even in his time no such smooth transitions were found. Instead as it still persists today the fossil record is known to show the abrupt appearance of complex life forms, which stay generally the same before disappearing the same way they appeared. That is known as stasis.

The gaps in the record are real, however. The absence of any record of any important branching is quite phenomenal. Species are usually static, or nearly so, for long periods, species seldom and genera never show evolution into new species or genera but replacement or one by another, and change is more or less abrupt. (Robert G. Wesson, 'Beyond Natural Selection', 1991, p. 45)

The problem of sudden appearance is the worst problem because according to evolution there needs to be simpler ancestors. However at the foundation of the hypothetical geologic column, there are two layers. The lower has no fossils except for few signs of bacteria, algae, and pollen. The strata on top suddenly bursts with all the living phyla (body shapes) and no new ones are added the further up we go in the column.

It is as though they [fossils] were just planted there, without any evolutionary history. Needless to say this appearance of sudden planting has delighted creationists. Both schools of thought (Punctuationists and Gradualists) despise so-called scientific creationists equally, and both agree that the major gaps are real, that they are true imperfections in the fossil record. The only alternative explanation of the sudden appearance of so many complex animal types in the Cambrian era is divine creation and both reject this alternative.''" (Richard Dawkins, 'The Blind Watchmaker', W.W. Norton & Company, New York, 1996, pp. 229-230)

The abrupt appearance of species, and clear lack of substantial change throughout a species’ range in the fossil record has caused a major rethink of gradualism. In an attempt to reconcile the differences between the fossil record and evolutionary theory, some evolutionists have adopted the theory of "punctuated equilibrium." Not surprisingly, many critics of evolution view "punctuated equilibrium" as simply an excuse for the absence of fossil evidence.

Related References

 * Evolution: The Fossils Still Say No!, by Duane Gish, 391 pages, 1996, ISBN 0890511128
 * Gradualism by Answers.com