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Rates of evolution - What is phyletic gradualism?


Phyletic gradualism

Phyletic gradualism is a hypothesis about the pattern of evolution. In contrast to the theory of punctuated equilibrium, it states the following:

• Evolution has a fairly constant rate.

• New species arise by the gradual transformation of ancestral species.

• The rate of evolution during the origin of new species is much like that at any other time.

For gradualists, the fact that fossil evidence shows species suddenly appearing with little signs of any transitional forms is due to the incompleteness of the fossil record.

Was Darwin a gradualist?

There is a historical controversy as to whether Darwin himself was committed to gradualism. It is most likely that he was a gradualist about the evolution of adaptations, not about the pattern of evolutionary rates.

The philosopher of science Daniel Dennett argues that evolution, as Darwin understood it, is a gradual process.

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