The Adaptation of Species

In 1859 the English naturalist Charles Darwin published The Origin of Species. The book contained two major arguments:

First, Darwin presented a wealth of evidence of evolution. He said that all living things on earth today are the descendants — with modifications — of earlier species.

Second, he proposed a mechanism — natural selection — to explain how evolution takes place.

Evolution involves two interrelated phenomena: with 1) adaptation, over the course of time, species modify their phenotypes in ways that permit them to succeed in their environment.

With 2) speciation, over the course of time, the number of species multiplies; that is, a single species can give rise to two or more descendant species. In fact, Darwin maintained that all species are related; that is, any two species on earth today have shared a common ancestor at some point in their history.

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