Origin, Chapter 6, Difficulties on Theory

This chapter is a preemptive strike against anticipated criticisms of Darwin’s ideas.

One obvious potential flaw in Darwin’s theory of common descent was the apparent lack of transitional forms linking different groups in the fossil record. Darwin himself asked, “Firstly, why, if species have descended from other species by insensibly fine gradations, do we not everywhere see innumerable transitional forms?” Darwin’s response to this question was to invoke the imperfection of the geological record, the fact that fossilization is the exception rather than the rule. Darwin wrote, “The crust of the earth is a vast museum, and the natural collections have been made only at intervals of time immensely remote.”

Darwin’s theory of gradual change made the prediction that transitional forms should exist, and this prediction has been borne out many times in the 150 years since publication of the “Origin” by new fossil discoveries.

Image: Archaeopteryx, whose discovery just after publication of the Origin lent support to Darwin's theory.