Darwin’s Early Ideas on Evolution:
Darwin's early ideas on evolution were strongly influenced by geology. He greatly admired Lyell and his original interpretation of evolution was that it was closely tied to geologic processes.
- Islands are the primary agent in stimulating organic change. Provides a means by which variants can reproduce in isolation.
- Variation in organisms is induced by geologic change. Idea of "unsettling" the species.
- Uplift of land would provide new habitats, and competition and natural selection would occur.
- Rising land led to speciation; fully elevated land to dispersal of these new species.
Big change in this theory was observation that variation occurred naturally. Darwin's study of barnacles demonstrated something that Wallace had long recognized--species vary in nature without perturbation. So geology was no longer necessary to his idea of natural selection.