DARWIN'S LEGACY

In Part Two, I articulated what was special about organisms in the biological order of things, and in Part Three, I examined the notion of genetic agency, particularly within evolutionary and developmental biology. In the three chapters in Part Four, I turn to groups as agents of natural selection and the idea of higher-level selection more generally.

Charles Darwin is usually the person who comes to mind for most people when asked about the theory of evolution. The disciplines that the theory has spawned, the evolutionary sciences, include paleontology, systematics, and population genetics, each with their own history, methodologies, and theoretical orientations. Evolutionary approaches have also begun to make newer inroads into the fragile sciences, including inroads within psychology, medicine, epidemiology, and anthropology. Despite the diversity within the evolutionary sciences and in evolutionary approaches elsewhere in the fragile sciences, the theory of evolution by natural selection associated with Darwin represents a core theory that all share.

It is common to distinguish two parts to the evolutionary views sometimes called “Darwin's theory,” the first concerning evolution and the second natural selection. We can summarize these as follows:

1. Common Descent: new species have descended from common ancestors over evolutionary time, that is, species have evolved.

2. Natural Selection: the chief mechanism by which evolution from common ancestors has occurred is the process of natural selection.

Common Descent is a view about the history of species that we currently find on the planet, the view that they have descended from a common ancestor or ancestors.