In this chapter, I examine three concepts of adaptedness and adaptation found in Darwin and two additional concepts of “Darwinian fitness” employed in current population biology and evolutionary theory. The examination reveals a number of conceptual confusions within evolutionary biology and shows that much of the philosophical literature about evolutionary theory has been concerned with vulgarizations of that theory. Several recent controversies in evolutionary theory, all of which focus on the degree of control that natural selection exercises over traits of organisms, are mentioned in passing. These controversies have been plagued by confusions regarding what it is for a trait to be an adaptation, the kinds of evidence required to support such a claim, and the units of analysis appropriate to applications of the concept of (an) adaptation. Removal of these confusions may contribute to the attempt to resolve the underlying biological disagreements about the relative importance of various units of selection, the existence of neutral mutations, “selfish” DNA, and so forth, but it will not be sufficient, by itself, to resolve those disagreements. Removal of those confusions is also an important step toward a deeper and more fruitful understanding of the structure and content of evolutionary theory.

ADAPTATION AND ADAPTEDNESS

In a book on The Development of Darwin's Theory of evolution by natural selection, the late Dov Ospovat (1981) argued, in effect, that a major key to understanding Darwin and his theory is provided by grasping the changes in Darwin's concepts of “adaptation” and “adaptedness” and the subsequent changes that Darwin's work helped to bring about in the use of cognate concepts by biologists.