Abstract

Biologists have long disputed the question of the correct level of nature at which to describe the action of natural selection. Species, groups, organisms, and genes have each been claimed to represent important units of natural selection, and there is still considerable controversy among biologists on the question. Philosophers have recently argued that resolution of the controversy requires conceptual clarification of claims about units of selection. Two different general approaches are taken to such clarification: through an analysis of the structure of evolutionary theory; through an examination of the ontological structure of natural selection processes. None of these philosophical proposals, however, is entirely satisfactory. ;This dissertation is divided into three Parts and five Chapters. Part I surveys the biological literature on the units of selection controversy. Chapter 1 provides an historical overview of the controversy from Darwin to the mid-1960s. Chapter 2 examines recent candidates for species, group, and genic selection. Part II turns to philosophical analyses. Chapter 3 examines and evaluates structural approaches, whereas Chapter 4 likewise looks at ontological approaches. Part III sets out a new, and more satisfactory, philosophical analysis of units of selection. The account offered in Chapter 5 explicitly builds upon the insights gained in examining previous proposals, while avoiding their difficulties. A definition of a unit of selection is proposed ) which is grounded directly in the biological literature. The proposed cases of species, group, organismic, and genic selection discussed in Chapter 2 are then reexamined with the help of . It is argued that clarifies the requirements for determining whether a given case is or is not an example of selection at a given level. It is shown how conceptual analysis and empirical investigations each must contribute to the resolution of the controversy. This study is intended as a comparative analysis of the methodology of philosophical contributions to scientific disputes, based upon a case study of an ongoing controversy in evolutionary biology