Abstract

Lineages are genealogical sequences of genes, cells, organisms, or other biological entities. They populate the natural world and are discussed in various fields in biology. However, they barely receive philosophical scrutiny. In this dissertation, I explore philosophical issues regarding the nature of lineages, as well as their conceptualization and representation in science. First, I offer a historical overview of lineages in biology. I describe how biologists characterize lineages in evolutionary biology, developmental biology, paleontology, and other areas. This overview reveals the importance of lineages to theorization, experimentation, modeling, and other scientific practices. These diverse practices motivate the philosophical issues discussed in the following chapters. Second, I address the question of what is a lineage. Biologists and philosophers define them as genealogical sequences of biological entities. This broad definition reveals a belief that many of those scholars share: lineage is a single unified category in science or, in other words, a single type of entity in biology. I argue against this position and, instead, defend pluralism: the existence of a plurality of lineage types in biology. Third, I analyze the very concept of lineage. This concept is imprecise, and this imprecision may be harmful to scientific communication and reasoning. Similar concerns apply to the concepts of molecular gene and evolutionary novelty. I compare the concept of lineage with these concepts. While all of them play beneficial roles in scientific integration, I argue that the concept of lineage facilitates a distinctive type of integration among scientists. Finally, I discuss how biologists represent lineages and why these representations matter to science. Biologists typically represent lineages in a simplistic, idealized way. Most philosophers consider these representations important to science only insofar as they result in improved theories and representations of nature. I argue that this view is limited. Representing lineages also results in collaboration among scientists and other social, non-representational activities that are central to science.