A common view is that species occupy a unique position on the Tree of Life. Evaluating this claim requires an understanding of what the Tree of Life represents. The Tree represents history, but there are at least three biological levels that are often said to have genealogies: species, organisms, and genes. Here I focus on defending the plausibility of a gene-based account of the Tree. This leads to an account of species that are determined by gene genealogies. On this view, (...) an exclusive group is a group of organisms that forms a clade for a higher proportion of the genome than any conflicting clade. Taxa occupy a unique position in what can be called the ‘primary concordance tree’. But each gene has its own historical ‘Tree of Life’. I conclude by arguing that both organismal pedigrees with their corresponding Tree as well as gene genealogies and their trees are objectively real and play important, but different, roles in biological practice. (shrink)

The project of this paper is to understand what a phylogenetic tree represents and to discuss some of the implications that this has for the practice of systematics. At least the first part of this task, if not both parts, might appear trivial—or perhaps better suited for a single page in a textbook rather than a scholarly research paper. But this would be a mistake. While the task of interpreting phylogenetic trees is often treated in a trivial way, their interpretation (...) is tied to foundational conceptual questions at the heart of systematics—questions whose answers are hotly disputed. I have previously argued that widely shared ideas about the meaning and interpretation of phylogenetic trees are inconsistent with species concepts other than some genealogical version of a phylogenetic species concept (Velasco 2008). Here I rely on a similar approach and concentrate on the implications of the necessary conditions underlying the inferences that we make using phylogenetic trees. I argue that common practices for the interpretation and use of trees are in conflict and that unacceptable principles about species as units of phylogeny must be given up. According to the view that I will develop, all phylogenetic trees depict the history of populations. The branches on trees represent collections of population lineages through time and the splits represent population lineage splits. This is true regardless of whether the tips of the trees are themselves populations, or are species or higher taxa. Although this conclusion might be paired naturally with a view that species must be monophyletic groups, this population-centric view of trees is independent of that view of species. If we still want to have species that are paraphyletic groups of populations, this is permissible as long as we also do not treat species as the units of phylogeny. This population-centric view opposes a species-centric view of phylogeny and might be called a “rank-free” approach since it entails that we do not need to determine which groups are species (which is partly a ranking question) in order to build a tree. This conclusion and the argument for it are meant to be consistent with, but not require, acceptance of the conclusions of Velasco (2008) regarding species. (shrink)

This article is Part II in a pair of articles on racial realism. In Part I, I defined “racial realism” and discussed the major attempts in the past twenty years among metaphysicians of race and biologists to defend racial realism from the viewpoint of what biologists mean by “race.” In this article, I continue discussing and critiquing how metaphysicians of race have conceived of and defended racial realism, but with a focus on how ordinary people use “race.” I focus on (...) two broad groups of racial realisms in this article: biological racial realism and social racial realism. After defining each one, I summarize a representative sample of recent attempts from metaphysicians of race to defend both types of racial realism. I also discuss major criticisms against each attempt. I end by sketching a new, radical pluralist way of being a racial realist, and I provide some empirical motivation for why it's promising. (shrink)

In this article, I discuss and critique how metaphysicians of race have conceived of and defended racial realism according to how biologists use “race”. I start by defining “racial realism” in the broadest accepted way in the metaphysics of race. Next, I summarize a representative sample of recent attempts from metaphysicians of race and biologists to defend racial realism and the main criticisms against each attempt. I discuss how metaphysicians of race have defended racial realism according to how ordinary people (...) use “race” in Part II. (shrink)

In this article, I will identify an argument for the conclusion that all human moral agents have stronger moral reasons regarding other human beings than they do regarding nonhuman animals, and I will explain why I think this argument is unsound. The argument employs an empirical claim, that all human beings are more closely genealogically related to all other humans than they are to any nonhuman animals, and a moral claim, that one’s genealogical relationship to an individual is a morally (...) relevant consideration. The moral claim is supported by a comparison between genealogically related individuals and a family. (shrink)

We argue for a new conventionalism about many kinds of evolutionary groups, including clades, cohesive units, and populations. This rejects a consensus, which says that given any one of the many legitimate grouping concepts, only objective biological facts determine whether a collection is such a group. Surprisingly, being any one kind of evolutionary group typically depends on which of many incompatible values are taken by suppressed variables. This is a novel pluralism underlying most any one group concept, rather than a (...) familiar pluralism claiming many concepts are legitimate. Consequently, we must help biological facts determine grouphood, even when given a single grouping concept. (shrink)