The Animal Sexes as Historical Explanatory Kinds (2020) Current Controversies in Philosophy of Science, eds. Dasgupta, Dotan, and Weslake, p. 177-197, Book Link

Though biologists identify individuals as ‘male’ or ‘female’ across a broad range of animal species, the particular traits exhibited by males and females can vary tremendously. This diversity has led some to conclude that cross-animal sexes (males, or females, of whatever animal species) have “little or no explanatory power” (Dupré 1986: 447) and, thus, are not natural kinds in any traditional sense. This essay will explore considerations for and against this conclusion, ultimately arguing that the animal sexes, properly understood, are “historical explanatory kinds”: groupings that can be scientifically significant even while their members differ radically in their current properties and particular histories. Whether this makes them full-fledged natural kinds is a question I take up at the very end.

Natural Kinds as Categorical Bottlenecks (2015) Philosophical Studies 172: 925-948,  Journal Link

Both realist and anti-realist accounts of natural kinds possess prima facie virtues: realists can straightforwardly make sense of the apparent objectivity of the natural kinds, and anti-realists, their knowability. This paper formulates a properly anti-realist account designed to capture both merits. In particular, it recommends understanding natural kinds as ‘categorical bottlenecks,’ those categories that not only best serve us, with our idiosyncratic purposes and cognitive capacities, but also those of a wide range of alternative agents. By endorsing an ultimately subjective categorical principle, this view sidesteps the epistemological difficulties facing realist views. Yet partly in consequence of the ubiquity of robust causal processes in our universe, it nevertheless identifies natural kinds that are fairly, though not completely, objective. 

Trashing Life’s Tree (2010) Biology & Philosophy 25: 689-709, Jounal Link

This paper evaluates recent critiques of a popular interpretation of the Tree of Life, one maintaining that–among non-meiotic life-forms–it represents the history of cellular lineages. I argue that some extant critiques of this ‘tree of cells’ are based on metaphysical confusions, and that there are prospects to defend a cellular interpretation of the Tree on principled grounds; though some of life’s history is not tree-like, the cellular tree is special in light of the central causal importance of cells themselves in influencing the course of evolutionary change.

Bacteria, Sex and Systematics (2007) Philosophy of Science 74: 69-95, JSTOR Link

This paper argues that traditional evolutionary conceptions of species face substantial difficulties when applied to most of life on earth, that is, to bacteria. I suggest that the more ‘pragmatic’ and not exclusively evolutionary approach to species pursued by many microbiologists is not borne of laziness, but instead is required by the causal contours of the bacterial world.