Published online by Cambridge University Press: 01 January 2022
Samir Okasha argues that clade selection is an incoherent concept, because the relation that constitutes clades is such that it renders parent-offspring (reproduction) relations between clades impossible. He reasons that since clades cannot reproduce, it is not coherent to speak of natural selection operating at the clade level. We argue, however, that when species-level lineages and clade-level lineages are treated consistently according to standard cladist commitments, clade reproduction is indeed possible and clade selection is coherent if certain conditions obtain. Despite clade selection's logical coherence, however, we share some of Okasha's pessimism. Whether or not clades are a unit of selection is ultimately a question of empirical support and theoretical import.
Thanks are due to Jim Griesemer, the Philosophical Pizza Munchers, and Samir Okasha for helpful discussions of the issues under consideration here. Matthew Haber was supported by NSF Research Grant #0137255. This work is fully collaborative: the authors are listed alphabetically.