Can fitness differences be a cause of evolution?

Grant Ramsey

The causal status of fitness and natural selection is increasingly called into doubt in the philosophical literature. For example, Elliott Sober argues that the fitness of individual organisms is holistic; i.e., it is dependent osn causally independent factors like census size. Others have argued that fitness differences cannot properly be causes of evolutionary change. In this paper I directly challenge the holistic conclusion, and thereby shed light on the debates over the causal status of fitness. I show that the causalists and statisticalists are—to a large degree—arguing past each other. There is a plurality of fitness concepts; some are legitimately causal, while others seem to be based, at least in part, on purely statistical parameters. But such facts say nothing about whether fitness in general is causal or statistical.

Phylogeny as population history

Joel D. Velasco

The construction and use of phylogenetic trees is central to modern systematics. But it is unclear exactly what phylogenies and phylogenetic trees represent. They are sometimes said to represent genealogical relationships between taxa, between species, or simply between “groups of organisms.” But these are incompatible representational claims. This paper focuses on how trees are used to make inferences and then argues that this focus requires that phylogenies represent the histories of populations.