The Debate over the Nature of Selection

Recent debate over the nature of selection centres upon the questions of whether selection is a type of causal process and how selection should be characterised. Three representative accounts of selection in this debate are critically examined in this thesis: Matthen and Ariew’s formal-pattern account, Bouchard and Rosenberg’s fitness-dependent characterisation of selection and Millstein’s fitness-independent characterisation of selection. Matthen and Ariew contend that there is no selection as a causal process as normally conceived; instead, selection is a formal pattern characterised by a mathematical theorem. Bouchard and Rosenberg assert that selection is a type of causal process identified by the fitter-than relation being the cause of difference in reproductive success. Millstein characterises selection to be such a causal process that trait-variations as population-level properties are causally relevant to differences in reproductive success. All these accounts will be shown to be seriously defective. However, the former two are so fundamentally mistaken that they will be rejected outright. On the other hand, Millstein’s account, while conceptually confused and metaphysically flawed as it stands, can be clarified and re-interpreted so that it can pave the way for a more satisfactory characterisation of selection. In this latter account, selections with respect to different trait-determinables are different types of population-wide, generation-long process each jointly identified by a plurality of distinct yet similar types of organismal-level generation-long process that are identified by different types of trait-determinates under a common trait-determinable being causally contributory to different ranges of determinate degrees of reproductive success.
The present thesis proceeds as follows. Chapter one introduces the background of the current debate, distinguishes what is at issue from what is not, and states some basic assumptions and the objective of the thesis. Chapter two examines the formal-pattern account. It is argued that selection as a formal pattern is, contrary to what Matthen and Ariew claim, not multiply realisable and has no explanatory utility at all. Meanwhile, their arguments against the ordinary talk of selection as a causal process will be refuted and the ordinary idea be clarified and re-established. Chapter three is devoted to Bouchard and Rosenberg’s account. I’ll show that, on the assumption that fitness is an organismal property, it is a second-order functional property, and therefore the assertion that fitness is causally responsible for reproductive success or the difference thereof suffers from the problem of metaphysically necessary dependency and the causal exclusion problem. Some specific attempts to solve the former problem and some general objections to the exclusion argument will be rejected. Chapter four explores Millstein’s fitness-independent characterisation. It will be revealed that selection in her account is actually a family of different types of process rather than a single type of process. This leads to a comparison between the fitness-dependent characterisation and the fitness-independent one and ultimately to the rejection of the posit of the property of fitness as well as the fitness-dependent characterisation. Yet, the posit of the so-called population-level properties also has the exclusion problem; Haug’s attempt to save their causal efficacy will be criticised and rejected. Their causal inefficacy and ontological redundancy prompts a re-interpretation of Millstein’s characterisation and eventually a more satisfactory alternative that does not rest upon any ontologically redundant or metaphysically suspicious posit and does not create any semantic twist or other unnecessary complications. Chapter five is the conclusion.