Online research in philosophy

argue that natural selection does not explain the genotypic arid phenotypic properties of individuals. On this view, natural selection explains the adaptedness of individuals, not by explaining why the individuals that exist have the adaptations they do, but rather by explaining why the individuals that exist are the ones with those adaptations. This paper argues that this ‘Negative’ view of natural selection ignores the fact that natural selection is a cumulative selection process. So understood, it explains how the genetic sequences that individuals inherit and that are responsible for their complex (and co-adapted) adaptations first arose in the gene-pool.

natural selection may show why all (most, some) humans have an opposable thumb, but cannot show why any particular human has one, Karen Neander ([1995a], [1995b]) argues that this is false because natural selection is 'cumulative'. It is argued here, on grounds independent of its cumulativity, that selection can explain the characteristics of individual organisms subsequent to the event. The difference of opinion between Sober and his critics turns on an ontological dispute about how organisms are identified and individuated. The assumption that Sober needs to make his point is extraneous to population genetics, and, for this reason, gratuitous.

The thesis that natural selection explains the frequencies of traits in populations, but not why individual organisms have the traits tehy do, is here defended and elaborated. A general concept of ‘distributive explanation’ is discussed.

It has been claimed that certain forms of individual essentialism render the Theory of Natural Selection unable to explain why any given individual has the traits it does. Here, three reasons are offered why the Theory ought to ignore these forms of essentialism. First, the trait-distributions explained by population genetics supervene on individual-level causal links, and thus selection must have individual-level effects. Second, even if there are individuals that possess thick essences, they lie outside the domain of the Theory. Finally, the contingency of sexual reproduction suggests that essentialism is misguided in this arena. 1 The problem 2 A reprise of the controversy 3 Enter individual essences 4 How can selection not have individual-level effects? 5 Why can't we get rid of essences we don't like? 6 Is sex necessary?

Can selection explain why individuals have the traits they do? This question has generated significant controversy. I will argue that the debate encompasses two separable aspects, to detrimental effect: (1) the role of selection in explaining the origin and evolution of biological traits and (2) the implications this may have for explaining why individuals have the traits they do. (1) can be settled on the basis of evolutionary theory while (2) requires additional, extra-scientific assumptions. By making a distinction between traits affected by a single factor and traits affected by multiple factors I show that selection can, under certain conditions, help explain the origin of traits. Resolving the first aspect enables us to critically assess the various incompatible and independent philosophical commitments made within the second aspect of the debate.

argues that when reproduction is sexual, natural selection can explain why individual organisms possess the traits they do. In stating his argument Matthen makes use of a conception of individual organisms as receptacles for collections of genes—a conception that cannot do the work Matthen requires of it. Either these receptacles are abstract objects, such as bare possibilities for organisms, or they are concrete. The first reading is too weak, since it allows selection to explain individual traits in both sexual and asexual contexts. The only concrete entities we might think of as receptacles for collections of genes are male or female gametes. It is true that in the sexual context selection explains why an individual gamete combines with a second gamete of one type rather than another; however, this is not to say that selection explains why an individual organism has the traits it does.

This paper investigates the conception of causation required in order to make sense of natural selection as a causal explanation of changes in traits or allele frequencies. It claims that under a counterfactual account of causation, natural selection is constituted by the causal relevance of traits and alleles to the variation in traits and alleles frequencies. The “statisticalist” view of selection (Walsh, Matthen, Ariew, Lewens) has shown that natural selection is not a cause superadded to the causal interactions between individual organisms. It also claimed that the only causation at work is those aggregated individual interactions, natural selection being only predictive and explanatory, but it is implicitly committed to a process-view of causation. I formulate a counterfactual construal of the causal statements underlying selectionist explanations, and show that they hold because of the reference they make to ecological reliable factors. Considering case studies, I argue that this counterfactual view of causal relevance proper to natural selection captures more salient features of evolutionary explanations than the statisticalist view, and especially makes sense of the difference between selection and drift. I eventually establish equivalence between causal relevance of traits and natural selection itself as a cause.

In this paper I argue against Sober's claim that natural selection does not explain the traits of individuals. Sober argues that natural selection only explains the distribution of traits in a population. My point is that the explanation of an individual's traits involves us in a description of the individual's ancestry, and in an explanation of the distribution of traits in that ancestral population. Thus Sober is wrong, natural selection is part of the explanation of the traits of individuals.

I have recently argued that origin essentialism regarding individual organisms entails that natural selection does not explain why individual organisms have the traits that they do. This paper defends this and related theses against Mohan Matthen's recent objections.