The evolutionary problem of the units of selection has elicited a good deal of conceptual work from philosophers. We review this work to determine where the issues now stand.

Evolutionary theory is awash with probabilities. For example, natural selection is said to occur when there is variation in fitness, and fitness is standardly decomposed into two components, viability and fertility, each of which is understood probabilistically. With respect to viability, a fertilized egg is said to have a certain chance of surviving to reproductive age; with respect to fertility, an adult is said to have an expected number of offspring.1 There is more to evolutionary theory than the theory of (...) natural selection, and here too one finds probabilistic concepts aplenty. When there is no selection, the theory of neutral evolution says that a gene’s chance of eventually reaching fixation is 1/(2N), where N is the number of organisms in the generation of the diploid population to which the gene belongs. The evolutionary consequences of mutation are likewise conceptualized in terms of the probability per unit time a gene has of changing from one state to another. The examples just mentioned are all “forwarddirected” probabilities; they describe the probability of later events, conditional on earlier events. However, evolutionary theory also uses “backwards probabilities” that describe the probability of a cause conditional on its effects; for example, coalescence theory allows one to calculate the expected number of generations in the past that the genes in the present generation find their most recent common ancestor. (shrink)

The Paradox of the Ravens (a.k.a,, The Paradox of Confirmation) is indeed an old chestnut. A great many things have been written and said about this paradox and its implications for the logic of evidential support. The first part of this paper will provide a brief survey of the early history of the paradox. This will include the original formulation of the paradox and the early responses of Hempel, Goodman, and Quine. The second part of the paper will describe attempts (...) to resolve the paradox within a Bayesian framework, and show how to improve upon them. This part begins with a discussion of how probabilistic methods can help to clarify the statement of the paradox itself. And it describes some of the early responses to probabilistic explications. We then inspect the assumptions employed by traditional (canonical) Bayesian approaches to the paradox. These assumptions may appear to be overly strong. So, drawing on weaker assumptions, we formulate a new-and-improved Bayesian confirmation-theoretic resolution of the Paradox of the Ravens. (shrink)

Clade selection is unpopular with philosophers who otherwise accept multilevel selection theory. Clades cannot reproduce, and reproduction is widely thought necessary for evolution by natural selection, especially of complex adaptations. Using microbial evolutionary processes as heuristics, I argue contrariwise, that (1) clade growth (proliferation of contained species) substitutes for clade reproduction in the evolution of complex adaptation, (2) clade-level properties favoring persistence – species richness, dispersal, divergence, and possibly intraclade cooperation – are not collapsible into species-level traits, (3) such properties (...) can be maintained by selection on clades, and (4) clade selection extends the explanatory power of the theory of evolution. (shrink)

Determining whether a homoplastic trait is the result of convergence or parallelism is central to many of the most important contemporary discussions in biology and philosophy: the relation between evolution and development, the importance of constraints on variation, and the role of contingency in evolution. In this article, I show that two recent attempts to draw a black-or-white distinction between convergence and parallelism fail, albeit for different reasons. Nevertheless, I argue that we should not be afraid of gray areas: a (...) clarified version of S. J. Gould's earlier account, based on a separation of underlying developmental mechanisms from the realized trait, still represents a useful approach. (shrink)

This paper pursues the question, To what extent does the propensity approach to probability contribute to plausible solutions to various anomalies which occur in quantum mechanics? The position I shall defend is that of the three interpretations — the frequency, the subjective, and the propensity — only the third accommodates the possibility, in principle, of providing a realistic interpretation of ontic indeterminism. If these considerations are correct, then they lend support to Popper's contention that the propensity construction tends to remove (...) (at least some of) the mystery from quantum phenomena. (shrink)

Sober (1992) has recently evaluated Brandon's (1982, 1990; see also 1985, 1988) use of Salmon's (1971) concept of screening-off in the philosophy of biology. He critiques three particular issues, each of which will be considered in this discussion.

I argue that to the extent to which philosophical theories of objective probability have offered theoretically adequate conceptions of objective probability , they have failed to satisfy a methodological standard -- roughly, a requirement to the effect that the conception offered be specified with the precision appropriate for a physical interpretation of an abstract formal calculus and be fully explicated in terms of concepts, objects or phenomena understood independently of the idea of physical probability. The significance of this, and of (...) the suggested methodological standard, is then briefly discussed. (shrink)

The origin and prevalence of transposable elements may best be understood as resulting from “selfish” evolutionary processes at the within-genome level, with relevant populations being all members of the same TE family or all potentially mobile DNAs in a species. But the maintenance of families of TEs as evolutionary drivers, if taken as a consequence of selection, might be better understood as a consequence of selection at the level of species or higher, with the relevant populations being species or ecosystems (...) varying in their possession of TEs. In 2015, Brunet and Doolittle made the case for legitimizing claims for an evolutionary role for TEs by recasting such claims as being about species selection. Here I further develop this “how possibly” argument. I note that with a forgivingly broad construal of evolution by natural selection we might come to appreciate many aspects of Life on earth as its products, and TEs as—possibly—contributors to the success of Life by selection at several levels of a biological hierarchy. Thinking broadly makes this proposition a testable Darwinian one. (shrink)

I explore the problem of ``probabilistic causal preemption'' in the context of a``propensity trajectory'' theory of singular probabilistic causation. This involvesa particular conception of events and a substantive thesis concerning events soconceived.

To clarify and illuminate the place of probability in science Ellery Eells and James H. Fetzer have brought together some of the most distinguished philosophers ...

Christopher Hitchcocks discussion of my use of screening-off in analyzing the causal process of natural selection raises some interesting issues to which I am pleased to reply. The bulk of his article is devoted to some fairly general points in the theory of explanation. In particular, he questions whether or not my point that phenotype screens off genotype from reproductive success (in cases of organismic selection) supports my claim that the explanation of differential reproductive success should be in terms of (...) phenotypic differences, not genotypic differences. I will respond to this and show why the two supposed counter-examples to my position fail. (shrink)

So-called evolutionary error theorists, such as Michael Ruse and Richard Joyce, have argued that naturalistic accounts of the moral sentiments lead us to adopt an error theory approach to morality. Roughly, the argument is that an appreciation of the etiology of those sentiments undermines any reason to think that they track moral truth and, furthermore, undermines any reason to think that moral truth actually exists. I argue that this approach offers us a false dichotomy between error theory and some form (...) of moral realism. While accepting the presuppositions of the evolutionary error theorist, I argue that contract-based approaches to morality can be sensitive to those presuppositions while still vindicating morality. Invoking Stephen Darwall’s distinction between contractualism and contractarianism, I go on to offer an evolutionary-based contractarianism. (shrink)

W&S correctly ask if groups can be like individuals in the harmony and cooperation of their parts, but in their answer, they ignore the importance of the difference between genetically related and unrelated components, and also misconstrue the import of the Hutterites.

In both biology and the human sciences, social groups are sometimes treated as adaptive units whose organization cannot be reduced to individual interactions. This group-level view is opposed by a more individualistic one that treats social organization as a byproduct of self-interest. According to biologists, group-level adaptations can evolve only by a process of natural selection at the group level. Most biologists rejected group selection as an important evolutionary force during the 1960s and 1970s but a positive literature began to (...) grow during the 1970s and is rapidly expanding today. We review this recent literature and its implications for human evolutionary biology. We show that the rejection of group selection was based on a misplaced emphasis on genes as "replicators" which is in fact irrelevant to the question of whether groups can be like individuals in their functional organization. The fundamental question is whether social groups and other higher-level entities can be "vehicles" of selection. When this elementary fact is recognized, group selection emerges as an important force in nature and what seem to be competing theories, such as kin selection and reciprocity, reappear as special cases of group selection. The result is a unified theory of natural selection that operates on a nested hierarchy of units. The vehicle-based theory makes it clear that group selection is an important force to consider in human evolution. Humans can facultatively span the full range from self-interested individuals to "organs" of group-level "organisms." Human behavior not only reflects the balance between levels of selection but it can also alter the balance through the construction of social structures that have the effect of reducing fitness differences within groups, concentrating natural selection (and functional organization) at the group level. These social structures and the cognitive abilities that produce them allow group selection to be important even among large groups of unrelated individuals. (shrink)

The thought that evolution invariably brings about progress deserves consideration, especially in light of the use of optimizing models of its operation. An extremely interesting collection of papers on evolution and optimality affords a suitable point of departure. In The Latest on the Best (1987), for example, some who believe that evolution should be viewed as an optimizing process join issues with others who do not.