Peter Godfrey-Smith

On the theoretical role of genetic coding

The role played by the concept of genetic coding in biology is discussed. I argue that this concept makes a real contribution to solving a specific problem in cell biology. But attempts to make the idea of genetic coding do theoretical work elsewhere in biology, and in philosophy of biology, are probably mistaken. In particular, the concept of genetic coding should not be used (as it often is) to express a distinction between the traits of whole organisms that are coded for in the genes and the traits that are not.

On the Evolution of Behavioral Heterogeneity in Individuals and Populations

A wide range of ecological and evolutionary models predict variety in phenotype or behavior when a population is at equilibrium. This heterogeneity can be realized in different ways. For example, it can be realized through a complex population of individuals exhibiting different simple behaviors, or through a simple population of individuals exhibiting complex, varying behaviors. In some theoretical frameworks these different realizations are treated as equivalent, but natural selection distinguishes between these two alternatives in subtle ways. By investigating an increasingly complex series of models, from a simple fluctuating selection model up to a finite population hawk/dove game, we explore the selective pressures which discriminate between pure strategists, mixed at the population level, and individual mixed strategists. Our analysis reveals some important limitations to the “ESS” framework often employed to investigate the evolution of complex behavior.

Indication and adaptation

This paper examines the relationship between a family of concepts involving reliable correlation, and a family of concepts involving adaptation and biological function, as these concepts are used in the naturalistic semantic theory of Dretskes Explaining Behavior. I argue that Dretskes attempt to marry correlation and function to produce representation fails, though aspects of his failure point the way forward to a better theory.

GENERALIZATION OF THE PRICE EQUATION FOR EVOLUTIONARY CHANGE

The Price equation is recognized as a general statistical description of evolutionary change with the potential to represent diverse processes. Here we present a new structurally symmetric equation for change that allows for arbitrary causal connectivity between ancestors and descendants, accounts for previously unaddressed processes (such as migration), and yields the Price equation as a special case.

Darwinism and cultural change

Evolutionary models of cultural change have acquired an important role in attempts to explain the course of human evolution, especially our specialization in knowledge-gathering and intelligent control of environments. In both biological and cultural change, different patterns of explanation become relevant at different ‘grains’ of analysis and in contexts associated with different explanatory targets. Existing treatments of the evolutionary approach to culture, both positive and negative, underestimate the importance of these distinctions. Close attention to grain of analysis motivates distinctions between three possible modes of cultural evolution, each associated with different empirical assumptions and explanatory roles.

An option space for early neural evolution

The origin of nervous systems has traditionally been discussed within two conceptual frameworks. Input–output models stress the sensory-motor aspects of nervous systems, while internal coordination models emphasize the role of nervous systems in coordinating multicellular activity, especially muscle-based motility. Here we consider both frameworks and apply them to describe aspects of each of three main groups of phenomena that nervous systems control: behaviour, physiology and development. We argue that both frameworks and all three aspects of nervous system function need to be considered for a comprehensive discussion of nervous system origins. This broad mapping of the option space enables an overview of the many influences and constraints that may have played a role in the evolution of the first nervous systems.

Varieties of Population Structure and the Levels of Selection

Group-structured populations, of the kind prominent in discussions of multilevel selection, are contrasted with ‘neighbor-structured’ populations. I argue that it is a necessary condition on multilevel description of a selection process that there should be a nonarbitrary division of the population into equivalence classes (or an approximation to this situation). The discussion is focused via comparisons between two famous problem cases involving group structure (altruism and heterozygote advantage) and two neighbor-structured cases that resemble them. Conclusions are also drawn about the role of correlated interaction in the evolution of altruism. 1. Introduction2. Two Kinds of Population Structure3. Objections and Replies4. Particles on a Line5. Conclusion Appendix: Neighborhoods and Selection Introduction Two Kinds of Population Structure Objections and Replies Particles on a Line Conclusion Appendix: Neighborhoods and Selection

A tortoise–hare pattern seen in adapting structured and unstructured populations suggests a rugged fitness landscape in bacteria

Significance The “adaptive landscape” characterizes the relationship between genotype and fitness. As the landscape becomes more rugged, evolution can become more constrained. During the modern evolutionary synthesis, different views about the process of adaptation reflected different assumptions about landscape topography, which motivated the empirical assessment of adaptive landscapes in biological systems. Here, we describe how evolutionary patterns within experimental populations can yield information about landscape topography. Specifically, metapopulations of Escherichia coli are evolved under different patterns of migration. We find bacteria reach higher fitness and accumulate more mutations under restricted migration than unrestricted migration, which is consistent with a rugged topography. In this way, experimental manipulation of population structure can provide insight into fundamental evolutionary constraints. In the context of Wright’s adaptive landscape, genetic epistasis can yield a multipeaked or “rugged” topography. In an unstructured population, a lineage with selective access to multiple peaks is expected to fix rapidly on one, which may not be the highest peak. In a spatially structured population, on the other hand, beneficial mutations take longer to spread. This slowdown allows distant parts of the population to explore the landscape semiindependently. Such a population can simultaneously discover multiple peaks, and the genotype at the highest discovered peak is expected to dominate eventually. Thus, structured populations sacrifice initial speed of adaptation for breadth of search. As in the fable of the tortoise and the hare, the structured population (tortoise) starts relatively slow but eventually surpasses the unstructured population (hare) in average fitness. In contrast, on single-peak landscapes that lack epistasis, all uphill paths converge. Given such “smooth” topography, breadth of search is devalued and a structured population only lags behind an unstructured population in average fitness (ultimately converging). Thus, the tortoise–hare pattern is an indicator of ruggedness. After verifying these predictions in simulated populations where ruggedness is manipulable, we explore average fitness in metapopulations of Escherichia coli. Consistent with a rugged landscape topography, we find a tortoise–hare pattern. Further, we find that structured populations accumulate more mutations, suggesting that distant peaks are higher. This approach can be used to unveil landscape topography in other systems, and we discuss its application for antibiotic resistance, engineering problems, and elements of Wright’s shifting balance process.

Dewey on Naturalism, Realism and Science

An interpretation of John Dewey’s views about realism, science, and naturalistic philosophy is presented. Dewey should be seen as an unorthodox realist, with respect to both general metaphysical debates about realism and with respect to debates about the aims and achievements of science.

On Folk Psychology and Mental Representation

Publisher Summary This chapter presents an overview of folk psychology and mental representation. Dretske, Fodor and many others think that some organisms, including people, contain inner states and structures which represent the world, and do so as a matter of objective fact. Philosophy should aim to describe the connections between facts about the use of difficult and controversial concepts, and facts about the parts of the world that the concepts are in some sense aimed at dealing with. Philosophy should link the empirical facts about human knowledge-ascriptions with the facts about how beliefs are regulated and how beliefs enable organisms to get around the world. From the point of view of Dennetts picture, the Dretske–Fodor view is mistaken because it does not take seriously the special properties of human interpretive practices; interpretation is not just an attempt to lay out the hidden structure of a complex machine. The first point that should be clear is that one needs more empirical knowledge about folk psychological interpretation.