André Ariew

The Trials of Life: Natural Selection and Random Drift *

We distinguish dynamical and statistical interpretations of evolutionary theory. We argue that only the statistical interpretation preserves the presumed relation between natural selection and drift. On these grounds we claim that the dynamical conception of evolutionary theory as a theory of forces is mistaken. Selection and drift are not forces. Nor do selection and drift explanations appeal to the (sub‐population‐level) causes of population level change. Instead they explain by appeal to the statistical structure of populations. We briefly discuss the implications of the statistical interpretation of selection for various debates within the philosophy of biology—the ‘explananda of selection’ debate and the ‘units of selection’ debate.

The Confusions of Fitness

The central point of this essay is to demonstrate the incommensurability of ‘Darwinian fitness’ with the numeric values associated with reproductive rates used in population genetics. While sometimes both are called ‘fitness’, they are distinct concepts coming from distinct explanatory schemes. Further, we try to outline a possible answer to the following question: from the natural properties of organisms and a knowledge of their environment, can we construct an algorithm for a particular kind of organismic life-history pattern that itself will allow us to predict whether a type in the population will increase or decrease relative to other types? 1. Introduction2. Darwinian fitness3. Reproductive fitness and genetical models of evolution4. The models of reproductive fitness 4.1 The Standard Viability Model 4.2 Frequency-dependent selection 4.3 Fertility models 4.4 Overlapping generations5. Fitness as outcome 5.1 Fitness as actual increase in type 5.2 Fitness as expected increase in type 5.2.1 Expected increase within a generation 5.2.2 Expected increase between generations 5.2.3 Postponed reproductive fitness effects6. The book-keeping problem7. Conclusion Introduction Darwinian fitness Reproductive fitness and genetical models of evolution The models of reproductive fitness 4.1 The Standard Viability Model 4.2 Frequency-dependent selection 4.3 Fertility models 4.4 Overlapping generations5. Fitness as outcome 5.1 Fitness as actual increase in type 5.2 Fitness as expected increase in type 5.2.1 Expected increase within a generation 5.2.2 Expected increase between generations 5.2.3 Postponed reproductive fitness effects 4.1 The Standard Viability Model 4.2 Frequency-dependent selection 4.3 Fertility models 4.4 Overlapping generations Fitness as outcome 5.1 Fitness as actual increase in type 5.2 Fitness as expected increase in type 5.2.1 Expected increase within a generation 5.2.2 Expected increase between generations 5.2.3 Postponed reproductive fitness effects 5.2.1 Expected increase within a generation 5.2.2 Expected increase between generations 5.2.3 Postponed reproductive fitness effects The book-keeping problem Conclusion

Innateness and Canalization

Cognitive scientists often employ the notion of innateness without defining it. The issue is, how is innateness defined in biology? Some critics contend that innateness is not a legitimate concept in biology. In this paper I will argue that it is. However, neither the concept of high heritability nor the concept of flat norm of reaction (two popular accounts in the biology literature) define innateness. An adequate account is found in developmental biology. I propose that innateness is best defined in terms of C. H. Waddingtons concept of canalization.

Selection and causation

We have argued elsewhere that natural selection is not a cause of evolution, and that a resolution‐of‐forces (or vector addition) model does not provide us with a proper understanding of how natural selection combines with other evolutionary influences. These propositions have come in for criticism recently, and here we clarify and defend them. We do so within the broad framework of our own ‘hierarchical realization model’ of how evolutionary influences combine.

Autonomous-Statistical Explanations and Natural Selection

Shapiro and Sober ([2007]) claim that Walsh, Ariew, Lewens, and Matthen (henceforth WALM) give a mistaken, a priori defense of natural selection and drift as epiphenomenal. Contrary to Shapiro and Sober’s claims, we first argue that WALM’s explanatory doctrine does not require a defense of epiphenomenalism. We then defend WALM’s explanatory doctrine by arguing that the explanations provided by the modern genetical theory of natural selection are ‘autonomous-statistical explanations’ analogous to Galton’s explanation of reversion to mediocrity and an explanation of the diffusion ofgases. We then argue that whereas Sober’s theory of forces is an adequate description of Darwin’s theory, WALM’s explanatory doctrine is required to understand how themodern genetical theory of natural selection explains large-scale statistical regularities. 1 Introduction 2 Shapiro and Sober’s ‘Epiphenomenalism Do’s and Don’ts’ 3 WALM’s Explanatory Doctrine 4 Galton’s Autonomous-Statistical Explanation 5 A Second Example: The Statistical Explanation of the Diffusion of Gases 6 Distinguishing Two Theories of Evolution by Natural Selection 7 A Possible Objection: Are Statistical Laws Sufficient for Explanation? 8 Conclusion 1 Introduction 2 Shapiro and Sober’s ‘Epiphenomenalism Do’s and Don’ts’ 3 WALM’s Explanatory Doctrine 4 Galton’s Autonomous-Statistical Explanation 5 A Second Example: The Statistical Explanation of the Diffusion of Gases 6 Distinguishing Two Theories of Evolution by Natural Selection 7 A Possible Objection: Are Statistical Laws Sufficient for Explanation? 8 Conclusion

Explanatory schema and the process of model building

In this paper, we argue that rather than exclusively focusing on trying to determine if an idealized model fits a particular account of scientific explanation, philosophers of science should also work on directly analyzing various explanatory schemas that reveal the steps and justification involved in scientists’ use of highly idealized models to formulate explanations. We develop our alternative methodology by analyzing historically important cases of idealized statistical modeling that use a three-step explanatory schema involving idealization, mathematical operation, and explanatory interpretation.

Nature/Nurture – A Philosophical Analysis

The debate about whether some attribute is ‘by nature’ or ‘by nurture’ has a long history and it covers numerous topics. For instance, Socrates proposed that our ideas of complex concepts come from memories that are innate within us. Even today thinkers believe that some of our ideas are part of our nature rather than our nurture. This theory has social and policy implications. If intellectual quotient (IQ) is a fixed part of nature, is it worthwhile to contribute tax dollars to improve ones nurturing environment? Or, more generally, some think that understanding human nature might affect how we ought to live. Influenced by Darwin and developments in genetics, the nature/nurture debate has reduced to a debate about whether our attributes are ‘genetic’ or ‘environmental’. Yet, the implications of the genetic theories of human nature are not obvious since genes alone do not produce any attributes. Key concepts: ‘Nativists’ employ ‘poverty of stimulus’ arguments to demonstrate that an idea or cognitive ability could not have been learned. ‘Empiricists’ believe that our beliefs about the world come from our perceptual connection to the world and not from our natures. IQ is likely to be influenced by nurturing environments. Likely, there is no such thing as the singular good life; rather there are numerous valid conceptions of the good life. The gene/environment dichotomy is false but that does not mean we cannot distinguish between robust and plastic developmental events. Keywords: nature; nurture; genetics; language; knowledge