Roberta L. Millstein

Natural Selection as a Population-Level Causal Process

Recent discussions in the philosophy of biology have brought into question some fundamental assumptions regarding evolutionary processes, natural selection in particular. Some authors argue that natural selection is nothing but a population-level, statistical consequence of lower-level events (Matthen and Ariew [2002]; Walsh et al. [2002]). On this view, natural selection itself does not involve forces. Other authors reject this purely statistical, population-level account for an individual-level, causal account of natural selection (Bouchard and Rosenberg [2004]). I argue that each of these positions is right in one way, but wrong in another; natural selection indeed takes place at the level of populations, but it is a causal process nonetheless. 1. Introduction2. A brief justification of population-level causality 2.1Frequency-dependent selection 2.2Accounts of causation3. The montane willow leaf beetle: a causal story4. The montane willow leaf beetle: a population-level story 4.1Response to ‘naïve individualism’ 4.2Response to ‘sophisticated individualism’5. Conclusion Introduction A brief justification of population-level causality 2.1Frequency-dependent selection 2.2Accounts of causation The montane willow leaf beetle: a causal story The montane willow leaf beetle: a population-level story 4.1Response to ‘naïve individualism’ 4.2Response to ‘sophisticated individualism’ Conclusion

Distinguishing drift and selection empirically: "the great snail debate" of the 1950s.

Biologists and philosophers have been extremely pessimistic about the possibility of demonstrating random drift in nature, particularly when it comes to distinguishing random drift from natural selection. However, examination of a historical case – Maxime Lamotte’s study of natural populations of the land snail, Cepaea nemoralis in the 1950s – shows that while some pessimism is warranted, it has been overstated. Indeed, by describing a unique signature for drift and showing that this signature obtained in the populations under study, Lamotte was able to make a good case for a significant role for␣drift. It may be difficult to disentangle the causes of drift and selection acting in a population, but it is not (always) impossible.

Interpretations of Probability in Evolutionary Theory

The ubiquitous probabilities of evolutionary theory (ET) spark the question: Which interpretation of probability is the most appropriate for ET? There is reason to think that, whatever we take probabilities in ET to be, they must be consistent with both determinism and indeterminism. I argue that the probabilities used in ET are objective in a realist sense, if not in an indeterministic sense. Furthermore, there are a number of interpretations of probability that are objective and would be consistent with deterministic evolution and indeterministic evolution. However, I suggest that evolutionary probabilities are best understood as propensities of population‐level kinds.

Chance and macroevolution

When philosophers of physics explore the nature of chance, they usually look to quantum mechanics. When philosophers of biology explore the nature of chance, they usually look to microevolutionary phenomena such as mutation or random drift. What has been largely overlooked is the role of chance in macroevolution. The stochastic models of paleobiology employ conceptions of chance that are similar to those at the microevolutionary level, yet different from the conceptions of chance often associated with quantum mechanics and Laplacean determinism.

Random Drift and the Omniscient Viewpoint

Alexander Rosenberg (1994) claims that the omniscient viewpoint of the evolutionary process would have no need for the concept of random drift. However, his argument fails to take into account all of the processes which are considered to be instances of random drift. A consideration of these processes shows that random drift is not eliminable even given a position of omniscience. Furthermore, Rosenberg must take these processes into account in order to support his claims that evolution is deterministic and that evolutionary biology is an instrumental science.

Mechanism and Causality in Biology and Economics

Acknowledgements.- Chapter 1. Towards the Methodological Turn in the Philosophy of Science Hsiang-Ke Chao, Szu-Ting Chen, and Roberta L. Millstein.- Part 1. Defining Mechanism and Causality.- Chapter 2. Mechanisms versus Causes in Biology and Medicine Lindley Darden.- Chapter 3. Identity, Structure, and Causal Representation in Scientific Models Kevin D. Hoover.- Part 2. Models and Representation.- Chapter 4. The Regrettable Lost of Mathematical Molding in Econometrics Marcel Boumans.- Chapter 5. Models of Mechanisms: The Case of the Replicator Dynamics Till Grune-Yanoff.- Chapter 6. Experimental Discovery, Data Model, and Mechanisms in Biology: An Example from Mendels Work Ruey-Lin Chen.- Part 3. Reconsidering Biological Mechanisms and Causality.- Chapter 7. Mechanisms and Laws: Clarifying the Debate Carl F. Craver and Marie I. Kaiser.- Chapter 8. Natural Selection and Causal Productivity: A Reply to Glennan Roberta L. Millstein.- Chapter 9. Is Natural Selection a Population-Level Causal Process? Rong-Lin Wang.- Part 4. Across Boundaries between Biology and Economics.- Chapter 10. Mechanisms and Extrapolation in the Abortion-Crime Controversy Daniel Steel.- Chapter 11. Causality, Impartiality and Evidence-Based Policy David Teira and Julian Reiss.- Chapter 12. Explaining the Explanations of 100 Million Missing Women Hsiang-Ke Chao and Szu-Ting Chen.Models of Mechanisms: The Case of the Replicator Dynamics Till Grune-Yanoff.- Chapter 6. Experimental Discovery, Data Model, and Mechanisms in Biology: An Example from Mendels Work Ruey-Lin Chen.- Part 3. Reconsidering Biological Mechanisms and Causality.- Chapter 7. Mechanisms and Laws: Clarifying the Debate Carl F. Craver and Marie I. Kaiser.- Chapter 8. Natural Selection and Causal Productivity: A Reply to Glennan Roberta L. Millstein.- Chapter 9. Is Natural Selection a Population-Level Causal Process? Rong-Lin Wang.- Part 4. Across Boundaries between Biology and Economics.- Chapter 10. Mechanisms and Extrapolation in the Abortion-Crime Controversy Daniel Steel.- Chapter 11. Causality, Impartiality and Evidence-Based Policy David Teira and Julian Reiss.- Chapter 12. Explaining the Explanations of 100 Million Missing Women Hsiang-Ke Chao and Szu-Ting Chen.

Thinking about populations and races in time

Biologists and philosophers have offered differing concepts of biological race. That is, they have offered different candidates for what a biological correlate of race might be; for example, races might be subspecies, clades, lineages, ecotypes, or genetic clusters. One thing that is striking about each of these proposals is that they all depend on a concept of population. Indeed, some authors have explicitly characterized races in terms of populations. However, including the concept of population into concepts of race raises three puzzles, all having to do with time. In this paper, I extend the causal interactionist population concept (CIPC) by introducing some simple assumptions about how to understand populations through time. These assumptions help to shed light on the three puzzles, and in the process show that if we want to understand races in terms of populations, we will need to revise our concept(s) of race.

The Role of Causal Processes in the Neutral and Nearly Neutral Theories

The neutral and nearly neutral theories of molecular evolution are sometimes characterized as theories about drift alone, where drift is described solely as an outcome, rather than a process. We argue, however, that both selection and drift, as causal processes, are integral parts of both theories. However, the nearly neutral theory explicitly recognizes alleles and/or molecular substitutions that, while engaging in weakly selected causal processes, exhibit outcomes thought to be characteristic of random drift. A narrow focus on outcomes obscures the significant role of weakly selected causal processes in the nearly neutral theory.

Re-Examining the Darwinian Basis for Aldo Leopold’s Land Ethic

Abstract Many philosophers have become familiar with Leopold’s land ethic through the writings of J. Baird Callicott, who claims that Leopold bases his land ethic on a ‘protosociobiological’ argument that Darwin gives in the Descent of Man. On this view, which has become the canonical interpretation, Leopold’s land ethic is based on extending our moral sentiments to ecosystems. I argue that the evidence weighs in favor of an alternative interpretation of Leopold; his reference to Darwin does not refer to the Descent, but rather to the Origin of Species, where Darwin discusses the interdependencies between organisms in the struggle for existence.

Natural Selection and Causal Productivity

In the recent philosophical literature, two questions have arisen concerning the status of natural selection: (1) Is it a population-level phenomenon, or is it an organism-level phenomenon? (2) Is it a causal process, or is it a purely statistical summary of lower-level processes? In an earlier work (Millstein, Br J Philos Sci, 57(4):627–653, 2006), I argue that natural selection should be understood as a population-level causal process, rather than a purely statistical population-level summation of lower-level processes or as an organism-level causal process. In a 2009 essay entitled “Productivity, relevance, and natural selection,” Stuart Glennan argues in reply that natural selection is produced by causal processes operating at the level of individual organisms, but he maintains that there is no causal productivity at the population level. However, there are, he claims, many population-level properties that are causally relevant to the dynamics of evolutionary processes. Glennan’s claims rely on a causal pluralism that holds that there are two types of causes: causal production and causal relevance. Without calling into question Glennan’s causal pluralism or his claims concerning the causal relevance of natural selection, I argue that natural selection does in fact exhibit causal production at the population level. It is true that natural selection does not fit with accounts of mechanisms that involve decomposition of wholes into parts, such as Glennan’s own. However, it does fit with causal production accounts that do not require decomposition, such as Salmon’s Mark Transmission account, given the extent to which populations act as interacting “objects” in the process of natural selection.