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Volume 7 (2015) Current Issue

Levels, Time and Fitness in Evolutionary Transitions in Individuality

Pierrick Bourrat

In this paper, I identify two major problems with the model of evolutionary transitions in individuality (ETIs) developed by Michod and colleagues, and extended by Okasha, commonly referred to as the “export-of-fitness view”. First, it applies the concepts of viability and fertility inconsistently across levels of selection. This leads Michod to claim that once an ETI is complete, lower-level entities composing higher-level individuals have nil fitness. I argue that this claim is mistaken, propose a correct way to translate the concepts of viability and fertility from one level to the other and show that once an ETI is complete, neither viability nor fertility of the lower level entities is nil. Second, the export- of-fitness view does not sufficiently take the parameter of time into account when estimating fitness across levels of selection. As a result fitness is measured over different periods of time at each level. This ultimately means that fitness is measured in different environmental conditions at each level and misleads Okasha into making the claim that the two levels are ontologically distinct levels of selection. I show that once fitness is measured over the same period of time across levels, the claim about two levels of selection can only be an epistemic one.

Exclusions, Explanations, and Exceptions: On the Causal and Lawlike Status of the Competitive Exclusion Principle

Jani Raerinne and Jan Baedke

The lawlike and explanatory status of ecologists’ Competitive Exclusion Principle (CEP) is a debated topic. It has been argued that the CEP is a ceteris paribus law, a non-lawlike regularity riddled with exceptions, a tautology, a causal regularity, and so on. We argue that the CEP is an empirically respectful and testable strict law that is not riddled with genuine exceptions. Moreover, we argue that the CEP is not a causal explanans in explanations, because it is a coexistence law, not a causal law. Rather than being an explanans, the CEP acts as a contrastive principle sharpening causal explanations. These results contrast with previous analyses of the CEP by Eliot (2011) and Weber (1999), which are also discussed. As a more general conclusion, we suggest that accounts of causal explanation in biology have neglected some of the roles that non-causal laws play in restricting, sharpening, and facilitating causal explanations.

Volume 6 (2014)

Proper activity, preference, and the meaning of life

Lucas J. Mix

Both popular and scientific definitions of life must account for the possibility of the sub-optimal operation of some function. Identifying the function in question and the criteria for optimality will be necessary steps in crafting a definition that is both intuitive and rigorous. I lay out a rule of thumb—the proper activity criterion—and a three-part typology of binary, range, and preference for understanding definitions of life. The resolution of “optimal” function within a scientific framework presents the central challenge to creating a successful definition of life. A brief history of definitions of life and explanations of biological function is presented to demonstrate the value of the typology. After analyzing three controversial cases—viruses, mules, and stars—I present three possible options for resolution: vitalism, reductionism, and instrumentalism. Only by confronting the consequences of each can we come to consensus about what is necessary and desirable from a common definition.