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Natural Selection Reconsidered



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Shiels, Reuben 


In this thesis, I inspect some key assumptions which tend to underpin mainstream accounts of natural selection, noting where those assumptions break down and taking this as a basis for fresh analysis.

First, I examine the assumption that natural selection inherently involves struggle or competition. I show selection can take place without zero-sum competition and that competition is not essential for selection to positively facilitate novel adaptations.

Moving on to fitness, I address the assumption that biological fitness should be measured as a function of the number of elements of some set of entities (offspring, gene copies or otherwise). Noting cases where selection seemingly acts in terms of persistence and somatic growth, and with these alternative fitness metrics not reducible to one another, I suggest a pluralist stance. Subsequently extending this rationale to the temporal dimension, I show that attempting to measure fitness over any single time frame often fails to capture the action of selection.

In later chapters, I explore the possibility of uniting my multiple fitness metrics via a single “common currency” metric. I rule out metrics based around resource or energy consumption, as per Van Valen and others, as unworkable. However, I find some potential in conceptualising the various aspects of fitness in terms of negative entropy. This fails to deliver a quantifiable common currency metric, but does address conceptual issues and allows for the unification of our account of biological fitness with the popular thermodynamic definition of life.

The need to buttress earlier arguments necessitates a concluding analysis of the Darwinian population concept. Contra complacent assumptions that they are readily defined, I find that there are no clear means to bound Darwinian populations in many cases. I also argue that analysis of the Darwinian population concept has been confounded by the conflation of pragmatic groupings, assembled for comparative inference, with causally bound Darwinian populations.





Lewens, Tim


Natural Selection, Fitness, Darwinian Population, Competition, Evolution, Philosophy of Biology, Thermodynamics


Doctor of Philosophy (PhD)

Awarding Institution

University of Cambridge
AHRC (1362290)