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Fitness and the Twins

Sober, Elliott (2019) Fitness and the Twins. Philosophy, Theory, and Practice in Biology, 12 (001). ISSN 2475-3025

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Abstract

Michael Scriven’s (1959) example of identical twins (who are said to be equal in fitness but unequal in their reproductive success) has been used by many philosophers of biology to discuss how fitness should be defined, how selection should be distinguished from drift, and how the environment in which a selection process occurs should be conceptualized. Here it is argued that evolutionary theory has no commitment, one way or the other, as to whether the twins are equally fit. This is because the theory of natural selection is fundamentally about the fitnesses of traits, not the fitnesses of token individuals. A plausible philosophical thesis about supervenience entails that the twins are equally fit if they live in identical environments, but evolutionary biology is not committed to the thesis that the twins live in identical environments. Evolutionary theory is right to focus on traits, rather than on token individuals, because the fitnesses of token organisms (as opposed to their actual survivorship and degree of reproductive success) are almost always unknowable. This point has ramifications for the question of how Darwin’s theory of evolution and R. A. Fisher’s are conceptually different.


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Item Type: Published Article or Volume
Creators:
CreatorsEmailORCID
Sober, Elliottersober@wisc.edu
Additional Information: ISSN: 1949-0739 (print)
Keywords: Darwin, Charles; Drift; Evolution; Fisher, R.A.; Fitness; Natural selection; Operationalism; Supervenience
Subjects: Specific Sciences > Biology
Specific Sciences > Biology > Evolutionary Theory
Specific Sciences > Biology > Systematics
General Issues > History of Science Case Studies
General Issues > Theory/Observation
Depositing User: Jordan Miller
Date Deposited: 24 Jul 2020 15:53
Last Modified: 27 Jul 2020 14:26
Item ID: 17654
Journal or Publication Title: Philosophy, Theory, and Practice in Biology
Official URL: https://quod.lib.umich.edu/p/ptpbio/16039257.0012....
DOI or Unique Handle: 10.3998/ptpbio.16039257.0012.001
Subjects: Specific Sciences > Biology
Specific Sciences > Biology > Evolutionary Theory
Specific Sciences > Biology > Systematics
General Issues > History of Science Case Studies
General Issues > Theory/Observation
Date: 8 September 2019
Volume: 12
Number: 001
ISSN: 2475-3025
URI: http://philsci-archive.pitt.edu/id/eprint/17654

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