Darwinian adaptation,population genetics and the streetcar theory of evolution |
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Authors: | Peter Hammerstein |
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Institution: | (1) Max-Planck-Institut für Verhaltensphysiologie, Abteilung Wickler, D-82319 Seewiesen, Germany, DE |
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Abstract: | This paper investigates the problem of how to conceive a robust theory of phenotypic adaptation in non-trivial models of
evolutionary biology. A particular effort is made to develop a foundation of this theory in the context of n-locus population genetics. Therefore, the evolution of phenotypic traits is considered that are coded for by more than one
gene. The potential for epistatic gene interactions is not a priori excluded. Furthermore, emphasis is laid on the intricacies
of frequency-dependent selection. It is first discussed how strongly the scope for phenotypic adaptation is restricted by
the complex nature of ‘reproduction mechanics’ in sexually reproducing diploid populations. This discussion shows that one
can easily lose the traces of Darwinism in n-locus models of population genetics. In order to retrieve these traces, the outline of a new theory is given that I call
‘streetcar theory of evolution’. This theory is based on the same models that geneticists have used in order to demonstrate
substantial problems with the ‘adaptationist programme’. However, these models are now analyzed differently by including thoughts
about the evolutionary removal of genetic constraints. This requires consideration of a sufficiently wide range of potential
mutant alleles and careful examination of what to consider as a stable state of the evolutionary process. A particular notion
of stability is introduced in order to describe population states that are phenotypically stable against the effects of all
mutant alleles that are to be expected in the long-run. Surprisingly, a long-term stable state can be characterized at the
phenotypic level as a fitness maximum, a Nash equilibrium or an ESS. The paper presents these mathematical results and discusses
– at unusual length for a mathematical journal – their fundamental role in our current understanding of evolution.
Received 22 April 1994; received in revised form 10 July 1995 |
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Keywords: | : Adaptation Optimality Nash equilibrium ESS N-locus genetics Epistasis Long-term evolution Rationality paradox |
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