Positive Darwinian selection

This theory, in Kimura s own words, states that The great majority of evolutionary mutant substitutions are not caused by positive Darwinian selection but by random fixation of selectively neutral or nearly neutral mutants (it is important to underline that the adjective neutral does not mean without function it only means that a mutation is adaptively indifferent, i.e. it is neither better nor worse than the previous one in respect to the organism s adaptation to the environment). 

Lee, Y.-H. and Vacquier, V.D. (1992). The divergence of species-specific abalone sperm lysins is promoted by positive Darwinian selection. Biol. Bull. 7S2 97-105. 

Smith, N.H., Maynard-Smith, J., and Spratt, B.G. (1995). Sequence evolution of the porB gene of Neisseria gonorrhoeae and N. memingitidis Evidence of positive Darwinian selection. Mol, Biol. Evol. 72 363-370. 

Swanson, W.J. and Vacquier, V.D. (1995b). Extraordinary divergence and positive Darwinian selection in a fusagenic protein coating the acrosomal process of abalone spermatozoa. Proc. Natl. Acad. Sci. USA. 92 4957-4962,... 

Vacquier, V.D., Swanson, W.J., and Lee, Y.-H. (1997). Positive Darwinian selection on two homologous fertilization proteins What is the selective pressure driving their divergence J. Mol. Evol. 44(Suppl. 1) S15-S22. 

The accommodation of some piece of evidence e by some theory T undoubtedly tells us something positive about T—namely that it is at least consistent with e. When, as sometimes happens, it begins to seem as if there is no possible explanation for some evidence within some theory, then even finding an accommodation of that evidence may give scientists more confidence in the theory. Something like this happened, for example, with Darwinian evolutionary theory and the widespread phenomenon of apparently altruistic behaviour—the consistency proof in that case coming in the form of the theories of kin selection and reciprocal altruism. 

Natural selection The differential selection, either positive or negative, of a genetic trait over evolutionary time as reflected in reproductive capacity this mechanism is the central tenet of Darwinian evolution. 

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