Frozen Evolution. Or, that’s not the way it is, Mr. Darwin. A Farewell to Selfish Gene.

We most often encounter a situation where the distribution of the frequency of individual phenotypes prior to selection and after selection have the same mean (same position of the maximum frequency); however, the distribution following selection is much narrower, as particularly individuals with extreme values of the monitored trait (the smallest and the largest) were removed from the population.This type of selection is called stabilizing or normalizing or centripetal (Fig. IV.7).. If the population is present under unchanging conditions, there is usually an optimal value of each quantitative trait, for example optimal body length.During evolution, the action of natural selection generally establishes a frequency of the alleles of the individual genes affecting the particular quantitative trait, so that most of the progeny formed through genetic recombination exhibit the optimal or almost optimal phenotype and are thus least affected by natural selection.Šmalgauzen and Waddington (Waddington 1953a)used the term stabilizing selection in a somewhat different sense (selection of alleles reducing the ability of aberrant genes to affect the phenotype).