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

The motor for an evolutionary trend could lie in a number of principally different evolutionary mechanisms.For example, this could be a result of the action of a certain selection pressure that would last throughout the existence of the particular phylogenetic line.However, it is not clear whether it is possible to assume that a single selection pressure could act over such a long time.In order for a selection pressure to be stronger than the effects of genetic drift, it would have to have a certain minimum intensity.However, this minimum intensity is so large that the relevant selection would result in the species changing its traits over a much shorter period of time than the existence of the species or even the existence of the phylogenetic line.The model of frozen plasticity (IV.9.2) offers a certain solution to this paradox.If a species were to be evolutionarily plastic only immediately following its formation, it could respond to the relevant selection pressure only during this possibly relatively short time period.The anagenesis of the trait would then be interrupted and would occur only in dependence on cladogenesis and the relevant evolutionary trend could extend over an arbitrarily long period of time.