Frozen plasticity theory
This theory suggests a mechanism of the origin of adaptive traits in sexual organisms. The classical Darwinian mechanism of the origin of adaptive traits by natural selection can explain the evolution of such traits only under a very special situation, e.g., in a genetically homogeneous population of asexual organisms. The frozen plasticity theory is much more general: It can also explain the origin and evolution of adaptive traits in a genetically heterogeneous population of sexual organisms.
The frozen plasticity theory suggests that sexual species can evolve new adaptations by accumulation of random mutations only when their members are genetically uniform, i.e., only after a portion of the population of the original species has split off, balanced on the edge of extinction for several generations, and then undergone rapid expansion. After a short period of time, corresponding to 1-2% of the duration of the species (estimated on the basis of paleontological data), polymorphism accumulates in the gene pool due to frequency-dependent selection; and thus, in each generation, new mutations occur in the presence of different alleles and therefore change their selection coefficients from generation to generation. The species ceases to behave in an evolutionarily plastic manner and becomes evolutionarily elastic on a microevolutionary time-scale and evolutionarily frozen on a macroevolutionary time-scale. It then exists in this state until such changes accumulate in the environment that the species becomes extinct.
The first version of the theory of frozen plasticity was presented in the paper: On the "origin" of natural selection by means of speciation. Flegr J. 1998, Riv Biol -Biol Forum 91:291-304.
Current version of the theory was presented in the papers:Flegr J. 2010: Elastic, not plastic species: Frozen plasticity theory and the origin of adaptive evolution in sexually reproducing organisms. Biology Direct, 5:2..
and in Flegr J. 2013: Microevolutionary, macroevolutionary, ecological and taxonomical implications of punctuational theories of adaptive evolution. Biology Direct, 8:1..