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

The ability of organisms to adaptively respond to environmental changes (evolvability) is usually considered to be an important advantage in interspecific competition. It has been suggested, however, that evolvability could be a double-edged sword that could present a serious handicap in fluctuating environments. The authors of this counterintuitive idea have published only verbal models to support their claims. Here we present the results of individual-based stochastic modelling of competition between two asexual species differing only by their evolvability. They show that, in changeable environments, less evolvable species could outperform their more evolvable competitors in a broad area of a parameter space, regardless of whether the conditions fluctuated periodically or aperiodically. Highly evolvable species prospered better nearly all the time; however, they sustained a higher probability of extinction during rare events of the rapid transient change of conditions. Our results offer an explanation of why sexually reproducing species, with their reduced capacity to respond adaptively to local or temporal environmental changes, prevail in most eukaryotic taxa in nearly all biotopes on the surface of Earth. These species may suffer several important disadvantages in direct competitive battles with asexual species; however, they might win in changeable environments in the more important sorting-according to-stability war

In a macroevolutionary timescale, evolvability itself evolves. Lineages are
sorted based on their ability to generate adaptive novelties, which leads to the optimization
of their genotype-phenotype map. The system of translation of genetic or
epigenetic changes to the phenotype may reach significant horizontal and vertical
complexity, and may even exhibit certain aspects of learning behaviour. This continuously
evolving semiotic system probably enables the origin of complex yet functional
and internally compatible adaptations. However, it also has a second, Bdarker^, side. As
was pointed out by several authors, the same process gradually reduces the probability
of the origination of significant evolutionary novelties. In a similar way to the evolution
of societies, teachings, or languages, in which the growing number of internal linkages
gradually solidifies their overall structure and the structure or interpretation of their
constitutive elements, the evolutionary potential of lineages decreases during biological
evolution. Possible adaptations become limited to small Bperipheral^ modifications.
According to the Frozen Evolution theory, some of the proximate causes of this
Bmacroevolutionary freezing^ are more pronounced or present exclusively in sexual
lineages. Sorting based on the highest (remaining) evolvability probably leads to the
establishment of certain structural features of complex organisms, e.g. the modular
character of their development and morphology. However, modules also Bmacroevolutionary
freeze^ whereas the hypothetical Bthawing^ of modules or their novel adaptive
combinations becomes rarer and rarer. Some possible ways out of this dead end include
the rearrangement of individual development, e.g. neoteny, radical simplification, i.e.
sacculinization, and transition to a higher level of organization, e.g. symbiosis or symbiogenesis. The evolution of evolvability is essentially a biosemiotic process situated
at the intersection of the genocentric modern synthesis and the evo-devo-centric
extended synthesis. Therefore, evolvability may eventually connect these three not
necessarily contradictory approaches.