Can Evolvability Be Subject To Darwinian Selection?
This question is very difficult to prove, but theories have been postulated which attempt to explain why evolvability is a selectable trait. The difficulty surrounding selection and evolvability is that evolvability is a trait of lineages as opposed to individuals and this is where the difficulty regarding selection comes in.
Kirschner et al (1998), proposed three reasons as to why they believe evolvability is a selective trait. His first reason relates to individuals. Kirschner believed that robustness within an individual was selected for because it held reward for fitness and development. As a result of robustness being selected for phenotypic variation would result as a by-product and hence evolvability.
His second reason applied to both individuals and clades. A clade is a taxonomic group of organisms all derived from one common ancestor. He stated that robust organisms are more likely to survive, changes in environmental conditions and would be less likely to acquire lethal mutations. As a result these individuals could mate with other clade members and thus when selective conditions change, they will be more likely to survive and diversify and their resultant populations would be selected for.
Kirschner’s final reason applied exclusively to clades. When environments are emptied through widespread extinction, either through ecological change, rapid changes in population density or when organisms enter new domains (i.e., air for birds and winged insects). Clades when introduced to these new environments are exposed to rapid changes and the evolvable mechanism which allows these clades to survive is selected for, thus meaning greater evolvability.
