Shifting balance theory Shifting balance theory The shifting balance theory is a theory of evolution proposed in 1932 by Sewall Wright, suggesting that adaptive evolution may proceed most quickly when a population divides into subpopulations with restricted gene flow. The name of the theory is borrowed from Wright's metaphor of fitness landscapes (evolutionary landscapes), attempting to explain how a population may move across an adaptive valley to a higher adaptive peak. According to the theory, this movement occurs in three steps: Although shifting balance theory has been influential in evolutionary biology, inspiring the theories of quantum evolution and punctuated equilibrium, little empirical evidence
Evolution of ageing unable to replicate that chromosome without cutting into genes. The dilemma is that classical evolutionary theory says that what is maintained in a lineage is that which ensures the viability of an organism and its offspring. Ageing can only cut off an individual's capacity to reproduce. So, according to classical theory, ageing could "only" evolve as a side effect, or epiphenomenon of selection. The disposable soma theory and antagonistic pleiotropy theory are examples in which a compensating individual benefit, compatible with classical evolution theory (See neo-Darwinism) is proposed. Nevertheless, there is accumulated evidence that ageing looks like an adaptation in