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
The Neutral Theory of Molecular Evolution in Darwinian evolution a slow pattern of selection in genetic lineages with increasing fitness through generations is expected. The molecular evidence showed that DNA changes more often than what was originally expected and no real pattern was found. Polymorphisms in proteins that have no effect to the function are neutral or nearly neutral and do not get selected for or against at all. This theory would mean that each change in DNA that is passed on to the next generation does not result in a morphological change that can be acted upon by natural selection. Genetic drift, or the result