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 as fact and theory evaluation of our theories and hypotheses." Fitzhugh concludes that the "certainty" of evolution "provides no basis for elevating any evolutionary theory or hypothesis to the level of fact." Dr William C. Robertson writing for National Science Teachers Association writes, "I have heard too many scientists claim that evolution is a fact, often in retort to the claim that it is just a theory. Evolution isn’t a fact. Rather than claiming so, I think scientists would be better served to agree that evolution is a theory and then proceed to explain what a theory is -- a coherent explanation that undergoes