Theshifting balance theory is a theory ofevolution proposed in 1932 bySewall Wright, suggesting that adaptive evolution may proceed most quickly when apopulation divides intosubpopulations with restrictedgene flow. The name of the theory is borrowed from Wright's metaphor offitness landscapes (evolutionary landscapes), attempting to explain how a population may move across anadaptive valley to a higheradaptive peak. According to the theory, this movement occurs in three steps:

1. Genetic drift allows a locally adapted subpopulation to move across an adaptive valley to the base of a higher adaptive peak.
2. Natural selection will move the subpopulation up the higher peak.
3. This new superiorly adapted subpopulation may then expand itsrange and outcompete orinterbreed with other subpopulations, causing the spread of newadaptations and movement of the global population toward the new fitness peak.

Although shifting balance theory has been influential inevolutionary biology, inspiring the theories ofquantum evolution andpunctuated equilibrium,^[1] littleempirical evidence exists to support the shifting balance process as an important factor in evolution.^[2]

This article includes a list ofgeneral references, butit lacks sufficient correspondinginline citations. Please help toimprove this article byintroducing more precise citations.(December 2012) (Learn how and when to remove this message)

• Wade, M.J.; Goodnight, C.J. (1998)."Perspective: the theories of Fisher and Wright in the context of metapopulations: when nature does many small experiments".Evolution.52 (6):1537–1553.doi:10.1111/j.1558-5646.1998.tb02235.x.PMID 28565332.S2CID 20901475.
• Wright, S (1931)."Evolution in Mendelian populations".Genetics.16 (2):97–159.doi:10.1093/genetics/16.2.97.PMC 1201098.PMID 17246615.
• Wright, S. 1932. The roles of mutation, inbreeding, crossbreeding and selection in evolution. Proceedings of the 6th International Congress of Genetics: 356–366.
• Wright, S.W. (1948)."On the roles of directed and random changes in gene frequency in the genetics of populations".Evolution.2 (4):279–294.doi:10.1111/j.1558-5646.1948.tb02746.x.PMID 18104586.S2CID 30360594.
• Wright, S.W. (1982)."The shifting balance theory and macroevolution".Annual Review of Genetics.16:1–19.doi:10.1146/annurev.ge.16.120182.000245.PMID 6760797.

• Evolutionary biology
• Population genetics

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