Fluctuating asymmetry

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Fluctuating asymmetry is one way in which an organism can deviate from bilateral symmetry, others being anti-symmetry and directional asymmetry.[1] Fluctuating asymmetry is defined as a random asymmetry about a zero mean value, usually of a low magnitude. It can be measured in the body—as in bilateral symmetry of finger lengths—or in a particular organ. It is related to concepts of symmetry such as facial symmetry, and is believed to measure the ability of the genome to successfully canalize and buffer development to achieve a normal phenotype under imperfect environmental conditions, as implied by Waddington's notion of canalization.[2] As such it is a key concept in evolution and development, and underlies concepts such as resilience or developmental stability—the ability to maintain a normal developmental course under stress.[1] More specifically, disease and infection are examples of environmental stressors associated with FA.[3] FA is positively correlated with the prevalence of parasites and disease in an organism, and negatively correlated with effective immune responses.[4] FA is a common tool to measure developmental stability of an organism, where a large FA suggests a low developmental stability [5] One specific example illustrating such a positive correlation is the relationship between a mother's morning sickness and the daughter's FA.[6] Morning sickness seems to be an adaptation for voiding and avoiding toxins during early fetal life, creating a positive correlation between morning sickness and thigh girth FA .[6] This interest to the application of FA as a measure of developmental stability has looked at studies on inbreeding and outbreeding depression, studies measuring genetic or environmental stress and measures of mate quality for sexual selection.[7][8][9][10]

In individual differences research, FA has been found to have a negative correlation to measurements of human traits such as social dominance,[11] working memory,[12] and intelligence.[13][14][15] In old age, facial symmetry has been associated with better cognitive aging.[16] Symmetry has been shown to affect physical attractiveness,[17] with humans exhibiting a preference for symmetrical faces.[18] Facial symmetry has also been positively correlated with higher occurrences of mating.[19] It has also been shown that FA is negatively correlated with IQ.[20] This is also shown to be the case with FA and facial attractiveness in men. It has been suggested this negative correlation may be due to our perceptions of attractiveness developing based upon developmental quality. [21] Other studies have also found that the voices of men and women with low fluctuating asymmetry are rated as more attractive,[22] suggesting that voice may be indicative of developmental stability. Additionally, fluctuating asymmetry has been shown to predict atypical asymmetry of the brain [23] Research has additionally shown that growth rates after birth positively correlate with FA. For example increased FA has been found in people who were currently obese. [24] It has been shown that women's fluctuating asymmetry of thighs (FAT) can be predicted by their mother's morning sickness during the third trimester of pregnancy.[25]

Research has also shown that the female partners of men with lower levels of fluctuating asymmetry (FA) experience a higher number of copulatory orgasms, compared to the female partners of males with higher levels of FA.[26]

There is no gender difference in the susceptibility of diseases depending on body fluctuating asymmetry (FA).[27]


  1. ^ a b Valen, Leigh Van (June 1962). "A Study of Fluctuating Asymmetry". Evolution 16 (2): 125–142. doi:10.2307/2406192. JSTOR 2406192. 
  2. ^ Waddington, Conrad Hal (1957). The Strategy of the Genes. George Allen & Unwin. p. 262. 
  3. ^ Thornhill, Randy; Gangestad, Steven W. (2008). The Evolutionary Biology of Human Female Sexuality. New York: Oxford University Press. p. 174. ISBN 978-0-19-534098-3. 
  4. ^ Møller, Anders Pape (2006). "A review of developmental instability, parasitism and disease: Infection, genetics and evolution" (PDF). Infection, genetics and evolution. doi:10.1016/j.meegid.2005.03.005. 
  5. ^ Zakharov V. M. 1989. Future prospects for population phenogenetics. Soviet Scientific Reviews, Sec. F, Physiology and General Biology Reviews 4 (3): 1-79.
  6. ^ a b Singh, D., Rosen, V. C. (2000). "Effects of maternal body morphology, morning sickness, gestational diabetes and hypertension on fluctuating asymmetry in young women.". Evolution and Human Behaviour, 22, 373-384. 
  7. ^ Graham, J. H. 1992. Genomic coadaption and development stability in hybrid zones. Acta Zool. Fenn. 191: 121-132.
  8. ^ Graham, J. H., D. C. Freeman and J. M. Emlen. 1993. Developmental stability: A sensitive indicator of populations under stress, pp. 1366158. /)I W. G. Landis, J. S. Hughes and M. A. Lewis (Eds.), Environmental Toxicology and Risk Assessment. American Society for Testing and Materials, Philadelphia, PA.
  9. ^ Tomkins, J. L. and L. W. Simmons. 1995. Patterns of fluctuating asymmetry in earwig forceps: No evidence for reliable signalling. Proc. Roy. Sot. Lond. B 259: 89-96.
  10. ^ Moller, A. P. 1994. Sexual Selection and the Barn Swallow. Oxford University Press. Oxford.
  11. ^ Furlow, B; Gangestad, SW; Armijo-Prewitt, T (1998-01-07). "Developmental stability and human violence.". Proceedings of the Royal Society B 265 (1390): 1–6. doi:10.1098/rspb.1998.0255. PMC 1688754. PMID 9470212. 
  12. ^ Yeo, RA; Hill, D; Campbell, R; Vigil, J; Brooks, WM (2000). "Developmental instability and working memory ability in children: a magnetic resonance spectroscopy investigation.". Developmental neuropsychology 17 (2): 143–59. doi:10.1207/S15326942DN1702_01. PMID 10955200. 
  13. ^ Furlow, FB; Armijo-Prewitt, T; Gangestad, SW; Thornhill, R (1997-06-22). "Fluctuating asymmetry and psychometric intelligence.". Proceedings of the Royal Society B 264 (1383): 823–9. doi:10.1098/rspb.1997.0115. PMC 1688437. PMID 9265189. 
  14. ^ Bates, T (1 January 2007). "Fluctuating asymmetry and intelligence". Intelligence 35 (1): 41–46. doi:10.1016/j.intell.2006.03.013. 
  15. ^ Prokosch, M; Yeo, R; Miller, G (1 April 2005). "Intelligence tests with higher -loadings show higher correlations with body symmetry: Evidence for a general fitness factor mediated by developmental stability". Intelligence 33 (2): 203–213. doi:10.1016/j.intell.2004.07.007. 
  16. ^ Penke, Lars; Bates, Timothy C.; Gow, Alan J.; Pattie, Alison; Starr, John M.; Jones, Benedict C.; Perrett, David I.; Deary, Ian J. (1 November 2009). "Symmetric faces are a sign of successful cognitive aging". Evolution and Human Behavior 30 (6): 429–437. doi:10.1016/j.evolhumbehav.2009.06.001. 
  17. ^ Wade, T. J. (2010). "The Relationships between Symmetry and Attractiveness and Mating Relevant Decisions and Behavior: A Review". Symmetry 2 (2): 1081. doi:10.3390/sym2021081. 
  18. ^ Grammer, Karl; Thornhill, Randy (1994). "Human (Homo sapiens) Facial Attractiveness and Sexual Selection: The Role of Symmetry and Averageness". Journal of Comparative Psychology 108 (3): 233–242. 
  19. ^ Thornhill, R; Gangestad, S (1994). "Fluctuating asymmetry and human sexual behaviour". Psychological Science 5: 297–302. 
  20. ^ Bates, Timothy C. (2007-01-01). "Fluctuating asymmetry and intelligence". Intelligence 35 (1): 41–46. doi:10.1016/j.intell.2006.03.013. 
  21. ^ Gangestad, S. W., Thornhill, R., Yeo, R. A. (1994). Facial attractiveness, developmental stability, and fluctuating asymmetry. Ethology & Sociology, 15, 73-85.
  22. ^ Little, A. C., Jones, B. C., & DeBruine, L. M. (2011). Facial attractiveness: evolutionary based research. Philosophical Transactions of the Royal Society of London B: Biological Sciences, 366, 1638-1659.
  23. ^ Davis, J. T; Gangestad, S. W; Lewine, J. D; Thoma, R. J; Yeo, R. A (2002). "Fluctuating asymmetry and the human brain". Laterality: Asymmetries of Body, Brain and Cognition 7: 45–58. 
  24. ^ Wells, Jonathan C. K.; Hallal, Pedro C.; Manning, John T.; Victora, Cesar G. (2006-02-01). "A trade-off between early growth rate and fluctuating asymmetry in Brazilian boys". Annals of Human Biology 33 (1): 112–124. doi:10.1080/03014460500480391. ISSN 0301-4460. PMID 16500816. 
  25. ^ Singh, D., & Rosen, V. C. (2001). Effects of maternal body morphology, morning sickness, gestational diabetes and hypertension on fluctuating asymmetry in young women. Evolution and Human Behavior, 22, 373-384.
  26. ^ Thornhill, Randy; Gangestad, Steven W.; Comer, Randall (1995). "Human female orgasm and mate fluctuating asymmetry" (PDF). Animal Behaviour 50: 1601–1615. doi:10.1016/0003-3472(95)80014-X. Retrieved 9 February 2016. 
  27. ^ "Gangsted2006">Gangsted, Steven; Thornhill, Randy (March 2006). "Facial sexual dimorphism, developmental stability, and susceptibility to disease in men and women". Evolution and Human Behavior 27 (2): 131–144. doi:10.1016/j.evolhumbehav.2005.06.001. Retrieved 8 February 2016.