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Factors causing fluctuating asymmetry

Fluctuating asymmetry (FA) is often considered to be the product of developmental stress and instability, caused by factors including infections, mutations, and toxins. [1] There are many possible variations which can contribute towards FA.

Genetic factors

Fluctuating asymmetry (FA) may result from a lack of immunity to diseases, as a positive correlation is seen between FA and the number of respiratory infections. [1][2]

Asymmetry may also result from increased levels of mutations and perturbations[1], consequently having a negative impact on genetic fitness.

There is some speculation that inbreeding contributes towards FA, but some evidence shows this is not the case. For example, ant colonies created by an inbreeding queen do not show significantly higher FA than those produced by a non-inbreeding queen. [3]

Environmental factors

Toxins and poisons are considered to increase fluctuating asymmetry (FA). Pregnancy sickness is argued as an adaptation for avoiding toxins during foetal development. Research has reported that when a mother has no sickness or sickness that extends beyond week 12 of gestation, the daughter shows higher FA (as demonstrated by measuring thigh circumferences). [4]

During development, infectious diseases can also lead to FA, as an association between these factors is frequently reported.[1][5]

Fluctuating asymmetry in human males is also seen to positively correlate with levels of oxidative stress. This process occurs when an organism creates excess reactive oxygen species (ROS) compared to ROS-neutralising antioxidants.[6] Oxidative stress may mediate the association seen between high FA and amount of infection during development.[1]

Developmental instability

Links to fitness and reproductive success.

Developmental instability of an organism can be reflected by their fluctuating asymmetry (FA).

Mate preferences and fluctuating asymmetry

Male physical attractiveness is rated lower when they show higher levels of oxidative stress, which is seen to increase as levels of fluctuating asymmetry increase. [6]

See also

Below is a copy/time-save of the main contributions I have made to the wikipedia article: Fluctuating asymmetry.

Causes of fluctuating asymmetry

Fluctuating asymmetry (FA) is often considered to be the product of developmental stress and instability, caused by both genetic and environmental stressors. Various specific factors causing FA include infections, mutations, and toxins.[7] According to Waddington's notion of canalisation, FA is a measure of the genome's ability to successfully buffer development to achieve a normal phenotype under imperfect environmental conditions.[8] This suggests that FA is a result of genetic and environmental factors.

Genetic factors

Increased levels of mutations and perturbations can lead to greater asymmetry.[7] In turn, this negatively impacts an individuals genetic fitness. FA may also result from a lack of genetic immunity to diseases, as those with higher FA show less effective immune responses.[9] Supporting this, there is an association between FA and the number of respiratory infections experienced by an individual, such that those with higher levels of FA have more infections.[7] Increased prevalence of parasites and disease in an organism is also seen more in individuals with greater levels of FA.[9] However, the research in this field is predominantly correlational, so caution must be taken when inferring causation. For example, greater levels of FA may weaken immune responses of an organism, rather than a lack of immunity causing FA.

There is some speculation that inbreeding contributes towards FA, but some evidence shows this is not the case. For example, ant colonies created by an inbreeding queen do not show significantly higher FA than those produced by a non-inbreeding queen.[10]

Environmental factors

During development, infectious diseases can lead to FA, as an association between these factors is frequently reported, such that those with higher FA report more infections.[7][11] Toxins and poisons are also considered to increase FA. Pregnancy sickness is argued to be an adaptation for avoiding toxins during foetal development. Research has reported that when a mother has no sickness or a sickness that extends beyond week 12 of gestation, the daughter shows higher FA (as demonstrated by measuring thigh circumferences). This could suggest that when a mother fails to expel environmental toxins when pregnant, they affect the foetus and lead to FA. [12]

Fluctuating asymmetry in human males is also seen to positively correlate with levels of oxidative stress. This process occurs when an organism creates excess reactive oxygen species (ROS) compared to ROS-neutralising antioxidants.[13] Oxidative stress may mediate the association seen between high FA and amount of infection during development.[7]

Other factors associated with fluctuating asymmetry

Antisocial behaviours

Some studies suggest a link between FA and aggression, but the evidence is mixed. In humans, criminal offenders show greater FA than nonoffenders.[14] However, other studies report that human males with higher FA show less physical aggression[15][16] and less anger[17]. Females show no association between FA and physical aggression,[16] but research has suggested that older female adolescents with higher facial FA are less hostile.[17]

The evidence is also mixed in other animals. In Japanese scorpionflies (Panorpa nipponensis and Panorpa ochraceopennis), FA differences between members of the same sex competing for food determined outcomes of interspecific contests and aggression better than body size or ownership of food.[18][19] Furthermore, cannibalistic laying hens (Gallus gallus domesticus) demonstrate more asymmetry than normal hens. [20] However, this link between FA and aggression is questionable, as victimised hens also showed greater asymmetry. Other research corresponds with this. Hen eggs injected prenatally with excess serotonin (5-HT) exhibited more FA at 18 weeks of age, but demonstrated less aggressive behaviours. It is suggested that the stress introduced during early embryonic stages via excess serotonin may create developmental instability, causing phenotypic and behavioural variations.[21]

References

  1. ^ a b c d e Thornhill, Gangestad, Randy, Steven W. (2008). The evolutionary biology of human female sexuality. Oxford, England: Oxford University Press. pp. 162–168. ISBN 0195340981.{{cite book}}: CS1 maint: multiple names: authors list (link)
  2. ^ Thornhill, Randy; Gangestad, Steven W. "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.
  3. ^ Keller, Laurent; Passera, Luc (1993-09-01). "Incest avoidance, fluctuating asymmetry, and the consequences of inbreeding in Iridomyrmex humilis, an ant with multiple queen colonies". Behavioral Ecology and Sociobiology. 33 (3): 191–199. doi:10.1007/BF00216600. ISSN 0340-5443.
  4. ^ Singh, Devendra; Rosen, Valerie C. "Effects of maternal body morphology, morning sickness, gestational diabetes and hypertension on fluctuating asymmetry in young women". Evolution and Human Behavior. 22 (6): 373–384. doi:10.1016/s1090-5138(01)00082-4.
  5. ^ Møller, Anders Pape (2006-03-01). "A review of developmental instability, parasitism and disease: Infection, genetics and evolution". Infection, Genetics and Evolution. 6 (2): 133–140. doi:10.1016/j.meegid.2005.03.005.
  6. ^ a b Gangestad, Steven W.; Merriman, Leslie A.; Emery Thompson, Melissa (2010-12-01). "Men's oxidative stress, fluctuating asymmetry and physical attractiveness". Animal Behaviour. 80 (6): 1005–1013. doi:10.1016/j.anbehav.2010.09.003.
  7. ^ a b c d e Thornhill, Gangestad, Randy, Steven W. (2008). The evolutionary biology of human female sexuality. Oxford, England: Oxford University Press. pp. 162–168. ISBN 0195340981.{{cite book}}: CS1 maint: multiple names: authors list (link)
  8. ^ WADDINGTON, C. H. "Canalization of Development and the Inheritance of Acquired Characters". Nature. 150 (3811): 563–565. doi:10.1038/150563a0.
  9. ^ a b Fink, Bernhard; Neave, Nick; Manning, John T.; Grammer, Karl (2006-08-01). "Facial symmetry and judgements of attractiveness, health and personality". Personality and Individual Differences. 41 (3): 491–499. doi:10.1016/j.paid.2006.01.017.
  10. ^ Keller, Laurent; Passera, Luc (1993-09-01). "Incest avoidance, fluctuating asymmetry, and the consequences of inbreeding in Iridomyrmex humilis, an ant with multiple queen colonies". Behavioral Ecology and Sociobiology. 33 (3): 191–199. doi:10.1007/BF00216600. ISSN 0340-5443.
  11. ^ Møller, Anders Pape (2006-03-01). "A review of developmental instability, parasitism and disease: Infection, genetics and evolution". Infection, Genetics and Evolution. 6 (2): 133–140. doi:10.1016/j.meegid.2005.03.005.
  12. ^ Singh, Devendra; Rosen, Valerie C. "Effects of maternal body morphology, morning sickness, gestational diabetes and hypertension on fluctuating asymmetry in young women". Evolution and Human Behavior. 22 (6): 373–384. doi:10.1016/s1090-5138(01)00082-4.
  13. ^ Gangestad, Steven W.; Merriman, Leslie A.; Emery Thompson, Melissa (2010-12-01). "Men's oxidative stress, fluctuating asymmetry and physical attractiveness". Animal Behaviour. 80 (6): 1005–1013. doi:10.1016/j.anbehav.2010.09.003.
  14. ^ Lalumière, Martin L.; Harris, Grant T.; Rice, Marnie E. (March 2001). "Psychopathy and developmental instability" (PDF). Evolution and Human Behavior. 22 (2): 75–92. doi:10.1016/S1090-5138(00)00064-7. Retrieved 25 March 2016.
  15. ^ Manning, J. T.; Wood, D. (1998-03-01). "Fluctuating asymmetry and aggression in boys". Human Nature. 9 (1): 53–65. doi:10.1007/s12110-998-1011-4. ISSN 1045-6767.
  16. ^ a b Furlow, Bryant; Gangestad, Steven W.; Armijo-Prewitt, Tara (1998-01-07). "Developmental stability and human violence". Proceedings of the Royal Society of London B: Biological Sciences. 265 (1390): 1–6. doi:10.1098/rspb.1998.0255. ISSN 0962-8452. PMC 1688754. PMID 9470212.
  17. ^ a b Muñoz-Reyes, José Antonio; Gil-Burmann, Carlos; Fink, Bernhard; Turiegano, Enrique (2012-11-01). "Facial asymmetry and aggression in Spanish adolescents". Personality and Individual Differences. 53 (7): 857–861. doi:10.1016/j.paid.2012.06.012.
  18. ^ Thornhill, R. (1992). "Fluctuating asymmetry and the mating system of the japanese scorpionfly, panorpa japonica". Animal Behaviour. 44 (5): 867–879.
  19. ^ Thornhill, Randy (1992-05-01). "Fluctuating asymmetry, interspecific aggression and male mating tactics in two species of Japanese scorpionflies". Behavioral Ecology and Sociobiology. 30 (5): 357–363. doi:10.1007/BF00170603. ISSN 0340-5443.
  20. ^ Yngvesson, Jenny; Keeling, Linda J. (2001-03-01). "Body size and fluctuating asymmetry in relation to cannibalistic behaviour in laying hens". Animal Behaviour. 61 (3): 609–615. doi:10.1006/anbe.2000.1616.
  21. ^ Dennis, Rachel L.; Fahey, Alan G.; Cheng, Heng W. (2013-03-01). "Alterations to Embryonic Serotonin Change Aggression and Fearfulness". Aggressive Behavior. 39 (2): 91–98. doi:10.1002/ab.21459. ISSN 1098-2337.
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