Biology and sexual orientation

The relationship between biology and sexual orientation is a subject of on-going research. While scientists do not know the exact cause of sexual orientation, they theorize that it is caused by a complex interplay of genetic, hormonal, and environmental influences.^[1]^[2]^[3] However, evidence is weak for hypotheses that the post-natal social environment impacts sexual orientation, especially for males.^[4]

Biological theories for explaining the causes of sexual orientation are favored by scientists.^[1] These factors, which may be related to the development of a sexual orientation, include genes, the early uterine environment (such as prenatal hormones), and brain structure. While the evolutionary explanation for heterosexuality in organisms that reproduce sexually is straightforwardly understood to be an adaptation resulting from greater reproductive success, evolutionary explanations for homosexuality rely upon other mechanisms of evolution such as kin selection and inclusive fitness or antagonistic pleiotropy that favors heterozygotes.

^ ^a ^b Frankowski BL (June 2004). "Sexual orientation and adolescents". Pediatrics. 113 (6): 1827–32. doi:10.1542/peds.113.6.1827. PMID 15173519.
^ Lamanna MA, Riedmann A, Stewart SD (2014). Marriages, Families, and Relationships: Making Choices in a Diverse Society. Cengage Learning. p. 82. ISBN 978-1305176898. Retrieved February 11, 2016. The reason some individuals develop a gay sexual identity has not been definitively established – nor do we yet understand the development of heterosexuality. The American Psychological Association (APA) takes the position that a variety of factors impact a person's sexuality. The most recent literature from the APA says that sexual orientation is not a choice that can be changed at will, and that sexual orientation is most likely the result of a complex interaction of environmental, cognitive and biological factors...is shaped at an early age...[and evidence suggests] biological, including inborn hormonal factors which play a significant role in a person's sexuality (American Psychological Association 2010).
^ Stuart GW (2014). Principles and Practice of Psychiatric Nursing. Elsevier Health Sciences. p. 502. ISBN 978-0323294126. Retrieved February 11, 2016. No conclusive evidence supports any one specific cause of homosexuality; however, most researchers agree that biological and social factors influence the development of sexual orientation.
^ Bailey JM, Vasey PL, Diamond LM, Breedlove SM, Vilain E, Epprecht M (September 2016). "Sexual Orientation, Controversy, and Science". Psychological Science in the Public Interest. 17 (2): 45–101. doi:10.1177/1529100616637616. PMID 27113562.

[Frankowski_2004-1] Frankowski BL (June 2004). "Sexual orientation and adolescents". Pediatrics. 113 (6): 1827–32. doi:10.1542/peds.113.6.1827. PMID 15173519.

[Lamanna_2016-2] Lamanna MA, Riedmann A, Stewart SD (2014). Marriages, Families, and Relationships: Making Choices in a Diverse Society. Cengage Learning. p. 82. ISBN 978-1305176898. Retrieved February 11, 2016. The reason some individuals develop a gay sexual identity has not been definitively established – nor do we yet understand the development of heterosexuality. The American Psychological Association (APA) takes the position that a variety of factors impact a person's sexuality. The most recent literature from the APA says that sexual orientation is not a choice that can be changed at will, and that sexual orientation is most likely the result of a complex interaction of environmental, cognitive and biological factors...is shaped at an early age...[and evidence suggests] biological, including inborn hormonal factors which play a significant role in a person's sexuality (American Psychological Association 2010).

[Stuart_2016-3] Stuart GW (2014). Principles and Practice of Psychiatric Nursing. Elsevier Health Sciences. p. 502. ISBN 978-0323294126. Retrieved February 11, 2016. No conclusive evidence supports any one specific cause of homosexuality; however, most researchers agree that biological and social factors influence the development of sexual orientation.

[Bailey_2016-4] Bailey JM, Vasey PL, Diamond LM, Breedlove SM, Vilain E, Epprecht M (September 2016). "Sexual Orientation, Controversy, and Science". Psychological Science in the Public Interest. 17 (2): 45–101. doi:10.1177/1529100616637616. PMID 27113562.

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