[[Causes of Homosexuality|Homosexuality has a number of causal factors]] that influence its ultimate origination in individuals; these factors will be addressed shortly. In addition, homosexuality has a variety of effects on individuals and [[society]]. Next, some of the historical events, [[Religion|religious]] matters, and [[law|legal]] matters relating to homosexuality will be covered. Finally, the latter part of the 20th century has seen a [[Homosexuality Research|large body of research]] on the [[Causes of Homosexuality|causes]] and effects of homosexuality.
===Homosexuality in Nature===
====Xenoestrogens and Xenoandrogens====
Environmental chemicals, specifically sex steroids such as [[xenoestrogens]] and [[xenoandrogens]], cause effects on the brain's gender preference and can result in homosexuality in nature.<ref name=hines>{{cite journal |last=Hines |first=Melissa |last2= |first2= |date=2011-02-17 |title=Prenatal endocrine influences on sexual orientation and on sexually differentiated childhood behavior |url=http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3296090/ |journal=Frontiers in Neuroendocrinology |volume=32 |issue=2 |pages=170-182 |doi=10.1016/j.yfrne.2011.02.006 |pmid=21333673}}</ref> Xenoestrogens and xenoandrogens alter the brain's [[sexual differentiation]] in a number of species, including rams, ferrets, zebra finches<ref>{{cite journal |last=Roselli |first=C.E. |last2=Stormshak |first2=F. |date=2009 |title=Prenatal Programming of Sexual Partner Preference |url=http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2668810/ |journal=J. Neuroendocrinol |volume=21 |issue=4 |pages=359-364 |doi=10.1111/j.1365-2826.2009.01828.x |pmid=19207819}}</ref>, gulls, primates, and rodents, resulting in the masculinization of female brains/behavior (e.g. 'lesbian gulls') and feminization of male brains/behavior. Due to concern over environmental health risks [[endocrine disruption]] was the primary theme of the 27th International Neurotoxicology Conference.<ref name=intersect>{{cite journal |last=Weiss |first=Bernard |last2= |first2= |date=2013-12-01 |title=The Intersection of Neurotoxicology and Endocrine Disruption |url=http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3458140/ |journal=Neurotoxicology |volume=33 |issue=6 |pages=1410-1419 |doi=10.1016/j.neuro.2012.05.014 |pmid=22659293}}<br>{{cite journal |last=He |first=Zhen |last2=Ferguson |first2=Sherry Ann |last3=Cui |first3=Li |last4=Greenfield |first4=Lazar John |last5=Paul3 |first5=Merle Gale |date=2013-10-15 |title=Development of the sexually dimorphic nucleus of the preoptic area and the influence of estrogen-like compounds |url=http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4145994/ |journal=Neural Regen Res |volume=8 |issue=29 |pages=2763–2774 |doi= |pmid=25206587}}<br>{{cite journal |last=Svechnikov |first=Konstantin |last2=Stukenborg |first2=Jan-Bernd |last3=Savchuck |first3=Iuliia |last4=Söder |first4=Olle |date=2014 |title=Similar causes of various reproductive disorders in early life |url=http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3901882/ |journal=Asian Journal of Andrology |volume=16 |issue=1 |pages=50-59 |doi=10.4103/1008-682X.122199 |pmid=24369133 }}</ref>
== Biblical statements concerning homosexuality ==