Sexual Orientation

Basically, there are two distinct divisions derived from the biological nature of the humans: the female and the male. Though this division is intended for reproduction purposes and as time progresses longer, various circumstances prompted for the development of sexual orientations among humans. These sexual orientations transcend beyond the biological sexual makeup of humans which are derived from behaviors that can be traced from animal and human predecessors. Evolutionary psychology is one way to trace behaviors such as sexual orientations from preceding events and through this, it will be determined how it can conceive of human sexual orientations focusing on homosexuality.

The process for utilizing evolutionary psychology in determining the origins of sexual orientations among humans entails the study of how animals sexually interact with each other because animals such as the primates are believed to have genetic relations with humans. Thus, these genetic characteristics can be said to be partially linked with human sexual orientation – homosexuality.[1] The orientation of homosexuality can be determined in two factors that are believed to be closely related by using evolutionary psychology. First, the nature of sexuality is a behavior that can be passed on from one generation as an adapted behavior. Another perspective is that sexuality can be a form of a hereditary attribute.

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 Nonetheless, this kind of process provides an evolutionary explanation which concentrates on the reason for behavioral existence.[2] Muscarella further elaborated how sexual orientations, specifically homosexuality, occur similarly with humans and primates. He stated that “for most of its evolutionary history, individuals would have exhibited both heteroerotic and homoerotic behavior, a characteristic seen in closely related to nonhuman primates.”[3] Group mindset which exists in the animal kingdom has an essential role when it comes to survival, especially on primates. It is believed that this need for survival among other animal groups has a lot to do with the greater attachment of young species with the older ones especially on male-male interactions, where the sexual behaviors are shared and in return, protection and social alliance are given.[4] Muscarella indicated on his study that sexual orientations exist because of increased or prolonged exposure of an individual to same sex (homosexual) or to opposite sex (hetero sexual) species. A longer interaction provides an attachment which can in turn become sexual and beneficial at the same time.[5] The relation of humans’ and animals’ sexual behavior especially with the same sex has been deemed as a natural and necessary part of life in order to survive and to achieve status.  Muscarella further stated that “the world appears to have a long history of institutionalized homosexuality between higher status and lower status makes which usually but not always involves significant age differences.”[6] This statement meant that sexual orientation can be a form of adaptive behavior.

Another aspect of evolutionary psychology which conceives of sexual orientations would the biological aspect. There are two separate studies done to show that homosexuality is influenced by biological factors. First of them has been conducted by Camperio-Ciani, Corna, and Capiluppi which focuses on the higher number of “homosexual frequency on the maternal line.”[7] Through a survey of 98 Italian male homosexuals and 100 Italian male heterosexuals they are able to conclude that indeed, there are more homosexuals in the maternal side. This is based on the biological factors which female productivity has on homosexual relatives. One of the possible reasons pointed out on why there are a prevalent number of homosexuals in the maternal line is because of the genetic component in X-chromosome which can be found in the females.[8] The results from the survey also concluded that a higher number of older brothers of a homosexual led to what the authors call “maternal immunization effect.”[9]

This particular study has suggested a possibility on the huge influence of biology in forming or establishing sexual orientation among humans – that homosexuality is not just a product of cultural influence or as a form of adaptive behavior. Another study which focuses about other biological influences of homosexuality is from work of Mustanski, Chivers, and Bailey. They gave further insights regarding the recent biological studies that are made which offer perspectives about the biological components of homosexuality. Such researches focus on hormonal influence and genetic factors which has been two of the main biological aspects pointed out for homosexuality.

It is believed that the hormones affect the physical and behavioral characteristic of a specie as proven by a test that has been conducted on a female guinea pig where it is injected with testosterone having its genitalia appearing more masculine and has mounting behavior than normal female guinea pigs.[10] This kind of result made it to the conclusion that it might be possible to humans since the subject for the experiment is in the mammalian group. The effects of sex hormones have the possibility of having similar effects to humans leading to homosexuality.[11] From this, a hypothesis is derived that “some gay men had decreased levels of circulating testosterone.”[12] This aspect extended further to the study of neurohormonal influences where hormonal characteristics are considered ‘cross-sex’ and has been conducted by using biological methods.

The second aspect that Mustanski and the others have touched upon is the research regarding the genetic influences to sexual orientation. The main hypothesis here is that “gay men are genetically female.”[13] The genetic perspective for homosexuality is similar to the study made by surveying Italian gay and straight men. Answering this hypothesis basing on chromosome structure did not provide an ample amount of evidence. Instead genetic patterns among homosexuals are explored into the study of,

      Family studies where the frequency and pattern of the familiality of homosexuality; twin adoption studies, to partition the population variance in sexual orientation into genetic and environmental components; and molecular genetics studies, to identify specific genes that influence an individuals sexual orientation.”[14]

The various studies that are reviewed by the authors somehow showed aspects in which biological factors contribute to the formation of homosexuality. Some of these factors can be derived before birth and the genetic factors can be evident within family interaction.[15]

From these different perspectives of evolutionary psychology regarding the origins of homosexuality, a study is made by Dr. Nimmons to showcase the causes of homosexuality by focusing on the act of violence. Normally, the biological and psychological being of a male associates him with the tendency for aggression and violence. However, Dr. Nimmons made a statement that gay men – despite of their natural physical makeup as males – are more nonviolent than their straight male counterpart. His analysis delved on police records containing raids and events of brawls and homicide within the city’s bars. He is able to compare that the numbers of assaults and fights in gay bars are lower and almost to zero than the significant high amount of violence inside establishments which cater to straight men.[16]

From the previous studies that have been discussed previously, Dr. Nimmons tried to associate the origination of gay male aggression both from the biological factors and the adaptive behavior coming from the public and private sphere. He refers to the various biological studies which show why despite biological male makeup of gays, they exude a different attitude from straight guys when it comes to violence. Such biological studies included findings that some part of a gay brain anatomy is physically different from the straight, gay men process sound differently, and studies about sibling relations.[17] On the other hand, he provided the social views which opposed biological studies stating that “notions of gay and homosexual – even gender itself – are best viewed as socially constructed boxes,”[18] which can change and can be distorted over time.

Dr. Nimmons somehow posed ambivalent approval for the studies regarding homosexual origins focusing on aggression. He thought of these studies as somehow leaning into the conventional thought that males who become gay have ‘feminine traits’ that is why they do not succumb to violence. The studies that he cited on his work entail prejudice about gays stating that “for whatever reason, we seem to differ from other men in some measurable, repeating, if unseen ways…All this research tells us is that, when it comes to boys and bias, tolerance is for pansies.”[19] Dr. Nimmons considers the attitude of gay men’s nonviolence attitude as a unique and untouched trait of male homosexuality.

He argues that nothing in scholarly studies have discussed this attribute of gay men which he considered as a significant trait of being gay and not just being a boy or man lover. He does not see satisfaction from the researches conducted by the likes of the previous studies discussed in the previous chapter. That the absence of such studies about gay male aggression is due to the fact, that those who conducted the study are outsiders of the gay circle. “Our habits of harmony are woven into our own native knowledge about our gay culture. This pattern could not exist if we didn’t constantly re-enact it each Saturday night we get together. We experience, and expect it to be this way. We create it.”[20]

Evolutionary Psychology may seem to be an ideal process to be able to understand such complex issues like homosexuality. It encompasses nearly all aspect of subjects such as biology, sociology, anthropology, and many others. As such, it can be considered as the most dynamic branch of science. It seems like in the researches that have been conducted by Muscarella, Camperio-Ciani, et al., and Mutanski, et al., focusing on sexuality offered possibilities about the origins of homosexuality both in the biological and social aspect. However, nothing has been made concrete and definite about these studies. It has been pointed out through the analysis of Dr. Nimmons about gay male aggression where both aspects of evolutionary psychology have not satisfied an explanation why gay men are not into violence despite their biological components as males. Homosexuality, as Dr.Nimmons indicated, is a unique culture which cannot be fully understood unless it is experienced.


[1] Andrea Camperio-Ciani, Francesca Corna, and Claudio Capiluppi, “Evidence for maternally inherited factors male homosexuality and promoting female fecundity,” The Royal Society (2004): 1.
[2] Frank Muscarella, “The Evolution of Homoerotic Behavior in Humans,” Journal of Homosexuality 40, no. 1 (2000): 52.
[3] Ibid, 53.
[4] “In some cases it has been suggested that the homosexual behavior reinforces relationships which may contribute to individual survival and ultimate reproductive success” Ibid, 56.
[5] This is derived from mostly isolated and vulnerable hominids which restricted access to the opposite sex and have the ability and opportunity to affiliate with same-sex species. Ibid, 55.

[6] Ibid, 60.
[7] Andrea Camperio-Ciani, et al. “Evidence for maternally inherited factors male homosexuality and promoting female fecundity,” The Royal Society (2004): 2.
[8] Ibid, 3.
[9] The maternal influence in the X-chromosome has a greater effect on the survey rather than the number of older brothers (14% : 6.7%), Ibid, 3.
[10] Brian Mustanski, Meredith l. Chivers, and J. Michael Bailey, “A Critical Review of Recent Biological Research on Human Sexual Orientation,” Annual Review of Sex Research 13, (2002): 91.
[11] Ibid.
[12] Ibid, 92.
[13] Ibid, 111.
[14] Ibid.
[15] Ibid, 129.
[16] David Nimmons, The Soul Beneath the Skin (New York: St. Martin’s Press, 2002), 17-18.
[17] Ibid, 27.
[18] Ibid.
[19] Ibid, 33.
[20] Ibid, 37.


Camperio-Ciani, Andrea., Corna, Francesca., and Claudio Capiluppi. “Evidence for maternally inherited factors male homosexuality and promoting female fecundity.” The Royal Society (2004): 1-5.

Muscarella, Frank. “The Evolution of Homoerotic Behavior in Humans.” Journal of Homosexuality 40, no. 1 (2000): 51-77.

Mustanski, Brian., Chivers, Meredith L., and J. Michael Bailey. “A Critical Review of Recent Biological Research on Human Sexual Orientation.” Annual Review of Sex Research 13, (2002): 89-140.

Nimmons, David. The Soul Beneath the Skin. New York: St. Martin’s Press, 2002.



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