Biological Explanations of Homosexuality

This paper is aimed to address the question of whether homosexuality is biologically based.

This topic is quite relevant today because homosexuality is a huge civil rights issue which is also conflicting with the church's moral standards. While many religious bodies claim that homosexuality is a choice and a "sin", many in the homosexual community have strongly refuted that claim, instead saying they were born this way and their sexual identity is not a choice for them.Currently one of the biggest debates regarding the rights of homosexuals is same sex marriage . If scientist are indeed able to show evidence that homosexuality is result of biologic or genetic factors and thus not a choice or a morality issue then we as a society might be able to make better headway in legalizing samesex marriage.

Each culture addresses the issue of homosexuality in various ways, while tolerance is slowly gaining momentum in the United States, many other cultures have long accepted and even embraced homosexual like style. Finding a biological explanation is important in helping countries who are strongly influenced by the Catholic churches's moral code to refute the churches' stance that homosexuality is a choice.Literature review In America today there is a large social debate over whether sexual orientation is influenced by environmental or biological factors. If sexual orientation is determined biologically the moral issue of the debate would be be relevant. If however homosexual behavior is a choice or a preference then the stance of homosexuality being immoral may have some justification.Research suggests that left handed homosexual men have less older brothers that expected (Blanchard ; Lippa, 2006).

Compelling evidence has shown that homosexuality in men is associated with having more older brothers and being left handed. Interestingly however having older brothers only increases the probability of developing homosexual behavior in males who are right handed not left handed. Blanchard (2006) recruited 2,486 participants to fill out questionnaires related to sexual orientation, older siblings and hand-preference. The participants were then separated into eight groups based on hand-preference, sexual orientation and sex and a three-way anova was done to compare them.

The results supported the prediction that left handed homosexual men had less older brother than expected. Left handed homosexual men ended up having more older sisters than older brothers and right handed homosexual men had more older brothers than sisters. one weakness in the research is that it cannot be determined if older brothers decrease the chances of homosexuality in left handed men. ANother weakness was that there was no distinction made between "genetic" left-handedness and "pathological" left-handedness.

future research should look at hand preference of family members to distinguish between the two.Previous research suggests that concentrations of sex hormones in fetal umbilical chord blood is related to birth order (Maccoby, Doering, Jacklin ; Kraemer 1979). Research has investigated the relationship of hormone levels and birth order as a potential biological cause of homosexuality in men. When analyzing three groups of newborns and looking at the concentration of five sex hormones from samples of umbilical-chord blood it data suggests that hormonal factors play a role in adult sexual orientation.The five hormones if interest that were assessed were estrone, testosterone, androstenedion, estradol and progesterone.

Past research had indicated that homosexual behavior is a result of postnatal environmental factors such as interaction with siblings and parents. However it has been argued that family environmental factors cannot explain for the differences (Waldrop ; Bell 1966). Research has explored the possibility that variations in hormonal concentrations in the prenatal environment are the main contributors to variation in sexual orientation post birth through studying umbilical chord blood from three samples of newborn infants.Researches conducted a longitudinal study in which behavioral development was being studied in these infants through birth through the age of six (Maccoby, Doering, Jacklin ; Kraemer 1979).

Their main objective was to asses whether and or how a newborn's sex and birth order were related to hormones in the umbilical chord blood. Five sex hormones were measured: progesterone, two estrogens (estrone and estradiol) and two androgens (testosterone and androstendione). The fist sample of infants consisted of 40 males and 35 females, the second consisted of 32 males and 42 females and the third consisted of 53 males and 54 females totaling to 256 newborns born between 1973 and 1974.Only infants with no complications during delivery (including caesarean births) and had an Apgar score of at least 7 were included in the samples. Right after delivery, and severance of the umbilical chord a sample of 12ml of blood was extracted and frozen for hormonal analysis.

After the mother agreed to enter her child in the six year longitudinal study the frozen samples of blood were then later tested for for the five sex hormones of interest, Andrrostenedione ( 4-androstene, 17-dione), testosterone (17?-hydroxy-4-androsten-3-one), estrone (3-hydroxy-1, 5 (10) -estratiene-3), 17 ?-diol), and estradiol (1, 3,5 (10)-estratiene-3), 17?-diol) were estimated in a laboratory by radioimmunoassay methods.Progesterone (4-pregnene-3,20-dione) was analyzed by a competitive method of protein binding. The hormones were then purified to to remove any potentially interfering steroids or contanaments. To study the relationship between birth-order and sex a syple 2x2 analysis of two sexes and first born versus later borns was used as well as a 2x2x3 analysis of two sexes, two birth outers and three samples. for the second and third samples birth order was not evaluated until children were behaviorally assessed at a later time. Due to drop outs (attrition) in the study the number of infants who remained came to a total of 234.

After studying the data collected it could be determined that males had a significantly higher level of testosterone in umbilical chord blood than females and that later-born males had lower levels of testosterone than first-born males. First-borns of both sexes had higher levels estradiol, progesterone anreven estrogen to some extent. the study also recognizes other influences for increase of testosterone in first-born infants such as stress, mothers age, birthweight, and length of labor. while they do recognize other possible variables they state that it is doubtful that these conditions would account for birth-order differences in testosterone.They concluded that only testosterone showed a birth-order effect and only in males. and that progesterone was the hormone that showed birth-order effect regardless of sex.

Another factor which could influence the results obtained was the spacing between births. for some samples this information could not be obtained which resulted in only 218 subjects being analyzed in the study. this because it was found that if more than 4 years passed between a first and second child's birth testosterone levels were relatively equal in male infants.Research examining whether there is a relationship between having older brothers and or sisters influences homosexuality in male children (Banchard, ; Bogart 1996) has indicated that regardless of cultural influences or demographics homosexual men have higher odds of having older brothers than heterosexual men. The subjects were chosen from a sample of 877 gay and straight men between the ages of 19 and 82 years of age from Canada. The homosexual groups mean number of siblings was 2.

43 and the mean age was 38.33 years old.The heterosexuals mean number of siblings was 2.25 and the mean age was 40 years of age. These means were compared with a two tailed t-test and there was no significant difference between means. Due to the negative stigma associated with homosexuality participants were not required to disclose their identity.

Participants were informed that the study was examining the relationship between sexual orientation and family background. the subjects were asked to fill out a 10 min questionnaire,which asked questions relating to paternity and age of siblings born to the same biological mother. Only full siblings from the same mother and father were included. The hypothesis was tested using logistic regression analysis and there were six predictor variables: the number of younger brothers, number of younger sisters, the number of older brothers, the number of older sisters, fathers age, and mothers age.

Their results confirmed their Hypothesis that homosexual men had a higher number of older siblings than heterosexual men, but that there was no relationship with having older sisters, younger sisters or younger brothers. The results showed that the odds of a male developing a homosexual identity increased by 33 percent with each older brother. It is interesting to note that only older brothers affect the chances of a younger sibling being homosexual while number of older sisters has no effect. Another factor could be that a mothers immune system may be able to remember the number of male children she has carried and since male fetuses are more antigenic she may have maternal immune reactions.There have been many studies on the relationship between homosexuality and birth order, however the reason for this relationship is still vague.

It is interesting that there has been no evidence to support that birth order has any effect the sexual orientation of women, while it is the strongest indicator for men. It has been suggested in recent research that the fraternal birth order effect is linked to height (Bogaert ; Liu, 2006). This indicates that the fraternal birth order effect physical development as well as sexual orientation.Interaction of Fraternal Birth Order and Handedness in the development of the male Homosexuality (Blanchard, Cantor, Bogaert, Breedlove, ; Ellis).

the study examines the interaction between two etiological markers of homosexuality in males. These to main factors are hand preference and the fraternal birth order. the fraternal birth order effect is lately based on the maternal immune hypothesis which hypothesized that each male child a woman carries increases her immunization to male-specific antigens by increasing anti-male antibodies which might effect masculinization of the infants brain. other studies ( bog aery, 2005) back up the fraternal birth order effect because the odds of developing homosexual behaviors in later-born males were not influenced by children being raised in different homes.Comparative data on the relationship between the second to fourth digit ratio has indicated a scientific connection between heritability, prenatal hormone transfer, and sexual orientation (Hiraishi, Sasaki, Shikishima, ; Ando, 2012). Using a sample of Japanese twins the relationship between homosexuality and second to fourth digit ratio has been examined.

This ratio may be influenced by prenatal hormones associated with homosexuality. The second to fourth digit ratio is the relative length of the index finger to the ring finger.The Keio Twin Project (KTP) recruited voluntary twin participants aged 14 to 30 years old from Tokyo. Out of the 5, 217 pairs of twins who were recruited, 2, 073 twins agreed to participate in the study.

Part of the research involved questionairs sent by mail which were then analyzed upon return. Included in the questionnaire was the Klein Grid, a questioner that assess sexual orientation, as well as questions about health, eating behavior, economic status, social status. the total number of participants who returned the questionares an a photocopy of their hands was 223.Participants signed consent and were informed of the purpose of the study and their right to drop out.

there were three main measures, Zygosity determination, finger-length measurement, and sexual orientation assessment. Zygosity was determined through physical resemblance and DNA information. there were 75 identical females, and 29 males as well as 22 fraternal females and 9 fraternal males. Sexual orientation was assessed using the Klein Grid which is comprised of questions relating to sexual attraction, sexual behavior, sexual fantasy, emotional closeness, social preference, sexual identification and heterosexual/homosexual life style during three phases in life (past, present, and future)Finger-length measurement ratios were calculated from measurements taken from the photocopies of left and right hands of the participants.

due to poor photocopies some images were excluded. they conducted a two-way mixed factorial ANOVA with right-left hands as the within-participants factor and sex as the between-participants factor. there was a big difference between sex, males had a much smaller 2D:4D than Females. also the right hand 2D:4D was much larger on the right hand. they found that non-heterosexual male MZ twins had larger and more feminized than their heterosexual co-twinsSexual Orientation in a U.

S. National Sample of Twin and Non-twin Sibling Pairs (Kendler, Thornton, Gilman, ; kessler 2000) this study rejects the proposal that homosexuality is simply learned behavior and analyzes genetic factors that may be playing a role in homosexualitySynthesisthe biq question being raised is whether homosexuality is a product of Biology or learning. There is quite a lot of research that presents evidence for prenatal causes of homosexuality. the maternal immune theory is well established because it relies on the very reliable fraternal birth order effect. there is also evidence from twin studies that indicates that homosexuality may be genetically heritable, or a result of the maternal immune theory because they shared the same prenatal environment.Conclusion if research in the field of biology can prove that homosexuality is biologically based, discrimination against homosexuals would most likely decrease because the argument that it is a choice could not be supported.

There is quite a lot of research that presents evidence for prenatal causes of homosexuality. the maternal immune theory is well established because it relies on the very reliable fraternal birth order effect. there is alsoThe Cause(s) Of Fraternal Birth Order Effect In Male Homosexuality (wiliam, James. 2004) aimed to research the Fraternal Birth Order Effect in Homosexuality. It has been established in previous research (ellis; Blanchard) ; (Bogart at al, 1997) ; (Green, 2000) that having a significant number of older brother can be an indicator to a higher likely hood of homosexuality, bisexuality and male-to female- transexuals.

The Fraternal Firth Order effect is a Theory that the more older Brothers, not sisters, a man had the more likely he is to be a homosexual.