Homosexuality - is it genetic?
Over the years there has been considerable debate about whether homosexuality is genetic -Â biologically determined by our DNA and genesÂ - or whether it is the result of environmental and other factors. This is often described as the 'nature v nurture' debate.
Over the years numerous research projects have been conducted. However there is no conclusive evidence that homosexuality is genetic.Â
Even Science Daily, in reporting in 2012 on the latest research proposal (on epigenetics), stated, "However, no major gene for homosexuality has been found despite numerous studies searching for a genetic connection."
The issue is of particular importance, since there are some who claim that if one is 'born that way' then you cannot change...
The book can be downloaded on his website. Click here for the 'My Genes' website.
NARTH - National Association forÂ Research &Â Therapy of Homosexuality
List of articles on NARTH website addressing the 'born that way' or 'genetic' theory.
Reprints/synopses of NARTH conference articles/reports and synopses of articles/resources.
The Biological Research on HomosexualityÂ
Studies on 'genes'
There have been three main studies conducted regarding homosexuality and genetics. Often those conducting the research are homosexuals themselves and are sometimes activists.
The results from the studies have never been replicated - and sometimes even theÂ researchers themselvesÂ have commented that the popular media have 'magnified' and expanded the results.
1. Dean Hamer - X chromosome
Dean Hamer investigated the X chromosomeÂ - but the results were inconclusive. They have not been replicated.
2. Pillard and Bailey - Twin studies
Of course, if it really was 'genetic' it should be 100% for identical twins since they share the same genes!
Bailey did a more authoritative study on Australian twins in 2000, using the Australian Twin Register to get people for the study. He acknowledged the 'selection bias' in his previous sample. The result was much lower. Neil Whitehead notes, "Jones and Yarhouse, for the important Australian Bailey et al. (2000) SSA twin study paper, find that for self-declared lesbians and homosexual men the pairwise concordance is 14% and 11% respectively." See My Genes Ch 10.
Neil also describes the difference between probandwise concordance (which is often used in the official studies - where each 'match' is counted twice, one for EACH of the homosexual brothers! This gives a 'higher figure') and pairwise concordance, which asks the question, "If one twin of an identical pair is SSA, what percentage of co-twins are also SSA?"
Jones and Yarhouse note that Bailey et al actually wrote that the study "did not provide statistically significant support for the importance of genetic factorsâ€ť for homosexual orientation." Jones and Yarhouse wrote a book - but a good overview of the book is here.
Even in the Australian study people on the Twins Register were asked if they would answer questions on sex - if they agreed they were sent a questionnaire. 28% refused to participate and 54% completed a questionnaire.
The Australian study: Genetic and Environmental Influences on Sexual Orientation and Its Correlates in an Australian Twin SampleÂ [Personality Processes and Individual Differences]
Discussion of the study in the following article:
Neil Whitehead has analysed the results of such studies. He writes, "From six studies (2000-2011): if an identical twin has same-sex attraction the chances that the co-twin has it too are only about 11% for men and 14% for women. This means that factors the twins have in common, such as genes and upbringing are mostly not responsible â€“ individual and idiosyncratic responses to random events and to common factors predominate." Source.
A 2013 article by Bryan Fischer of the American Family Association, refers to Jason Collins, a US basketballer 'coming out' as a homosexual. First, it is noted that he had a female fiancee for eight years!Â
Almost immediately the pro-homosexual groups starting labelling the AFA and Bryan Fischer as a 'hate group' - see here - and the article was removed!
3. Simon Le Vay - hypothalamus
In 1991, Le Vay published "A difference in hypothalamic structure between heterosexual and homosexual men" in Science. The study reported that the hypothalamus of homosexual and heterosexual men were different. However the data was not conclusive.
A further study on the hypothalamus was published in 2001 by Byrne and others.
Research into other possible 'causes'
Other possible 'causes' for homosexuality have been investigated. Some research has been done about the possibility of the influence of hormones in the womb. Other studies have looked at the 'fraternal birth order effect (FBOE)' - part of that is a speculation that a mother's body produces antibodies whilst pregnant that leads to the child being homosexual.
Dr Warren Throckmorton writes about one study investigating this. He notes that there is no actual evidence for this theory, but that there were numerous headlines announcing the 'study' and the 'results'!
He then notes that the media ignored another study, in 2002, published in the American Journal of Sociology, by Peter Bearman (Columbia) and Hannah BrĂĽckner (Yale). They studied factors related to same-sex attraction. They assessed 20,745 young people, and attributed homosexuality to environment and sociological factors and found NO link to the fraternal birth order 'theory'.
They concluded, â€śOur results support the hypothesis that less gendered socialization in early childhood and preadolescence shapes subsequent same-sex romantic attraction.â€ť They added, "If same-sex romantic attraction has a genetic component, it is massively overwhelmed by other factors."