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Transsexuals and Birth Order March 21, 2010

Posted by Geekgirl in Gender Identity, heredity, in the womb, transsexual.

Arch Sex Behav. 2010 Mar 16. [Epub ahead of print]

Birth Order and Ratio of Brothers to Sisters in Spanish Transsexuals.

Gómez-Gil E, Esteva I, Carrasco R, Almaraz MC, Pasaro E, Salamero M, Guillamon A.

Unidad de Identidad de Género, Instituto Clínic de Neurociencias, Servicio de Psiquiatría, Hospital Clínic, Universidad de Barcelona, Barcelona, Spain, esgomez@clinic.ub.es.

Three Western studies have shown that male-to-female (MF) homosexual transsexuals tend to be born later than their siblings and to come from sibships with more brothers than sisters. The objective of this study was to determine whether these variables would be replicated in 530 MF and female-to-male (FM) Spanish transsexuals according to sexual orientation. The results showed that MF homosexual transsexuals had significantly more older brothers than the non-homosexual MF group. Compared with the expected rates in the general population, birth order was significantly higher in both MF (Slater’s Index = 0.59; Fraternal Index = 0.61; Sororal Index = 0.58) and FM homosexual transsexuals (Slater’s Index = 0.65; Fraternal Index = 0.68; Sororal Index = 0.67), and sibling sex ratio was significantly higher than expected in homosexual MF (sex ratio = 0.55) but not in homosexual FM transsexuals. No significant differences were found in the non-homosexual subgroups. The replication of the later birth order and sibling sex-ratio effect in MF homosexual transsexuals corroborates previous findings in a variety of groups from different cultures and may suggest a common mechanism underlying the etiology of transsexualism.

PMID: 20232130 [PubMed – as supplied by publisher]



1. Cristan - March 22, 2010

What is a “male-to-female (MF) homosexual transsexual”? I would think that it would mean that this study is researching lesbian-identified transsexuals since are are talking about female-identified transwomen. However, I’m betting that the study is actually tracking heterosexual-identified transwomen and that the researchers are showing that their basic understanding of transsexuals hasn’t yet progressed further than the scholarly views of 1980.

Geekgirl - March 22, 2010

That is a really good question! I didn’t even pick up on that. Since the article is from Spain, I wonder if something was lost in translation?
I only have access to the abstract, I’ll see if I can locate more information.
Good catch, Cristan.

2. science_girl - March 22, 2010

“may suggest a common mechanism underlying the etiology of transsexualism” is pure speculation. Correlation does not equal causation.

3. Emelye Waldherr - March 24, 2010

The term, “homosexual transsexual” must have been taken from the widely discredited and reviled by the trans community, theories of Dr Raymond Blanchard and is associated with the “autogynephilia” diagnosis he invented. The use of the term may be based in the ignorance or bias of the translator. I suggest they research the controversy over Dr Blanchard’s unproven theory and modify their rhetoric accordingly.

Without reading the whole study I cannot be certain but I suspect the use of the term doesn’t affect the results, however. Once again, we have additional evidence of biological influences that cause gender incongruence in transsexuals. Studies like this need to be more widely publicized so the general population gets educated about trans issues.

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