Homosexuality & Genetics

The history of the biological determination of homosexuality which aims to find inborn characteristics which determine sexual orientation contrasts with the approach which treats sexual orientation as a social construct.

• Simon LeVay, (1991), “A Difference in Hypothalamic Structure Between Heterosexual and Homosexual men” in the Simon LeVay sectionThe investigation used the brains of 35 men, most of whom had died of AIDS, and the brains of 6 women. It was found that the hypothalamus was smaller in the gay-identified men (and women) than in the heterosexual men.
• Laura S. Allen and Roger A. Gorski, (1992), “Sexual orientation and the size of the anterior commissure in the human brain”At the University of California an investigation looked at the anterior commissure (a bundle of nerve fibres interconnecting the two cerebral hemispheres) of the brains of 109 men, 34 of whom identified as gay. The structure was larger in the gay-identified men than the heterosexual men.
• Sandra Witelson, (1994)At McMaster University in Canada an investigation of the corpus callosum of the brain found that it was 13% thicker in gay-identified men.
• Jeff Hall and Doreen Kimara, (1994), “Dermatoglyphic asymmetry and sexual orientation in men”At the University of Western Ontario, the fingerprints of 66 gay-identified men and 182 heterosexual men were examined and it was found that 30% of the gay men had more ridges on their left hand than their right, compared with 14% of the heterosexual men.This result may be important because fingerprints are known to be largely set for life by 16 weeks after conception, and therefore are unlikely to be determined by lifestyle.

  See also Prints put the finger on gays, 8th. February, 1998.

• Simon LeVay and Dean H. HamerData pooled from six different twin studies showed that 50% of identical twins of lesbians also self-identified as lesbians, compared with 16% of fraternal twin sisters, and 13% of singlet sisters. The same number (13%) of singlet brothers of gay men also self-identified as gay, but a higher percentage of gay male identical (57%) and fraternal (24%) twins reported the same sexual self-identification.
• Dean H. Hamer, Stella Hu, Victoria L. Magnuson, Nan Hu, and Angela M. L. Pattatucci, (1993), “A Linkage Between DNA Markers on the X Chromosome and Male Sexual Orientation” in the Dean Hamer sectionTaking 40 families in which two brothers were gay, the brothers’ X chromosomes were examined and it was found that 33 of the 40 pairs of brothers shared a marker at the tip of the X chromosome, the Xq28 region. A control group of 314 pairs of brothers drawn from the general population showed a sharing of the marker in about 50% of the cases.

• SOURCE: http://www.knittingcircle.org.uk/genehistory.html