Appendix I
A Review of Select Publications and Reports on Sexual Dimorphism
“Born gay? The psychobiology of human sexual orientation” — PERGAMON ,
Elsevier Science Ltd, PII: S0191-8869(02)00140-X; http://www.elsevier.com/locate/paid, by
Qazi Rahman, Glenn D. Wilson Department of Psychology, Institute of Psychiatry,
University of London, De Crespigny Park, London SE5 8AF, UK Received 26
November 2001; received in revised form 1 April 2002; accepted 27 April 2002. Qazi
Rahman is supported by the Medical Research Council of the United Kingdom. This
work is also supported by a grant from the British Academy to Dr. Wilson. Extract
and Summary:
Neurodevelopment and the sexual differentiation of the brain
Theories concerning the etiogenesis of sexual orientation that focus on the sexual
differentiation of the brain have enjoyed growing support ... The prenatal
neurohormonal, or androgen theory, following Ellis and Ames’ (1987) classic paper, is
dominant by far, but there are two others; maternal immunization and recently, the
notion of developmental instability. All draw implicitly on the established taxonic
nature of sexual orientation (examined earlier) which implicates a canalization of
prenatal neurodevelopmental processes that could account for the covariation
between sexual orientation and its correlates. Early sex-atypical differentiation of the
brain has been evidenced in several domains: somatic and morphological variations,
neuroanatomy and neuropsychology ...
The evidence for sex differences in neuroanatomy sets the stage for investigations
into within sex dimorphism, notably in the brains of homosexuals and heterosexuals
(Breedlove, 1992; Matsumoto, 2000; Swaab & Hofman, 1995). The first reported
difference in neuroanatomy between homosexuals and heterosexuals showed that the
supra-chiasmatic nucleus (SCN), a region involved with circadian rhythms and sexual
behavior, was larger and more elongated in homosexual men (Swaab & Hofman,
1990).This shape is characteristically found in women.
LeVay (1991) reported that an area of the hypothalamus, the third interstitial nucleus
of the anterior hypothalamus (INAH-3), was smaller in homosexual men than in
heterosexual men. This area is also typically smaller in women (Byne et al., 2000,
2001; LeVay, 1991). Allen and Gorski (1992) reported the midsagittal plane of the
anterior-commissure (AC) to be larger in homosexual men than in heterosexual men
and women, a region larger in women than in men generally (Allen & Gorski,