“Sexual Dimorphism and Homosexual Gender Identity”, 1970 (; similar):
Proposes that the classification of homosexuality as hereditary or constitutional vs. acquired is outmoded. It is suggested that the differentiation should be between chronic, obligative, or essential vs. transient, facultative, or optional.
Cytogenetics and statistical genetics do not elucidate etiology, but new research on fetal hormonal differentiation of sexual morphology, and especially of sexually dimorphic hypothalamic differentiation offers promising leads. The sum total of the sex-differential effects of assignment and rearing on gender identity differentiation is known, through observations of hermaphrodites, to be profound.
Postpubertally, homosexuality does not correlate with hormonal measures presently available or with assessments of neuroperceptual sex differences in erotic arousal. It is concluded that sexual dimorphism of brain functioning in gender identity is the end product of sequential events of critical periods, with pre-natal and postnatal effects interacting, and the end product being extremely durable.