Biodemographic comparisons of homosexual and heterosexual men in the kinsey interview data

Abstract

Relations between sexual orientation and several biodemographic variables previously reported to differentiate between homosexual and heterosexual men were examined. Subjects were 4948 white, postpubertal males, who were never reared in foster homes, orphanages, or other institutions, and were never arrested or convicted on criminal charges. These were dichotomously classified as homosexual (n = 844) or heterosexual (n = 4104). Data came from survey interviews conducted by staff members of The Kinesey Institute for Research in Sex, Gender, and Reproduction from 1938 to 1963. Results extended previous findings that, compared with heterosexual controls, homosexual men have a later birth order, an earlier onset of puberty, and a lower body weight. Sexual orientation was weakly related or unrelated to height, paternal age, and sibling sex ratio. A more detailed analysis of the late birth order of the homosexual group showed that homosexual men have a greater number of older brothers than do heterosexual men, but they do not have a greater number of older sisters, once their number of older brothers has been taken into account.

Biological versus nonbiological older brothers and men’s sexual orientation

“…Finally, note that most of our prior studies found no difference between heterosexual and homosexual men in parental (e.g., maternal) age or found that an older parental age in homosexual samples was probably a consequence of a late (fraternal) birth order (8,9,23). That homosexual men in the present study had younger (and not older) mothers relative to the heterosexual men provides additional support that the fraternal birth-order effect does not occur because of a potential confounding influence of an elevated parental age in the mothers of homosexual men.…”

“…The most consistent biodemographic correlate of sexual orientation in men is the number of older brothers, originally observed by Blanchard and Bogaert (8) in a Canadian sample in the 1990s but since then found in samples from different eras and from different countries, both by us and independent investigators (2,7,(9)(10)(11)(12). Evidence does not exist that sibling characteristics reliably correlate with women's sexual orientation (13,14).…”

Fraternal Birth Order and Extreme Right-Handedness as Predictors of Sexual Orientation and Gender Nonconformity in Men

“…One mechanism for this is the maternal immune hypothesis, which proposes that the accumulating antibodies to male specific antigens with each successive male fetus carried results in feminizing of the male brain leading to homosexuality (Blanchard & Bogaert 1996). FBO is considered the most reliable biodemographic correlate of sexual orientation, but it cannot account for all the variation since there are gay men with no older brothers (Zucker, Blanchard, Kim, Pae, & Lee, 2007).…”

Fertility in the Mothers of Firstborn Homosexual and Heterosexual Men

“…In the full samples for Blanchard and Bogaert (1996b) and Blanchard and Lippa (2007), the homosexual groups had larger numbers of total siblings; in the firstborn subsamples from these same studies, the homosexual groups had smaller numbers of younger siblings. In the full sample for Blanchard and Bogaert (1996a), the homosexual and heterosexual groups had virtually identical numbers of total siblings; in the firstborn subsample from this study, the homosexual group had a smaller number of younger siblings than the heterosexual group.…”

“…This section of this article presents some more specific information about the subjects from which the firstborn subgroups were drawn. Blanchard and Bogaert (1996a) These authors investigated birth order in a subsample age 18 and older to minimize any possible distorting effects of incomplete sibships (Blanchard & Bogaert, 1996a, p. 560). The mean number of siblings (older brothers ?…”