Sibling Sex Ratio and Sexual Orientation in Men and Women: New Tests in Two National Probability Samples
- 123 Downloads
One line of research on the etiology of sexual orientation has examined sibling sex ratio, the ratio of brothers to sisters collectively reported by a group of individuals, but this research has only used clinical and/or convenience samples. In the present study, homosexual men and women’s sibling sex ratio was examined in two national probability samples. Results indicated that homosexual men had a sex ratio of 129.54 male live births to 100 female live births. This ratio was within the range of elevated sex ratios found in some previous studies of homosexual men, although it was only marginally significant (p = .09) relative to the known human sex ratio with regard to live births. Additional analyses indicated that this effect was likely the result of a high fraternal birth order (i.e., an elevated number of older brothers) in homosexual men. The sibling sex ratio for lesbians was 122.58 male live births to 100 female live births, which did not significantly differ from the known human sex ratio with regard to live births. The results for lesbians, however, should be interpreted with caution because the sample size (and resulting power) was low. The results in men add to research suggesting that homosexual men, unselected for gender identity or gender role behavior, do not have elevated sibling sex ratios. These results also suggest that research should concentrate on finding the cause(s) of the fraternal birth order effect, the consistent finding that homosexual men have an elevated number of older brothers.
Keywords:sexual orientation homosexuality sibling sex ratio fraternal birth order
Unable to display preview. Download preview PDF.
- Blanchard, R., & Bogaert, A. F. (1996a). Biodemographic comparisons of homosexual and heterosexual men in the Kinsey interview data. Archives of Sexual Behavior, 25, 551–579.Google Scholar
- Blanchard, R., & Bogaert, A. F. (1996b). Homosexuality in men and number of older brothers. American Journal of Psychiatry, 153, 27–31.Google Scholar
- Blanchard, R., Zucker, K. J., CohenKettenis, P. T., Gooren, L. J. G., & Bailey, J. M. (1996). Birth order and sibling sex ratio in two samples of Dutch gender-dysphoric homosexual males. Archives of Sexual Behavior, 25, 489–508.Google Scholar
- Bogaert, A. F. (2002). A review of recent research on fraternal birth order and sexual orientation development. Canadian Journal of Human Sexuality, 11, 101–107.Google Scholar
- Hyde, J. S., & DeLamater, J. (2000). Understanding human sexuality (7th ed.). Boston: McGraw-Hill.Google Scholar
- James, W. H. (1987). The human sex ratio. Part 1: A review of the literature. Human Biology, 59, 721–752.Google Scholar
- Lang, T. (1936). Beitrag zur Frage nach der genetischen bedingtheit der homosexualität [A contribution regarding the question of the genetic determination of homosexuality]. Zeitschrift für die gesamte Neurologie und Psychiatrie, 155, 702–713.Google Scholar
- Lang, T. (1960). Die homosexualität als genetisches problem [Homosexuality as a genetic problem]. Acta Geneticae Medicae et Gemellologicae, 9, 370–381.Google Scholar
- Laumann, E. O., Gagnon, J. H., Michael, R. T., & Michaels, S. (1994). The social organization of sexuality: Sexual practices in the United States. Chicago: University of Chicago Press.Google Scholar
- Slater, E. (1958). The sibs and children of homosexuals. In D. R. Smith & W. M. Davidson (Eds.), Symposium on nuclear sex (pp. 79–83). London: Heinemann Medical Books.Google Scholar
- Wellings, K., Field, J., Johnson, A., & Wadsworth, J. (1994). Sexual behaviour in Britain: The National Survey of Sexual Attitudes and Lifestyles. London: Penguin Books.Google Scholar