Advertisement

Archives of Sexual Behavior

, Volume 47, Issue 1, pp 47–48 | Cite as

Reasons for Caution About the Fraternal Birth Order Effect

  • Brendan P. ZietschEmail author
Commentary

The etiology of sexual orientation is an intriguing and poorly understood topic. Genes appear to play an important role, which raises the Darwinian paradox as to why genes for homosexuality would be maintained in the population (Zietsch et al., 2008). In terms of non-genetic influences, harsh childhood environments and childhood sexual abuse are associated with adult homosexuality, though the causality needs clarification and the mechanisms are not known (Zietsch et al., 2012). Also in this mix is the fraternal birth order effect (FBOE)—the focus of the target article (Blanchard, 2017). Numerous studies have found that homosexual men have a disproportionate number of older brothers relative to heterosexual men, though, again, the mechanisms by which this variable might relate to development of sexual orientation are unknown (notwithstanding the “maternal immune hypothesis” [Blanchard & Bogaert, 1996], for which I know of no direct evidence).

The target article concludes, based on a...

Notes

Acknowledgements

Thanks to Fiona Barlow and Kana Imuta for helpful comments on an earlier draft. Funding was provided by Australian Research Council (Grant No. FT160100298).

References

  1. Bearman, P. S., & Brückner, H. (2002). Opposite-sex twins and adolescent same-sex attraction. American Journal of Sociology, 107, 1179–1205. doi: 10.1086/341906.CrossRefGoogle Scholar
  2. Blanchard, R. (2017). Fraternal birth order, family size, and male homosexuality: Meta-analysis of studies spanning 25 years. Archives of Sexual Behavior. doi: 10.1007/s10508-017-1007-4.Google Scholar
  3. Blanchard, R., & Bogaert, A. F. (1996). Homosexuality in men and number of older brothers. American Journal of Psychiatry, 153, 27–31.CrossRefPubMedGoogle Scholar
  4. Blanchard, R., & VanderLaan, D. P. (2015). Commentary on Kishida and Rahman (2015), including a meta-analysis of relevant studies on fraternal birth order and sexual orientation in men. Archives of Sexual Behavior, 44, 1503–1509. doi: 10.1007/s10508-015-0555-8.CrossRefPubMedGoogle Scholar
  5. Bogaert, A. F. (2005). Sibling sex ratio and sexual orientation in men and women: New tests in two national probability samples. Archives of Sexual Behavior, 34, 111–116. doi: 10.1007/s10508-005-1005-9.CrossRefPubMedGoogle Scholar
  6. Bogaert, A. F. (2010). Physical development and sexual orientation in men and women: An analysis of NATSAL-2000. Archives of Sexual Behavior, 39, 110–116. doi: 10.1007/s10508-008-9398-x.CrossRefPubMedGoogle Scholar
  7. Francis, A. M. (2008). Family and sexual orientation: The family-demographic correlates of homosexuality in men and women. Journal of Sex Research, 45, 371–377. doi: 10.1080/00224490802398357.CrossRefPubMedGoogle Scholar
  8. Frisch, M., & Hviid, A. (2006). Childhood family correlates of heterosexual and homosexual marriages: A national cohort study of two million Danes. Archives of Sexual Behavior, 35, 533–547. doi: 10.1007/s10508-006-9062-2.CrossRefPubMedGoogle Scholar
  9. Lombardi, C. M., & Hurlbert, S. H. (2009). Misprescription and misuse of one-tailed tests. Austral Ecology, 34, 447–468.Google Scholar
  10. Poasa, K. H., Blanchard, R., & Zucker, K. J. (2004). Birth order in transgendered males from Polynesia: A quantitative study of Samoan fa’afafine. Journal of Sex and Marital Therapy, 30, 13–23. doi: 10.1080/00926230490247110.CrossRefPubMedGoogle Scholar
  11. Purcell, D. W., Blanchard, R., & Zucker, K. J. (2000). Birth order in a contemporary sample of gay men. Archives of Sexual Behavior, 29, 349–356.CrossRefPubMedGoogle Scholar
  12. Simmons, J. P., Nelson, L. D., & Simonsohn, U. (2011). False-positive psychology. Psychological Science, 22, 1359–1366. doi: 10.1177/0956797611417632.CrossRefPubMedGoogle Scholar
  13. Simonsohn, U., Nelson, L. D., & Simmons, J. P. (2014). p-curve and effect size. Perspectives on Psychological Science, 9, 666–681. doi: 10.1177/1745691614553988.CrossRefPubMedGoogle Scholar
  14. Thornton, A., & Lee, P. (2000). Publication bias in meta-analysis. Journal of Clinical Epidemiology, 53, 207–216. doi: 10.1016/S0895-4356(99)00161-4.CrossRefPubMedGoogle Scholar
  15. Zietsch, B. P., Morley, K. I., Shekar, S. N., Verweij, K. J. H., Keller, M. C., Macgregor, S., … Martin, N. G. (2008). Genetic factors predisposing to homosexuality may increase mating success in heterosexuals. Evolution and Human Behavior, 29, 424–433.Google Scholar
  16. Zietsch, B. P., Verweij, K. J. H., Heath, A. C., Madden, P. A. F., Martin, N. G., Nelson, E. C., … Lynskey, M. T. (2012). Do shared etiological factors contribute to the relationship between sexual orientation and depression? Psychological Medicine, 42, 521–532. doi: 10.1017/s0033291711001577.

Copyright information

© Springer Science+Business Media, LLC 2017

Authors and Affiliations

  1. 1.Centre for Psychology and Evolution, School of PsychologyUniversity of QueenslandBrisbaneAustralia

Personalised recommendations