Abstract
Research on the biological determinants of male homosexual preference has long realized that the older brother effect (FBOE, i.e., a higher fraternal birth rank of homosexuals) and the antagonist effect (AE, i.e., more fertile women have a higher chance of having a homosexual son) can both generate family data where homosexual men have more siblings and more older siblings than heterosexual men. Various statistical approaches were proposed in the recent literature to evaluate whether the action of FBOE or AE could be discriminated from empirical data, by controlling for the other effect. Here, we used simulated data to formally compare all the approaches that we could find in the relevant literature for their ability to reject the null hypothesis in the presence of a specified alternative hypothesis (tests based on regression, Bayesian modeling, or contingency tables). When testing for the FBOE, the relative performance of the different tests was different depending on the specific function generating the older brother effect. Even if no tests were found to always perform better than the others, some tests performed systematically poorly, and some tests displayed a systematic high rate of type-I error. For testing the AE, the relative performance of the tests was generally not changed across all parameter values assayed, providing a clear ranking of the various proposed approaches. Pros and cons for each candidate test are discussed, taking into consideration power and the rate of type-I error but also practicability, the possibility to control for confounding variables, and to consider alternative hypotheses.
Similar content being viewed by others
Availability of Data and Materials
Not applicable.
Code Availability
Scripts and code are available online https://doi.org/10.5281/zenodo.7857346.
References
Ablaza, C., Kabátek, J., & Perales, F. (2022). Are sibship characteristics predictive of same sex marriage? An examination of fraternal birth order and female fecundity effects in population-level administrative data from the Netherlands. Journal of Sex Research, 59(6), 671–683. https://doi.org/10.1080/00224499.2021.1974330
Apostolou, M. (2020a). Does fraternal birth order predict male homosexuality, bisexuality, and heterosexual orientation with same-sex attraction? Evidence from a greek-speaking sample from Greece. Archives of Sexual Behavior, 49(2), 575–579. https://doi.org/10.1007/s10508-019-01466-3
Apostolou, M. (2020b). The evolution of same-sex attraction. Springer.
Barthes, J., Crochet, P.-A., & Raymond, M. (2015). Male homosexual preference: Where, when, why? PLoS ONE, 10(8), e0134817. https://doi.org/10.1371/journal.pone.0134817
Bennett, B. M., & Hsu, P. (1960). On the power function of the exact test for the 2x2 contingency table. Biometrika, 47, 393–398.
Blanchard, R. (2012). Fertility in the mothers of firstborn homosexual and heterosexual men. Archives of Sexual Behavior, 41(3), 551–556. https://doi.org/10.1007/s10508-011-9888-0
Blanchard, R. (2014). Detecting and correcting for family size differences in the study of sexual orientation and fraternal birth order. Archives of Sexual Behavior, 43(5), 845–852. https://doi.org/10.1007/s10508-013-0245-3
Blanchard, R. (2018a). Fraternal birth order, family size, and male homosexuality: Meta-analysis of studies spanning 25 years. Archives of Sexual Behavior, 47(1), 1–15. https://doi.org/10.1007/s10508-017-1007-4
Blanchard, R. (2018b). Older brothers and older sisters odds ratios in 36 samples of homosexual males [Letter to the Editor]. Archives of Sexual Behavior, 47(4), 829–832. https://doi.org/10.1007/s10508-018-1160-4
Blanchard, R., Beier, K. M., Gómez Jiménez, F. R., Grundmann, D., Krupp, J., Semenyna, S. W., & Vasey, P. L. (2021). Meta-analyses of fraternal and sororal birth order effects in homosexual pedophiles, hebephiles, and teleiophiles. Archives of Sexual Behavior, 50, 779–796. https://doi.org/10.1007/s10508-020-01819-3
Blanchard, R., & Bogaert, A. F. (1996). Homosexuality in men and number of older brothers. American Journal of Psychiatry, 153, 27–31.
Blanchard, R., Krupp, J., VanderLaan, D. P., Vasey, P. L., & Zucker, K. J. (2020). A method yielding comparable estimates of the fraternal birth order and female fecundity effects in male homosexuality. Proceedings of the Royal Society B: Biological Sciences, 287(1923), 20192907. https://doi.org/10.1098/rspb.2019.2907
Blanchard, R., & Lippa, R. A. (2007). Birth order, sibling sex ratio, handedness, and sexual orientation of male and female participants in a BBC internet research project. Archives of Sexual Behavior, 36(2), 163–176. https://doi.org/10.1007/s10508-006-9159-7
Blanchard, R., & Lippa, R. A. (2021). Reassessing the effect of older sisters on sexual orientation in men. Archives of Sexual Behavior, 50, 797–805. https://doi.org/10.1007/s10508-020-01840-6
Blanchard, R., & Skorska, M. N. (2022). New data on birth order in homosexual men and women and a reply to Vilsmeier et al. (2021a, 2021b). Archives of Sexual Behavior, 51, 3319–3349. https://doi.org/10.1007/s10508-022-02362-z
Bogaert, A. F., & Skorska, M. (2011). Sexual orientation, fraternal birth order, and the maternal immune hypothesis: A review. Frontiers in Neuroendocrinology, 32, 247–254.
Bogaert, A. F., Skorska, M. N., Wang, C., Gabrie, J., MacNeil, A. J., Hoffarth, M. R., VanderLaan, D. P., Zucker, K. J., & Blanchard, R. (2018). Male homosexuality and maternal immune responsivity to the Y-linked protein NLGN4Y. Proceedings of the National Academy of Sciences, 115(2), 302–306. https://doi.org/10.1073/pnas.1705895114
Camperio-Ciani, A., Battaglia, U., & Liotta, M. (2016). Societal norms rather than sexual orientation influence kin altruism and avuncularity in tribal Urak-Lawoi, Italian, and Spanish adult males. Journal of Sex Research, 53(2), 137–148. https://doi.org/10.1080/00224499.2014.993748
Camperio-Ciani, A., Corna, F., & Capiluppi, C. (2004). Evidence for maternally inherited factors favouring male homosexuality and promoting female fecundity. Proceedings of the Royal Society London, B, 271, 2217–2221.
Camperio-Ciani, A., Iemmola, F., & Blecher, S. R. (2009). Genetic factors increase fecundity in female maternal relatives of bisexual men as in homosexuals. Journal of Sexual Medicine, 6(2), 449–455. https://doi.org/10.1111/j.1743-6109.2008.00944.x
Daoud, J. I. (2017). Multicollinearity and regression analysis. Journal of Physics: Conference Series, 949(1), 012009. https://doi.org/10.1088/1742-6596/949/1/012009
de Valpine, P., Paciorek, C., Turek, D., Michaud, N., Anderson-Bergman, C., Obermeyer, F., Wehrhahn, C., Rodrìguez, A., Temple Lang, D., Zhang, W., Paganin, S., & Hug, J. (2020). Nimble: MCMC, particle filtering, and programmable hierarchical modeling (0.10.1) [Computer software]. https://CRAN.R-project.org/package=nimble.
de Valpine, P., Turek, D., Paciorek, C. J., Anderson-Bergman, C., Lang, D. T., & Bodik, R. (2017). Programming with models: Writing statistical algorithms for general model structures with NIMBLE. Journal of Computational and Graphical Statistics, 26(2), 403–413. https://doi.org/10.1080/10618600.2016.1172487
Gavrilets, S., & Rice, W. R. (2006). Genetic models of homosexuality: Generating testable predictions. Proceedings of the Royal Society London, B, 273, 3031–3038.
Geweke, J. (1991). Evaluating the accuracy of sampling-based approaches to the calculation of posterior moments. In Bayesian statistics (Vol. 4, pp. 169–193). Clarendon Press. https://doi.org/10.21034/sr.148.
Green, P. J. (1995). Reversible jump Markov chain Monte Carlo computation and Bayesian model determination. Biometrika, 82(4), 711–732. https://doi.org/10.1093/biomet/82.4.711
Iemmola, F., & Camperio-Ciani, A. (2009). New evidence of genetic factors influencing sexual orientation in men: Female fecundity increase in the maternal line. Archives of Sexual Behavior, 38, 393–399.
Khovanova, T. (2020). On the mathematics of fraternal birth order effect and the genetics of homosexuality. Archives of Sexual Behavior, 49, 551–555. https://doi.org/10.1016/j.jtbi.2004.04.021
Nila, S., Crochet, P.-A., Barthes, J., Rianti, P., Juliandi, B., Suryobroto, B., & Raymond, M. (2019). Male homosexual preference: Femininity and the older brother effect in Indonesia. Evolutionary Psychology, 17(4). https://doi.org/10.1177/1474704919880701
R Core Team. (2020). R: A language and environment for statistical computing [Computer software]. https://www.R-project.org/.
Raymond, M., & Crochet, P.-A. (2023). Carving non-proximal explanations for same-sex sexual orientation [Commentary]. Archives of Sexual Behavior, 52, 3007–3012. https://doi.org/10.1007/s10508-022-02497-z
Raymond, M., Turek, D., Durand, V., Nila, S., Suryobroto, B., Vadez, J., Barthes, J., Apostolou, M., & Crochet, P.-A. (2023). Increased birth rank of homosexual males: Disentangling the older brother effect and sexual antagonism hypothesis. Peer Community Journal, 3, e22. https://doi.org/10.24072/pcjournal.247
Slater, E. (1962). Birth order and maternal age of homosexuals. Lancet, 1, 69–71.
Vanderlaan, D. P., Blanchard, R., Zucker, K. J., Massuda, R., Fontanari, A. M. V., Borba, A. O., Costa, A. B., Schneider, M. A., Mueller, A., Soll, B. M. B., Schwarz, K., Da Silva, D. C., & Lobato, M. I. R. (2017). Birth order and androphilic male-to-female transexualism in Brazil. Journal of Biosocial Science, 49(4), 527–535. https://doi.org/10.1017/S0021932016000584
Zuur, A. F., Ieno, E. N., & Elphick, C. S. (2010). A protocol for data exploration to avoid common statistical problems. Methods in Ecology and Evolution, 1(1), 3–14. https://doi.org/10.1111/j.2041-210X.2009.00001.x
Acknowledgements
This is contribution 2024.043 of the Institut des Sciences de l’Evolution de Montpellier (UMR CNRS 5554). This work has been realized with the support of MESO@LR-Platform at the University of Montpellier, and benefited from the ISEM computing facility at ISI service.
Funding
The authors declare that they have received no specific funding for this study.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Conflict of interest
The authors have no conflicts of interest to declare.
Ethical approval
Not applicable.
Informed consent
Not applicable.
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary Information
Below is the link to the electronic supplementary material.
Rights and permissions
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
About this article
Cite this article
Raymond, M., Turek, D. & Crochet, PA. Testing Fraternal Birth Order Effects and Antagonistic Effects for Homosexual Men: Power Comparison of Various Methods. Arch Sex Behav (2024). https://doi.org/10.1007/s10508-024-02820-w
Received:
Revised:
Accepted:
Published:
DOI: https://doi.org/10.1007/s10508-024-02820-w