Abstract
Transgendered belief—the conviction that one is the opposite gender to one’s natal gender—may be influenced by prenatal sex steroids. We consider this possibility by examining the relationship between digit ratio (2D:4D—a suggested correlate of fetal testosterone and estrogen), natal gender, felt gender, and transsexual drug therapy in a large online survey (the BBC Internet Study). There were 209,317 participants who reported their gender, their felt gender, and whether they were taking/had taken transsexual drug therapy (male-to-female (MtF) or female-to-male (FtM)). Participants included natal males who felt male (M→M, n = 104,939) and those who felt female (M→F, n = 4760) and natal females who felt female (F→F, n = 84,904) and those who felt male (F→M, n = 4705). Transsexual drug therapy (MtF and FtM) was reported by 830 and 223 participants, respectively. Digit length was determined by direct self-measurement. Mean 2D:4D of M→F and MtF individuals was higher (more “feminized”) than for M→M and natal males, respectively. These effects were found in the total sample, the most numerous ethnic group (Whites) and the two largest national White samples (the UK and the USA). The mean 2D:4D of F→M and FtM participants did not differ from that of F→F and natal females, respectively. We conclude that M→F and MtF individuals may have experienced lower prenatal testosterone and higher estrogen than M→M and natal males, respectively. There was no evidence for an effect of prenatal sex steroids on transgendered belief or transsexualism in F→M and FtM individuals.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Fink, B., & Manning, J. T. (2018). Direct versus indirect measurement of digit ratio: new data from Austria and a critical consideration of clarity of report in 2D:4D studies. Early Human Development, 127, 28–32. https://doi.org/10.1016/j.earlhumdev.2018.09.007.
Galis, F., Ten Broek, C. M., Van Dongen, S., & Wijnaendts, L. C. (2010). Sexual dimorphism in the prenatal digit ratio (2D:4D). Archives of Sexual Behavior, 39(1), 57–62. https://doi.org/10.1007/s10508-009-9485-7.
Hisasue, S. I., Sasaki, S., Tsukamoto, T., & Horie, S. (2012). The relationship between second-to-fourth digit ratio and female gender identity. Journal of Sexual Medicine, 9(11), 2903–2910. https://doi.org/10.1111/j.1743-6109.2012.02815.x.
Kraemer, B., Noll, T., Delsignore, A., Milos, G., Schnyder, U., & Hepp, U. (2009). Finger length ratio (2D:4D) in adults with gender identity disorder. Archives of Sexual Behavior, 38(3), 359–363. https://doi.org/10.1007/s10508-007-9262-4.
Králík, M., Ingrová, P., Kozieł, S., Hupková, A., & Klíma, O. (2017). Overall trends vs. individual trajectories in the second-to-fourth digit (2D:4D) and metacarpal (2M:4M) ratios during puberty and adolescence. American Journal of Physical Anthropology, 162(4), 641–656. https://doi.org/10.1002/ajpa.23153.
Leinung, M., & Wu, C. (2017). The biological basis of transgender identity: 2D:4D finger length ratios implicate a role for prenatal androgen activity. Endocrine Practice, 23(6), 669–671. https://doi.org/10.4158/EP161528.
Malas, M. A., Dogan, S., Evcil, E. H., & Desdicioglu, K. (2006). Fetal development of the hand, digits and digit ratio (2D:4D). Early Human Development, 82(7), 469–475. https://doi.org/10.1016/j.earlhumdev.2005.12.002.
Manning, J. T. (2002). Digit ratio: A pointer to fertility, behavior and health. New Brunswick, NJ: Rutgers University Press.
Manning, J. T. (2017). Prenatal sex steroids and transgender identity: Is there a link with digit ratio? Endocrine Practice, 23(6), 738–740. https://doi.org/10.4158/EP171843.CO.
Manning, J. T., & Fink, B. (2018). Digit ratio (2D:4D) and personality and individual differences. In V. Zeigler-Hill & T. K. Shackelford (Eds.), The SAGE handbook of personality and individual differences (pp. 40–50). Thousand Oaks: SAGE Publications.
Manning, J. T., Scutt, D., Wilson, J., & Lewis-Jones, D. I. (1998). The ratio of 2nd to 4th digit length: A predictor of sperm numbers and concentrations of testosterone, luteinizing hormone and oestrogen. Human Reproduction, 13(11), 3000–3004. https://doi.org/10.1093/humrep/13.11.3000.
Manning, J. T., Churchill, A. J., & Peters, M. (2007). The effects of sex, ethnicity, and sexual orientation on self-measured digit ratio (2D:4D). Archives of Sexual Behavior, 36(2), 223–233. https://doi.org/10.1007/s10508-007-9171-6.
Manning, J. T., Trivers, R., & Fink, B. (2017). Is digit ratio (2D:4D) related to masculinity and femininity? Evidence from the BBC internet study. Evolutionary Psychological Science, 3, 316–324. https://doi.org/10.1007/s40806-017-0098-4.
Mas, M., Alonso, C., Hernandez, P., Fernandez, M., Gutierrez, P., Salido, E., & Baez, D. (2009). Androgen receptor CAG and GGN polymorphisms and 2D:4D finger ratio in male to female transsexuals. Journal of Sexual Medicine, 6(Suppl 5), 419–420. https://doi.org/10.1111/j.1743-6109.2009.016081.x.
Polderman, T. J., Kreukels, B. P. C., Irwig, M. S., Beach, L., Chan, Y.-M., Derks, E. M., et al. (2018). The biological contributions to gender identity and gender diversity: Bringing data to the table. Behavior Genetics, 48(2), 95–108. https://doi.org/10.1007/s10519-018-9889-z.
Pozzebon, J. A., Visser, B. A., & Bogaert, A. F. (2015). Vocational interests, personality, and sexual fantasies as indicators of a general masculinity/femininity factor. Personality and Individual Differences, 86, 291–296.
Reimers, S. (2007). The BBC internet study: General methodology. Archives of Sexual Behavior, 36, 147–161. https://doi.org/10.1007/s10508-006-9143-2.
Sadr, M., Khorashad, B. S., Talaei, A., Fazeli, N., & Honekopp, J. (2020). 2D:4D suggests a role of prenatal testosterone in gender dysphoria. Archives of Sexual Behavior, 49, 421–432. https://doi.org/10.1007/s10508-020-01630-0.
Salmon, C. A., & Hehman, C. A. (2018). Second to fourth digit ratio (2D:4D), tomboyism, and temperament. Personality and Individual Differences, 123, 131–134.
Schneider, H. J., Pickel, J., & Stalla, G. K. (2006). Typical female 2nd–4th finger length (2D:4D) ratios in male-to-female transsexuals. Possible implications for prenatal androgen exposure. Psychoneuroendocrinology, 31(2), 265–269. https://doi.org/10.1016/j.psyneuen.2005.07.005.
Veale, J. F. (2011). Biological and psychosocial correlates of gender-variant and gender-typical identities [dissertation]. Albany (New Zealand): Massey University.
Veale, J. F., Clarke, D. E., & Lomax, T. C. (2010). Biological and psychosocial correlates of adult gender-variant identities: new findings. Personality and Individual Differences, 49(3), 252–257. https://doi.org/10.1016/j.paid.2010.03.045.
Voracek, M., Kaden, A., Kossmeier, M., Pietschnig, J., & Tran, U. S. (2018). Meta-analysis shows associations of digit ratio (2D:4D) and transgender identity are small at best. Endocrine Practice, 24(4), 386–390. https://doi.org/10.4158/EP-2017-0024.
Vujović, S., Popović, S., Mrvošević Marojević, L., Ivović, M., Tančić-Gajić, M., Stojanović, M., et al. (2014). Finger length ratios in Serbian transsexuals. The Scientific World Journal, 763563, 1–4. https://doi.org/10.1155/2014/763563.
Wallien, M. S., Zucker, K. J., Steensma, T. D., & Cohen-Kettenis, P. T. (2008). 2D:4D finger-length ratios in children and adults with gender identity disorder. Hormones and Behavior, 54(3), 450–454. https://doi.org/10.1016/j.yhbeh.2008.05.002.
Author information
Authors and Affiliations
Corresponding author
Additional information
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Manning, J.T., Trivers, R. & Fink, B. Digit Ratio (2D:4D), Transgendered Belief, and Transsexual Drug Therapy in the BBC Internet Study. Evolutionary Psychological Science 6, 380–388 (2020). https://doi.org/10.1007/s40806-020-00247-9
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s40806-020-00247-9