Archives of Sexual Behavior

, Volume 43, Issue 2, pp 299–310

Biological Markers of Asexuality: Handedness, Birth Order, and Finger Length Ratios in Self-identified Asexual Men and Women


  • Morag A. Yule
    • Department of PsychologyUniversity of British Columbia
    • Department of Obstetrics and GynaecologyUniversity of British Columbia
  • Boris B. Gorzalka
    • Department of PsychologyUniversity of British Columbia
Original Paper

DOI: 10.1007/s10508-013-0175-0

Cite this article as:
Yule, M.A., Brotto, L.A. & Gorzalka, B.B. Arch Sex Behav (2014) 43: 299. doi:10.1007/s10508-013-0175-0


Human asexuality is defined as a lack of sexual attraction to anyone or anything and it has been suggested that it may be best conceptualized as a sexual orientation. Non-right-handedness, fraternal birth order, and finger length ratio (2D:4D) are early neurodevelopmental markers associated with sexual orientation. We conducted an Internet study investigating the relationship between self-identification as asexual, handedness, number of older siblings, and self-measured finger-lengths in comparison to individuals of other sexual orientation groups. A total of 325 asexuals (60 men and 265 women; M age, 24.8 years), 690 heterosexuals (190 men and 500 women; M age, 23.5 years), and 268 non-heterosexuals (homosexual and bisexual; 64 men and 204 women; M age, 29.0 years) completed online questionnaires. Asexual men and women were 2.4 and 2.5 times, respectively, more likely to be non-right-handed than their heterosexual counterparts and there were significant differences between sexual orientation groups in number of older brothers and older sisters, and this depended on handedness. Asexual and non-heterosexual men were more likely to be later-born than heterosexual men, and asexual women were more likely to be earlier-born than non-heterosexual women. We found no significant differences between sexual orientation groups on measurements of 2D:4D ratio. This is one of the first studies to test and provide preliminary empirical support for an underlying neurodevelopmental basis to account for the lack of sexual attraction characteristic of asexuality.


AsexualitySexual orientationFinger length ratios2D:4DHandednessBirth order

Copyright information

© Springer Science+Business Media New York 2013