Archives of Sexual Behavior

, Volume 35, Issue 6, pp 739–742 | Cite as

Population Differences in Finger-Length Ratios: Ethnicity or Latitude?

  • John C. LoehlinEmail author
  • Dennis McFadden
  • Sarah E. Medland
  • Nicholas G. Martin

The relative length of the second and fourth fingers (the 2D:4D ratio) has been taken to be an indicator of prenatal exposure to testosterone, and hence possibly relevant to sexual orientation and other sex-differentiated behaviors. Studies have reported a difference in this ratio between Caucasian males in Britain and in the U.S.: higher average 2D:4D ratios were obtained in Britain. This raises the question of whether differences among different Caucasian gene pools were responsible or whether some environmental variable associated with latitude might be involved (e.g., exposure to sunlight or different day-length patterns). This question was explored by examining 2D:4D ratios for an Australian adolescent sample. The Australians were predominantly of British ancestry, but lived at distances from the equator more like those of the U.S. studies. The Australian 2D:4D ratios resembled those in Britain rather than those in the U.S., tending to exclude hypotheses related to latitude and making differences in gene pools a plausible explanation.

Key Words

2D:4D ratio finger lengths masculinization ancestry latitude 



We are grateful to Ann Eldridge, Marlene Grace, Narelle Hansell, and David Smyth for assistance with the Australian data.


  1. Brown, W. M., Hines, M., Fane, B. A., & Breedlove, S. M. (2002). Masculinized finger-length patterns in human males and females with congenital adrenal hyperplasia. Hormones and Behavior, 42, 380386.CrossRefPubMedGoogle Scholar
  2. Buck, J. J., Williams, R. M., Hughes, I. A., & Acerini, C. L. (2003). In-utero androgen exposure and 2nd and 4th digit length ratio: Comparisons between healthy controls and females with classical congenital adrenal hyperplasia. Human Reproduction, 18, 976979.CrossRefPubMedGoogle Scholar
  3. Lutchmaya, S., Baron-Cohen, S., Raggatt, P., Knickmeyer, R., & Manning, J. T. (2004). 2nd to 4th digit ratio, fetal testosterone and estradiol. Early Human Development, 77, 2328.CrossRefPubMedGoogle Scholar
  4. Manning, J. T. (2002). Digit ratio: A pointer to fertility, behavior, and health. New Brunswick, NJ: Rutgers University Press.Google Scholar
  5. McFadden, D., Loehlin, J. C., Breedlove, M. C., Lippa, R. A., Manning, J. T., & Rahman, Q. (2005). A reanalysis of five studies on sexual orientation and the relative length of the 2nd and 4th fingers (the 2D:4D ratio). Archives of Sexual Behavior, 34, 341–356.CrossRefPubMedGoogle Scholar
  6. Ökten, A., Kalyoncu, M., & Yaris, N. (2002). The ratio of second- and fourth-digit lengths and congenital adrenal hyperplasia due to 21-hydroxylase deficiency. Early Human Development, 70, 4754.CrossRefPubMedGoogle Scholar
  7. Putz, D. A., Gaulin, S. J. C., Sporter, R. J., & McBurney, D. H. (2004). Sex hormones and finger length: What does 2D:4D indicate? Evolution and Human Behavior, 25, 182199.CrossRefGoogle Scholar
  8. Schultz, T. F., & Kay, S. A. (2003). Circadian clocks in daily and seasonal control of development. Science, 301, 326328.CrossRefPubMedGoogle Scholar
  9. Wright, M. J., & Martin, N. G. (2004). The Brisbane Adolescent Twin Study: Outline of study methods and research projects. Australian Journal of Psychology, 56, 6588.CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, Inc. 2006

Authors and Affiliations

  • John C. Loehlin
    • 1
    • 3
    Email author
  • Dennis McFadden
    • 1
  • Sarah E. Medland
    • 2
  • Nicholas G. Martin
    • 2
  1. 1.Department of PsychologyUniversity of TexasAustinUSA
  2. 2.Queensland Institute of Medical ResearchBrisbaneAustralia
  3. 3.Department of PsychologyUniversity of TexasAustinUSA

Personalised recommendations