Finger-Length Ratios in Female Monozygotic Twins Discordant for Sexual Orientation

  title={Finger-Length Ratios in Female Monozygotic Twins Discordant for Sexual Orientation},
  author={Lynn S. Hall and Craig T. Love},
  journal={Archives of Sexual Behavior},
The second to fourth finger digit ratio (2D:4D ratio) is a sex-dimorphic characteristic in humans that may reflect relative levels of first trimester prenatal sex hormones. Low interdigital ratio has been associated with high levels of androgens. It has been reported in unrelated women that low 2D:4D ratio is associated with lesbian sexual orientation, but because of the nature of those samples, it was not possible to conclude whether lower ratio (and hypothetically, higher androgen levels) in… 

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Examination of patterns in identical twins with discordant sexual orientations found males had more masculinized 2D:4D ratios than females, and this sex difference did not vary by sexual orientation.

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Prenatal androgen levels are suggested to influence sexual orientation in both sexes. The 2D:4D digit ratio has been found to associate with sexual orientation, but published findings have often been

Sexual orientation and the second to fourth finger length ratio: a meta-analysis in men and women.

It is found that heterosexual women had higher (more feminine) left- and right-hand 2D:4D than did lesbians, but there was no difference between heterosexual and gay men.

Genetic and Environmental Influences on 2D:4D Finger Length Ratios: A Study of Monozygotic and Dizygotic Male and Female Twins

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Intrauterine Position Effects on Anogenital Distance and Digit Ratio in Male and Female Mice

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Sex dimorphism in digital formulae of children.

Test for a sex difference in the relative lengths of the finger bones, including the second-to-fourth digit ratio (2D:4D), using left-hand radiographs taken in young children indicate that relative digit lengths are sex-dimorphic in children, and suggests that 3D: 4D may be a better marker of perinatal sex differentiation.

The Second to Fourth Digit Ratio (2D:4D) in a Japanese Twin Sample: Heritability, Prenatal Hormone Transfer, and Association with Sexual Orientation

The existence of non-shared environmental influences that affect both 2D:4D and sexual orientation are suggested, which are in the predicted direction according to the prenatal hormone transfer hypothesis.



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  • 2000

Dermatoglyphic analysis of total finger ridge count in female monozygotic twins discordant for sexual orientation

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Differences in Finger Length Ratios Between Self-Identified “Butch” and “Femme” Lesbians

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Monozygotic (MZ), same‐sex dizygotic (DZ), and opposite‐sex (OS) twins from the Minnesota Twin Registry responded to a sexual orientation survey. Using the relative frequencies of heterosexuals,

Finger-length ratios and sexual orientation

The androgen-sensitive pattern of finger lengths is examined, and there is evidence that homosexual women are exposed to more prenatal androgen than heterosexual women are, and men with more than one older brother, who are more likely than first-born males to be homosexual in adulthood, are exposure to more pregnancies than eldest sons.

Second to fourth digit ratio and male ability in sport: implications for sexual selection in humans.

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    Evolution and human behavior : official journal of the Human Behavior and Evolution Society
  • 2001

Heritable factors influence sexual orientation in women.

Heritabilities were significant using a wide range of assumptions about both the base rate of homosexuality in the population and ascertainment bias and self-reported history of childhood gender nonconformity.

Masculinized Finger Length Patterns in Human Males and Females with Congenital Adrenal Hyperplasia

Results are consistent with the idea that prenatal androgen exposure reduces the 2D:4D and plays a role in the establishment of the sex difference in human finger length patterns, and finger lengths may offer a retrospective marker of perinatal androgens exposure in humans.

Second-trimester markers of fetal size in schizophrenia: a study of monozygotic twins.

The study suggests that various second-trimester prenatal disturbances in the epigenesis of one twin in a pair discordant for schizophrenia may be related to the fact that only one of the twins expresses his or her genetic predisposition toward schizophrenia.