Finger Length May Be Linked to Sexual Orientation, Study Finds
A review of 51 studies suggests prenatal hormone exposure may influence both finger length ratios and sexual orientation.
A new analysis suggests the ratio between the index and ring fingers may reflect prenatal hormone exposure — and could be linked to sexual orientation later in life.
Dozens of studies over the past several decades have explored the idea, often with conflicting results. Many also failed to account for bisexuality or sexual fluidity when classifying sexual orientation, according to the New York Post.
In the new analysis, published in Frontiers in Medicine, researchers from Memorial University of Newfoundland and Labrador reviewed 51 prior studies to assess whether finger length ratios could indicate prenatal hormone exposure and predict sexual orientation.
The ratio, known as 2D:4D, compares the index finger to the ring finger. In “typical” males, the ratio is lower, meaning the index finger is shorter than the ring finger.
An oft-cited 2010 study found that women with a lower, more “male-typical” 2D:4D ratio were more likely to be gay. It found no such link in men and did not account for bisexuality.
In the new analysis, which combined data from more than 200,000 people, heterosexual men had lower 2D:4D ratios than heterosexual women — as expected. But gay and bisexual men showed slightly higher, more “female-typical” ratios on both hands, though the differences were small.
Among women, heterosexual participants had higher 2D:4D ratios than lesbians. Bisexual participants, meanwhile, tended to have ratios closer to heterosexual individuals — though the findings were less clear-cut.
“Bisexual women are more similar to heterosexual women in digit ratios, but there may be further nuance,” the authors wrote. “Those falling in the middle of the scale or between heterosexual and bisexual on the scale are more like heterosexual women, while those falling between bisexual and homosexual are more similar to lesbians in digit ratios.”
Researchers say differences in 2D:4D ratios may be linked to prenatal hormone exposure. Higher testosterone levels may “masculinize” the hands and increase the likelihood of homosexuality in women, while lower androgen exposure or higher estrogen levels may “feminize” ratios and be associated with same-sex attraction in men.
The researchers called for further study into the relationship between finger ratios and sexual orientation.
“While sexual orientation differences in digit ratios are expected to be smaller than sex differences, we offer several possible limitations to current work that can be addressed in future research,” the authors wrote. “These include the potential existence of subgroups among non-heterosexual individuals that differ in the biological factors contributing to their sexual orientation, as well as the importance of distinguishing between androphilic and gynephilic orientations when investigating the relationship between digit ratios and male sexual orientation.”
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