Finger pointing: Why bias against 2D:4D ratios doesn't add up.

Area of Science:

• Evolutionary biology
• Developmental psychology
• Endocrinology

Background:

• The 2D:4D digit ratio is a proposed retrospective marker for prenatal androgen exposure.
• Previous research indicated a sex difference in digit ratios and lower ratios in lesbians compared to heterosexual women.
• A recent commentary questioned these findings, suggesting allometric artifacts and publication bias.

Purpose of the Study:

• To respond to criticisms regarding the validity of the 2D:4D digit ratio as a marker of prenatal androgen exposure.
• To present new data on digit ratios in relation to sexual orientation.
• To further investigate the role of prenatal androgens in human sexual orientation.

Main Methods:

• Analysis of existing literature and a new dataset.
• Measurement of the 2D:4D digit ratio from the right hand.
• Statistical comparison of digit ratios across groups of heterosexual, bisexual, and lesbian women.

Main Results:

• The right-hand 2D:4D ratio remains a reliable non-invasive indicator of prenatal androgen exposure.
• Lesbians exhibit significantly lower right-hand 2D:4D ratios than heterosexual women, consistent with higher prenatal androgen exposure.
• Bisexual women show intermediate digit ratios, not significantly different from either gay or straight women.

Conclusions:

• The 2D:4D digit ratio is a valid retrospective marker for prenatal androgen exposure.
• Prenatal androgen exposure is implicated in the development of sexual attraction towards women in adulthood.
• These findings support the role of hormonal influences during prenatal development on adult sexual orientation.