Prenatal exposure to testosterone determines the length ratio between the index finger (D2) and the ring finger (D4), creating a lasting morphological difference between the sexes that can also be correlated with sexual orientation.

noli's read

Research, notably the work of Dr. Marc Breedlove and meta-analyses on the 2D:4D ratio, confirms that this ratio is indeed considered a potential biological marker of in utero androgen exposure. Observational studies show a statistical trend where men exhibit a lower ratio (index finger shorter than the ring finger) than women, although there is significant overlap between the sexes. Regarding sexual orientation, the evidence comes from observational studies that suggest associations, but these results remain debated within the scientific community due to the complexity of genetic and environmental factors. It is crucial to note that the 2D:4D ratio is a population measure and not an individual diagnostic tool. The idea that this ratio is 'entirely dependent' on prenatal testosterone is a simplification, as other developmental factors also influence hand morphology.

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