I read this article which has the following quote:
The ratio between index and ring finger is believed to be linked to exposure to the male hormone testosterone in the womb.
And I wonder what determines the amount of exposure to testosterone in the womb. Is it testosterone produced by the fetus itself, in which case the baby's own genetics is the answer, or does this exposure the article speaks of more likely refer to testosterone produced by the mother and exposed to the baby?
Please provide some more detail about the exposition of a baby.