I remember learning about this in Psychology a few years ago, and I heard it again today on 'Child in our time'. There is a theory that if your left hand ring finger is longer than your left hand index finger, you will have a more masculine brain.
"Since the relative lengths of our fingers seem to stay fixed throughout our lives, they are robust markers of what our early life was like in the womb-fetal fossils, if you will. Take a close look at your own hands. Pay particular attention to your index and ring fingers. In women, the two fingers tend to be almost equal in length, as measured from the crease nearest the palm to the fingertip. In men, the ring finger tends to be much longer. The ratio of the lengths of the index finger to the ring finger is called the 2D:4D ratio, and low ratios are considered "masculine", high ratios "feminine"."
This is such a dodgy theory! Lol, you can read the New Scientist article here.