There have been several studies that show that the 2D:4D ratio (the length of your index finger divided by the length of your ring finger) is correlated with levels of prenatal testosterone. People whose ring finger is longer are more likely to have developed characteristics associated with higher testosterone e.g. athleticism, better spatial awareness, more analytic personality, worse social skills. Most men have a lower ratio than most women.
Some studies are also suggesting its also a predictor of adhd and autism.
I am fascinated, especially because it doesn't work for me because I have a mutation that means it's extremely different on each side haha.
It'd be cool if people could measure it on themselves and post on here so I could see if there actually is a link with autism. Obviously it won't be very accurate/scientific but I thought it'd be interesting anyway.