Fingers

Our fingers, apparently, provide a window into our souls (via Secular Blasphemy):

The length of a man’s fingers can reveal how physically aggressive he is, Canadian scientists have said.
The shorter the index finger is compared to the ring finger, the more boisterous he will be, University of Alberta researchers said.

But the same was not true for verbal aggression or hostile behaviours, they told the journal Biological Psychology after studying 300 people’s fingers.

The trend is thought to be linked to testosterone exposure in the womb.