Jewish folklore says that the indentation is where an angel touched the baby, to erase his memory of his life with God before being born.

I was told that the fact that the second and fourth fingers of my hands are almost even is a sign that I was exposed to testosterone in the womb, and is why I'm so very like my father sometimes.

Since then, I've been looking at other women's hands. But I'd have no way of knowing if the testosterone thing is true.