What's the deal behind the relationship between autism and finger length?

well, ever since i knew i had Asperger Syndrome, i knew there was something with the index-ringfinger ratio, but up till now i’m not really sure how and what, for instance this is my hand, my ring is longer then my index, but don’t all people have that? is it a difference between men and women ? if anyone knows, i’d appreciate it, cheers!