What is it that makes some people born with extra finger(s)?

[Marvin the Martian]

As in, on one hand (which has four fingers - 5 colloquially), the child ends up having 5 fingers (6 colloquially)?

 

[Sexbomb Sophie]

Clearly the child is a freak of nature...WTF an extra finger. Eww I would kill it, fry it and sell it to KFC

 

[Runner]

A mutation in DNA can cause people to be born with extra fingers.

 

[☆Krystal☆]

God does that

 

[LOSER]

most people would say god, or a freak, but I say evolution.