Herpetology
This article has been popping up all over today. Excerpted:
The snake - 16 inches long and the thickness of a little finger - is now being studied at the Life Sciences Department at China's West Normal University in Nanchang.
Snake expert Long Shuai said: "It is truly shocking but we won't know the cause until we've conducted an autopsy.
While the appearance of the snake is certainly odd, it is pretty obvious looking at the picture that what happened was that the snake was eating something - probably a lizard - and through some sort of mishap was punctured out through his side by the leg/foot of his prey. The animal he swallowed, along with probably a lot of infection and horribleness, is visible on either side of and around the foot. The thing that's surprising about it is that the snake was able to live as long as it did in that condition.
There is nothing about this that seems even vaguely like the way natural selection and mutations work. A snake could be born with two heads because it has the genetic blueprint for a snake head. It can not produce a fully developed leg of some other animal randomly out of the side of its body.