Torah Rocks,
1.) As I pointed out to Ben Levi it is not just “similarities” in structure. There is a nested hierarchy in nature that is predicted by common descent. I elaborated more a couple of comments earlier.
2.) Why does it follow that animals will automatically migrate to evrey place on earth where they can live? Why wouldn’t oceans and mountain ranges etc. stop this from happening?
3.) When there is enough evidence to support something and enough things can be accurately predicted by it that is a reason to believe it happened.