Doc Savage said:
Well said, Moe. And let's not forget that the reptile-to-bird absurdity...namely that an evolving wing would make a bad leg long before it made a good flight mechanism.
You just leave one little thing out of the equation... evolution is a result, not a cause. Parts you need don't evolve to worse, only better. However parts you find lacking use may start getting into something odder.
So this critter in question finds profits from better evolution as its back legs get stronger, up to a point where it becomes one standing on just two legs, not four. At that point, the front ones are useless, and logically free to evolve into something else.
I know, it's not the best explanation, but still plausible. Nevertheless, helps if you do your homework before you start disregarding.
And to bite Clinton's hide, atheism
does require faith. There is no solid proof for God's non-existence, just strong belief that there is no one. Vice-versa too, of course.