sorry but god could have created the first life and evolution is how it got here, though there are many evidences towards it being natural, sticking god where he's not needed kills your arguments.
ANd on same designer means same design fails, unless you want to claim god is incompetent, because not only does he use simular designs, he uses the same designs and then modifies them, like with humans, he took the design of monkey, took all the same base genes, and then modified, or broke them to get a human. And we can see this in our DNA, we have many of the genes for making a monkey that we no longer need or use, but are still there, just broken. We have many genes for smells we can no longer use and so on.
It be like if god built a car using parts from a truck and just bending and reshaping the parts and those that are left over are welded to the frame of the car, they have no use, but are still there for some weird reason.
Like the car doesn't even run in diesel, but all the parts a car would need to run on disel is still there, they just have small parts missing, and holes in them.