My friend the professor likes the (admittedly incomplete but apt) analogy that the environment is the "big fly-swatter of life". It's got a random mesh to it and when it comes down, only those things that fit between the holes survive. No intent. No watching for the swatter and scrambling for an opening in the mesh...

....in fact, as he points out, when we think we are scrambling for the openings in the mesh, we, through unintended consequences, merely change the mesh of the swatter.