Because evolution cannot anticipate the future. It doesn't know any perfect state, only comprimises between competing design parameters.Duly noted.
So spider, what in the world is so far out about the idea of progressing through evolution to a perfect state of human existence?
Because it's a constant battle, an arms race. Parasites and diseases have an advantage in that they can evolve faster, their generations can be as short as 24 hours.Then why do we have so many parasites and diseases still?