The brain is a part of the evolutionary process, problems we can solve through intelligence ARE being addressed through evolution, just not in the way people normally think of it. Evolution gave us these great brains, are you telling me that using them to prolong our lives is somehow NOT a part of the natural process? A hundred years ago, we had a huge problem with polio, thanks to modern medicine, it is no longer a problem. How is this any less a result of evolution than if we had waited a few hundred thousand years and become immune to polio "naturally"? Both methods involved a species defending itself against a threat to its genetic survival, the only difference is that our way was much faster.
Which is kind of the point. Evolution is, by and large, a method for a species to develop beneficial traits that help it survive. And quite frankly, evolving to the point where we HAVE modern medicine is a lot more effective of an evolutionary path than evolving our immune systems to the point where we don't NEED modern medicine. There are no "unnatural" traits, our intelligence is more valuable than having a strong immune system in the evolutionary scheme of things. We have evolted past the need for that sort of thing, just like being the biggest, strongest human around no longer has the survival value it once had.