Your post is completely fucking idiotic, moronic, and any other adjective I can think of that ends in -ic. In fact, it shows such a total lack of thought that it makes me wonder how you could even be a functioning adult in society.
First of all, your main assumption is that natural selection has as its main goal the improvement of the species (i.e. we evolve to become smarter, stronger, etc.) It's a piss poor assumption. Natural selection results in species that evolves to fit its environment; as humans change the environment (for example, better health care leads to being able to survive and reproduce under conditions that previously made survival more difficult), people who otherwise wouldn't have reproduced now can, and do.
Secondly, the theory of Evolution is not something you believe in, like some fucking nonsensical religion, but rather it's a scientific model on which useful predictions can be made. (see sig)
So please stop posting utter shit.
No, Natural Selection is survival in a given environment. Pure and simple.
Of course, an argument can be made that we alter our environment, but frankly, you'd have to argue really really hard to say we have achieved an environment where a mentally disabled, or congenitally and physically disabled individual is able to survive without significant and constant peer aid.
You could also argue that humans are an environment we create (society) that allows this.
1) Singular humans (relatives) allow this, but I would argue that does not constitute an actual environment.
2) Multiple humans (society) allow this.
I might actually buy this, however, that means:
A) Humanity, through socialization, has evolved itself to be an environment that protects its weak, which I have to say, a lot of people would beg to differ based on the way our cut-throat world often operates.
Finally, check your understanding of the word "believe" and then come back.