does necessity means rationality or positivity?

no, natural selection is not evil, not according to how I define evil. Evil is a human concept, just as good is, which holds no meaning without human conscience. an action is evil if the doer believed it was evil. when a rock falls off a cliff and kills someone, this is not an evil action. when we kill and eat plants, this is not evil...nor when we kill and eat cows, nor when indian cannibals kill and eat other people. when another person performs something we consider to be atrocious, we cannot instantly assume that this action was evil...we must know why the action was done. if they took sadistic pleasure out of it, and enjoyed the feeling of breaking their morals, then it is evil. but if they have a different perspective on life, or lack the cognitive ability to understand their actions, then they are no more evil than the rock falling off a cliff...regardless of what they have done. Im not using this to justify that such people should be allowed to do whatever they want, however.

so rational necessity is alway right, altough it may be cruel.

there is always a way of making a situation work, for men, the solution is war and it is inevitable, if an only if there is no other way out, but if you are truly just, and a reasonable, logical being, not irrational, then you can't blame one for wanting to survive, you do what you have to do therefore is it evil? you tell me, it depends on the intentions and where the heart is.