More contradictions

Human nature goes against itself if one truly thinks about it.
It is within human nature to try to save others, yet if everybody gets saved, we weaken our gene pool and decrease or species rate of survival. So it is within our nature of survival to slowly weaken our chances of this very thing that we are trying to preserve. We keep people who have been born with defects alive, we keep people with incredibly weak body parts alive, and we keep those with health problems alive too. Natural selection works by ensuring only the strong survive, but in our following our nature, we have ensured the weak also survive, thus polluting our gene pool and giving us more defects. I find this incredibly ironic. However, I am not saying that we should stop keeping people alive however, because once again, this is only our nature and the nature of the universe. Who is to say that one must follow the nature of the universe in order to be good, or one must follow one's own nature? All this is is what we are predisposed to do, nothing more, nothing less.

If human nature is so contradictory, does that mean that we will never be able to discover it completely?