Put any living specie in a setting where their life is threatened to cease and what will most do? They will fight to exist. Understand? Am I still confusing you? Before anything else, the need to exist comes first. That's human nature. it has always been human nature. Thus my statement was very clear. Human nature is to exist as any living specie's natural instinct be it bird, fish, insect, rodent, etc is to exist. Understand?And what do you mean by, "Human nature is to exist as any living specie"? I can't exist as any specie, I can only exist as human.
I'll say it this way if it helps. Your natural instinct to exist is no different than most any other living mammal's natural instinct to exist. For most all living things be they cells or mammals, to exist is the first and primary natural instinct.