One grasps to hold on to themselves as a Valuable Member of Society, as we are taught a children. But this ideal is false. No one can hold onto anything more than themselves. The people they "love" are those they hold higher than anyone else. Those that keep them from being alone. If one does not directly affect you, then do you care about them other than a faceless shadow? No. People mourn over others losses because they translate the situation to themselves. "What if it had been my daughter?" Thus selfishness is the lifeblood of society. This emotion that is regarded as a sin is truly not; If one feels complete apathy, if one can not feel sorrow or remorse or joy in any situation, aren't they "inhuman" by societies standards? So really, selfishness is nothing more than love, and the one thing that makes us all human.
Fiction also plays on this. We can get closer to characters then we can get to everyone else. A character (if done well) is completely ripped open and exposed to the audience. These characters become more real and we have a much closer attachment to them then we have to a stranger; these vulgar fictions allow us to feel something deeper outside of our own lives. This again makes us human.
The simple fact is we do not exist past our own minds. The different fluctuations in our thoughts and in our words show us that none of our actions are common to any percent of the population. It is impossible to care for every single living thing; it is far beyond our capacity. Some of us live, loving the whole like a curse (like Kira); others feel nothing for the cold greyness that surrounds them (like me). So we dig our roots in and try to make some sort of connection to others, no matter how superficial it may be. We are merely plants, trees who do not live outside our branches. As a whole, we are truly simple creatures. But apart, we are beautiful and vibrant, full of selfishness and compassion. Our simple, meaningless, selfish bonds are what makes us human.