Imagine if you were the last person alive, how life would be? It would be meaningless. You couldn't just exist like that. You'd cease to do so. You're a social creature. God created you in pairs, and evolution made you stay that way. You're attracted to at least some other form of human; be it compassion, sexual, greed or any other. You just are. You can't spend an hour in a room, soundproof enough to make you hear your blood gushing through your veins. You'd suffocate while perfectly breathing. You'll just want to escape. Leave the place. And be with some other human.
But just imagine for once. Just imagine how would life be, if you were the last man alive... the only man alive.