I find a fundamental flaw in the logic that people are cutthroat survivalists by our very human nature. This is completely contradictory to history. If that was our nature, how would we have developed society and civilization? The edginess that people have in game towards others is due to the fact that everyone represents a distinct threat. Suppose everyone started without a gun, but had a melee weapon of some sort that was pretty weak. People could still hurt and kill each other but it would be more difficult. Also this would encourage more teaming up as zombies would be harder to handle on your own. As an example of this, realize that in real life, the stranger standing next to you might attack you with his bare hands. He could potentially kill you. Does that make you nervous and wary of him? No, not really unless he is really big, has a bad attitude towards you and you're alone. Now imagine he has a gun in his hand, and he is otherwise not threatening in any way. He's not even looking at you. Your mind is going to be racing because he is a major threat. Even if he is completely non threatening in his demeanor, his capacity to do you harm is exceptionally high. It is that perceived threat in my opinion, which causes a great deal of the pk'ing in the game, besides those that do it for the lulz.