Is a belief in a god really necessary?

People have slaughtered each other in wars, inquisitions, and political actions for centuries and still kill each other over beliefs in religions, political ideologies, and philosophies. These belief-systems, when stated as propositions, may appear mystical, and genuine to the naive, but when confronted with a testable bases from reason and experiment, they fail miserably. I maintain that beliefs create more social problems than they solve and that beliefs, and especially those elevated to faith, produce the most destructive potential to the future of humankind. Is a belief in a god really necessary for our species?