We're fortunate(or unfortunate) enough to be alive in one of the most critical periods of human history. If things generally go right in the next 50-60 years, we won't have to worry much about us killing.... us, and focus on our lives that happen to live on the knife edge of the universe, and make the struggle for surviving in such a universe. The earth won't last forever, after all. However...

Billions of us believe that the creator of the universe wrote some books which dictate the way we should live our lives. These books make claims that are just not compatible. This is illustrated in the Israeli/Palestinian conflict, among other religious skirmishes on our planet. But they are just that, skirmishes. If there's a great war in the 21st century, it will be a religious war. Consider that billions of people support martyrdom in defense of Islam. Consider that our technology advances exponentially, this will not stop. The ability for a single one of us, or a small group of us, to remove the rest from this planet, also becomes available exponentially. The one danger here is belief without evidence. The belief that it will rain, regardless of how this belief reflects reality, puts an umbrella in our hands. At worst we are inconvenienced ever so mildly if this belief doesn't reflect reality. Unfortunately, this was putting it mildly. We cannot have a cold war with a large portion of the world, a world which is angry at us, because they are confident that they have it right, we have it wrong, and they are willing to die to prove it. "You've got to die some day." - A high ranking military official in Pakistan, commenting on nuclear war.