This essay examines the possibility of humans dying off within the next 10 years:
Although the author throws in all the bad news he can think of, his premise is worthy of consideration. We certainly are capable of killing each other, and very little is being done to stop us from accomplishing that goal.
My two cents? Every species gets a shot, and if you blow it then it's time to go. Our belief in human primacy is not supported by the facts. Life will go on without us and probably do just fine.