A majority of Americans seriously question or doubt that the universe was created 13.8 billion years ago in a "big bang." An Associated Press/GfK poll found that 51 percent of those surveyed questioned the famous theory explaining the origin of the universe. Another concept Americans tend to question: global warming. About four in 10 polled said they are not too confident or outright disbelieve that the Earth is warming as a result of human activity. Around the same percentage also questioned that life on Earth evolved through a process of natural selection. While disheartening to see how many Americans seriously doubt scientific concepts, more than 95 percent do believe smoking causes cancer.