Atheism is the disbelief in any creator God, not just the one believed in by fundamentalist Christians. Clearly, there are an infinite number of possible beliefs on human and universal origins, with fundamentalist Christianity representing one of them. Atheism, itself, makes no statement about origins, except to say they believe no living being created the universe, which suggests it was some kind of mindless, mechanical process. At least that is my understanding of atheism. It is agnostics that keep an open mind on the matter.
Originally written in response to a comment here.