How could it happen that there's so much confusion in the flood story regarding the number of animals and birds Noah was supposed to take with him?
The answer is that there are (at least) two different stories of the flood woven into one seemingly continuous story by an editor who alternated passages from two different authors. One of the stories was written by an author who referred to the deity exclusively as "God," never as "Lord," while the other story was written by an author who exclusively called the deity "Lord," but never "God." I will leave it to the interested reader to confirm this on their own (see, for example, http://members.aol.com/jalw/two_animals_or_seven.html).
The "God" author thought that Noah took two of each kind of animal, while the "Lord" author believed that seven were taken. You will see that in those blocks of text where "God" is the deity, the writer refers to "two," while in those blocks of text where "Lord" is used, there are seven animals.
As further evidence that there are two different authors at work, the readers may notice that the ONLY time the sons of Noah are mentioned is in the passages written by the author who called the deity "GOD." When the LORD author speaks of Noah's family, he never mentions sons.
It is just as easy to show that two or more authors contributed separate--and conflicting--accounts of the creation. I will discuss that in a future post. For a preview of what I will say, readers may go to http://sol.sci.uop.edu/~jfalward/creationcontradictions.html.
Joseph F. Alward
"Skeptical Views of Christianity and the Bible"
http://members.aol.com/jalw/joseph_alward.html