Why did God need Noah to save two of every animal from the flood?

[Statilius the Epicurean]

The flood narrative in Genesis is derivative of earlier Mesopotamian flood myths, which have the same motif of animals being preserved by entering the hero's ark. The purpose of the stories are to provide an etiology for why floods happen. I would guess that the animal motif exists to give reassurance in a flood that while divine forces may be mad at you the Near Eastern farmer, the divine forces aren't going to destroy you and your animals in their entirety.