“Children's books popularly portrayed Noah’s ark with all of the animals two- by -two, but the Biblical record tells us that he has instructed to take every clean beast and bird by sevens “to keep the species alive on the face of all the earth.” Why was it necessary for seven of each ‘clean animal’ to be taken aboard the ark in order to keep those species alive? How did Noah identify the clean animals? Exodus hadn't been written yet.

A greater number of clean animals was necessary precisely because these were the animals which God required to be offered in sacrifice. The fact that Noah immediately built an altar and offered burnt offerings to God upon exiting the ark shows us that this requirement was well known to him. God had provided instruction in how He was to be worshipped, and had ensured that Noah had all that he needed to comply.” (Comin, 12-13)