Augustine of Hippo : Christ was also represented in Noah, and the world, in that ark. For why were all living creatures shut up in that ark except to signify all the nations? For God did not lack the capability of creating anew every species of living things. For when no creatures were in existence, did he not say, "Let the earth bring forth" and the earth brought forth? So from the same source as he made them then, he could remake them. God made them by a word, so God could remake them by a word. — TRACTATES ON THE GOSPEL OF John 9.11.1 Augustine of Hippo : UNEQUAL NUMBER OF CLEAN AND UNCLEAN ANIMALS. — In relation to what is written: And of clean flying creatures and of unclean flying creatures, and of clean cattle and of unclean cattle, and of all things that creep upon the earth , undoubtedly clean and unclean, though not expressed in the Scripture, entered two by twos in with Noah into the Ark, male and female (Gen. 7:9). Why is it that he first distinguished two of each species from the unclean, and now he says that two of each species, the same of the clean animals and unclean animals. The answer is, because it has nothing to do with quantity, but with the sex of animals: in all pure or unclean species, there is male and female. [ — QUESTIONS ON GENESIS, Q. 7 (tr. J. Litteral, draft)