And God said, Let the waters bring forth abundantly the moving creature that hath life, and fowl that may fly above the earth in the open firmament of heaven. And God created great whales, and every living creature that moveth, which the waters brought forth abundantly, after their kind, and every winged fowl after his kind: and God saw that it was good. And God blessed them, saying, Be fruitful, and multiply, and fill the waters in the seas, and let fowl multiply in the earth. And the evening and the morning were the fifth day. And God said, Let the earth bring forth the living creature after his kind, cattle, and creeping thing, and beast of the earth after his kind: and it was so. And God made the beast of the earth after his kind, and cattle after their kind, and every thing that creepeth upon the earth after his kind: and God saw that it was good. (Genesis 1:20-25)
As well as in the creation of plants (vv. 11-13), the constant refrain of these verses is after their kind (in Heb. leminehem). It is a further indication of one of the author’s interests. He lived around the sixth century BC and he belonged to the powerful and influential priestly class who built the jewish cultural hegemony. The jewish life was based on the Temple, the worship and the calendar. The Genesis’ authors loved to order, to classify and to divide. We have already seen this in the first four days of creation. God separated the light from the darkness, the land from the waters, and day from night (vv. 1-10). Recovering the lost identity requires a separation from what is foreign to the principles employed to build a religious community.
If you read superficially these verses it seems strange that God creates the sea monsters (in Heb. tannim). You must locate the account in the cultural and religious background in which its authors lived. In the Babylonian tales that recounts the creation of the world – e.g. Enuma Elish – the waters were inhabited by Tiamat, the sea monster that Marduk, the king of the gods, defeated. He then created the heavens and the earth with the pieces of the dismembered corpse. The name Tiamat is perhaps echoed in the Hebrew tehom. This is the name that appears in the second verse, and that is usually translated as abyss inhabited by sea monsters. The abyss is one of the images that describe the chaos. In so doing, the Genesis’ authors were much more speculative than the Babylonian authors. However, even the Bible speaks of sea monsters. For example, we know the Leviathan in the Book of Job (Capp. 40 ff.).
Both the birds, the fish and land animals are described as living beings, that is, as nefesh chayyah. This expression is also used for humans. Man is a living being too and he is blessed as birds and fish. Apparently, the animals receive no special blessing. In fact, in verse 25 the author says simply: and God saw that it was good. The blessing of the land animals comes later alongside the man that is created on the sixth day (v. 31). Then the text says that animals – like humans – are very good things. So the land animals enjoy a different status with respect to the other living beings.
The animals are classified into three categories: domestic animals (cattle), creeping thing and beasts of the earth. Among the creeping thing (in Heb. remesh) there are not only reptiles, but also insects that crawl on the ground. However it is not possible to look for concepts of modern zoology in ancient texts that belong to a very ancient culture. In any case it was a culture very careful to identify species and categories (see Lev 20).