You are trying to read the story in a purely technical sense (how to save dinosaurs, how to save trilobits... well, they did not make it anyway), instead of trying to understand the point - people were corrupted, the civilization was destroyed and Noah and animals living with people (for example cows) were saved so that the a new civilization could be built again.
So the Ark and the 120 years was all just useless fluff? Isn't it funny that in Gods Inspired Word, He talks about the corruption of all people,
Genesis 6:
5 And God saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually.
6 And it repented the Lord that he had made man on the earth, and it grieved him at his heart.
7 And the Lord said, I will destroy man whom I have created from the face of the earth; both man, and beast, and the creeping thing, and the fowls of the air; for it repenteth me that I have made them.
So that you are willing to buy!
But then when it comes to how he is going to destroy all (not just some) flesh from the face of the land (you are sure He meant just the Mesopotamian Valley)
13 And God said unto Noah, The end of all flesh is come before me; for the earth is filled with violence through them; and, behold, I will destroy them with the earth.
14 Make thee an ark of gopher wood; rooms shalt thou make in the ark, and shalt pitch it within and without with pitch.
So all this below and chapter 7,8,9,10,and 11 are all just myth, fable or intense imagination? After all the genealogies are a continuous narrative and the genealogies show how the gentile nations were settled! Is that what you are trying to say?
15 And this is the fashion which thou shalt make it of: The length of the ark shall be three hundred cubits, the breadth of it fifty cubits, and the height of it thirty cubits.
16 A window shalt thou make to the ark, and in a cubit shalt thou finish it above; and the door of the ark shalt thou set in the side thereof; with lower, second, and third stories shalt thou make it.
17 And, behold, I, even I, do bring a flood of waters upon the earth, to destroy all flesh, wherein is the breath of life, from under heaven; and every thing that is in the earth shall die.
18 But with thee will I establish my covenant; and thou shalt come into the ark, thou, and thy sons, and thy wife, and thy sons' wives with thee.
19 And of every living thing of all flesh, two of every sort shalt thou bring into the ark, to keep them alive with thee; they shall be male and female.
20 Of fowls after their kind, and of cattle after their kind, of every creeping thing of the earth after his kind, two of every sort shall come unto thee, to keep them alive.
21 And take thou unto thee of all food that is eaten, and thou shalt gather it to thee; and it shall be for food for thee, and for them.
22 Thus did Noah; according to all that God commanded him, so did he.