Maybe this excerpt from "Reading the Old Testament: An Introduction" can help:
"The Book of Genesis covers a vast amount of time, stretching from the beginning of the world down to about 1500 B.C. According to geologists, the earth is at least four billion years old, and some anthropologists believe that we humans have been around at least two million of those years. The authors of Genesis did not know much about this long history, nor did they care. They wished to sketch instead a few highlights about human origins that had particular religious significance for Israel's view of life, and to record a few traditions about their own ancestors that would help them understand how they came to be a people and a nation." (Boadt pg.109)
... and furthermore, we might consider asking ourselves whether many of the stories contained in the Old Testament are History, or Myth, giving consideration to the following excerpts from the same book cited above:
"The stories certainly disturb the modern historian. They have no particular 'facts' that can be located in a given moment, no eyewitness reports, and no direct connections to other events that are known. If taken literally, the dates they do offer cannot be reconciled with the findings of geology about the age of the earth, nor do the lifespans of people conform to the ages of ancient human remains studied by anthropologists. They are much more like "model" stories of how things should have been at the beginning, and resemble the literary creations of other ancient peoples. In all of them the moment of creation was not like any subsequent period of time. In that time the gods spoke directly to people. To the ancient mind it was a golden age; it was primeval time before history began.
In ancient thought, such time was expressed by means of certain traditional themes or motifs that were different from everyday language and experience. This type of literature is known everywhere as myth. Myths are not all of one kind, nor do they only speak of creation. They also tell stories of the gods, or of legendary heroes of old, or of the origins of customs and ethnic groups. In many cases, the myth is tied closely to a ritual action in worship and forms the dramatic explanation for an actual celebration. In other cases, the myth is etiological, which means 'explaining the causes' of something, such as why a holy place has its name, or why the gods made a certain creature, or why some tribe follows unusual customs. Myth allows us to speak of events of primal importance at the very beginning of time because it does not depend on knowing the scientific facts, but upon understanding the inner meaning of what happened and what purpose stands behind the event. It especially concerns itself with divine beings and their relation to the human world. It is not history in the strict sense, bit it surely is not anti-historical either. It is at least profoundly historical in outlook, for all ancient peoples knew that gods acted according to their relation with humanity. Past events and experience formed the grounds for future expectations of divine acts. By understanding the past we can better direct our lives, our worship, our prayers, to the gods, and better know what choices to make in the present moment.
The common themes and motifs used in myths are the symbols cherished by all ancient civilizations. Thees include creation in or near water, a fight among the gods for order in the universe, the defeat of chaos by a hero god, the making of humans from mud or other lowly material, and a death and rebirth of the hero god parallel to the annual winter and spring cycle of nature. They explore the basic contrasts of nature: sun and earth, light and darkness, water and drought, male and female, gods and human creatures.
Genesis 1-11 incorporates many such elements into its stories, and many of its individual incidents find parallels in the myths of other ancient Near Eastern peoples, especially the Canaanites, Babylonians and Egyptians. Clearly, the biblical tradition did not hesitate to make use of these literary forms. But this does not mean that the biblical 'myth' always has the same view of the world as does the original pagan story. So we must be careful to distinguish our use of the word 'myth' on two levels.
On the first level, myth is a story using traditional motifs and themes. It is not scientific or historical in outlook as we would expect; it is more like folktale, but it does convey how the Israelites saw the shape of the world---it was their "science," so to speak. A very good example of this use of myth is the description of the Garden of Eden in Genesis 2: life originated in the East; there was a central source of water which split into the great rivers of the earth; the first man was made out of dust and the first woman out of a rib; God planted two special and unusual trees in the garden---the tree of life and the tree of good and evil; there was harmony between humans and animals in the beginning. These were all familiar parts of ancient descriptions of the world, and since Israel accepted them as true, we can say that the Bible contains many myths simply because ancient Israelites were not as sophisticated in their knowledge as we are.
On a second level, however, myth is a "theological" explanation of our relation to the gods, and often refers to ancient beliefs of a polytheistic nature in which natural powers were manifestations of the divine, where the gods were symbols of fertility and bound to the seasonal pattern of rainy and dry seasons, where each year the gods must reassert their power over the forces of chaos that threaten the world. When myth is used in this sense, we must be more careful about calling the biblical stories myths, for the authors of Genesis consciously intended to refute and contradict such a view of religion by reworking the traditional stories to remove any idea that there is more than one God, that the world is subject of chaos, that God is callous or uncaring, or that superstitious sexual practices are needed to renew nature. By telling the story of Genesis 1-11 as they did, stressing Yahweh's freedom and power versus human refusal of responsibility, the Israelites demythologized the myths---they destroyed the heart of pagan belief and reinterpreted the real meaning of the world in light of the one God who had revealed himself as Savior and Ruler to Moses." (Boadt pgs. 130-132)
My thoughts: I think it helps when reading many of the stories contained within the Old Testament to regard them as containing important lessons, and not concern ourselves so much with the historical portrayal of God we sometimes find in them, as expressed by their ancient Israelite authors (and there were several authors/editors involved over many centuries). For example, take the story of Lot's wife, who turned into a pillar of salt upon looking back. Compare the message contained within this story to the very words of our Lord Jesus Christ, who teaches us that "Anyone who puts a hand to the plow and then looks back is not fit for the Kingdom of God." (Luke 9:62) In other words, once we have chosen to repent; to turn from our sin in order to enter into communion with God in the Holy Spirit (which is the definition of the Kingdom of Heaven according to the Apostle Paul in Romans 14:17), then we must never turn back to pursuing sin, but remain always on the path of righteousness. If we do turn back again towards sin, then our spirit, deprived of the grace of the Holy Spirit, becomes stagnant -- dead as a pillar of salt -- a spiritual state that renders it extremely difficult to effectively turn back again towards God with a saving repentance.
Hopefully this one example will help us to understand how we should approach our Old Testament readings. There are of course countless others that we could allude to. Please note that these excerpts I've shared here are from a textbook that has been assigned for me to study because of my participation in the late vocations program with Saint Vladimir's Seminary. The texts on the Old Testament that I was assigned to study while enrolled at St. Tikhon's Seminary back in the late 80's were similar in their approach.
