I am an agnostic but I suspect that the book of Genesis is a sort of metaphor. If you are a very intelligent person, who has a good grasp of evolution and believe that there is some sort of intelligence acting upon the universe, how would you explain it to a bunch of sheep-herdsmen? You would write an epic, easy to remember poem, and phrase complex concepts in simple terms which the herdsmen could understand.
Let's take Genesis, for instance, and treat it as a metaphor for the scientific explanation we use today. Please look for the italics as the explanation in modern language. Of course, the interpretation below is my own and it is rather liberal. Theres absolutely no guarantees that it is what the author meant. But is a good guess nonetheless, or so I think. I have a lot more respect for Christians who understand Genesis in these terms, as opposed to those who take it literally. If they do take it literally, it means that they havent really evolved much beyond those illiterate sheep-herdsmen for which this book was intended.
Genesis 1
1 First God made heaven & earth
First the universe and then earth appeared
2 The earth was without form and void, and darkness was upon the face of the deep; and the Spirit of God was moving over the face of the waters.
The primitive earth had no features as we know them today, the atmosphere did not allow light to get through, but life was forming in the oceans.
3 And God said, "Let there be light"; and there was light.
The atmosphere changed enough for light to penetrate to the surface of the earth
4 And God saw that the light was good; and God separated the light from the darkness.
5 God called the light Day, and the darkness he called Night. And there was evening and there was morning, one day.
Light had a positive impact on life, which started to be affected by day and night. An era passed
6 And God said, "Let there be a firmament in the midst of the waters, and let it separate the waters from the waters."
The first continent took shape amidst the oceans
7 And God made the firmament and separated the waters which were under the firmament from the waters which were above the firmament. And it was so.
The cycle of water started to occur, as the water in the oceans was separated from the water in the atmosphere (clouds)
8 And God called the firmament Heaven. And there was evening and there was morning, a second day.
The early earth was an amazing place. Another era went by.
9 And God said, "Let the waters under the heavens be gathered together into one place, and let the dry land appear." And it was so.
10 God called the dry land Earth, and the waters that were gathered together he called Seas. And God saw that it was good.
The continents and the oceans as we know them took shape.
11 And God said, "Let the earth put forth vegetation, plants yielding seed, and fruit trees bearing fruit in which is their seed, each according to its kind, upon the earth." And it was so.
Vegetal life now appeared on dry land and diversified.
12 The earth brought forth vegetation, plants yielding seed according to their own kinds, and trees bearing fruit in which is their seed, each according to its kind. And God saw that it was good.
Each vegetal life form had different adaptations for reproduction.
13 And there was evening and there was morning, a third day.
Another era passed
14 And God said, "Let there be lights in the firmament of the heavens to separate the day from the night; and let them be for signs and for seasons and for days and years,
15 and let them be lights in the firmament of the heavens to give light upon the earth." And it was so.
The stars could be seen from Earth and also had a role to play in the ecosystem
16 And God made the two great lights, the greater light to rule the day, and the lesser light to rule the night; he made the stars also.
17 And God set them in the firmament of the heavens to give light upon the earth,
18 to rule over the day and over the night, and to separate the light from the darkness. And God saw that it was good.
The cycle of life was determined by the sun and the moon, each with a specific role to play.
19 And there was evening and there was morning, a fourth day.
Another age passed.
20 And God said, "Let the waters bring forth swarms of living creatures, and let birds fly above the earth across the firmament of the heavens."
Life diversified in the oceans. The first insects on earth started to fly.
21 So God created the great sea monsters and every living creature that moves, with which the waters swarm, according to their kinds, and every winged bird according to its kind. And God saw that it was good.
The first great marine reptiles and dinosaurs appeared. The first birds also started to diversify.
22 And God blessed them, saying, "Be fruitful and multiply and fill the waters in the seas, and let birds multiply on the earth."
These animals continued to reproduce and diversify.
23 And there was evening and there was morning, a fifth day.
Another age passed
24 And God said, "Let the earth bring forth living creatures according to their kinds: cattle and creeping things and beasts of the earth according to their kinds." And it was so.
25 And God made the beasts of the earth according to their kinds and the cattle according to their kinds, and everything that creeps upon the ground according to its kind. And God saw that it was good.
The modern land animals appeared and diversified.
26 Then God said, "Let us make man in our image, after our likeness; and let them have dominion over the fish of the sea, and over the birds of the air, and over the cattle, and over all the earth, and over every creeping thing that creeps upon the earth."
Eventually, the human animal appears, endowed with the ability of abstract thought.
27 So God created man in his own image, in the image of God he created him; male and female he created them.
28 And God blessed them, and God said to them, "Be fruitful and multiply, and fill the earth and subdue it; and have dominion over the fish of the sea and over the birds of the air and over every living thing that moves upon the earth."
The early humans appeared and started to migrate across the surface of the Earth.
29 And God said, "Behold, I have given you every plant yielding seed which is upon the face of all the earth, and every tree with seed in its fruit; you shall have them for food.
The basis of their alimentation was vegetal
30 And to every beast of the earth, and to every bird of the air, and to everything that creeps on the earth, everything that has the breath of life, I have given every green plant for food." And it was so.
All animals ultimately depend on the plants for energy
31 And God saw everything that he had made, and behold, it was very good. And there was evening and there was morning, a sixth day.
Another age passed.
Now, Genesis 2 is somewhat redundant, as it repeats the explanation for the appearance of the Earth and life, in somewhat different terms, in verses 1-7. Lets start again at 8.
Genesis 2
1 Thus the heavens and the earth were finished, and all the host of them. 2 And on the seventh day God finished his work which he had done, and he rested on the seventh day from all his work which he had done. 3 So God blessed the seventh day and hallowed it, because on it God rested from all his work which he had done in creation. 4 These are the generations of the heavens and the earth when they were created. In the day that the LORD God made the earth and the heavens, 5 when no plant of the field was yet in the earth and no herb of the field had yet sprung up--for the LORD God had not caused it to rain upon the earth, and there was no man to till the ground; 6 but a mist went up from the earth and watered the whole face of the ground-- 7 then the LORD God formed man of dust from the ground, and breathed into his nostrils the breath of life; and man became a living being.
8 And the LORD God planted a garden in Eden, in the east; and there he put the man whom he had formed.
Early man formed somewhere in the East [of Africa]
9 And out of the ground the LORD God made to grow every tree that is pleasant to the sight and good for food, the tree of life also in the midst of the garden, and the tree of the knowledge of good and evil.
Early mans native environment was quite rich. Primitive humans reproduced [tree of life] and developed religion.[knowledge of good and evil]
10 A river flowed out of Eden to water the garden, and there it divided and became four rivers. 11 The name of the first is Pishon; it is the one which flows around the whole land of Havilah, where there is gold; 12 and the gold of that land is good; bdellium and onyx stone are there. 13 The name of the second river is Gihon; it is the one which flows around the whole land of Cush. 14 And the name of the third river is Tigris, which flows east of Assyria. And the fourth river is the Euphrates.
Out of the original homeland, several streams of migration occurred. The first went up the Nile. The second colonized Ethiopia (to the east of the original Rift Valley). The third and fourth migration waves went to the Middle East.
15 The LORD God took the man and put him in the garden of Eden to till it and keep it.
16 And the LORD God commanded the man, saying, "You may freely eat of every tree of the garden;
17 but of the tree of the knowledge of good and evil you shall not eat, for in the day that you eat of it you shall die."
Life was plentiful for ancestral man. However, Death held a special mystery, for which religion provided an explanation and put it into perspective.
18 Then the LORD God said, "It is not good that the man should be alone; I will make him a helper fit for him."
19 So out of the ground the LORD God formed every beast of the field and every bird of the air, and brought them to the man to see what he would call them; and whatever the man called every living creature, that was its name.
Complex language also appeared at this time, with humans having the ability to transmit names given to the world around them.
20 The man gave names to all cattle, and to the birds of the air, and to every beast of the field; but for the man there was not found a helper fit for him.
Some animals were domesticated. With the appearance of language and animal domestication, social structures emerged, as some people were needed to take upon subordinate positions in society.
21 So the LORD God caused a deep sleep to fall upon the man, and while he slept took one of his ribs and closed up its place with flesh;
22 and the rib which the LORD God had taken from the man he made into a woman and brought her to the man.
In the meantime, out of human DNA [a rib], God had created women.
23 Then the man said, "This at last is bone of my bones and flesh of my flesh; she shall be called Woman, because she was taken out of Man."
24 Therefore a man leaves his father and his mother and cleaves to his wife, and they become one flesh.
Men and women are meant to create strong bonds (marriage), if they procreate.
25 And the man and his wife were both naked, and were not ashamed.
At this time, religion had not created the idea that reproduction is sinful.