Please tell me the interpretation of the original authors, and how you derive this.
This is a complicated answer, but a few thoughts.
Well, firstly you have to remember that the ancient authors were not in any sense of the word, scientifically minded. They lived in a world full of myth, legend, fable and poetry; and that is how they investigated truth: through story.
They were, in any case, incapable of doing much in the way of investigative science, as they didn't have any way of accurately measuring the world. They didn't even have a zero, or a seperate number system, or any real concept of really large numbers (billions, trillions, that sort of thing.) They did, however, have very sophisticated ways of explaining the world called stories.
The problem is that so many fundamentalists make the mistaken equation of truth = fact. But a fact is something that can be observed using empirical observation, and as that observation gets better, facts change. It used to be "factual" that light in the universe travelled through a substance called "phlogiston". Since then, it's been discovered that such a substance doesn't exist. Facts change as new information is discovered; truth does not change.
Except where facts impact on truth (such as the Incarnation, which needs a real historical Jesus to have existed), the Bible writers are more concerned with finding the real, universal truths of God's relationship to us, than in getting everything down as scientifically accurate as possible.
Genesis 1 has all the stylistic marks of a poem or a chant, not a history. Genesis 2 is fable-like in structure.
And then again, of course, there's the evidence. The overwhelming amount of evidence in favour of evolution means that there are only two alternatives.
A) If you say that the Bible has to be "literal" and scientifically and historically accurate in a very 19th century modernistic manner, then you may as well throw it away, because it just doesn't hold water.
B) If, however, you allow for the possibility that God reveals himself through story, poetry, symbolic language of all kinds, parable, myth, legend - and history as well - then not only can you say the Bible is true, but that it's true in all its fullness.
Personally, if I were to compare the writers of the Bible to anyone in the modern era, I would compare them to Milton rather than Newton, to the TS Eliot of the Four Quartets rather than Stephen Hawking.
And I think the Bible is all the better for that: it becomes deeper, richer and probably stranger as a result. Please note: I am not saying there are no facts in the Bible, and that sometimes these facts don't at times matter (see above.) But the Bible is concerned above with Truth.