I'm sure you're right. There seems to be a dual purpose to most scripture, one is symbolic, a language trying to bring abstract spiritual concepts into some order of understanding and then a secondary meaning which is not really science, not really literal and yet tries to impart the scope and majesty of physical reality.
Genesis is a very clever piece of writing for its time. It satisfies the basic needs of Bronze Age people who questioned the big HOWS and WHYS. It wove in a storyline from the most popular story of the time, Gilgamesh, borrowed from it heavily and added its own spin to then supply a deeper spiritual subtext.
I think for those in ages past who read this work as literal, it still imparted some great import and the great complexity and sweep of physical existence, be it via a god, or natural order, or whatever, because nobody knows what God is or how the pre-existing substance of the universe began the physical reality we are part of. Science in that age could be little more than a story without details.
The symbolic, spiritual content of Genesis, which is really the only aspect that it is concerned about, it a very complex rendering of the spiritual journey of every single human being, should they take that journey, of course.
It is a story out of time and place. There are no generational links to Adam. Adam was not the first anything, nor did he cause original sin, death, etc. This is just the fundamentalists getting a bit excited and having no understanding of what the Bible's purpose really is.
Adam - every individual human, male and female, because the human spirit is not defined by sex. Eve - the human spirit which is easily corrupted. The snake - a creature that is attached to the earth via its entire body - materialism, attachment, self before God. Eve made from Adam - the essential foundational relationship that underpins humanity, the first nation, the family, a husband and wife. Tree of Good and Evil - The earth, the human domain which is bound up in relative states. The Tree of Life - The teachings that come from God via the likes of Krishna, Buddha, Moses, Jesus, etc, etc, from age to age. Adam and Eve as the first humans - signifies the oneness of the human race, the oneness of religion, be we black, white or brindle.
And so on and so forth. It's a complex story with a great many meanings, and as you say, it even has a very generalised literal component which we have been able to refine in great detail by the gift of science.
But for a religious person to call it a literal work is blasphemy. That's like putting small children in charge of a nuclear reactor.
