It was pretty sweet in the garden. No winter. Lots of food. Adam and Eve lying around naked-- not that they knew they were naked, of course. That came later. There was death but nobody knew what it was.
Being first, Adam wasn't all there. He walked around like an idiot naming everything. It wasn't his fault. His brain was packed in grease when he woke up. It was years before it worked right. Eve was smart right off, being human 2.0.
But like any monkey with an oversized brain and not much to do, both of them got bored. Adam less than Eve since he spent a lot of time figuring out how to name things. Should the word reflect the sound of the thing? The smell? What about things that looked like a combination? Like an elephant: snake on both ends and a hippo in between. Even Adam had a few doubts about that one.
Eve, created unstupid, found it much harder to keep herself entertained. The obvious solution never occurred to her. Adam and Eve had the equipment for sex but not the skills or motivation.
In the middle of the garden was the tree. You know the one. A lot of the stories have two trees, the other being the tree of life. But you can't really imagine anybody would leave immortality just lying around, would you? As it was, there were worms, flies and fruit bats filled with the knowledge of Good and Evil, copulating wildly around the tree in a pointless effort to relieve the depression of their inevitable mortal demise.
There wasn't much variety in the garden.
Eve was walking around staring at the same maple (Look, Eve! A Maple!), fig (Look, Eve! A Fig!) and cranberry (Look Eve... You get the idea.) until she was ready to scream. If they'd invented fire at that point Eve would have burned the garden to the ground and happily danced in the ashes. It's not surprising she'd gravitate towards the forbidden.
The snake actually lived in the tree. Being off limits, it was the one place in the garden he could find privacy. (Look, Eve! A Snake!... Ow. My heel.) The serpent was cursed with a good understanding of things to come (Thou shalt crawl on thy belly on the ground! Well, duh! No arms!) and was none too keen on his prospects.
"Hi," said Eve.
The snake nodded.
"So," she says. "Is there anything to do around here?"
The snake shrugged. (Something to see for someone without arms.) "There are always these apples."
"Those are forbidden."
"What's so special about them?"
"Knowledge of Good and Evil."
The snake sighed. "With good and evil you get the rest of the package: tight dresses, moral decisions, scientific inquiry, multiple orgasms."
At the point the snake realized how truly bereft these two ignorant mammals were and gave Eve a sample. From what we know about the snake it was, no doubt, a pretty good sample.
When Eve could breathe again she had an inkling of what was at stake.
"I'd be naked," she said, scandalized and excited at the same time.
"More to the point," said the snake. "You would know what nakedness was for."
Eve bit into the apple without hesitation.