>>From this we see that the garden is more like a defensive sort of covering and an enclosed place of protection than a horticultural paradise. In the ancient middle east, gardens were not as we know them today, they were in fact most often enclosures containing lush vegetation.<<
This idea resonates with me. However, I'm compelled to put a finer point on it:
As we're told Adam was placed in the garden to "dress it and to keep it."
Strong's identifies "dress" and "keep" respectively, as:
'abad; a prim. root; to work (in any sense); by impl. to serve, till, (caus.) enslave, etc . . . .
shamar; a prim. root; prop. to hedge about (as with thorns), i.e. guard; gen. to protect, attend to, etc . . . .
Which not only underscores your sense of the garden being "like a defensive sort of covering and an enclosed place of protection," but also, IMHO, offers some insight as to the pupose for which this Adam was created.
You'll note that "dress," in the above quote is also defined as meaning "work." To me, it necessarily follows that work must be purposeful, otherwise the effort is a vanity -- and hopelessly circular. In the interjection, or insertion of Genesis, Chapter Two into the chronology being presented in Chapter One, there is some hint of a purpose behind the forming of this Adam:
And every plant of the field before it was in the earth, and every herb of the field before it grew: for the Lord God had not caused it to rain upon the earth, and there was not a man to till the ground. But there went up a mist from the earth, and watered the whole face of the ground. And the Lord God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul (Gen 2:5-7, my emphasis).
The suggestion I find in this passage is that the forming of this Adam, at this juncture in God's creative process, was critical to all that followed. The writer(s) of Chapter Two first affirm the chronology of Chapter One, and are then quite deliberate in "placing" the advent of this Adam somewhere on or around the third day (lol - three and a half days might appeal to the more prophetically minded). Before the plants and grasses and herbs and trees, it was first necessary that this Adam be formed.
Why before? Certainly, besides water and earth, plant-life itself is crucial to the foodchain -- I mean, everthing flows naturally from flora to fauna. Plant's grow just fine without a "man to till the ground." Certain animals, insects and birds forage just fine on this plantlife. Certain predators obtain their needs just fine on those foragers. The cycle is whole and complete without "a man to till the ground . . ."
Or is it?
>>Remember that the tree is like a closed door, a protective object. It was placed there to keep harm away from Adam and Eve. In order for the protective place to be a refuge and not a prison, God gave Adam and Eve a key to unlock the door to the outside. Had He not, the ‘garden’ would have been a prison. He gave them the key to leave the place of protection, but it remained locked so that nothing could enter without their letting it in.<<
I still don't see Adam and Eve's purpose in this. As yet, they seem superfluous to the creation -- lol -- sort of like garden gnomes. As "key masters" surely they were responsible for more than just keeping God company in the cool of the evenings . . .