Our Garden Of Eden is still ahead of us.
You can't really believe that we frolicked with lions and tigers many millennia ago when we were little better than an animal and dumber than a rock, can you?
The Garden of Eden wasn't even a rational myth. That would be Pandora's Box. That was a myth that sought answers and warned us of the possible misstep that we stepped right into with myths like The Garden of Eden. If you are looking for more of an explanation, that would be in a couple of the earliest books.
Once we truly become human is when we will learn to love, maintain an emotional balance, think rationally, and fulfill our sentient state. For all intents and purposes, it will be a Garden Of Eden, as long as you don't expect utopia. If you expect an existence in which humanity can finally respect itself, then you are thinking in the right direction.
If you are looking for our demise that would be the mindless approach to life that we currently maintain.