What If? A Brief History of the Ages & Whats Yet to Come
One could interpret the story of Noah and his sons as the spread of the Adamic religion or law. I doubt highly that with todays knowledge of the human race and the many similar stories of the diluvial apocalypse that any abstract minded free thinker could believe that Noah and his family were the only survivors.
They are the survivors (imo) who spread the Adamic law north, south, east and west. Eventually they met up with the original Chinese ( Asians ), Europeans, north and south Americans and others.
Your version is however very interesting.
I wonder if the curse of Canaan is not somehow related to the 70 and 7 fold curse promised by Adam on anyone who lay arm on the descendants of Cain. If I recall right, the first promise was a 7 fold curse and ironically there are 7 generations from Seth's first son to the father of Noah. All of those, including Noah, lived or had potential to live a thousand years. As you say, the sons of Noah lives shorter lives. Afterwards the age would not surpass 120.
Today, on average we live 72 years or so. 72 times 70 fold is roughly 5000 years. Who's to say what one fold or generation is but with a certain margin of error, from the time Noah's sons were born to today we could well be at the end of that 70 + 7 fold curse period.
I know that is all speculation but the entire mystery of Adam and Eve and the Garden of Eden is speculative in nature, and it is brought to us by prophets and interpreters of prophetic sacred scripts.
You mention agriculture and soil erosion.
An abstract thinker who understands the precession of the equinoxes and the astrological ages associated to it could easily speculate that in the age of Gemini ( circa 6000 BC - a few thousand years before Adam ) some powerful rulers knew of the art and science of pollination and of irrigation via dam building or such. Interestingly the age of Gemini is marked by the twin stars of Pollux and Castor. Us Frenchman know a beaver to be a castor and a builder of dams. Pollux seems to be closely associated to pollination, not to sound bells in my mind.
What if ???
A story could go that two great leaders existed in the age of Gemini. One was master of the art and science of agriculture. The other was master of the art and science of construction or irrigation. Together they ruled the world ( or the known world ). Power to rule both arts is a very probable cause for one master to try to kill the other. What if ??????????
The age of Taurus comes along. The bull becomes sacred. Did the people of the age of Gemini begin to consume meat and is that possibly what brought about the demise of Eden? The age of Aries followed and much war was witnessed and the diluvial apocalypse changed everything.
We moved in the age of Pisces and a new prophet, some believe the ultimate prophet, is said to have returned to remind us of our soulful roots. Today we still argue about the existence of that godman. Some completely deny it.
And we move into the age of Aquarius; and into an age which some believe the paternal driven global zeitgeist will be challenged by a maternal or female energy.
What if ???