***Extrapolate: extend the application of (a method or conclusion) to an unknown situation by assuming
that existing trends will continue or similar methods will be
applicable.
And a river went out of Eden to water the garden;
and from thence it was parted,
and became into four heads.
The name of the first is Pison:
that is it which compasseth the whole land of Havilah, where there is gold;
And the name of the second river is Gihon:
the same is it that compasseth the whole land of Ethiopia.
And the name of the third river is Hiddekel:
that is it which goeth toward the east of Assyria.
And the fourth river is Euphrates.
Genesis 2:10,11,13,14
--From out of Eden the world was divided by 4 rivers.
--Likely flowed to the bottom of the earth converging into a massive lake for the sea creatures, such as whales, etc.
--Likely at the point where the rivers parted out of Eden may have been a large lake.
--Picture these two large mini-seas as a sort of sea world for sea creatures.
--Likely these locations could have been on either side of the polar caps of earth, for the earth is knocked off it's axis, probably by the meterorite/astroid bombardment that took place during the Flood that busted apart the tectonic plates. Remember, as science has shown, the earth was lush and warm at that time.
So what would have been the top and bottom of earth are now moved off original point.
Q: Why does Moses give existing names (such as Ethiopia, Assyria, etc.) if they didn't exist yet?
A: for the hearers/readers it indicates directions on the map....notice that Euphrates is simply named, for at that time, in the other direction on earth, they didn't know what was out there--(for example they would have been unaware of the Olmecs and had no name or knowledge of the Americas).
--Likely, for a source of water, humans from Eden would have lived 
along the rivers.
--Humans would likely have stayed close together as they multiplied, for both survival and safety. (Example: Cains offspring stayed within contact distance of Seth and the others for they intermarried).
Humans didn't likely spread over the entire earth.
--Traversing the earth would have been dangerous for fallen mankind because you need water. But circling Eden to reach each head of the river would greatly shorten distance for travel and one could sail down and back up the rivers for exploration.
***This leads us to an answer as to why we find dinosaur bones and animals buried by the Flood but not people.
---The small (compared to today) human population would have 
been clustered in key locations along the rivers. In the Flood the humans were simply swept up and buried during the massive upheavals that convulsed the earth.
---Animals, on the other hand, were spread everywhere. So where there is land today (remember that 75% of earth is now ocean) you have pockets of animals buried on the surface. The smaller, 
congregating human populations were simply engulfed and buried en masse in most cases.
---The term "Fossil Fuel" (Gas, Oil, Coal, Natural Gas) comes from the fact that it one time was living vegetation. The Pre-Flood world that was buried.
***Now WHY is the Euphrates named "Euphrates"?
Well, likely the settlers in the plain of Shinar named it after the Pre-
Flood river.
And it came to pass, as they journeyed from the east, that they found a plain in the land of Shinar; and they dwelt there. Genesis 11:2
Q: And why would that be?
A: Likely it was the river they had heard the most about, because it was probably the one Noah had lived near and maybe the bulk of the human race at the Flood.
***The River Euphrates is symbolically featured prominently in the 
end times as part of the worldwide Rebellion against God.
Not just because of spiritual Babylon located there, but go back even further to the beginning, it may have been where the Pre-Flood humans primarily lived .....and Rebelled...along the Pre-Flood Euphrates.
And the sixth angel poured out his vial upon the great river Euphrates; and the water thereof was dried up, that the way of the kings of the east might be prepared.
And the great city was divided into three parts, and the cities of the nations fell: and great Babylon came in remembrance before God, to give unto her the cup of the wine of the fierceness of his wrath.
Revelation 16:12,19
***These were just some random thoughts of mine...nothing to be dogmatic about .....all we know for sure is .....by which the world that then existed perished, being flooded with water....
2 Peter 3:6
Also see Links below for more....
SUMERIAN CREATION-FLOOD STORY: THE ERIDU GENESIS
BABYLONIAN CREATION-FLOOD STORY: THE ATRA-HASIS EPIC