This theory is my deciphering. If others believe something similar, I haven’t heard of it, but that wouldn't be the first time.
Growing up in the white, rural Midwest, I didn't meet met a black person until I was 17.
But 1960s TV had a lot of bad news about blacks, and evolution inferred that each race came from a different color of monkey.
From a white perspective, black monkeys suffered from genetic shortcomings.
After all, this was the original reason for Darwin's research: the negro race's apparent inability to function at the same level as white society.
After I got Jesus-saved, I began to look at blacks differently. I had always assumed that whites were created by God,
but wasn’t sure if blacks had a different origin, as evolution suggested.
I began to investigate the origins of the races via the Old Testament, in the late ‘80s and through the ‘90s.
Below is a graph about early human life. https://www.preceden.com/timelines/234513-patriarchs-of-ancient-israel.
While there is debate about the actual timeline of Biblical Patriarchs, I chose this chart because of its clear graphics.
There were at least five generations of Noah and descendants that lived at least 400 years post-Flood.
(God timed the Flood to begin shortly after Noah’s father and grandfather died).
After the flood, the people were regenerating, and decided to build the Tower of Babel.
God disapproved, confounded their language and they scattered.
Then came the separation of the continents ‘during the time of Peleg’ (Genesis, Chapter 10), after Peleg was born, but before having any children. This was an ancient method of timekeeping. So the initial separation of the continents happened within a 30-year segment of history.
Cataclysmic, no doubt. According to this chart, Peleg lived from 2279 to 2040 B.C.
Notice how lifespans were cut in half, yet again, after Peleg.
Genesis 4 This is the account of the heavens and the earth when they were created, when the Lord God made the earth and the heavens.
5 Now no shrub had yet appeared on the earth and no plant had yet sprung up, for the Lord God had not sent rain on the earth and there was no one to work the ground, 6 but streams came up from the earth and watered the whole surface of the ground.
Before the Flood, I believe everyone was white-skinned, because the earth was covered with clouds and UV rays did not reach the earth the way they do now.
This means there were clouds, but they never emptied themsleves.
Therefore melanin was not needed, but was in reserve in our genetic code, not a slowly-evolved product of necessity, but by the foresight of God.
The crux of the theory; in those post-flood generations, which I call the “deceleration era” (because human lifespans were winding down),
humans adapted to increased UV rays. This seemed to be a two-step process:
1) the initial adjustment after the flood.
2) the separation of the continents during Peleg's youth, when ocean gyres came to be, hence cloudless deserts were formed.
Melanin levels of each people group adjusted to their post-Babel locations, in relation to the equator after the continental separation.
Their shortening lifespans locked melanin ratios into our DNA.
We no longer live long enough to adjust our melanin levels to environmental relocation.