If civilization falls, will people go back to their natural habitat?

[Unitive_Mystic]

So I have been studying evolution and seeing how people from different parts of the world adapt to their enviroment. So the data I have gathered so far is that humans with a darker skin tone gives them the advantage in areas closer to the equator, people with lighter skin tone are adapted to lower light levels further away from the equator. Here is the further information.

"Surprisingly, the team found no immune genes under intense selection, which is counter to hypotheses that diseases would have increased after the development of agriculture.

The paper doesn’t specify why these genes might have been under such strong selection. But the likely explanation for the pigmentation genes is to maximize vitamin D synthesis, said paleoanthropologist Nina Jablonski of Pennsylvania State University (Penn State), University Park, as she looked at the poster’s results at the meeting. People living in northern latitudes often don’t get enough UV to synthesize vitamin D in their skin so natural selection has favored two genetic solutions to that problem—evolving pale skin that absorbs UV more efficiently or favoring lactose tolerance to be able to digest the sugars and vitamin D naturally found in milk. “What we thought was a fairly simple picture of the emergence of depigmented skin in Europe is an exciting patchwork of selection as populations disperse into northern latitudes,” Jablonski says. “This data is fun because it shows how much recent evolution has taken place.”

Anthropological geneticist George Perry, also of Penn State, notes that the work reveals how an individual’s genetic potential is shaped by their diet and adaptation to their habitat. “We’re getting a much more detailed picture now of how selection works.”

That being said, in today's modern day civilization we have the technology to help us live outside our natural habitat (sunscreen, sunglasses, skin cancer treatment). If civilization falls we won't have access to this equipment, sunglasses break and sunscreen expires. Where will people of different races go? Will Caucasian and Europeans move up north as well as Afircans and Mexicans move down south? Will they move at all? If not, how will they live outside their natural habitat without modern conveniences.