system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:How did the first white people happen?

When humans moved from Africa to Europe their skin didn't need to protect them from the sun as much any more.  


But that's not how evolution works right? Your genes don't just change to suit your environment. Was there a mutation that lightened the skin?  If so how did we go from a full dark population to a full white one in those regions?  Is it similar to albinism at all?  If the mutation is random does it still happen in African populations?
gpt
>Was there a mutation that lightened the skin?

Yes, but there are more than one that alter the complexion of skin tone. 

>If so how did we go from a full dark population to a full white one in those regions? 

People with these mutations bred with one another to create offspring, and eventually the phenotype reached equilibrium in the population. This process took thousands of years.

> Is it similar to albinism at all?

No

Albinism is a pathology. The mutations that gave rise to white people are not seen as pathological as they show selective benefits given they reside in colder regions. Albinism, on the other hand, has not shown to have any benefits for survival. 

> If the mutation is random does it still happen in African populations?

Interesting question since there are populations in Sub Saharan Africa that have lighter phenotypes. The Igbos, for instance, have  segments of the population where people have fair skin although not having any European ancestry. These are mutations but not the ones that  non-Africans possess.