It’s adaptation, not evolution.
There is some confusion about the term evolution. While Darwin proposed the phenomenon, it was not until Gregor Mendel did is work along with others that the principles of genetics were established. Darwin new that more useful traits became the dominant ones over time amoung species. He did not know anything about dominant and recessive genes, nor about mutations. Adaptation in the biological sense is the building up of a reservoir of favorable genes among a population. In the social sense, it is learning to change one’s behavior to function better in difficult circumstances.
Thus, the white skin mutation in African homo sapiens as it became more common enabled our ancestors to push the Neanderthals out of Europe. This was a genetic adaptation, or evolution.
On the other hand, when Greenland became much colder in the Middle Ages as a result of The Little Ice Age, the residents failed to learn and adopt the living and hunting strategies of the Inuit natives and their settlements died out. This was a failure of social adaptation.