Population migrations over time have changed the color of our skin.
Barely 5,000 years ago, people in Western Europe still had dark skin. It was the migrations of Anatolian cultivators and lighter-skinned Yamnaya peoples that initiated this change by introducing into the European gene pool the light variants of two genes linked to skin color.
Homo sapiens moved to less sunny latitudes
For twenty years, a very widespread hypothesis has been that when A wise man came out of Africa 175,000 years ago the populations that migrated to less sunny northern latitudes have, by natural selection, gradually lost the pigmentation that protected them from the UV rays of the sun in order to synthesize enough vitamin D.
Except that, as Andrea Hanel, an epigenetics researcher at the University of Eastern Finland, points out, having dark skin does not prevent the synthesis of vitamin D, because it takes place in the upper layers of the body.epidermis, while the pigments are concentrated in the deeper layers. Another inconsistency, pointed out by a study published in 2017 in the journal Science: many variants of genes coding for light skin have existed for 270,000 years in Africa.
There is therefore certainly a reason other than sunshine that explains the spread of this gene in the population.