Light skinned people lack melanin because they arose where clothing wasn't optional and sunshine was lacking.

The theory is the lighter skinned people survived in the colder northern climates expressly because their lighter skin allowed more sunlight in, and thus produced adequate amounts of Vitamin D even when clothed for the cold climate.

Those with more melanin and thus dark skin did not produce enough Vitamin D, and died out in the northern darker environments. They did well and produced even darker ancestors in the equatorial areas where the sun was intense and clothing was optional.

And skin cancer is a result of over exposure to the sun.

Sunburn isn't cancer. Skin cancer became prevalent only over the last few decades which is exactly when they started telling us to avoid 'too much" sun.

Dr. Ken Berry explains it in this 12 minute video. There are plenty of other doctors and studies that agree with him.

https://www.youtube.com/watch?v=tpGRZGgxJLo

Sunburn is... too much sun on skin for too long. A threshols reacjrd moe quickly if you have less melanin Then it heals. If you have on sunscreen, you have added carcinogens.

Bad diets, I assume. People on Carnivore diets report much milder or fast healing burns.

In layman terms, from what I've read, consuming seed oils in food interferes with your body's Melanin production, which can make you susceptible to sunburns and skin cancer.