Humans acquired dark skin in Africa about 1.5 million years ago to protect bodies from ultra-violet rays of the sun, which can cause skin cancer.

• 大约150万年以前，非洲人形成了深色皮肤，以此使皮肤免受太阳光紫外线的伤害，因为紫外线照射能引发皮肤癌。