Dark skin gives you some protection from sun, but not nearly enough - somewhere around SPF 10 IIRC.

Increased melanin level helped, but didn’t solve the problem. It’s evolution driven, so it gave people living in more sunny places enough of protection, so they can reproduce.

Except East Asians, who according to my information (...I couldn't find a reference quickly) descended not-so-long ago from something like Inuit or Siberians. At least they can get tanned, it seems, as easily or better than Central Europeans.