Is curly hair considered to be a trait that developed through evolution due to climate?

Do certain nationalities have more curly haired people? Or, certain parts of the world? Is it considered to be similar to skin color and has some sort of evolutionary explanation? I was telling my husband how curly his hair looked today. His hair is curly always, but he let it dry without any styling lotion and it was especially tight curls today. For whatever reason I said something about his genes from the desert. His father’s side is from the middle east.

It would make sense from an evolutionary standpoint. He never has to worry about a sunburn on the top of his head. My thin straight hair gets me plenty of burn, especially where my hair parts. His hair has no part. A few of my other friends who are curly are red heads with very fair skin. My husband has olive skin.

I have no idea if curly occurs more in some parts of the world or if there is an evolutionary explanation or theory. If you know anything about what science thinks on the subject I’m interested.