Well, have read that thinner noses warm the air, which undergoes turbulence when inhaling, preventing irritation of the mucous membranes of the nose and lungs.
Someone I knew back when I was in college had a similar theory; but the way he put it was that people who live in hot climates 1) have larger nasal passages so that they can move a lot of air in and out of their lungs to help cool the body and 2) evolve languages that involve large amounts of air moving in and out of the lungs. He said that people in cold climates evolved languages that are more economical of air, to minimize the quantity of air that needs to be warmed before entering the lungs.