Folic acid is stored in the skin and is needed to prevent neural tube defects and consequent death of the fetus. Sunlight destroys it. Each race requires the same amount of folic acid. The human race evolved from central Africa and black skin was required by Mother Natures to prevent folic acid destruction by the sun. As people migrated north their skin became lighter because there was less exposure to the sun, since they wore more and more clothing and hence more protection from the sun with cooler and colder climates. Their folic acid was preserved from less sun destruction. This process took hundreds of thousands of years.
Wider noses/nostrils with large turbinates accommodate a greater need for humidifying the very dry air