Variations in skin colors is a recent evolutionary development, report UTMB’s Norbert Herzog and David Niesel in this week’s installment of Medical Discovery News. Humans didn’t develop different skin tones until 50,000 to 100,000 years ago — when modern man migrated northward out of Africa. That’s when skin color began to lighten. For years, scientists believed evolutionary pressures produced lighter skin because in these higher latitudes the sun is less intense. Given the same amount of sun exposure, lighter skin will produce more vitamin D compared to darker skin. Though many ideas continue to be explored, the most likely explanation for the development of lighter skin tones is vitamin D production. People with dark skin need six times the exposure to sun light to produce the same amount of vitamin D as light-skinned people. As for the rainbow of human skin colors, we see today, it’s likely many factors made that happen. MDN airs locally at 10 a.m. Saturday on KUHF.