The Science of Hair Growth: From Curly Hair to Stem Cells.

Researchers at Pennsylvania State University used a thermal manikin to study how heat is transferred from the body to the atmosphere under different hair conditions. They found that tightly curled hair offers the best protection from the sun’s radiation and heat, and minimizes the need to sweat to stay cool, which would help conserve water and avoid dehydration. The hair on our heads probably evolved as a way to reduce the amount of heat gain from solar radiation, thereby keeping humans cool without the body having to expend extra resources. This probably gave early humans an evolutionary advantage by allowing our brains to grow.