The Surprising Ways Hair Helped Early Humans Stay Cool and Regrow Hair Today

A new study has found that tightly curled hair provides the best protection from the sun's radiative heat while minimizing the need to sweat to stay cool. The research examined the role human hair textures play in regulating body temperature and can shed light on an evolutionary adaptation that enabled the human brain to grow to modern-day sizes. As early humans evolved to walk upright in equatorial Africa, the tops of their heads increasingly took the brunt of solar radiation, and scalp hair likely 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.