How Curly Hair May Have Helped Early Humans Stay Cool
Key Highlights :
Humans have evolved in many ways over the millennia, and one of the most interesting adaptations is the evolution of hair texture. A new study published in the journal PNAS on Thursday sheds light on how the evolutionary adaptation of hair texture may have enabled human brains to grow to modern-day sizes. The research focused on how human hair textures play a role in regulating body temperature, and how tightly curled hair may have helped early humans stay cool while conserving water.
The research team, which included scientists from Penn State, used a thermal manikin – a human-shaped model that uses electric power to simulate body heat – in a climate-controlled wind tunnel to study heat transfer between human skin and the environment, and from human hair wigs. They simulated solar radiation under four scalp hair conditions – none, straight, moderately curled, and tightly curled – and measured the amount of heat gained from each.
The results showed that while all hair types reduced solar radiation to the scalp, tightly curled hair provided the best protection from the sun’s radiative heat while minimising the need to sweat to stay cool. This is likely because early humans began walking upright in equatorial Africa, where the top of the head receives far more intense solar radiation as heat. As the human brain grew larger, it generated more heat, and sweating came at the cost of losing water and electrolytes. Therefore, researchers believe that scalp hair likely evolved as a way to reduce the amount of heat gain from solar radiation and keep humans cool without having to lose electrolytes and water.
The findings of this study can help us better understand how human hair evolved, and also provide insight into how different hair types may be better suited to thrive in specific conditions. For example, the findings could be used to help athletes and members of the military understand if a certain hairstyle will make them overheat more easily.
Overall, this research provides an interesting look into how the evolution of hair texture may have helped early humans stay cool and conserve water, while allowing their brains to grow to modern-day sizes.
