Human scalp hair as a thermoregulatory adaptation

The study examines the thermoregulatory function of human scalp hair, proposing its evolution as an adaptation to hot and arid environments. Using a thermal manikin and human hair wigs, it demonstrates that scalp hair, particularly tightly curled hair, significantly reduces heat gain from solar radiation. This adaptation minimizes the need for sweat to offset heat gain, offering a thermoprotective advantage by reducing the need for evaporative cooling. The research suggests that tightly curled hair may have evolved to protect early hominins against excessive solar radiation, potentially alleviating thermoregulatory constraints on brain size. However, the study notes limitations, such as the use of manikins and a narrow range of hair types, and suggests further research on the full-body thermoregulatory impact of scalp hair.