Curly hair likely evolved as an adaptation in early humans to help regulate body temperature by promoting heat loss while also conserving water.
Curly Hair and Thermoregulation: A Potential Evolutionary Advantage
A recent study published in PNAS suggests that curly hair may have provided an advantage to early Homo sapiens in warmer climates. Here's a breakdown:
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The Cooling Effect: Curly hair, compared to straight hair, reduces heat gain from solar radiation. This is because the curls create more space between the scalp and the hair's outer surface, allowing for better airflow and heat dissipation.
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Water Conservation: While promoting cooling, curly hair also helps minimize water loss through sweating. Efficient thermoregulation means less sweating is needed to maintain a stable body temperature.
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Brain Size and Energy Demands: The evolution of larger brains in humans required significant energy expenditure. Efficient thermoregulation would have been crucial in allowing the brain to grow to its modern size without overheating.
Simulation-Based Evidence
Researchers used thermal manikins with different hair textures (straight, moderately curly, and tightly curly) in climate-controlled chambers to simulate the effects of sun and wind on the scalp. These simulations demonstrated that curly hair textures significantly reduced heat flux to the scalp compared to straight hair.
Implications for Human Evolution
These findings suggest that the evolution of hair texture played a crucial role in the adaptation of early humans to different environments. Curly hair may have been particularly advantageous in the hot, sunny climates of Africa, where early humans originated. As humans migrated to cooler regions, other hair textures may have become more prevalent due to different selective pressures.
