Scientists finally discover why some hair is curly – it all starts under the skin

Scientists have pinpointed the underlying cause of curly hair, revealing that the secret lies not in external factors like washing or humidity, but deep beneath the skin within the hair follicle.

Research, including studies from 2005 and more recent evidence, indicates that the shape of the hair follicle is the key determinant of whether hair grows straight or curly. If a follicle is positioned vertically, the hair emerges straight. However, if the follicle is angled or curved, like a golf club, the emerging hair shaft is already bent. This initial bend is further influenced by the asymmetrical division and maturation of cells on opposite sides of the follicle.

This asymmetry leads to variations in the composition of keratin and other materials along the hair shaft's circumference. Consequently, the hair strand develops an uneven structure, making it more prone to bending and twisting in a specific direction, resulting in curls. In contrast, follicles that produce straight hair tend to have a more symmetrical structure.

While the follicle's shape is the primary factor, the composition of the individual hair strand also contributes to its texture and coarseness. Scientific literature suggests that the follicle's structure dictates whether hair grows in a spiral, a sharp curve, or straight. Once the hair emerges from the scalp, it retains the shape determined at its origin. This genetic predisposition explains why hair types often run in families.

It's important to note that scientific classifications do not support the idea of hair types being strictly linked to race. A comprehensive review indicates that a wide spectrum of hair shapes exists within all populations, regardless of origin. While certain curl patterns may be more common in specific genetic lineages, the fundamental mechanism of hair formation is rooted in the complex structure of the follicle, which is ultimately determined by an individual's genes.