Humans appear “hairless," not because we have less hair follicles, but because our hair is thinner, shorter, and more transparent than that of other mammals. The outermost layer of the hair is called the cuticle, and it is composed of dead, overlapping cells that form a hard protective coating, like shingles on a house. Caucasian hair (left) typically has ~5 layers in the cuticle whereas Asian hair (right) has up to 12, making it wider. Asian hair has a round fiber and is straight. Wavy and curly hair have oval or irregularly-shaped fibers. The shape of the hair follicle determines the shape of the fiber.
Image: Scanning electron micrograph of a hair fiber from a Caucasian blonde female (left) and an Asian male (right). The overlapping cells of the cuticle are readily apparent on both fibers.
