Why Is Hair Curly?

It has been thought that hair is curly because of the shape of the hair follicle (from which it grows) or because different halves of the hair fiber grow at different rates. These have not been proven.

Based on more recent research, it appears that curly hair is determined by the chemical composition (proteins) of cells in the cortex of hair fibers and how the strands of proteins are arranged in the hair’s cortex.