Why do we have different hair textures?

Round follicles produce straight hair, oval ones make wavy hair, and flattened or hook-shaped follicles grow curly to coily hair. The shape is set by genes inherited from both parents. The angle at which the follicle sits in the skin also matters: follicles that grow at a steep angle tend to produce curlier hair. The protein bonds within the hair shaft, especially disulphide bonds between keratin molecules, lock in the shape. Humidity can temporarily alter these bonds, which is why hair frizzes in damp weather. Human hair texture varies widely across populations due to thousands of years of evolution in different climates.