Why do some people have straight hair while others have curly hair?
Having curly hair myself, this is something I have wondered about. The rest of my family has very straight hair, while I have curly hair and I was curious as to what factors determine hair type.
“That shape depends on the shape of the hair follicle. This tiny structure guides the hair fiber up a sort of tube as it grows. The inside of the tube determines if the hair is curly or straight — ovals produce curly hair and circular tubes yield straight hair.” npr.org
Not everyone has the same kind of curly or straight hair. People with African ancestry have a different type of curly hair than those from Europe. People from Asia have different straight hair than those from Europe.
The amount of curl in curly hair is dependent on the shape of the follicle and the shaft.
"The direction that hair grows out from the scalp also determines if it will be curly. Within the follicle, the hair bulb may lie at a certain angle. This angle will determine in which direction hair will grow when it emerges from the scalp. Curly hair grows out of the scalp at a sharp angle because their bulbs sit to one side within their hair follicles. Hair also twists as it grows out of the scalp. Even straight hair twists, but only a little, so there aren't as many twists in straight hair. The more twists there are in hair as it grows, the curlier the hair will be."
Read more: How Does Hair Grow Curly? | eHow.com http://www.ehow.com/how-does_5011167_hair-grow-curly.html#ixzz26GmVVnic