Head Hair

Name: Head Hair

Description: Hair texture is measured by the degree of which one's hair is either fine or coarse, which in turn varies according to the diameter of each individual hair. There are usually four major types of hair texture: fine, medium, coarse and wiry. Within the four texture ranges hair can also be thin, medium or thick density and it can be straight, curly or wavy. Hair conditioner will also alter the ultimate equation and can be healthy, normal, oily, dry, damaged or a combination. Hair can also be textured if straighteners, crimpers, curlers, etc are used to style hair. Also, an expert hairdresser can change the hair texture with the use of special chemicals.

Hair is genetically programmed to be straight, curly or wavy, and it tends to change over time.

For many years, it was believed that the shape of a person’s hair was determined by the individual hair shafts, and that curly hair was curly because the cross-section of the hair shaft was flatter and had more intertwined layers than straight hair, which was round. But scientists have determined that whether your hair is curly or straight is determined by the shape of the follicle itself and the direction in which each strand grows out of its follicle. Curly hair is shaped like an elongated oval and grows at a sharp angle to the scalp.

Curly hair has a different biological structure from straight hair. It tends to be much drier than straight hair because the oils secreted into the hair shaft by the sebaceous glands can more easily travel down the shaft of straight hair. People with very curly hair may find that this hair type can be dry and often frizzy.

Hair, whether it is curly or straight, is affected by the amount of humidity in the air. It serves as a "truth serum" for the hair, forcing water back into the hair fiber and forcing hair shaft to return to its original structure. This may be more noticeable in somebody with curly hair because it tends to get frizzy when the humidity rises.

Hair texture variation is likely to have resulted from a significant event in human evolutionary history. Evolutionary biologists agree that the evidence suggests that genus Homo arose in East Africa approximately 2 million years ago. During this time body size increased in response to richer dietary intake. This increase was most likely a reflection of rapidly increasing brain size among members of this genus, which facilitated an increasing intellectual capacity that made more varied dietary access possible (i.e. via new hunting and scavenging techniques etc.). Jablonski et al (2004) postulate that as body size increase, it became evolutionarily necessary to expel heat from the body at a more rapid rate. As a result, humans developed the ability to sweat. They also lost body hair in order to facilitate sweat evaporation and hence cooling of the body.