The document discusses three functions of hair: regulating body temperature, protecting the body from damage, and displaying racial characteristics. Hair keeps us warm by trapping heat when standing on end in cold temperatures. It protects the skin from UV rays, temperature changes, and fluid loss. Racial hair structures differ in color and texture due to genetic factors; for example, Africans have more hair color variation while Caucasians display more types due to lower melanin levels.

2. How our hair protects us

5. Controlling the loss of life sustaining fluids such as blood and water

7. Racial characteristics of hair structure and colour (cont.) Black is the most common hair colour in the world, and is due to a large amount of eumelanin. Brown is also common, and is due to eumelanin mixed with a bit of pheomelanin. Blond is only found in about 2% of the world's population. It is due to very small amounts of melanin. Slight amounts of black, brown, and red make for all the variations we see in blonds - such as ash, flaxen, and strawberry blond. And red hair is the rarest of all, about 1% of the world. It is due to high levels of pheomelanin plus low levels of eumelanin.If you are curious, grey hair is due to nothing but a little black melanin, and white hair is a matter of no melanin at all. Light coloured hair is found primarily in Scandinavia and the Baltic sea area. Blond and red hair was probably more common in Europe centuries ago (as witnessed by Greek and Roman accounts), but being recessive, it has slowly receded northward. But you can still find blonds and redheads in places like Afghanistan and northern Pakistan, where the descendants of Indo-European invaders live.