Human hair growth
The three stages of hair growth are the anagen, catagen, and telogen phases. Each strand of hair on the human body is at its own stage of development. Once the cycle is complete, it restarts and a new strand of hair begins to form. The rate or speed of hair growth is about 1.25 centimetres or 0.5 inches per month, or about 15 centimetres or 6 inches per year.
Human hair color
Red hair ranges from light strawberry blond shades to titian, copper, and completely red. It is caused by a variation in the "Mc1r" gene and is recessive. Red hair has the highest amounts of pheomelanin, around 67%, and usually low levels of eumelanin. At 1–2% of the population, it is the least common hair color in the world. It is most prominently found in the British Isles. Scotland has the highest proportion of redheads; 13 percent of the population has red hair and approximately 40 percent carry the recessive redhead gene.