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.
Evolution of the brain
The evolutionary history of the human brain shows primarily a gradually bigger brain relative to body size during the evolutionary path from early primates to hominids and finally to "Homo sapiens". Human brain size has been trending upwards since 2 million years ago, with a 3 factor increase. Early australopithecine brains were a little larger than chimpanzee brains. The increase has been seen as larger human brain volume as we progressed along the human timeline of evolution (see Homininae), starting from about 600 cm in "Homo habilis" up to 1600 cm in "Homo neanderthalensis" (male averages). 
The increase in brain size topped with Neanderthals; 
Brain size of "Homo sapiens" varies significantly between population (races), with male averages ranging between about 1,200 to 1,450 cm.