The color of human hair is determined by the concentration and ratio of two types of melanin: (brown-black) and pheomelanin (red-yellow).
Evolutionary biologists suggest that dark hair and skin evolved as an adaptation to intense solar radiation, particularly in equatorial regions. Biochemistry, Melanin - StatPearls - NCBI Bookshelf - NIH dark hair
: Most individuals with dark hair possess two functional copies of the MC1Rcap M cap C 1 cap R The color of human hair is determined by