Dark Hair 90%

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

gene, which signals melanocytes to produce eumelanin instead of pheomelanin.

: Most individuals with dark hair possess two functional copies of the MC1Rcap M cap C 1 cap R