Complex sentence: As blond hair tends to turn brunette with age, natural blond hair is rare in adulthood, with claims of the world's population ranging from 2% naturally blond to 16 percent.
Split into simpler sentences: As blond hair tends to turn brunette with age, natural blond hair is rare. Natural blond hair is rare in adulthood, with claims of the world's population ranging from 2% naturally blond to 16 percent.