According to your textbook, boys from which racial group have the earliest average age for the onset of puberty?

Boys of African American origins

African-American children, boys in particular, have the earliest onset of puberty. While White and Hispanic children have a mean onset at around age 10, African-American boys are beginning at barely over 9 years of age. This is over one year earlier than for children living in the 1960s and 1970s.