A stunning new study in the medical journal Pediatrics says girls are commencing puberty earlier than ever, with many starting to develop breasts as early as the age of 7. According to medical researcher Dr. Frank M. Biro, ethnicity and body composition are two key factors determining when girls begin to mature physically. "We found that girls who are African American matured before whites, and that's been shown in several studies," he said, "White girls are maturing earlier than they had before, compared to 20 years earlier." In Biro's study, 10 percent of whites, 23 percent of African Americans, and 15 percent of Hispanic girls had breast development indicative of the onset of puberty at the age of 7. These percentages are even higher than similar statistics in a landmark 1997 study on the same, causing worry among medical professionals that the puberty age may still be falling.