Boys Hitting Puberty Earlier, Too It's age 9 in the earliest cases, says study By John Johnson, Newser Staff Posted Oct 20, 2012 12:12 PM CDT 34 comments Comments (Shutterstock) (Newser) – It's widely accepted at this point that girls are reaching puberty earlier than they used to, and now the same appears to be true of boys. A comprehensive new study says boys are entering puberty somewhere between six months and two years earlier than the textbooks think, reports CNN. In the earliest cases, African-American boys reach puberty just after age 9, with whites and Hispanics about a year later. The research doesn't say why, notes HealthDay, and researchers call for more study into the question. They mention diet, obesity, a lack of physical exercise, and a host of environmental factors as possible culprits. "We have now a huge discrepancy between when the body starts to mature physically and when overall maturity is achieved," says the study's author. "So, there may be a big and growing gap here, which can cause all sorts of concern for guidance and teaching."