A new study shows that on average boys are reaching the milestone a year earlier. It also suggests that earlier trends toward puberty aren't limited only to girls.
Other reports find they are also developing sexually at increasingly younger ages.
The study on boys finds they are reaching puberty between 12 and 15 years old.
A decade ago that leap was seen between the ages 13 through 16.
There's more on this report in the Archives of Pediatrics and Adolescent Medicine.