Boys are reaching puberty earlier than ever, as much as two years before benchmark ages.
According to a study released Saturday by the American Academy of Pediatrics, the first extensive look at puberty in American children in 25 years, boys in the US are hitting the developmental milestone between the ages of 9 and 10, instead of 11, the formerly accepted average age.
The trend varies, with African American boys seeing genital enlargement, one of puberty's earliest signs, by age 9, and Hispanic and white children reaching it at age 10, the Wall Street Journal reported.
The study follows similar research on girls, who are showing breast enlargement earlier—some as early as age 7 or 8, Reuters reported.
The research did not reach any conclusions about what is causing the sped-up development, but the study's lead author Marcia Herman-Giddens from the University of North Carolina's School of Public Health has speculated that it has to do with our environment and not evolution.
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"The changes are too fast," Herman-Giddens said, according to CNN. "Genetics take maybe hundreds, thousands of years. You have to look at something in the environment. That would include everything from (a lack of) exercise to junk food to TV to chemicals."
However, unlike girls, whose earlier puberty has been found to increase the risk of breast cancer, there does not seem to be any immediate cause for concern with boys.
"If it's true that boys are starting puberty younger, it's not clear that means anything negative or has any implications for long-term," said Dr. William Adelman, a member of the American Academy of Pediatrics' committee on adolescence, the Associated Press reported.