The gap between the first appearance of breast buds and menstruation grew wider by as much as a year and a half between the 1960s and the 1990s, according to research published in the October 2006 journal Current Opinion in Obstetrics and Gynecology. The time from breast buds to bleeding, according to Herman-Giddens, is now close to three years.
In short, that finely tuned biological process may have reached a tipping point. Since the 1960s, Herman-Giddens says, the decline in the age of maturity has crossed the line from positive reasons, such as better diet, to negative ones, such as eating too much, exercising too little and the vast unknowns of chemical pollution.
The lack of adequate explanation has some experts worried. "Over the course of a few decades, the childhoods of U.S. girls have been significantly shortened," Steingraber says.
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Redefining 'average'
The new average age of puberty, some fear, may be like the new average weight -- typical, but terrible.
"My fear," Herman-Giddens says, "is that medical groups could take the data and say 'This is normal. We don't have to worry about it.' My feeling is that it is not normal. It's a response to an abnormal environment."
Dr. Paul Kaplowitz, chief of endocrinology at Children's National Medical Center in Washington, D.C., and lead author of a special article Oct. 4, 1999, in the journal Pediatrics suggesting a redefinition of early puberty, isn't so sure. Too many girls are being labeled abnormal, he contends.
"Maybe we shouldn't be worrying so much about those girls," he says. "The chance of finding a serious condition in a 7-year-old with pubic hair is very, very small."
There have always been rare cases of extremely early puberty, called precocious puberty. One report, going back to 1834 in Butler County, Ky., was of a baby girl whose hips and breasts began to grow soon after she was born. By the age of 1, she was menstruating and at age 10, she gave birth to a 7-pound baby. Such extreme cases today would be examined and treated.
But the beginnings of breasts, and the first pubic hair, at ages 8, 7 or even 6 for African Americans falls at the low end of today's new normal range.
With statisticians proving that "average" is younger than recently thought, environmental activists are asking whether hormones in food, pesticides in produce or phthalates in plastics and cosmetics could be contributing to breast buds in third-graders. Social scientists have lifestyle suspicions. Does the stress of fatherless households, or the stimulating effects of sexually suggestive television shows, have anything to do with earlier signs of puberty? The suspicions remain difficult to prove.
