Young girls' bodies are maturing faster than their brains can keep up.
A new study from Cincinnati Children's Hospital finds 42-percent of African American girls have hit puberty by age 8.
The result is little girls in teenage bodies.
"Simply because one is physically more mature does not mean they are any more socially mature or psychologically mature," explains Dr. Frank Biro of the Cincinnati Children's Hospital.
The study looks at how many 7- and 8-year-old girls recently showed signs of puberty and compares the numbers to a similar study from 13 years ago.
Over that time period the age at which girls hit puberty decreased among all races, and even though the percentage of young white girls entering puberty isn't as high as other races, their numbers doubled.
Researchers say the rise in childhood obesity could be one cause for the increase, as well as environmental toxins.
"Whether food that they've eaten, or products that are used for personal care products, as well as products that could be used at their homes," says Dr. Biro.
Other research has linked an early puberty with an increased risk for breast cancer.
For that reason, this study looked specifically at breast maturity in young girls.
Whether that also plays a role in cancer development remains to be seen.