Evolution does not share your bias, though. In fact, this probably has damned little to do with evolution in the Darwinian sense.
http://www.webmd.com/children/guide/causes-symptoms#1
http://www.webmd.com/children/guide/causes-symptoms#1
Quote:Doctors diagnose early puberty when this normal process starts early and continues to progress through growth spurts and bone maturation, usually for reasons we don't understand. Girls who show significant signs of puberty and its progression before age 7 and boys before age 9 are considered precocious. About 1 out of 5,000 children are affected.