Indeed, there have been many cases of early puberty.
For instance, Lina Medina gave birth at the age of 5 years, 7 months and 21 days. Encyclopaedia Wikipedia says:
"Lina Medina (born September 27, 1933 in Paurange, Peru) gave birth at the age of 5 years, 7 months and 21 days and is the youngest confirmed mother in medical history. This world record is closely followed by a similar case in Russia."
Also, a 9-year old Thai girl gave birth:
The news item is from the New Straits Times, 10/3/2001.
In our world today, we still have people especially in the third world countries, marry very young girls. Why should we call someone who married a 9-year old girl 1400 years ago a child molester, when many people still practice it today? The girl above even gave birth at the age of 9!
Aisha's (our Prophet's wife) parents agreed by their own will and choice to marry their daughter to our Prophet Muhammad صلى الله عليه وسلم, and they were proud of it too as they married her to the best person on the face of the earth.