I forgot to add that...
The Hormones, Synthetic Hormones, and other Chemicals that have Hormone-Like Activity in the Human Body are responsible for many disorders, not just "Girls developing early".
Since Girls develop early, when they are still not-so-old, they stop menstruating, that is, they lose their fertility at an early age.
Another thing...
A biological process that is not meant to start so early can cause ovarian problems, this leads to fertility problems too, but in some women the drama doesn't end there because due to Hormonal disruption they experience serious difficulties during child birth. Why?
Because the uterus must contract, and a Hormone called Oxytocin must be generated by the body in order to achieve those natural contractions "as easily as possible". There is of course, a synthetic Oxytocin, but it is not as effective.
Oxytocin is a chemical that seems to be linked somehow to "empathy", it's of course an even deeper topic, but I just wanted to point out that, even on very small amounts, Hormones have a strong impact on everybody's health.
Men are affected by the Hormones from the Pill too, and fishes, and other animals too. We can say it is not ecological either, but besides the Hormones, we have antibiotics, painkillers, anti-depressants, and many other types of drugs on the drinkable water.
I will stop here, I know I could extend myself even more, but I'd be probably going off topic because "girls developing too early" is just the tip of the iceberg...