Got another theory for you. Growth Hormones in our food. They can make Chickens grow twice as fast to the point where they get so fat they break their legs according to a Waianae farmer. Just because they call it Bovine Growth Hormones doesn't mean it has no effect on Humans. They can speed up the aging process. I guessing it affect the Embryo and might be the cause of  puberty at an earlier age. Some day we might learn the truth.