thanks to chemicals like BPA according to this source
http://naturalsociety.com/age-10-the-new-norm-for-puberty-in-girls-thanks-to-bpa/
andre evans said:There is an ongoing and unusual trend that is steadily becoming more recognized by the public. Why are girls going into puberty at such young ages? Furthermore, what are the causes and implications of this strange new trend?
Girls as young as 7 are now beginning to undergo body changes that their mothers hadn’t experienced until years later. At this rate, by the time that they’ll be taught about puberty in the school curriculum, they will have already finished it. This trend is so puzzling, and yet slowly is becoming considered an inevitable “new norm” rather than being highlighted as an aggravated health condition.
Toxic BPA is featured in the vast majority of plastics used commercially today. This chemical has the property of mimicking estrogen when leeched into the body. The delicate hormonal balance in the developing human body is being offset by the introduction of BPA and other chemicals into an average child’s life. Nearly out of the womb, children who are given plastic toys, pacifiers or bottles all come under the influence of this hormone disruption incredibly early.
http://naturalsociety.com/age-10-the-new-norm-for-puberty-in-girls-thanks-to-bpa/