My easy child got her first period last August, one month after turning 10. She was hairless and her chest flat as a Scrabble board, but the moodiness started very soon after that. She had cramps and was in tears about her body betraying her, she was most definitely not a happy camper and I felt so badly for her. I was surprised as well because she is thin and active, not on any medications.
Almost a year later, she is wearing a bra and getting pubic hair, completely backward from what I went through (and I was older).
A lot of little girls are getting their first periods at age 9 in our area. We live in a Northeastern suburb, no chemical plants around, no agriculture...I'm wondering if hormones in the meat we eat, or even more disgusting to contemplate, excreted hormones that wind up in our drinking water sources (I seem to recall reading a few years ago that wild fish caught in streams and ponds sometimes had high levels of estrogen and progesterone absorbed from the residue of birth control pills, etc. that go through the water treatment system unchanged) have something to do with it. Uggh.