i remember years ago an article said it was from eating pork (genetically quite similar to human) which had tons of hormones injected so they would grow up faster for more profit turnover. i wonder if theres puberty age data from groups that dont eat pork.
It's not talked about, but little girls who are getting their periods at nine years old probably should be given puberty blockers, at least for two maybe three years. Of course, I say this flippantly without having performed research into the long-term impacts of being on puberty blockers for one or two years and then going off of them.
It's a miserable thing to experience menstruation years before your peers do.