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It was, for example, beneficial to _hide_ pubertyNo, they accounted for that sort of thing when working out the estimates.
> My instinct tells me
I think your instincts are correct. Available resources seem to be one of the dials by which the onset of puberty is calibrated. Modern children suffer less from malnutrition, which means earlier puberty.
But your instinct is badly-calibrated. You should research the topic in detail, before believing you know anything about it. Vaccines, food, and additives? Growth hormones aren't allowed in feed in the UK, and that's where my "9 years old" figure came from. You're right to speculate, but this speculation is all wrong. Instead, you should look in the direction of plastic additives, which are known to be endocrine disruptors: we don't have much evidence that those are the cause, but that was my first guess after reduced malnutrition, and it's also the guess of the author of the paper linked in my previous comment.
It's fortunate for you that your instincts are broadly correct, since this means you can learn more about the topic without much risk of cognitive dissonance: you can keep your mind open, without risking your worldview. For those of us for whom this is more personal, this knowledge is hard-won. (Sure, after the fact, knowing that reality agrees with what I needed to be true – with a few irritating exceptions –, it doesn't seem like a big deal. Indeed, the fact that I needed these things to be true, without first deciding that, was strong evidence that there was a real phenomenon… but I couldn't afford to take that into account, because couldn't a form of insanity also have caused such a subjective experience? … I digress.)
Point is: research the topic before making claims about what policy should or shouldn't be, especially where persecuted minority groups are concerned. Bigoted sentiment, and lies, that you've picked up from your social environment are not particularly reliable sources of moral guidance.
> Eventually I just had to read up on everything myself
You have something in common with trans people, then. (I swear, the average trans person knows more about endocrinology than the average cis doctor.) The purpose of the medical system is to keep populations in overall good health: it's not great at treating individual issues that aren't immediately life-threatening. (See also: handling acute conditions well, but chronic illness extremely poorly, to the point of denying that it exists at all.)
The medical system is especially not good at dealing with bigotry: the whole system functions on the presumption of good faith, with mechanisms in place to catch specific, individual abuses. Systematic issues, like "let's sterilise the undesirables!" or "let's torture the neurodivergent!" or "let's tell women they're menopausal, or that they need to lose weight, when they present with stroke symptoms", are only addressed once the general consensus is that they need to be addressed. Systematic lifestyle issues, too, are only addressed once there's widespread understanding that they need to be addressed: look at how the "healthy amount of alcohol" keeps getting knocked down a bit, every few years.