https://www.dailymail.co.uk/health/article-10834835/Young-girls-starting-undergo-puberty-young-six-years-old.html

American girls are now reaching puberty as young as SIX in
phenomenon scientists think may be linked to childhood
obesity, chemicals in plastic and stress

.. . .

Evil Plastic again ...

Sorry, but the USA has been awash in plastics since
the early 50s - and the old ones leeched so many of
those plasticizers you could taste 'em.

This is not a disease, not any clear cause-effect,
probably not really important at all. Some will want
to drug girls for this imaginary illness - make it illegal.

This has been a LONG-term trend, generations, and it's
not just the fat girls either. The old medical wisdom
was that early puberty would result in freaks with really
short arms and legs due to bones hardening early. As
any can see though, this hasn't been the case. Modern
American women have been getting taller - and with
somewhat longer legs too. The "wisdom" was wrong -
more like a puritan religious prejudice pretending to
be The Science IMHO.

We are looking at an 'epigenetic' effect here. That's
the result of a huge spectrum of influences that affects
how existing genes are expressed. The difference between
a lap dog and a Great Dane is epigenetic, not really
genetic at all. In this case WE supplied the adaptive
pressures.

What pressures are shaping THIS phenom are going to be
unknown for quite a while. In the end it won't make any
difference - what we see now will be the new normal.
Maybe Nature knows something we don't see yet, an adaptive
REASON for this.

Oh, there's a statistical quirk that may also be involved
here. There have always been a lot of early pregnancy news
stories - mostly from South America. Well now there are
a LOT more people from south-of-the-border HERE - and
their normal has statistically blended with our old normal.
The more who come from the south, the lower our "average
age" will become.