Girls are getting their first period younger and younger, the main reason is prosperity and not because puberty starts kicking in early. The female hormonal cycle that causes ovulation and accordingly menstruation jumpstarts when that girls bodyfat reaches a certain level, this is a scientific proven fact.
quote from:
http://www.pponline.co.uk/encyc/0617.htm"The first menstrual period of an adolescent girl is known as the menarche. Studies have proven that intense exercise can delay the onset of menarche by disrupting the hormonal patterns that control menstruation. A girl who has not reached menarche by age 15 would be considered abnormal by most doctors. But this does not necessarily imply that she has a medical problem. She may be a late starter for genetic reasons. Or it could be that her exercise habit has kept her body fat levels below what is needed to trigger menstruation."
quote from:
http://findarticles.com/p/articles/mi_m0675/is_6_20/ai_94981928"Why, given a group of women with similar exercise programs and low percentages of body fat, do some experience menstrual problems and others do not? The answer usually relates to nutrition. Women with amenorrhea may be striving to maintain a weight lower than appropriate for their genetics. When the cost of achieving this desired leanness is inadequate nutrition, menstruation will cease."
As both articles clearly state a woman with her bodyfat below a certain level (depending on her genetics) will not menstruate. So if a girl would stay below that weight she would never menstruate. Because of our prosperity we gain more bodyfat and thus modern girls menstruate sooner. Because if keeping somebody from reaching a certain amount of bodyfat prevents menstruation, allowing her to reach that bodyfat at an earlier then normal age, will allow menstruation to start op sooner then is to be expected naturally.
The link between breastcancer and early first period, late first child is simply explained due to hormones. The longer a woman waits before getting her first child the longer her body is exposed to the hormones,
quote from:
"Pregnancy-Related Factors that Protect Against Breast Cancer
Some factors associated with pregnancy are known to reduce a woman’s chance of developing breast cancer later in life:
The younger a woman has her first child, the lower her risk of developing breast cancer during her lifetime.A woman who has her first child after the age of 35 has approximately twice the risk of developing breast cancer as a woman who has a child before age 20.
A woman who has her first child around age 30 has approximately the same lifetime risk of developing breast cancer as a woman who has never given birth.
Having more than one child decreases a woman’s chances of developing breast cancer. In particular, having more than one child at a younger age decreases a woman’s chances of developing breast cancer during her lifetime.
Although not fully understood, research suggests that pre-eclampsia, a pathologic condition that sometimes develops during pregnancy, is associated with a decrease in breast cancer risk in the offspring, and there is some evidence of a protective effect for the mother.
After pregnancy, breastfeeding for a long period of time (for example, a year or longer) further reduces breast cancer risk by a small amount."
"Other Breast Cancer Risk Factors Not Related to Pregnancy
At present, other factors known to increase a woman’s chance of developing breast cancer include age (a woman’s chances of getting breast cancer increase as she gets older), a family history of breast cancer in a first degree relative (mother, sister, or daughter),
an early age at first menstrual period (before age 12), a late age at menopause (after age 55), use of menopausal hormone replacement drugs, and certain breast conditions."
I could have misread the how fat english have become article. And that people with obesity have grown by 33% instead of the average weight going up.
