The 1970s And Beyond
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In the late 1980s, a maternal-child health researcher named Marcia Herman-Giddens began to worry about the number of girls she saw in her practice who showed signs of puberty below the age of ten (research in the early 1970s had demonstrated, overall, that the average age of staring one’s period was 12.8).
Herman-Giddens posited that exposure to plastics, hormones in milk and meat, and childhood obesity could all be contributing to these seemingly increasing episodes of “precocious puberty.” Despite what her research hypothesized, the average age of menarche today is about 12.5 — not a far cry from the 12.8 that was reported in the ‘70s.
There are lots of theories as to why the number has continued to fall. One is directly related to another health concern that has defined the modern age: childhood obesity. In the days of yore, human diets depended on what could be foraged for, but nowadays we have access to all kinds of high-fat, preservative-laden food — and it’s cheap.
Children are reaching higher weights earlier than they ever have in the past as a result of this type of diet — and for young girls, that means their bodies are equipped with enough hormone-producing fat cells that menarche is signaled earlier.
Other research has posited that it’s evolution at work: with the rate of divorce increasing, girls’ bodies are thrown into an evolutionary tailspin when their childhood environment becomes highly variable. The theory essentially states that due to the uncertainty in their environment, menses begins sooner to prepare them for adulthood.
The research also shows that even if an unrelated male is present after the father has left, such as a step-father, menses still begins earlier because the presence of a male biologically signals a reproductive opportunity, thus accelerating menarche. If, however, the step-father is supportive, invested, and plays a consistent role in the child’s life, the outcomes are reversed in that population of young women.
Another pervasive theory in Western culture relates to exposure to toxins, not just in food but in our environment. When it comes to throwing hormones out of whack, some of the most potent chemicals are found in plastics — like water bottles, shower curtains and vinyl floors.
These chemicals, called phthalates, can’t be metabolized by our bodies, which means they build up in our systems over time. These chemicals mainly affect the endocrine system, which is responsible for — you guessed it — hormone regulation. They can also harm fat cells, making them a seemingly perfect culprit to explain the multiple factors that influence early menarche.
One question that science is still struggling to understand as the age of menarche continues to lower is this: Will earlier periods have long-term health effects? Preliminary studies have linked earlier periods to depression and other mental health conditions, probably at least somewhat as a result of early maturation necessitated by the start of puberty.
Other research looks at more global implications: What does it mean for the population as a whole that girls are menstruating earlier? Secular trends in reproductive health disease incidence seem to correspond to earlier menarche, which has scientists wondering if those early periods set the course for a young woman to develop diseases like Polycystic Ovary Syndrome, Endometriosis and and other metabolic syndromes.
If you enjoyed this, be sure to check out our brief history of birth control and historical (and historically painful!) contraception methods.
