There are cases of modern athletes and women in the 19th century not having a first period until late teens. Meanwhile there’s also cases of menarch under the age of 10. The actual difference has to do with estrogen levels and body fat levels. Essentially body fat has a hormonal effect of estrogen, and enough of it or lack of it can contribute to having periods or not. If you want to think in terms of evolution, then during times of extreme famine getting pregnant may be a hindrance to survival, whereas times of plenty would be a more opportune time to get pregnant.
This may be out dated information, though. It could be I haven’t read the studies debunking the articles I had read from over a decade ago.
Latest Answers