Just when a girl has her first period is genetically based. It is determine by more that 100 parts of the the human genome. It is not affected by more good food, etc., as was once believed. Furthermore, good food intake is not making girls menstruate earlier.
Going into adulthood sooner is a danger to health. The chances of getting type 2 diabetes, cardiovascular disease and breast cancer is increased. These findings come from an international study carried out in 166 institutions.
It seems that diseases are usually limited to a few parts of the genome, while menstruation involves a surprisingly large number. It is whole-body function. Indeed, one's physical and social surroundings could also play a part in triggering genes.
Yes, a better diet has lowered the onset of menstruation from 17 years of age in the 1800s to 12.5 years in the 1960s. Since that time, however, it has remained at that point. It must be noted that many diseases that delayed the onset of periods have been significantly reduced. Many got seriously ill from infections in times past.
Health by Ty Buchanan