Menarche

By age thirteen, most girls in industrialized societies have attained menarche. Interestingly, this number has not been consistent throughout history. It appears that menstrual age has been decreasing from between fifteen and sixteen in the last half of the eighteenth century, to twelve to thirteen in the present day, at a rate of three months per decade (Tanner 1962). Various reasons have been hypothesized. Alarmists decry this trend and blame it on a multiplicity of factors from hormones in food to mass media. Since nutrition and the standard of living have improved in the last 200 years, one explanation is that the time for menarche has always been the same biologically, but was delayed because of the lack of essential nutrients for the chemical pathways to trigger hormone synthesis. Genetically, humans have always had the potential for certain biological phenomena to express themselves, but environmental conditions retarded both growth and development.