first period earlier on average than they did in the 1950s and '60s
That is a extremely narrow scope, quite possibly interfering with heavy industrialization as stated before. The historical data therein are not really discussed; but in such narrow scope it is true that the age of menarche has gone down - its just that there is more to it.
That is a extremely narrow scope, quite possibly interfering with heavy industrialization as stated before. The historical data therein are not really discussed; but in such narrow scope it is true that the age of menarche has gone down - its just that there is more to it.