Biological medium, environmental health and ovarian maturation: age of the first period (Spain)
The rhythm of growth, development and maturity of the body’s different systems greatly depend on available energy and nutrients. Improved environmental conditions (as regards food, repeated infections, child labour) are linked to an earlier sexual maturity and an increase in size.
The women in the picture were born between 1860 and 1912, and did not show a change in the age of sexual maturity. Grandmothers, daughters and granddaughters shared the difficult environmental conditions associated with the subsistence farming they lived in, so that the age of their first period (menarche) was around14.5 years for the three generations.
However, among women born after1960 a clear tendency was detected for a fall in the age of sexual maturity which drops to 13 years.
The decrease in the age of sexual maturity determines an increase in the ages of menarche which are considered premature (before 12 years old). For example, the proportion of early maturities among rural women in rural León studied in 1974 was 11%, and only 4% among rural women in Morocco studied in 1989.