What Started the Biggest Population Boom in History?

How Iran’s explosive expansion warns us about our overpopulated future —and shows us how to fix it.

i. Horses

WHEN HOURIEH SHAMSHIRI MILANI entered medical school in 1974, just thirteen of seventy students in her class at the National University of Iran were women. “And of those thirteen, only two of us wore the scarf.”

During the reign of Mohammad Reza Shah Pahlavi, the final Shah of Iran, head covering was rare among educated women. In 1936, seeking to modernize the country, his father, Reza Shah Pahlavi, had decreed that all Iranian women be unveiled. When Reza Shah was forced to abdicate in 1941 by the invading British because of his cordial ties with Germany, the rule was relaxed, and hijab became a matter of personal choice. In Shamshiri’s family, they chose to wear it. She would choose to do so still, although now there is no choice.

In the alcohol-free piano bar of the Espinas Hotel in central Tehran, her hair concealed under flowered silk, Dr. Shamshiri is a handsome woman with striking eyebrows. She was born in Tabriz in northwest Iran, near the border with what was then the Soviet Union. In that region known as Iranian Azerbaijan, a woman felt naked in public with her head uncovered. Her family…