If teenage girls in the developing world are given the opportunity of completing a secondary school education, the explosive growth in the global population could be curbed significantly, says a leading expert in human numbers.
Joel Cohen, professor of populations at the Rockefeller University in New York, said that putting girls in developing countries through secondary school is one of the single most important factors that cause them to have fewer babies in later life.
That could cut the expected growth in the human population by as much as three billion by 2050.
The current global population is 6.7 billion but would rise to as much as 11.9 billion by then if current trends continue.
"Secondary education increases people's capacity and motivation to reduce their own fertility, improve the survival of their children and care for their own and the families' health," the Independent quoted Professor Cohen, as telling Nature.
"Education promotes a shift from the quantity of children in favour of the quality of children. This transition reduces the future number of people using environmental resources and enhances the capacity of individuals and societies to cope with environmental change," Cohen said.
The United Nations estimates by 2050, the world population will hit 9.1 billion and that most of this increase will be in developing countries in Africa and southeast Asia.
However, this "medium" estimate is based on fertility rates, that is the number of babies each woman has, declining from today's 2.55 children per woman to slightly over two children per woman by 2050.
On an average, if each woman has half a child more than the UN estimates, then by 2050 the world population could be as high as 10.8 billion.
Professor Cohen said that if each woman has half a child less, it could be as low as 7.8 billion.
"Thus a difference in fertility of a single child per woman between now and 2050 alters the 2050 estimate by three billion, a difference equal to the entire world population in 1960," he said.
"Secondary education has the potential to influence that outcome dramatically. Although there are other factors at work, in many developing countries, women who complete secondary school average at least one child fewer per lifetime than women who complete primary school only," he added.
The study is published in the journal Nature.