The world’s peak population may be smaller than expected

“I have ten children,” says Rahama Sa’ad squatting outside her shack on the outskirts of Kano, the biggest city in northern Nigeria. “It’s the will of God,” she explains, as chickens, children and grandchildren scramble around her. In northern Nigeria big families are easy to find. Abdulkadar Dutse, a local businessman in Kano, is one of 35 siblings split among the four wives of his father.

Such stories of big families inform much of how the world thinks about sub-Saharan Africa, not just now but over coming decades. At conferences and in cabinet meetings across the continent, politicians and policymakers fret about how to educate, employ, house and feed a population that the UN expects to grow at breakneck speed from around 1.2bn people now, to 3.4bn people by 2100. In southern Europe, populists stoke up fears that hundreds of millions of Africans may try to cross the Mediterranean to escape poverty, war or hunger. Across the rich world, environmentalists fear the impact on the climate and planet of an extra 2bn people.