KANO, Nigeria -- The boy stepped into the grubby street, looking both ways for traffic. He was wearing the clothes he wore yesterday and seemingly all the days before: a pair of too-big cotton pants and a black shirt so tattered that it seemed ready to fall off his body. His bony shoulders peeked through the holes where the sleeves once were stitched.

At an intersection, the 10-year-old beggar weaved between idling cars, his feet clapping the asphalt in mismatched flip-flops, one yellow, one red. He held out a plastic bowl and tried to lock eyes with the people behind the smudged car windows, hoping for a flash of sympathy, a rolled-down window, an outstretched arm proffering a crumpled bill.

Until a year ago, Ghaddafi Auwalu lived with his family on their small plot outside this fast-growing city in northern Nigeria. His parents sent him away, Ghaddafi said, for reasons that might be difficult for faraway people to understand: They had too many children, and they couldn't afford to look after him.

"I'm less of a burden to my mom if I am here," said the polite boy, the 11th child in a family of 12, not unusually large for this part of West Africa. "Now she'll have more time for my sisters and brothers."

Although it's frequently portrayed as a continent decimated by epidemics, starvation and war, Africa is gripped by one of the greatest population explosions ever recorded. Over the past 60 years, while birth rates in the rest of the developing world declined by half, Africa's population quadrupled to 1 billion, an epic baby boom that threatens to trap a generation of children in poverty and strangle economic progress across the world's neediest continent.