The Alam family lives in one of the more squalid corners of Dhaka, the capital of Bangladesh, and make their living in a pretty typical way: by deploying their teenaged daughters.
Each morning, 14-year-old Panchali walks down the mud lanes to her house-cleaning job in the nearby high-rise apartments, and 16-year-old Amolika goes out to spend 10 hours at a garment factory. Their brother, Sumon, 17, has a far less rewarding job unloading trucks and carrying heavy objects on bamboo poles, as does his father.
Together, the two teenage girls earn about three-quarters of the family's income. That's not unusual here, or in any of the fast-growing cities of Asia, Africa, the Middle East and South America: These places are the domain of the adolescent girl.
What you see in the streets and workshops and houses of the fast-growing parts of the world are young women, generally under 21, working hard. What you see aboard the trains and minivan-buses and horse-carts of the world are teenage girls, moving to the city.
As in Europe in the 19th century, young women often make up the largest group of people leaving villages for the city, sent to work alone, often in domestic service or garment piecework, and save their families. Half the world's urban population is under 25, and considerably more than half of these are young women, because the men so often stay behind.
The girls tend to have more job opportunities in the informal, hustle-based economies of modern cities; they also tend to be treated far, far worse than anyone else, abused sexually, mutilated, impregnated, forced into prostitution, married to strangers. They are both the main agents of change and its predominant victim.
The opportunity and the danger tend to amplify each other. Fear of such fates, and other mythic images of debased innocence stoked by the terrifying shock of sudden change, leads the fathers and brothers of newly urbanized daughters into the hysterical comfort of extreme religious and political beliefs. The cruel ascetic offshoots of Islam in much of the Arab world, the violent political perversions of Hinduism in India and the waves of fundamentalist Christianity across the Southern Hemisphere, are in large part responses to, or manipulations of, anxieties over the idealized images of one's daughter.
In fact, you could say that the most potent forces in the world right now - both the most promising opportunities for improvement and the most menacing and destabilizing movements and ideologies - are all centred around the mythic figure of the teenage girl.
This dual role will be brought into stark contrast next week with the release of a major study, by the charity Plan, of the situation of adolescent girls in the world's cities. Titled "Because I Am a Girl," it rightly recognizes that the fate of these girls and young women is precisely the fate of their countries and communities.
In many ways, the flight into urban work is turning girls into powerful figures - in large part by letting them escape marriage. In Bangladesh, the study notes, 31 per cent of adolescent girls who had migrated from rural to urban areas for work were married by the age of 18, compared to 71 per cent in rural areas, and "adolescent girls in cities are more likely than their rural cousins to go to school, marry later, give birth more safely and have more of a say in their own lives."
And this flight often allows them to escape a fate that would turn them into baby-making machines: In Addis Ababa, a quarter of all women in the city between 10 and 19 had moved there from the village in order to escape early marriage.
That can change the world: Over and over, studies have found that the level of poverty reduction and economic growth in a country is directly correlated to the levels of education attained by women - more so than any other factor.
But the risks are real. Sexual predation is an ever-present concern in societies that still treat women little better than livestock. A study in Lima found that 41 per cent of girls between 10 and 24 had "experienced coerced sex." Similar figures, or worse, were found around the world.
The flip side of this risk is the ideological defensiveness that leads fathers to marry off daughters earlier, cover their heads (even in countries, such as Bangladesh and Turkey, where this isn't traditional), mutilate their genitals and throw them into the hands of religion. Of course, this is the same thinking that leads men to rape teenage girls - thus creating a self-sustaining cycle of backwardness.
Beyond this idealization and victimization are the actual lives of hundreds of millions of real girls, on the streets of the world's major cities, avoiding dark corners and doing most of the hard work.Report Typo/Error
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