I think one of the biggest attributes to young motherhood in African countries, is the high statistics of dying at a young age in that area of the world. And since all culture comes from some sort of reasoning way down the line, young marriage is burned into the culture to have young and fertile women who ca deliver babies before they die. There is a lot of sickness in that area of the world, there for, more people die at a much younger age because just how they live and what their culture is built on.