In this paper we attempt to describe the general picture reasons behind the world population explosion during the 20th century. In general we comment that if, according to some, at the end of the 20th century there were too many people, this was has a consequence of scientific innovation, circulation of information, and economic growth, leading to a dramatic improvement in life expectancies. Nevertheless, a crucial variable shaping differences in demographic growth is fertility. In this paper we identify as important exogenous variables affecting fertility female education levels, infant mortality, and racial identity and diversity. It is estimated that three additional years of schooling for mothers leads on average (at the world level ) to one child less per couple. Even if we can identify a worldwide trend towards convergence in demographic trends, the African case needs to be given more attention, not only because of its different demographic patterns, but also because this is the continent where the worldwide movement towards a higher quality of life has not yet been achieved for an important share of the world's population.