It is relatively easy for demographers who study population to look back and recount how population has grown in the past. There is little to no debate about whether the species Homo sapiens has been growing on the planet Earth, and that most of that growth has taken place in an extremely short period of time, in terms of overall human history. It took over a millennium for human population to grow from less than 400 million at the time of Christ to 1 billion at the beginning of the nineteenth century. It took over another century for the global population to reach 2 billion in 1930. It then took only thirty years for the population to reach 3 billion in 1960, fifteen more years to get to 4 billion in 1975, and another twelve years before the 5 billion mark in 1987. On October 12, 1999, the United Nations...