An easy way to start a long, heated debate is to mention global population. Thomas Malthus famously ignited furious arguments in the 19th century when he warned that, absent fertility-control policies, exponential population growth would outpace improvements in agriculture and cause recurrent bouts of famine and pestilence. Industrialisation would postpone the crisis, but not forever.
These arguments were still raging in the 1960s, when Paul and Anne Ehrlich added fuel to the fire with their bestseller, The Population Bomb. Their fears were reasonable, given the data. By 1975, the global population doubled to 4 billion -- in just under 50 years. It has just doubled again, reaching 8 billion last November. This raises a new question: Will the population double again to 16 billion?
