Malthus Yet Again (And Some More on Demographic Transition)
The details of Malthus's argument are a bit dated, but the logic is enduring. It is the central pillar of Darwin's theory of Natural Selection. The fundamental notion is that any population is ultimately constrained by available resources, and this applies to bacteria on a petri dish, lemmings in a field, or humans on planet Earth. Of course Malthus knew that humans could make more land available for agriculture by clearing forests, draining swamps, irrigation of dry lands, etc. Modern techniques that apply fertilizer and pesticides to capture more of the potential productivity have a similar effect. The Malthusian point, though, is that ultimately these cannot compete with exponential increase in population. A population increasing at 2% per year would outweigh the Earth in less time than has elapsed since modern humans first left Africa.
Rapid modern advances in food production and distribution have largely eliminated the food constraint on survival for the moment. This enabled a very rapid increase in population in Africa, Asia, and much of South America. Europe and the European populated colonies had already largely completed a demographic transition, so their population growth rates were much slower. It is not coincidental that those countries became much richer while the others became a lot poorer.
Since the invention of modern birth control methods in the middle of the Twentieth Century, several Asian countries drastically decreased their fertility rates, and subsequently saw dramatic increases in their per capita GDP. (The data can easily be viewed in graphical form at gapminder.com)
The mechanism is straightforward to understand. Economic progress depends on capital formation and investment. When women have many children, time and resources need to be invested in care and feeding, so little is available for investment. Women with one or two children have the time to work in production, and more resources for investment in everything from education to economic infrastructure. There is nothing coincidental about the fact that fertility decrease coincides with education and liberation of women.