Malthus’ 1798 essay proposed the first mathematical model in both Ecology and Economics and so helped found both “eco” disciplines. Although empirically incorrect as a model of human population, Malthusian ideas prevailed in biological sciences as bedrock foundation for Darwin’s theory of evolution, Von Liebig’s law of the minimum, etc. However, in Political Economy and later Economics, Malthus’s ideas were from the first (and remain today) rejected by a majority of the discipline. Reformers like Godwin, Condorcet and Marx, et al. saw no limits to human population that couldn’t be cured by social reforms. The Ultimate Resource by marketing professor Julian Simon (2^nd edition 1996), is even more optimistic.  “Direct measures of material, human well-being correlate positively with population growth and there is no theoretical upper limit. Simply put, things are getting better and better, not in spite of population growth, but because of it! The reason is simple as well: the "ultimate resource" is human imagination and we will not only never run out of it, but we will get more of it as population increases.”[1] In 1988 F.A. Hayek opined that when market economies spread throughout the world, population growth will spontaneously cease as incomes rise and converge. Many economists agree that falling population growth rates mean population levels are no longer a major issue. So there is a considerable gulf between Malthus’s legacy in Ecology and Economics. This paper explores the history of Malthusian and neo-Malthusian thinking with a view to moving the two “eco” disciplines towards consensus on population policies. My conclusion is that Simon correctly points out serious flaws in Malthus’ model—humans are different. However, it also seems clear that countries that have become prosperous did so in significant part because they reduced fertility rates rather than vice versa.

Results/Conclusions

The best strategy for improving per capita incomes in the resources limited 21^st century, under a wide variety of scenarios, will be population falling faster than output. Simon’s naïve forecasts assume the human niche will expand indefinitely (a perspective called Cornucopianism) whereas a shrinking niche seems at least equally possible. Population policies should therefore become one of the key political debates of the 21^st century.