In the second part of the twentieth century, especially in the context of developing countries, Malthus ideas influenced the planners and social scientists a great deal. They explored the negative linkages between population and human welfare. Two important theorists of this period adopting Malthusian line are Hardin and Ehrlich. Hardin, a professor of Human Ecology at the University of California , having very strong views on the matter, even raised doubt about the ethics of saving lives in poverty stricken developing countries. Paul R. Ehrlich was an entomologist, associated with Stanford University , who specialized in studies of butterflies.

To Hardin, poverty and epidemics are nature's way of maintaining demographic equilibrium. By preventing deaths without putting a condition that the developing countries should control their population size, the developed countries are creating a situation in which a much larger number of people would die in the developing countries in the future. And those acting altruistically today will be responsible for greater misery in the future.