Thomas Malthus was an economist who influenced Darwin's developing theory of evolution. Malthus observed that the birthrate among humans exceeded the death rate. If this trend continued, soon there would not be enough resources to support human population growth. He reasoned that the only things capable of stopping human population growth were famine, disease, and war. Darwin applied this thinking to animals and plants as well, noting that far more offspring were produced than survived to a reproductive age. 2. How did Charles Darwin build on the work of Thomas Malthus to develop the idea of evolution by natural selection