Both Charles Darwin and Alfred Russel Wallace acknowledged the influence of the economist Thomas Malthus in the development of their ideas about natural selection. Specifically, Malthus's ideas about geometric population growth implied that:

Natural selection

Explanation:

Malthus's ideas about geometric population growth implied that: resources in every generation would be limited, therefore individuals in every generation would have to compete for those resources

Thomas Malthus argued that the food supply increased linearly while population size increased exponentially The central theme of Malthus' work was that population growth would always overpower food supply growth, creating perpetual states of hunger, disease, and struggle The natural, ever-present struggle for survival caught the attention of Darwin, and he extended Malthus' principle to the evolutionary scheme Malthus' writings ultimately inspired Darwin's theory of evolution by natural selection

resources in every generation would be limited, therefore individuals in every generation would have to compete for those resources.