Darwin read an essay on populations by T.R. Malthus, the key idea of which was that "animal and plant populations, including human populations, tend to increase beyond the capacity of their environment to support them." This helped formulate his idea of natural selection, as an animal with better genetic traits will be more likely to survive the competition for scarce resources and be able to breed and pass on their genes to offspring.
Work Step by Step
Read essay, key idea lead Darwin to hypothesis on natural selection.