Final answer:
The theory of natural selection as a mechanism of evolution was proposed by Charles Darwin and influenced by the works of earlier thinkers such as Lyell and Malthus. Darwin presented his arguments in 'On the Origin of Species' after years of exploration and study of natural variation within species.
Step-by-step explanation:
Natural selection, as a mechanism of evolution that acts on variants within populations and ultimately leads to the evolution of different species, was proposed by Charles Darwin and Alfred Russel Wallace. They provided the foundation for the understanding that not all members of a population will survive, but those that are most fit will reproduce at a higher rate, passing on their traits. Over time, this process results in changes in the characteristics present within a population and can lead to the emergence of new species.
For natural selection to occur, variation among individuals in a population is essential, primarily arising through changes in DNA. The selective pressures of the environment then dictate which individuals are more likely to survive and reproduce. Darwin first presented his comprehensive arguments for evolution by natural selection in his 1859 book, On the Origin of Species.
Darwin also drew upon the ideas of earlier thinkers, such as Lyell's evidence of Earth's old age and Malthus's ideas on population growth, which helped shape his understanding of the natural world and the process of evolution by natural selection.