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“The present is the key to the past” is a phrase often used to describe the main idea of James Hutton’s uniformitarianism, which inspired both Charles Lyell and Charles Darwin. Hutton was the first scientist to present this theory, in 1785, which consisted of the belief that by observing the natural processes that occur in the present, scientists would be having a look into the processes that also shaped the past. Hutton believed that Earth was really old, and that it had been shaped by small gradual changes that occur because of geologic events like earthquakes.

For example, when an earthquake happens the Earth’s crust lifts up, which eventually forms mountains. Uniformitarianism influenced and supported Darwin’s theory of evolution because it pointed at the fact that the Earth was ancient. Darwin thought, during this long time of earth’s existence, it wouldn’t make sense that species would stay the same as they had been in the beginning, they would either evolve with the fittest genes or go extinct.

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Malthu’s work called Essay on the Principle of Population published in 1798 influenced Darwin’s theory on natural selection. In his essay, Malthus explained that when the conditions surrounding a human population were good, meaning there was enough food and resources, humans would reproduce. However, humans reproduced way more rapidly than the supply of resources did, causing a shortage.

This shortage would cause a decrease in the population, due to problems like famine, and the population would stay moderated until the cycle repeated itself. Darwin recognized that animals, like humans, depended on resources like food and competed for them between each other. To avoid losing this competition or facing issues like starvation, the best genes of a species would be maintained throughout its bloodline  for a better chance at surviving.

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Lamarck published a book called Zoological Philosophy in 1809 which preceded Darwin’s evolution theory. Lamarck believed that changes in the environment promoted changes in animal traits, who would modify their behavior or physique to adapt to their environments. He also believed that the modification in the animal would not only happen on the exterior but internally and the organs of the animal would also change. He assumed that these animals would transfer their modified organs to their offspring.

Lamarck influenced Darwin’s evolution theory by acknowledging that the environment changes and because animals want to survive, they adapt themselves and eliminate those traits that are making them weaker. However, Lamarck made the drastic assumption that the elimination of weaker traits would transform organs, and these organs would be inherited by the kids. Darwin did not believe that “better” organs were inherited by the children rather that the best genes were preserved for the whole species through natural selection.

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Charles Lyell changed the way geology was studied forever by publishing in his book named “Principles of Geology” a uniformitarian scientific theory. He was against what most geologists believed, that one-time only supernatural events like Noah’s flood had shaped the Earth, rather he believed the Earth’s natural formations are a result of innumerable small changes that have happened for a long-time and that never stop happening.

These physical changes were empirical as Darwin saw after he experienced an earthquake in Chile and the Earth’s crust rose. The uniformitarian theory influenced Darwin’s natural selection theory, because he thought the changes observed in the Earth’s structure could also be observed in animals, which had evolved through small variations during a lot of years. Darwin thought just as natural forces like earthquakes affected the Earth’s formation, there were natural processes such as inheritance and competition that would moderately affect the characteristics of a species.

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Alfred Russel Wallace went on a trip to Indonesia, where he studied and collected more than 100,000 species. In this trip he made two principal discoveries: that animals were unique for each region, even if they were close to each other, and that animals evolved. He drew a line, now called Wallace line, which divided Australia and Asia based on their biomass. In 1858, he attributed species evolving to changes in their environment and wrote a paper on it, which he shared with Charles Darwin.

Both excited to prove that natural selection was real, wrote a paper together and published it. A year later, in 1859, Darwin published the infamous book called the Origin of Species explaining evolution and the process of natural selection. Writing the paper with Wallace the year before, who was like a mentor to Darwin, was the base for a successful career.