While traveling aboard the HMS Beagle, Charles Darwin read the Principles of Geology by Charles Lyell (1797–1875). Catastrophism was the popular theory of the time about the forces driving geological change. Lyell’s theory suggested that geologic change was not solely the result of random catastrophes. Rather, he proposed that geologic formations were most often the result of everyday occurrences like storms, waves, volcanic eruptions, and earthquakes that could be observed within an individual lifetime. This idea, that the same geologic processes at work today were also present during our evolutionary past, is known as Uniformitarianism. This conclusion also led Lyell and, before him, James Hutton (1726–1797), to suggest that Earth must be much older than the previously accepted age of 6,000 years, because these uniform processes would have required many millions of years to generate the structures he observed. Reading Lyell’s work gave Darwin a new perspective as he traveled through South America and sought a mechanism by which he could explain his thoughts on evolution.