Charles Darwin was born in 1809 in England to an esteemed family with intellectual lineage. He studied medicine at university but found geology more interesting. His mentors introduced him to new ideas in geology and the emerging concept of deep time. In 1831, Darwin joined the HMS Beagle voyage as a naturalist. During the 5-year voyage, Darwin intensely studied geology, actively witnessed earthquakes and volcanic eruptions, discovered giant fossil mammals in Argentina, and began questioning theories about the fixity of species. His geological observations on the voyage formed the basis for his later theories about evolution and natural selection.