Charles Robert Darwin (1809-1882) was an English naturalist and traveler who demonstrated that all living organisms evolve over time from common ancestors. Darwin was born in Shrewsbury, Shropshire and studied natural history from a young age. After graduating from university, in 1831 Darwin served as a naturalist on the HMS Beagle expedition, traveling around the world for nearly five years and studying geology and natural history. His observations on the voyage, such as the uniqueness of Australian marsupials, led Darwin to develop his theory of evolution by natural selection. After returning to England in 1836, Darwin worked to publish his theories over several decades, releasing On the Origin of Species in 1859.