A key figure in the development of the theory of evolution in the 19th century was Charles Darwin. His landmark work, "On the Origin of Species," published in 1859, introduced the concept of natural selection as a mechanism for evolution. Darwin's observations during his voyage on the HMS Beagle, particularly in the Galápagos Islands, led him to understand variations in species and their adaptation to environments. While the idea of evolution had existed prior, Darwin's scientific approach and the evidence he provided revolutionized biological sciences, establishing a foundation that would not only influence biology but also challenging prevailing views on creation and species development.