British scientist Charles Darwin (1809–1882) developed the theory of evolution (the theory that living organisms developed slowly over long periods of time) after years of meticulous note-taking on his journeys around the world. He originally trained for a career in medicine and the ministry but lost interest in both during his studies. He turned his attention to studying the natural world when he met the botanist (a scientist specializing in the study of plants) J. S. Henslow (1796–1861), who offered him a chance to take a five-year research cruise on board a boat called The Beagle. These five years of intensive study took Darwin to the coasts of South America, the Galápagos Islands, the Andes Mountains, Australia, and Asia. After this voyage Darwin was encouraged by geologist (a scientist specializing in the origin, history, and structure of the Earth) Charles Lyell (1797–1875) to publish his conclusions about the natural world in a book. He was finally prompted to write the book after receiving word that British biologist A. R. Wallace (1823–1913) had developed almost identical theories about the origins of life through studies in the East Indies and on the Amazon River in Brazil. In 1858 Darwin published his work along with Wallace's theory. The next year he published the famous The Origin of Species, which was embraced by the scientific community as a credible theory on evolution. He expanded on this work with The Descent of Man in 1871.
Darwin's primary findings stemmed from his close observations of nature and led him to conclude that all life originated from a simple protoplasm (the fundamental material from which all living things are composed). He noted that the struggle for survival leads a species (a group of living organisms that interbreeds to produce offspring) to adapt in numerous ways to meet the challenges of its environment. This results in great variation through the process of natural selection, in which characteristics that enable a species to survive more effectively are "selected" by the organism and passed on through its genes (units of hereditary information) to future generations. Modern scientific advances have expanded on Darwin's theories while also substantiating his findings. His theories are considered to be the cornerstone of modern genetic science.
Further Information: Bowlby, John. Charles Darwin: A New Life. New York: Norton, 1992; "Charles Darwin." Electric Library. [Online] Available http://www.encyclopedia.com/articles/03445.html, November 8, 2000; "Charles Robert Darwin." MSN Encarta. [Online] Available http://encarta.msn.com/index/conciseindex/59/0595D000.htm, November 8, 2000; Mayr, Ernst. One Long Argument: Charles Darwin and the Genesis of Modern Evolutionary Thought. Cambridge, Mass.: Harvard University Press, 1993.