Alfred Russel Wallace (8 January 1823 – 7 November 1913) was a British naturalist, explorer, and biologist. He is known for independently conceiving the theory of evolution through natural selection. Wallace did extensive fieldwork, identified the faunal divide called the Wallace Line, and was considered the 19th century's leading expert on the geographical distribution of animal species, leading some to call him the father of biogeography, or more specifically of zoogeography. An account of his adventures in Southeast Asia, titled The Malay Archipelago, was published in 1869. He worked on warning coloration in animals, and on reinforcement, a way that natural selection could contribute to speciation by encouraging barriers against hybridisation. He was also a social activist, critical of the social and economic system of 19th-century Britain. He was one of the first prominent scientists to raise concerns over the environmental impact of human activity. (Full article...)