Alfred Russel Wallace (1823–1913) was a British naturalist, explorer, geographer and biologist, best remembered as the co-discoverer, with Darwin, of natural selection. His extensive fieldwork and advocacy of the theory of evolution led to him being considered one of the nineteenth century's foremost biologists. He was later moved by a variety of personal experiences to examine the concept of spirituality, but his exploration into the potential for compatibility between spiritualism and natural selection alienated him from the scientific community. He was also a social activist, highly critical of unjust social and economic systems in nineteenth-century Britain, and one of the first prominent scientists to express concern over the environmental impact of human activity. He was a prolific writer on a wide range of topics, and this two-volume autobiography, published in 1905, shows the scope of his activities during his long life.