The theory of natural selection. Alfred Russel Wallace (1823-1913) was a naturalist, explorer and writer. Born in Monmouthshire, he started his career as a collector of natural history specimens. He did extensive fieldwork first in the Amazon River basin, and then in the Malay Archipelago, where he identified the Wallace line dividing the fauna of Australia from that of Asia. In the Malay expedition he obtained 126,500 specimens, among them over 200 new species of birds and over 1,000 new insects. He also did important work on the orang-utan. Wallace is best known for independently proposing a theory of natural selection which prompted Charles Darwin to publish his own more developed and researched theory sooner than intended. He became one of the world’s most famous scientists. He is also known for espousing opinions now seen as scientifically eccentric, such as his opposition to vaccination and his interest in spiritualism and the paranormal. His interests were wide, including a commitment to social progress and women’s rights as well as science. These interests are reflected in his personal library of some 470 books, donated in 1993 by the University of Oxford Museum. They are now catalogued online, with provenance information, and located at shelfmarks SD 8270-8742. This article was published on 2024-08-21