Pitt Rivers' interests in archaeology and ethnology began in the 1850s, during postings overseas, and he became a noted scientist while he was a serving military officer. His interest began with the evolution of the rifle, which extended to other weapons and tools, and he became a collector of artifacts illustrating the development of human invention. His collection became famous, and, after being exhibited in 1874–1875 at the Bethnal Green Museum, was presented in 1885 to the University of Oxford. He was elected, in the space of five years, to the Ethnological Society of London (1861), the Society of Antiquaries of London (1864) and the Anthropological Society of London (1865). By the time he retired he had amassed ethnographic collections numbering tens of thousands of items from all over the world. Influenced by the evolutionary writings of Charles Darwin and Herbert Spencer, he arranged them typologically and (within types) chronologically. He viewed archaeology as an extension of anthropology and, as consequence, built up matching collections of archaeological and ethnographic objects to show longer developmental sequences to support his views on cultural evolution. This style of arrangement, designed to highlight evolutionary trends in human artefacts, was a revolutionary innovation in museum design.