Between 1863 and 1870, two organisations competed for the same scholarly territory. The Ethnological Society of London and the Anthropological Society — founded in 1863 by James Hunt, a figure associated with increasingly hardline views on racial difference — were separate bodies with overlapping interests and genuine hostility between them. In 1871, after years of rivalry, the two merged to form the Anthropological Institute of Great Britain and Ireland. The merger required both sides to subordinate their competing agendas to a shared institution. Permission to add the prefix Royal was granted in 1907, reflecting the Institute's established status in British learned society. A Royal Charter followed in October 2020.

The RAI's collection is the kind of resource that scholars travel to consult and researchers build careers around. Its photographic library alone holds over 75,000 historic prints, negatives, lantern slides, and other images, the earliest dating from the 1860s. These are photographs of people taken during the era of colonial expansion — images made in the context of imperial power, carrying all the complexity and ethical weight that entails, but also providing visual documentation of cultures and ways of life that would otherwise be unrecorded. The archive and manuscript collection spans more than 150 years, documenting both the history of the discipline and the history of the Institute itself. The RAI's library was given to the British Museum in 1976 and now forms the core of the museum's Anthropology Library at the Centre for Anthropology — effectively Britain's national anthropological library.

The Institute's highest honour is the Huxley Memorial Medal and Lecture, established in 1900 in memory of Thomas Henry Huxley — the biologist and champion of Darwin's evolutionary theory, known in his day as Darwin's Bulldog. The medal is awarded annually by ballot to a scientist distinguished in any field of anthropological research. The Rivers Memorial Medal, founded in 1923 in memory of William Halse Rivers — the psychiatrist and anthropologist who pioneered fieldwork methods and treated shell-shocked soldiers during World War I — recognises a recent body of work making a significant contribution to social, physical, or cultural anthropology over a five-year period. Both awards connect the present institution to the foundational figures of British anthropology.

Anthropology as a discipline emerged from an era of European imperialism, and the Royal Anthropological Institute cannot be separated from that history. Many of its founding figures operated within a framework of assumptions — about race, culture, and human development — that subsequent scholarship has dismantled. The Institute today describes its remit as spanning biological, evolutionary, social, cultural, visual, and medical anthropology, as well as related fields including human genetics, archaeology, and linguistics. Its approximately 1,800 Fellows and Members include academic anthropologists alongside practitioners who apply the discipline in education, medicine, and development. The International Festival of Ethnographic Film, held every two years in partnership with universities and other hosts, reflects the Institute's effort to make the field accessible beyond academic circles. The work of understanding human diversity continues, with more caution and more self-awareness than its founders possessed.