In the last years of the 19th century a small part-Sioux girl was musing on the wide world about which she was learning at school. “In some of the countries,” she wrote, “the people have very strange ways, and are very queer themselves.” By 1930 that girl, Ella Cara Deloria, had been commissioned by Columbia University to return to the Great Plains to investigate the ceremonies and beliefs of her father’s people. She made a note – one that could be read as a reproof to her own childish self. She was to remember that people outside the dominant culture were not “queer” – just different. “Get nowhere unless prejudices first forgotten. Cultures are many; man is one. Boas.”

Boas was Professor Franz Boas. To Charles King, author of this illuminating biographical history of the then new-fangled study of “anthropology”, Boas was the founder and wise steersman of the science, and an indefatigable advocate for the important concept that one of his protégées was to call “cultural relativity”.

Born into a Jewish family in Westphalia, Boas had first come to the US in 1884 from Baffin Island. He had spent a hard, cold winter there living with the Inuit and learning “that we have no right to impose our ideals upon other nations, no matter how strange it may seem to us that they enjoy the kind of life they lead”. He had observed that peoples who were then unquestioningly described as “primitive” had impressive skills and knowledge of their own. More importantly, they had their own histories. Rather than living in the timeless stasis usually associated with pre-industrial societies, they travelled; they learned from other groups; they were the complex products of a variety of influences. They were not “undeveloped”: – rather they had developed in pursuit of different aims from those that Westerners took for granted. King argues that it is largely thanks to Boas, and his students, and students’ students, that these ideas now seem commonplace. In the 1880s they were startling and – to many – dangerous.

With an imperfect grasp of English, Boas struggled to establish himself in the US. King introduces us to the rivalrous pantheon of academics and museum curators then interesting themselves in the study of alien peoples. At the World’s Fair in Chicago in 1893 Boas curated an exhibition. Only a “trickle of professors” bothered with his display. Buffalo Bill’s Wild West Show, making a thrilling spectacle of recent genocide, was far more popular.

Boas seldom boasted about the major turnaround his insights constituted. Not so King, who has a swaggering way with words, a great gift for nicely balanced epigrammatic prose and a shameless taste for grandiose shout-lines. To him, Boas’s ideas constitute the “prehistory of the seismic social changes of the last hundred years”.

In 1920 Boas noted one of those “seismic” changes. By this time he was professor at Columbia. He wrote to a friend that in recent years something “curious” had happened: “All my best students are women.” This is where King’s narrative shifts gear. Boas’s early career is the saga of a man making his way laboriously through a crowd. But once King moves on to those curiously talented women, four storylines come into view, and four remarkable characters leap out.

The first of them is Ruth Benedict. As a young wife Benedict was shy, hard of hearing and intermittently suicidal, but in her mid-thirties she enrolled in a class taught by a female protégée of Boas’s, who urged students to imagine “everything you think of as normal become strange and unfamiliar”. Uneasy with normality, Benedict was encouraged.

In 1924 she set out for New Mexico to do fieldwork among the indigenous people of Zuni. There she encountered a matrilineal society, where women owned all the property and men worked for them. How exhilaratingly different from the world within which, as a woman, she was never – even when she became a professor – permitted to eat in the Columbia faculty dining room. There was more. Among the people of Zuni, gender was unstable. A biological man could assume a female role, doing woman’s work, wearing a dress, forming a sexual relationship with another man. “One of the most striking facts…” Benedict later wrote, “is the ease with which our abnormals function in other cultures.” She had found a field in which her sense of being a misfit could make her pre-eminent. Nearly 20 years later, her book on Japan, The Chrysanthemum and the Sword, would become one of the most celebrated studies of a non-Western culture ever written.

Benedict’s sense of herself as an “abnormal” had to do with her relationship with another of Boas’s brilliant female students, Margaret Mead. The two women loved each other, but seldom lived together as lovers.

Mead caused trouble and inspired strong feelings. “Philadelphia girl plans cannibal sojourn” announced newspaper headlines when Mead set out for Manus in 1928. Her previous field trip, undertaken at 23, had resulted in the bestselling Coming of Age in Samoa. She had been married. She had had an affair with a much older anthropologist, Edward Sapir. Sapir adored her but was later to say “she is… a loathsome bitch flattened out to a malodorous allegory”. She used people (both her academic peers, and the South Sea Islanders she studied) and then abandoned them. Her second and third husbands were to be tormented by her refusal to be paired “as with oxen, say, or socks”.

Traditionalists sniffed at her books, but Mead’s fieldwork yielded revelations. She didn’t confine herself to minutiae: as King writes, “there was little talk of demons and taboos, fishing practices or basketry techniques”. Instead she talked, as her male predecessors never had, to girls and women, uncovering a world of emotion and desire that would reverberate, not only through anthropological theory, but also through her readers’ understanding of their own lives.

Mead became a celebrity – “One of Uncle Sam’s most brainy women, and a world authority on ethnology” as the press described her. Boas helped her to get a job at the American Museum of Natural History, but she never became a tenured professor. King’s other two female subjects were even more marginalised by the academic establishment. One was Deloria, whose work among the Sioux resulted in the linguistically ground-breaking Dakota Grammar, but who subsequently settled down to teaching in a remote school while living precariously in a motel.

The other was Zora Neale Hurston. Hurston grew up in Florida, daughter of a preacher in the all-black town of Eatonville. By her mid-thirties she was in Harlem, and studying under Boas at Barnard College. The Harlem Renaissance was at its most brilliant but African-American culture was still routinely patronised. A historian with the foundation sponsoring Hurston’s field-trip began an essay with the words, “The author considers the Negro as human.” When Boas urged Hurston to go south to do fieldwork among her own people, he was, albeit with best intentions, signalling that, to white Americans, black Americans were as alien – and perhaps as inferior – as the Polynesians.

Hurston approached her subject matter unconventionally. Anthropologists tended to use the present tense: a “savage” swims, eats, tells, knows, in a perpetually unchanging present. Hurston wrote about the people she described in the past tense, as though their lives – like her own – were part of a narrative that could continue into an unpredictable future. She wrote up her findings in the form of a conversation between her subjects and herself, honestly acknowledging that she was part of the interaction, not a godlike impartial observer. It was a fresh method, and it led her away from academe into literature. Her sensational fictionalised memoir, Their Eyes Were Watching God, made her a bestselling author. But her life ended sadly – a sequence of menial jobs, a false charge of molesting three boys, death in a county-run “home for indigents”.

Deloria had learned that other peoples were neither “queer” nor “strange”, but in time of war such enlightenment gets snuffed out. After the Japanese surrender in 1945 Ruth Benedict wrote “no Western nation has ever shown such dignity and virtue in defeat”. At a time when a senior American admiral could describe the Japanese as looking like the progeny of “female apes and the worst Chinese criminals” such generosity made Benedict suspect. She was refused a job on General MacArthur’s staff during the postwar occupation of Japan. Her postbag was full of hate-mail accusing her of “communist sympathies”.

Franz Boas died in 1942, when his homeland was controlled by genocidal racists, and his adopted country was closing its mind. Now though, as King writes with a typically fine flourish, Boas can be seen to have been “on the front line of the greatest moral battle of our time” and he, along with the talented women who learnt from him, won out in the end.

Lucy Hughes-Hallett’s most recent book is “Fabulous” (Fourth Estate)

The Reinvention of Humanity: A Story of Race, Sex, Gender and the Discovery of Culture

Charles King

Bodley Head, 448pp, £25