Over the past 30 years, Daniel Everett has spent long periods in one of the earth's remotest places, pursuing something still more remote, the origins of human language. In 1977, he, his wife Karen and their three young children went to live with a hunter-gatherer tribe called the Piraha, who occupy a few scattered jungle villages on the banks of the Maici, a tributary of the Amazon. It is not a place many would choose as home. In the river, hazards range from 30ft anacondas to microscopic fish keen to enter your bodily orifices. On land,there are tarantulas, scorpions and swarms of mosquitoes that darken the air and bite through your clothes. Everett and his wife went there as missionaries, aiming to translate the bible into Piraha. Others had tried to do this, on and off, for 200 years, but they had all given up, finding the Pirahas recalcitrant and their language impossible. It does not even sound like a language - more, it has been said, like the melodic chattering of exotic songbirds.

Everett, however, was resolute. The son of a drunken Texan cowboy, he had played guitar in rock bands and was into drugs until, at high school, he met Karen, whose parents were missionaries, and became a born-again Christian. Although Karen and their eldest daughter almost died of malaria in the first few months, he - and they - stuck it out, and he has become not just the world's first non-Piraha Piraha-speaker, but a professor of linguistics whose discoveries question basic modern assumptions about what language is.

Far from finding the Pirahas recalcitrant, he liked them from the start, perhaps because of his own easy-going youth. They are, he reports, patient, kind, peaceful and contented. They care for the elderly and handicapped and laugh a lot. They have no chiefs or authority figures, and are admirably laid-back. There is no trace among them of the colourful rituals or the rich oral history that primitive peoples are supposed to have. They do not paint themselves or wear feathers or have ceremonies. The dead are buried haphazardly and there is no such thing as marriage. Couples live together, and when one of them tires of it he or she goes and lives with someone else. They have no myths about how the world began, no fictions and no art except necklaces made of seeds, teeth and drink-can pull-tabs, which women wear to ward off evil spirits. They live for the present, incurious about the past and uncaring for the future. They never preserve food, and although they make rudimentary tools and weave palm-leaf baskets they throw them away once used and make new ones next time. They are fit and lean and, as Everett's photographs show, have beautiful, broad, innocent faces, like beings straight out of Eden.

True, they can seem callous. Women are left to give birth alone and when things go wrong they are not aided. Everett heard of a young mother who screamed for help for hours until she and the baby died, while the Pirahas sat passively by. When he and Karen adopted an orphaned newborn baby, feeding it hourly through a plastic tube, the Pirahas waited until they went out and then poisoned it. Everett attributed both incidents to a kind of Darwinian realism, which he came to regard as healthy. The Pirahas, he deduced, believe you must be fit to survive, and see no point in prolonging the existence of the unfit. But perhaps the baby incident also revealed resentment of his interference, in line with the Pirahas' normal hostility to intruders. Once, when a number of them got drunk on liquor supplied by a river trader, he overheard them plotting to murder him. He marched into their hut and confiscated their weapons, and they were seemingly too drunk or cowed to resist. Next day they apologised.

Piraha is unrelated to any known language, and is at once simple and unfathomably complex. It has one of the smallest sets of speech sounds in the world, consisting of three vowels and eight consonants for men (three vowels and seven consonants for women). It has no comparatives, and its nouns do not have different plural and singular forms. Each verb, on the other hand, can have up to 16 suffixes that modify its meaning, with the result, Everett works out, that there are 65,536 possible forms for every Piraha verb. It has no fixed colour terms, no numbers and no words for “all” or “every”. Its sentences are simple assertions containing one verb and they never have relative clauses embedded in them. According to the theories of Noam Chomsky, the dominant force in modern linguistics, embedded relative clauses are a vital feature of all human language, distinguishing it from animal noises, and this is one reason why Everett's revelations have caused such a furore.

His disagreement with Chomsky goes further. He does not believe that humans have a “universal grammar” hard-wired into their brains. On the contrary, he argues, grammar and all other features of a language evolve within a culture and reflect its mind-set. In his view, an “immediacy of experience principle” (IEP) underlies the Pirahas' life and language. They have no interest in the past and their language has no perfect tense. They have no words for numbers or colours because these are general and generalisation violates the IEP. For Pirahas, a thing is its own particular colour, not “red” or “green”. Five men and five Brazil nuts have nothing in common, though our generalising mentality thinks they have. Everett ran numeracy and literacy classes that the Pirahas eagerly attended, but none of them ever learnt to count up to 10, or to understand that the random marks they made on paper were different from the words Everett wrote out for them to copy.

What they can do is, however, far more fascinating than what they cannot. Their language has a wide array of tones, stresses and syllable lengths, and its speakers can dispense with vowels and consonants altogether and convey their meaning by whistling, singing or humming. Hum-speech is particularly used by mothers talking to small children. Perhaps hearing this is something like hearing the very beginning of language, when it was just emerging from the rhythmic noises made by our human ancestors.

Everett did not convert the Pirahas to Christianity. The IEP dictates that they believe only what they see, or hear from a reliable eyewitness, and once they realised Everett had not met Jesus they lost interest. He, however, found their viewpoint so persuasive that he abandoned his religious faith. To an outsider this seems odd, particularly as his decision meant the end of his marriage to Karen and the break-up of his family. For one thing, although the Pirahas have no word for God, they believe in spirits and see them frequently, so they are not a good model for the rational atheism Everett has embraced. Further, he stresses the vital importance of caring about other cultures and languages, especially endangered ones such as the Pirahas, of whom barely 300 remain alive. Yet it is a leading Piraha characteristic that they despise other cultures, calling themselves “straight heads” and speakers of other languages “crooked heads”. It is impossible to imagine them taking an interest in comparative linguistics, and if they are wrong on this it is not apparent why Everett thinks them right in religion. However, these quibbles do not in the least detract from the power of his remarkable book. It is written with an immediacy even a Piraha might envy, and its conjunction of physical and intellectual adventure is irresistible.

Don't Sleep, There Are Snakes by Daniel Everett
Profile £15 pp320

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