Globish: How the English Language Became the World’s Language:
"Take Urarina, a language spoken in a remote Amazonian jungle in Peru. Before its discovery, linguists had never encountered a dialect with an object-verb-subject word order. Had its speakers died out before it was documented, linguists might have come to the mistaken conclusion that the human brain was simply not wired to learn such an odd structure naturally. The same could be said for the extremely bizarre language of Pirahã, which is said to possess no relative clauses, no words for individual numbers and the smallest repertoire of phonemes of any language in the world (though Hawaiian comes close). Dialects such as these provide scientists with a virtual map of the limits and possibilities of human cognition; the opportunity to learn what we can before it’s too late is rapidly slipping away. Consider the Bororo people of old Brazil, who tell time by gesturing to different parts of the body, each of which correspond to a different position of the sun in the sky. Would we have imagined such a thing possible if we hadn’t been there to witness it?
...[K]nowledge is often embedded in language itself. When a culture abandons its native tongue for a monolithic, multi-national language like Spanish, English or French, centuries worth of biological and environmental observations are suddenly and permanently erased. The Kayapo people, for instance, have developed 85 different words for “bee,” each specifying minute differences in flight patterns, mating rituals, habitat, nest structures, and quality of wax. Were their language to die, their rich, apian knowledge would die with it. Similarly, the word for “yak” in Tuvan can indicate any number of a yak’s qualities, including color, size, sex, age, and fertility, simply through the inflection of vowels. A dialect of the North-East Ambae island people called Lolovoli is grammatically embedded with information about their geography, such the relative size, elevation, distance and preferred means of transport to and from the island’s various sites, much of which is communicated through suffixes alone. If we look carefully at the way information is built into a language, we learn not only about the speakers and their unique view of the world, we also learn about the world itself." ...
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The book to read seems to be K. David Harrison, When Languages Die: The Extinction of the World's Languages and the Erosion of Human Knowledge 2007.
Also see this review of One Thousand Languages: Living, Endangered, Lost.