German: Biography of a Language. By Ruth H. Sanders. Oxford University Press; 248 pages; $29.95 and £17.99. Buy from Amazon.com, Amazon.co.uk

MOST people regard grammar books and dictionaries as a codified set of rules prescribing dos and don'ts. For professional scholars of language, though, they are more like history books. Languages are constantly in flux, but it takes a rather long view to show just what a contingent and transitory thing a language can be at any point in time. Ruth Sanders, a professor of German Studies at Miami University in Ohio, takes just such a view in her new book, telling the millennia-long story of German and how it got that way.

Ms Sanders neatens the history by choosing six turning points to trace the development of German or, more accurately, the Germanic languages. During the third millennium BC, speakers of Proto-Indo-European reached most of Europe. Ms Sanders's biography ranges widely over not just linguistics, but also over archaeology and genetic history to tell the story of these prolific Indo-Europeans and their languages; an eighth of this slim book has passed before the reader first encounters the first Germanic-speakers (on the coasts of Denmark). No one knows what made the Germanic language branch off from the Indo-European family. Whether the pre-existing population in Scandinavia influenced it, or if it had already branched off when it arrived, is hard to say for certain at this distance. But Ms Sanders does usefully correct a common misconception. Languages do not usually spread because newcomers replace indigenous peoples. Rather, those already there often take up the new settlers' tongue.

The next turning point was courtesy of Arminius, also known as “Hermann the German”, a Roman-trained soldier; in 9AD he stopped a Roman advance eastward across the Rhine. At the battle of Teutoburg forest, the troublesome locals ambushed three Roman legions. As a result, the Roman borders, known as “limes” (from which comes the word “limits”) stopped at the Rhine. Whereas the Germanics took up as many Roman ways of life as they could afford, they never took up their language as the conquered—primarily Celtic—people of France and Spain had. Germanic marauders would later devastate the empire itself, but in another twist, those who settled in Italy, Gaul and Spain did in fact begin speaking Late Latin. Arminius had saved a bit of the map for German.

At another of Ms Sanders's turning points, the Germanic dialects had split into High (mountainous, southern) and Low (northern, flatland) varieties, giving modern (High) German ich, for example, while old Anglo-Saxon had ic and Dutch, ik. Perhaps the most celebrated turning point in the history of the German language is the work of another rebel against Rome, Martin Luther. His belief in salvation through personal faith alone, not the intermediation of the Church, led him to violate a longstanding prohibition on translating the Bible into vernacular languages. Luther had to compromise between the many different “Germans” that filled the German lands in those days, hundreds of years before there was a single German state (the creation of which is Ms Sanders's fifth turning point). Luther borrowed an emerging standard used by the Holy Roman Empire, “chancellery German”, as a base with some currency in different regions.

Luther's genius was to infuse his translation with the words he heard on the street in his bit of Saxony, in east-central Germany. He obsessively asked friends and fellow scholars which dialectal words would be most widely understood. The common touch was so successful that a Catholic opponent complained that “even tailors and shoemakers…read it with great eagerness.” It was the bestseller of the century and remains the most popular German translation. Rarely has a single man had such a mark on a language. The German of Luther's Bible was nobody's native language in his day. Today it is so universal that it threatens Germany's once-vibrant dialects with death by standardisation.

Ms Sanders's work contains some disappointments. Occasionally she reintroduces the same fact as if it were new. And with under 250 pages to tell her tale, there is little room to spare. There are no examples of the earthy Saxonisms that Luther made into today's standard German. Ms Sanders reports that the Latin theodiscus is the first mention of German's name for itself (Deutsch), but not where theodiscus comes from. (The answer is that theud was a Germanic root meaning “people”, so that Deutsch meant “Peoplish” to its speakers.) The chronological tables contain more errors than they should. The last turning point, German's cultural revival after two crushing world wars, feels too brief.

Ms Sanders's book is a biography, not of the modern German language proper, but of the Germanic languages and the people who speak them. She takes in the development of Yiddish, Dutch, Icelandic and of course English, as well as others. As such it is an ingenious telling of just how German emerged from the primordial Germanic soup, and how many other ways it could have been if, say, Luther had been born 100 miles farther north. For all its flaws, this is an enjoyable yet still-scholarly read for the historian, linguist and Germanophile alike. It would be a fine thing to have more such brief histories, made easily readable to the non-specialist, of the major world languages.