Human speech contains more than 2, 000 different sounds, from the common "m" and "a" to the rare clicks of some southern African languages. But why are certain sounds more common than others? A ground-breaking, five-year study shows that diet-related changes in human bite led to new speech sounds that are now found in half the world's languages.

More than 30 years ago, the scholar Charles Hockett noted that speech sounds called labiodentals, such as "f" and "v", were more common in the languages of societies that ate softer foods. Now a team of researchers led by Damián Blasi at the University of Zurich, Switzerland, has found how and why this trend arose.

They discovered that the upper and lower front teeth of ancient human adults were aligned (对齐), making it hard to produce labiodentals, which are formed by touching the lower lip to the upper teeth. Later, our jaws changed to an overbite structure(结构), making it easier to produce such sounds.

The team showed that this change in bite was connected with the development of agriculture in the Neolithic period. Food became easier to chew at this point. The jawbone didn't have to do as much work and so didn't grow to be so large.

Analyses of a language database also confirmed that there was a global change in the sound of world languages after the Neolithic age, with the use of "f" and "v" increasing remarkably during the last few thousand years. These sounds are still not found in the languages of many hunter-gatherer people today.

This research overturns the popular view that all human speech sounds were present when human beings evolved around 300, 000 years ago. "The set of speech sounds we use has not necessarily remained stable since the appearance of human beings, but rather the huge variety of speech sounds that we find today is the product of a complex interplay of things like biological change and cultural evolution," said Steven Moran, a member of the research team.

In 1916, two girls of wealthy families, best friends from Auburn, N. Y.—Dorothy Woodruff and Rosamond Underwood—traveled to a settlement in the Rocky Mountains to teach in a one-room schoolhouse. The girls had gone to Smith College. They wore expensive clothes. So for them to move to Elkhead, Colo. to instruct the children whose shoes were held together with string was a surprise. Their stay in Elkhead is the subject of Nothing Daunted: The Unexpected Education of Two Society Girls in the West by Dorothy Wickenden, who is a magazine editor and Dorothy Woodruff's granddaughter.

Why did they go then? Well, they wanted to do something useful. Soon, however, they realized what they had undertaken.

They moved in with a local family, the Harrisons, and, like them, had little privacy, rare baths, and a blanket of snow on their quilt when they woke up in the morning. Some mornings, Rosamond and Dorothy would arrive at the schoolhouse to find the children weeping from the cold. In spring, the snow was replaced by mud over ice.

In Wickenden's book, she expanded on the history of the West and also on feminism, which of course influenced the girls' decision to go to Elkhead. A hair-raising section concerns the building of the railroads, which entailed（牵涉）drilling through the Rockies, often in blinding snowstorms. The book ends with Rosamond and Dorothy's return to Auburn.

Wickenden is a very good storyteller. The sweep of the land and the stoicism（坚忍）of the people move her to some beautiful writing. Here is a picture of Dorothy Woodruff, on her horse, looking down from a hill top: "When the sun slipped behind the mountains, it shed a rosy glow all around them. Then a full moon rose. The snow was marked only by small animals: foxes, coyotes, mice, and varying hares, which turned white in the winter."

The Government's sugar tax on soft drinks has brought in half as much money as Ministers first predicted it would generate, the first official data on the policy has shown.

First announced in April, 2016, the tax which applies to soft drinks containing more than 5g of sugar per 100ml, was introduced to help reduce childhood obesity（肥胖）. It is believed that today's children and teenagers are consuming three times the recommended level of sugar, putting them at a higher risk of the disease.

Initially the sugar tax was expected to make £520m a year for the Treasury. However, data of the first six months showed it would make less than half this amount. At present it is expected to generate £240m for the year ending in April 2019, which will go to school sports.

It comes after more than half of soft drinks sold in shops have had their sugar levels cut by manufacturers（制造商）so they can avoid paying the tax. Drinks now contain 45 million fewer kilos of sugar as a result of manufacturers' efforts to avoid the charge, according to Treasury figures. Since April drinks companies have been forced to pay between 18p and 24p for every litre of sugary drink they produce or import, depending on the sugar content.

However, some high sugar brands, like Classic Coca Cola, have accepted the sugar tax and are refusing to change for fear of upsetting consumers. Fruit juices, milk-based drinks and most alcoholic drinks are free of the tax, as are small companies manufacturing fewer than 1m litres per year.

Today's figures, according to one government official, show the positive influence the sugar tax is having by raising millions of pounds for sports facilities（设施）and healthier eating in schools. Helping the next generation to have a healthy and active childhood is of great importance, and the industry is playing its part.