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.

Like most of us, I try to be mindful of food that goes to waste. The arugula (芝麻菜) was to make a nice green salad, rounding out a roast chicken dinner. But I ended up working late. Then friends called with a dinner invitation. I stuck the chicken in the freezer. But as days passed, the arugula went bad. Even worse, I had unthinkingly bought way too much; I could have made six salads with what I threw out.

In a world where nearly 800 million people a year go hungry, "food waste goes against the moral grain," as Elizabeth Royte writes in this month's cover story. It's jaw-dropping how much perfectly good food is thrown away — from "ugly" (but quite cat able) vegetables rejected by grocers to large amounts of uneaten dishes thrown into restaurant garbage cans.

Producing food that no one eats wastes the water, fuel, and other resources used to grow it. That makes food waste an environmental problem. In fact, Royte writes," if food waste were a country, it would be the third largest producer of greenhouse gases in the world. "

If that's hard to understand, let's keep it as simple as the arugula at the back of my refrigerator. Mike Curtin sees my arugula story all the time — but for him, it's more like 12 boxes of donated strawberries nearing their last days. Curtin is CEO of DC Central Kitchen in Washington. D.C., which recovers food and turns it into healthy meals. Last year it recovered more than 807, 500 pounds of food by taking donations and collecting blemished (有瑕疵的) produce that otherwise would have rotted infields. And the strawberries? Volunteers will wash, cut, and freeze or dry them for use in meals down the road.

Such methods seem obvious, yet so often we just don't think. "Everyone can play a part in reducing waste, whether by not purchasing more food than necessary in your weekly shopping or by asking restaurants to not include the side dish you won't eat." Curtin says.

    I have a special place in my heart for libraries. I have for as long as I can remember. I was always an enthusiastic reader, sometimes reading up to three books a day as a child. Stories were like air to me and while other kids played ball or went to parties, I lived out adventures through the books I checked out from the library.

    My first job was working at the Ukiah Library when I was 16 years old .It was a dream job and I did everything from shelving books to reading to the children for story time.

    As I grew older and became a mother, the library took on a new place and an added meaning in my life. I had several children and books were our main source(来源) of entertainment. It was a big deal for us to load up and go to the local library, where my kids could pick out books to read or books they wanted me to read to them.

    I always read ,using different voices ,as though I were acting out the stories with my voice and they loved it !It was a special time to bond with my children and it filled them with the wonderment of books .

    Now, I see my children taking their children to the library and I love that the excitement of going to the library lives on form generation to generation.

    As a novelist, I've found a new relationship with libraries. I encourage readers to go to their local library when they can't afford to purchase a book. I see libraries as a safe haven(避风港) for readers and writers, a bridge that helps put together a reader with a book. Libraries, in their own way, help fight book piracy(盗版行为) and 1 think all writers should support libraries in a significant way when they can. Encourage readers to use the library. Share library announcements on your social media. Frequent them and talk about them when you can.