No one knows for sure when advertising first started. It is possible that it grew out of the discovery that some people did certain kinds of work better than others did them. That led to the concept of specialization, which means that people would specialize, or focus, on doing one specific job.

    Let's take a man we'll call Mr. Fielder, for example. He did everything connected with farming. He planted seeds, tended the fields, and harvested and sold his crops. At the same time, he did many other jobs on the farm. However, he didn't make the bricks for his house, grind the wheat for his flour, or cut his trees into boards. He also did not make the plows(犁), the work boots, or any of the other hundreds of things a farm needs. Instead, he got them from people who specialized in doing each of those things.

    Suppose there was another man we shall call Mr. Plowright. Using what he knew about farming and working with iron, Mr. Plowright invented a plow that made farming easier. Mr. Plowright did not really like farming himself and wanted to specialize in making really good  plows. Perhaps, he thought, other farmers will trade what they grow for one of my plows.

    How did Mr. Plowright let people know what he was doing? Why, he advertised, of course. First he opened a shop and then he put up a sign outside the shop to attract customers. That sign may have been no more than a plow carved into a piece of wood and a simple arrow pointing to the shop door. It was probably all the information people needed to find Mr. Plowright and his really good plows.

    Many historians believe that the first outdoor signs were used about five thousand years ago. Even before most people could read, they understood such signs. Shopkeepers would carve into stone, clay, or wood symbols for the products they had for sale.

    A medium, in advertising talk, is the way you communicate your message. You might say that the first medium used in advertising was signs with symbols. The second medium was audio, or sound, although that term is not used exactly in the way we use it today. Originally, just the human voice and maybe some kind of simple instrument, such as a bell, were used to get people's attention.

    A crier, in the historical sense, is not someone who weeps easily. It is someone, probably a man, with a voice loud enough to be heard over the other noises of a city. In ancient Egypt, shopkeepers might hire such a person to spread the news about their products. Often this primitive form of advertising involved a newly arrived ship loaded with goods. Perhaps the crier described the goods, explained where they came from, and praised their quality. His job was, in other words, not too different from a TV or radio commercial in today's world.

    Nola is a 41-year-old northern white rhino (犀牛) that lives at the San Diego Zoo Safari Park in Escondido, California. She is one of only four remaining northern white rhinos in the world, and the only one in the western part of the earth. The other three live in Kenya (肯尼亚).

    Rhinos have lived on earth for more than 40 million years, but they are now at the risk of dying out. Hunters illegally hunt rhinos for their horns (角), which are used for art, jewelry, and decorations. They sell the horns for thousands of dollars per pound, though it is not allowed by law. Rhino horns are also prized as a key part in traditional medicine, even though scientific tests have proven that the horns cannot cure illnesses. Experts say that every eight hours, one rhino will be hunted.

    Scientists are trying to find ways to prevent rhinos from dying out. In 1975, the San Diego Zoo Institute for Conservation Research started the Frozen Zoo, a program through which researchers have collected cell samples (细胞样品) from more than 8, 000 different animal species until now, including the northern white rhino. Scientists hope that by studying the rhino cells, they will gain greater understanding of the species, and will find ways to increase its number.

    Jeanne Loring works with the Frozen Zoo. Loring's research focuses on pluripotent stem cells, which are cells that can renew and become any cell type. Coloring's lab at TSRI is working together with scientist Oliver Ryder of the San Diego Zoo to use plenipotentiary stem cells to try to increase the number of the northern white rhino. Loring said the goal is to start producing new rhinos through this method over the next couple of years.

    Ever walked to the shops only to find, once there, you've completely forgotten what you went for? Or struggled to remember the name of an old friend? For years we've accepted that a forgetful brain is as much a part of aging as wrinkles and gray hair. But now a new book suggests that we've got it all wrong.

    According to The Secret Life of the Grown-up Brain, by science writer Barbara Strauch, when it comes to the important things, our brains actually get better with age. In fact, she argues that some studies have found that our brain hits its peak between our 40s and 60s — much later than previously thought.

    Furthermore, rather than losing many brain cells as we age, we keep them, and even produce new ones well into middle age. For years it's been assumed that brain, much like the body, declines with age. But the longest, largest study into what happens to people as they age suggests otherwise.

    This continuing research has followed 6,000 people since 1956, testing them every seven years. It has found that on average, participants performed better on cognitive (认知的) tests in their 40s and 50s than they had done in their 20s. Specifically, older people did better on tests of vocabulary, verbal memory (how many words you can remember) and problem solving. Where they performed less well was number ability and perceptual speed — how fast you can push a button when ordered. However, with more complex tasks such as problem-solving and language, we are at our best at middle age and beyond. In short, researchers are now coming up with scientific proof that we do get wiser with age.

    Neuroscientists are also finding that we are happier with aging. A recent US study found older people were much better at controlling and balancing their emotions. It is thought that when we're younger we need to focus more on the negative aspects of life in order to learn about the possible dangers in the world, but as we get older we've learned our lessons and are aware that we have less time left in life: therefore, it becomes more important for us to be happy.

    Poet William Stafford once said that we are defined more by the detours(绕行路) in life than by the narrow road toward goals. I like this image. But it was quite by accident that I discovered the deep meaning of his words.

    For years we made the long drive from our home in Seattle to my parents' home in Boise in nine hours. We traveled the way most people do: the fastest, shortest, easiest road, especially when I was alone with four noisy, restless kids who hate confinement(限制) and have strong opinions about everything.

    Road trips felt risky, so I would drive fast, stopping only when I had to. We would stick to the freeways and arrive tired.

    But then Banner, our lamb was born. He was rejected by his mama days before our planned trip to Boise. I had two choices: leave Banner with my husband, or take him with me. My husband made the decision for me.

    That is how I found myself on the road with four kids, a baby lamb and nothing but my everlasting optimism to see me through. We took the country roads out of necessity. We had to stop every hour, let Banner shake out his legs and feed him. The kids chased him and one another. They'd get back in the car breathless and energized, smelling fresh from the cold air.

    We explored side roads, catching grasshopper in waist-high grass. Even if we simply looked out of the car window, at baby pigs following their mother, or fish leaping out of the water, it was better than the best ride down the freeway. Here was life. And new horizons(见识).

    We eventually arrived at my parents' doorstep astonishingly fresh and full of stories.

    I grew brave with the trip back home and creative with my disciplining technique.

    On an empty section of road, everyone started quarreling. I stopped the car, ordered all kids out and told them to meet me up ahead. I parked my car half a mile away and read my book in sweet silence.

    Some road trips are by necessity fast and straight. But that trip with Banner opened our eyes to a world available to anyone adventurous enough to wander around and made me realize that a detour may uncover the best part of a journey-and the best part of yourself.

    Americans wear black for mourning (哀悼) while Chinese wear white. Westerners think of dragons as monsters. Chinese honor them as symbols of God. Chinese civilization has often shown such polarities (对立)with the West, as though each stands at extreme ends of a global string. Now in the University of California, Berkeley, a psychologist, has discovered deeper polarities between Chinese and American cultures—polarities that go to the heart of how we reason and discover truth.

    His findings go far toward explaining why American cultures seem to be aggressive and Chinese cultures so passive, when compared to each other. More importantly, the research opens the way for the peoples of the East and the West to learn from each other in basic ways. The Chinese could learn much from Western methods for determining scientific truth, said Kaiping Peng, a former Beijing Scholar, who is now a UC Berkley assistant professor of psychology. And Americans could profit enormously from the Chinese tolerance for accepting contradictions in social and personal life, he said.

    "Americans have a terrible need to find out who is right in an argument," said Peng. "The problem is that at the interpersonal level you really don't need to find the truth, or maybe there isn't any." Chinese people, said Peng, are far more content to think that both sides have advantages and disadvantages, because they have a whole awareness that life is full of contradictions. They do far less blaming of the individual than do Americans, he added.

    In studies of interpersonal (人际的) argument, for example, when subjects were asked to deal with contradictory information resulting from conflict between a mother and a daughter or a student and a school, Peng found that Americans were "non-compromising (折中), blaming one side—usually the mother—for the causes of the problems, demanding changes from one side to attain a solution and offering no compromise" in dealing with the conflict. Compared to this angry, blaming American method, the Chinese were paragons (模范) of compromise, finding fault on both sides and looking for solutions that moved both sides to the middle.

This winter, the U. S. state of California received unusually large amounts of rain and snow. Now, people worry that some areas will flood as the snow in the Sierra Nevada Mountains melts (融化).

Ron Caetano lives about half-way between the cities of Los Angeles and San Francisco. He is preparing to leave in case his community, called the Island District, floods.

More than 100 years ago, the Island District area was under a large lake named Tulare Lake. At one time, Tulare Lake was the largest freshwater lake west of the Mississippi River. But reservoirs (水库) and watering systems for agriculture caused it to disappear. However, in very rainy years, farmland can still get covered with water.

Experts say reservoirs near the area will likely receive three times more water than they can hold this year. That means officials must increase the amount of water they release (释放) from the reservoirs. If too much water is released, the area might flood.

The Island District has organized a community network to help prepare for floods. People are placing sandbags close to elderly neighbors' houses to block possible flooding. And they are looking at reports from water officials, county officials, and from each other.

California has had very dry weather in recent years. Both cities and farm communities acclaimed this year's winter rains. If the weather gets warmer slowly, the snow will not melt quickly and there may be little or no flooding. But if the weather gets hot quickly, that will bring trouble from too much melting snow.

Officials announced plans to close parts of Yosemite National Park because of threats of flooding. The park is about 270 kilometers east of San Francisco in the Sierra Nevada Mountains.

Nicholas Pinter is with the University of California, Davis Center for Watershed Sciences. He said the lake's size has always changed because of California's weather. He described the surrounding area this way. "It has been an engineering problem all along," he said. "This is a bathtub (浴缸) with no way out."