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    When people first walked across the Bering Land Bridge thousands of years ago, dogs were by their sides, according to a study published in the journal Science.

    Robert Wayne of the University of California, Los Angeles, and Jennifer Leonard of the Smithsonian Institute, used DNA material—some of it unearthed by miners in Alaska—to conclude that today's domestic dog originated in Asia and accompanied the first humans to the New World about 10,000 to 15,000 years ago. Wayne suggests that man's best friend may have enabled the tough journey from Asia into North America. “Dogs may have been the reason people made it across the land bridge,” said Wayne. “They can pull things, carry things, defend you from fierce animals, and they're useful to eat.”

    Researchers have agreed that today's dog is the result of the domestication(驯化) of wolves thousands of years ago. Before this recent study, a common thought about the precise origin of North America's domestic dog was that Natives domesticated local wolves, the descendents(后代) of which now live with people in Alaska, Canada, and the Lower 48.

    Dog remains from a Fairbanks-area gold mine helped the scientists reach their conclusion. Leonard, an evolutionary biologist, collected DNA from 11 bones of ancient dogs that were locked in permafrost(永冻层) until Fairbanks miners uncovered them in the 1920s. The miners donated the preserved bones to the American Museum of Natural History in New York City, where they remained untouched for more than 70 years. After borrowing the bones from the museum, Leonard and her colleagues used radiocarbon techniques to find the age of the Alaska dogs. They found the dogs all lived between the years of 1450 and 1675 A.D., before Vitus Bering and Aleksey Chirikov who were the first known Europeans to view Alaska in 1741. The bones of dogs that wandered the Fairbanks area centuries ago should therefore be the remains of “pure native American dogs,” Leonard said. The DNA of the Fairbanks dogs would also expose whether they were the descendents of wolves from North America.

    Along with the Fairbanks samples, the researchers collected DNA from bones of 37 dog specimens(标本) from Mexico, Peru, and Bolivia that existed before the arrival of Columbus. In the case of both the Alaska dogs and the dogs from Latin America, the researchers found that they shared the most genetic material with gray wolves of Europe and Asia. This supports the idea of domestic dogs entering the New World with the first human explorers who wandered east over the land bridge.

    Leonard and Wayne's study suggests that dogs joined the first humans that made the adventure across the Bering Land Bridge to slowly populate the Americas. Wayne thinks the dogs that made the trip must have provided some excellent service to their human companions or they would not have been brought along. “Dogs must have been useful because they were expensive to keep,” Wayne said. “They didn't feed on mice; they fed on meat, which was a very guarded resource.”

     The first living creatures to travel in space were the dogs of the Soviet Unions space program.Beginning in 1951 dogs flew aboard sub－orbital flights to the height of 63 miles and higher.They helped to test the equipment that would later be used by humans.The first pair of dogs to fly，on July 22，1951，were named Tsygan and Dezik.

     Space dogs would make history on November 3，1957.On this date，just one month after the historic launch of the world's first artificial satellite，Sputnik，the Soviet Union shocked the world again by launching Sputnik 2.This satellite contained the first living creature to travel in space，a dog named Laika.Laika was to have orbited for a week or more until her food and oxygen ran out.In fact，Laika lasted only hours in orbit before over heating in her capsule(太空舱) took her life.

     That next step，occurred in August 1960，when the dogs Belka and Strelka made 18 orbits of earth and returned alive.Like Laika before them，they became distinguished ， featured in newspapers and magazines around the world.

     Six more orbital dog flights over the next eight months further tested the equipment necessary for humans to follow in the dogs' footsteps.That historic event happened on April 12，1961，when Yuri Gagarin became the first human to travel in space.

     The role of the space dogs had proven important in advancing the exploration of space.But，they would make one final flight.In 1966，traveling aboard the Cosmos 110 satellite，the dogs Ugolek and Veterok spent 22 days in orbit.Once again dogs led the way.Humans would not achieve a space flight that long for eight more years，in Skylab 2.

    Why do Americans struggle with watching their weight, while the French, who consume rich food, continue to stay thin? Now a research by Cornell University suggests how life style and decisions about eating may affect weight. Researchers concluded that the French tend to stop eating when they feel full. However, Americans tend to stop when their plate is empty or their favorite TV show is over.

    According to Dr. Joseph Mercola, a health expert, the French see eating as an important part of their life style. They enjoy food and therefore spend a fairly long time at the table, while Americans see eating as something to be squeezed between the other daily activities. Mercola believes Americans lose the ability to sense when they are actually full. So they keep eating long after the French would have stopped. In addition, he points out that Americans drive to huge supermarkets to buy canned and frozen foods for the week. The French, instead, tend to shop daily, walking to small shops and farmers' markets where they have a choice of fresh fruits, vegetables, and eggs as well as high-quality meats for each meal.

    After a visit to the United States, Mireille Guiliano, author of French Women Don't Get Fat, decided to write about the importance of knowing when to stop rather than suggesting how to avoid food. Today she continues to stay slim and rarely goes to the gym.

    In spite of all these differences, evidence shows that recent life style changes may be affecting French eating habits. Today the rate of obesity — or  extreme overweight — among adults is only 6%. However, as American fast food gains acceptance and the young reject older traditions, the obesity rate among French children has reached 17% — and is growing.

    Long before they can actually speak, babies pay special attention to the speech they hear around them. Within the first month of their lives, babies' responses to the sound of the human voice will be different from their responses to other sorts of hearing stimulation. They will stop crying when they hear a person talking, but not if they hear a bell or the sound of a rattle. At first, the sounds that a baby notices might be only those words that receive the heaviest emphasis and that often occur at the ends of utterances(讲话，说话). By the time they are six or seven weeks old, babies can detect the difference between syllables pronounced with rising and falling tones. Very soon, these differences in adult stress and intonation can influence babies' emotional states and behavior. Long before they develop actual language comprehension, babies can sense when an adult is happy or angry, attempting to begin or end new behavior, and so on, merely on the basis of clues such as the rate, volume, and melody of adult speech.

    Adults make it as easy as they can for babies to pick up a language by exaggerating(夸张) such clues. One researcher observed babies and their mothers in six diverse cultures and found that, in all six languages, the mothers used simplified utterances and nonsense sounds, and transformed certain sounds into baby talk. Other researchers have noted that when mothers talk to babies who are only a few months old, they exaggerate the pitch, loudness, and intensity of their words. They also exaggerate their facial expressions, hold vowels(元音) longer, and emphasize certain words.

    More significant for language development than their response to general intonation is observation that tiny babies can make relatively fine distinctions between speech sounds. In other words, babies enter the world with the ability to make those precisely perceptual（知觉的，感性的） recognition that are necessary if they are to acquire listening language.

    Babies obviously obtain pleasure from sound input, too: even as young as nine months they will listen to songs or stories, although the words themselves are beyond their understanding. For babies, language is a sensory-motor delight rather than the route to boring meaning that it often is for adults.

The Amazon Clipper

    Join the Amazon Clipper for an exciting journey through the world's most plentiful river and largest typical jungle. The river is surely an excellent way to get to know the complex secrets of the Amazon rainforest.

    Day 01 Wednesday: Departure

    The boat departs from the Tropical Experience Hotel at 11:30 am. Once on board, you'll be introduced to the staff and to your room. The hotel will be ready to serve some delicious food for lunch. You'll then navigate towards the Pagodao River.

    Day 02 Thursday: Amazon

    In the morning you'll have a hike in the forest with a specialist guide. You'll have the chance to know the local vegetation(植物) ,as well as spend some time with a native family. You'll see how they prepare manioc (树薯) flour, very typical of the Amazon dietary culture. You'll then sail through Anavilhanas, the largest fresh water archipelago (群岛)in the world.

    Day 03 Friday: Amazon

    Today you'll sail to Praia Grande or another white sand beach. Hopefully there will be some time to swim! Then, you'll take a canoe trip on Lake Acajatuba, to observe the typical vegetation. Then, you'll stop at Paricatuba to see some abandoned buildings from the rubber growing age.

A key part of protecting endangered species is figuring out where they're living. Using environmental DNA, or eDNA, to track species isn't new. For a few years now, researchers have been using DNA in water.

Two teams of scientists — one in Denmark led by Dr Kristine Bohmann and one in the UK led by Dr Elizabeth Clare — came up with the same question at about the same time: Could they identify the animals in an area from DNA that was simply floating in the air? DNA in the air is usually so small that it would take a microscope to see it. "I thought the chances of collecting animal DNA from air would be slim though much time had been spent on it, but we moved on," said Bohmann who was trying to think of a crazy research idea for a Danish foundation that funds far-out science.

One team collected samples from different locations at Denmark's Copenhagen Zoo, and the other at Hamerton Zoo Park in the UK. Clearly, they both chose the zoos. "We realized we have the Copenhagen Zoo," Bohmann recalls. In fact, both the zoos in the UK and Denmark were almost like the zoos that were custom-built for the experiments: The animals in the zoos were non-native, so they really stuck out in DNA analyses. "If we detect a flamingo (火烈鸟), we're sure it's not coming from anywhere else but the zoo," Bohmann says.

In the laboratory, by comparing their samples with examples of DNA from different animals, the scientists succeeded in identifying many different animals at the zoos.

Neither team knew that the other team was working on a similar experiment. The two were nearing submission to a scientific journal when they discovered about the other experiment. Rather than compete to rush out a publication first, they got in touch and decided to publish their findings as a pair. "We both thought the papers are stronger together," says Clare.

"The next step is to figure out how to take this method into nature to track animals that are hard to spot, including endangered animals," says Bohmann.