Early people lived by hunting animals and gathering grains. After a tribe(部落） had lived in an area for some time, its food supply would begin to reduce. Then the tribe had to move to new hunting grounds where there was more food.

    This way of life caused special problems for the tribes. They were forced to depend on luck, as well as on their hunting skills. If they could find no game, the whole tribe was in danger of starving. And when the hunters had good luck one day, they were not sure to find game the next time. The tribes moves often because much land was needed to support their people.

    Finally, people learned that they could grow their food. At first, the women of tribes raised patches of wild grain. Later, people discovered that they could plant their own seeds. Farming slowly became a way of life.

    As people turned away from hunting to farming, their life changed. When the food supply became more constant, they no longer moved from place to place. The success of their crops depended partly on the weather, but there were also things they could do to help crops grow.

    In the past, a tribe had to travel many miles for food. Now , only a small amount of land was necessary to feed the whole tribe. The tribe could grow in size because farming provided a way to feed people.

    Recently, we've been talking about how we need better teachers. There's no doubt that great teacher can help in a student's learning but here's what some new studies are also showing: We need better parents.

    Every three years, the organization called O.E.C.D. organizes exams as part of the Program for International Student Assessment(评估), or PISA, which tests 15-year-olds on their abilities to deal with real problems. America's 15-year-olds have not done as well as students in Singapore, Finland and Shanghai in the PISA exams.

    To better understand the reasons, the PISA team, starting with four countries in 2006, and then adding 14 more in 2009, went to the parents of 5,000 students. They interviewed them about how they raised their kids and then compared it with the test results for each of those years. Two weeks ago, the PISA team published the main finding of its study.

    Fifteen-year-olds whose parents often read books with them during their first year of primary school get much higher scores in PISA 2009 than students whose parents don't often read with them or not at all. Parents' concern for their children is strongly connected with better results in PISA.

    According to Schleicher, the leader of the team, just asking your children how their school    day was and showing great interest in their learning can help a lot. It is something every parent can do, no matter what their education level is.

    The study found that getting parents concerned about their children's learning at home is more powerful than parents attending parent-teacher meetings, volunteering in classrooms,   taking part in money-raising, and showing up at back-to-back nights.

    To be sure, nothing can replace a good teacher. But let's stop putting the whole duty on teachers. We also need better parents. Better parents can make teaching more beneficial.

    Larry Bird was born in 1965 in a small town in the Middle Western State of Indiana. He was tall, and good at playing basketball. He attended Indiana State University. Bird led the team into the College Basketball Championship Game.

    After completing his college studies, Larry Bird began playing professional basketball for the Boston Celtics. He remained with the Celtics for all his professional career. During those 13 years, Larry Bird was named the Most Valuable Player of the Year three times. He scored more than 21, 000 points, and he played in 13 of the highest scoring games in his team's history. Once he scored 60 points in just one game.

    During his very successful basketball career, Larry Bird suffered a number of injuries. In 1989, he stopped playing because of pain in his feet. He returned in 1990, but the pain in his feet returned too. In the next two years he experienced more medical problems, and he missed many games.

    Larry Bird did play on the Dream Team－the first Olympic Team with professional players. However, after winning the gold medal in Barcelona, he announced that he would retire from professional basketball. Larry Bird said he would have liked to play a little longer, but he could not because of his health problems. He also said it was a good time to leave the game. He wanted to be remembered as a winner.

    Most dog owners believe their dogs experience guilt, but animal behaviorists say the "guilty look" of a dog is simply a reaction to you and that dogs lack the ability to feel shame.

    Alexandra Horowitz, a psychology professor and principal investigator at the Horowitz Dog Cognition Lab at Columbia University once carried out a study on dog "guilt". She videotaped 14 dogs in a series of trials and observed how they reacted when their owners left the room after instructing them not to eat a treat. When the owner was gone, Horowitz gave some of the dogs the forbidden treat. Then she would tell the owners whether their dogs had eaten the treat or had behaved. However, Horowitz wasn't always honest with them.

    Horowitz found that the dogs' "guilty looks" had little to do with whether they'd eaten the treat or not. In fact, dogs that hadn't eaten it but were scolded by misinformed owners tended to exhibit the most elements of the "guilty look".

Horowitz says this shows that the dogs' body language is actually a response to their owner's behavior—not an experience of shame for a misdeed. Why then, do dogs look so ashamed when we scold them?

Maybe that look of guilt is the result of a learned association. When you scold your dog for chewing up a pair of slippers, he quickly learns that if he lowers his head and tucks his tail, the undesirable response—raised voice and angry expression—is more likely to disappear.

    Researchers have discovered the first Earth-sized planet. It was first marked by scientists' using NASA's Kepler telescope (望远镜), so it's called Kepler﹣186f. It lies about 500 light years from Earth and goes around its star. The planet is the right distance from its star for water: not too close or not too far. Water is one important condition that scientists guess is necessary for life. So it could have water and possible life. It's called a true Earth cousin.

    "This planet is an Earth cousin, not an Earth twin," said Barclay, who is among a team of scientists reporting on the discovery in the magazine Science this week.

    "It's very exciting to find a planet similar to the Earth," Barclay said. "It's not easy work because things change as we get more measurements."

    Scientists don't know anything about the air of Kepler-186f, but it will be a task for future telescopes which can study for chemicals that have something to do with life.

    "It's possible for life to live in this planet, but that doesn't mean there is life in it," Barclay said.

    So far, scientists have found nearly 1,800 planets in the universe.

    "The past year has seen a lot of progress in the search for Earthlike planets. Kepler﹣186f is very important because it is the first planet that is the same temperature and is almost the same size as Earth," scientist David Charbonneau wrote in an email.

    A new officer with the Huntington Park Police patrols (巡逻) local parks 24 hours a day seven days a week. He doesn't need rest, coffee breaks, a salary or medical insurance, and that is because it is a Robocop.

    The main function of the Robocop is to scan and film the surroundings. Besides cameras with night vision that report 360 degrees, it also has a distress button which is located here, so if somebody is to need assistance or they want to contact the communication center, they can do it by way of that distress button. There are people that are monitoring on the other end.

    This newest police employee is self-charging. It's easy to program it and make changes to the software if necessary. Its maintenance (维护) costs are roughly 75 thousand dollars a year. It travels the entire park. It is a programmed path, but the police are able to change the path and adapt it.

    The Robocop can record the license plates (车牌) of passing cars and check them against an online database of stolen cars. It can also help locate a lost iPhone because it is able to determine a smartphone's MAC address. The police can see from the robot if something wrong happens and then come and figure it out.

    The Robocop can't replace its human handlers. The whole goal is to give police more time to do things machines can't do. The police have been having some concerns about safety of the parks and want an extra set of eyes that will help patrol a 24/7.Robocop's creators believe this model known as K5 is best used for providing security at public places like hospitals, parking lots, parks and airports. So far, it seems to be working out just fine.