I fell in love with Yosemite National Park the first time I saw it, when I was 13. My parents took us there for camping. On the way out, I asked them to wait while I ran up to E1 Capitan, a1 rock of 3,300 feet straight up. I touched that giant rock and knew 2 I wanted to climb it. That has been my life's passion (钟爱) ever since—3 the rocks and mountains of Yosemite. I've long made Yosemite my 4.
About 15 years ago I started seeing a lot of 5 like toilet paper, beer cans, and empty boxes, around the area. It's6 me why visitors started respecting the place 7 and treated such a beautiful home-like place this way.
I tried 8 trash (垃圾) myself, but the job was too big. I would9 an hour or two on the job, only to find the area trashed all over again weeks later. Finally, I got so 10 it that I decided something had to change.
As a rock-climbing guide, I knew 11about organizing any big event. But in 2014, together with some climbers, I set a date for a 12. On that day, more than 300 people 13 Over three days we collected about 6,000 pounds of trash. It was amazing how much we were able to14 I couldn't believe the15we made —the park looked clean!
Each year volunteers come for the cleanup from everywhere. In 2016 alone, 2,945 people picked up 42,330 pounds of trash and16132 miles of roadway.
I often hear people17about their surroundings. If you are one of them, I would say the only way to change things is by 18rather than complaining. We need to teach by 19.You can't blame others 20 you start with yourself.
The world is like a big trampoline(蹦床). We are all jumping on it. I have jumped to many places on this big trampoline. My family took me to Kenya and Israel. My community took me to Appalachia, North America, and I took myself to the Bahamas and Belize. How 1 can one teenager be to go to all these places！
Each trip left a vivid picture in my mind. It 2 me that we are all living on one trampoline. Everything we do 3 everyone else. My first trip to Kenya was a shock! People walked to work, four hours each way. One picture 4 in my mind: a Kenyan woman at seven in the morning making her 5 to work, barefoot, down the side of a dusty road. I went to Israel a couple of years later. I found two races (种族) trying to jump on the same 6. In the village of Akko, I saw Israelis and Arabs working side by side. In Jerusalem, however, I found 7 holes in the walls of Israeli homes. In Appalachia, I saw people go to bed hungry. In Belize and the Bahamas, I realized how 8 our trampoline has become. Natural resources are running out. Animal life is in danger. We all live on the same trampoline. Every 9 we take sends ripples(波澜) across the trampoline. If everyone could understand how they affect one another, we would make the trampoline 10.
Scientists find that hardworking people live longer than average men and women. Career women are 1 than housewives. Evidence shows that the 2 are in poorer health than the job-holders. A study shows 3 the unemployment rate increases by 1%, the death rate 4 correspondingly (相应地) by 2%. All this comes down to one point: work is 5 to health.
Why is work good for health? It is 6 work keeps people busy, away from loneliness and solitude (孤独). Researches show that people feel 7, worried and lonely when they have nothing to do. Instead, the happiest are those who are 8. Many high achievers who love their careers feel that they are happiest when working hard. Work serves as a 9 between man and reality. By work, people 10 each other. By collective (集体的) activity, they find friendship and warmth. This is helpful to health. The loss of work 11 the loss of everything. It affects (影响) man spiritually and makes him liable to (易于) 12.
13, work gives one a sense of achievement (成就感). Work makes one feel his 14 and status in society. When a 15 finishes his writing or a doctor successfully 16 a patient or a teacher sees his students 17, all of them will be happy beyond 18.
From the above we can 19 the conclusion (结论) that the more you 20, the happier and healthier you will be. Let us work hard, study well and live a happy and healthy life.
One of the most remarkable things about the human mind is our ability to imagine the future. In our1 we can see what has not yet happened. For example, while we are looking forward to2 a new place or country, we 3what it will be like. We predict the 4 people will eat, dress and act. Of course, we do not always predict things 5.Things are often very different from the way we6 them to be. One of the7dreams in history is the dream of a German scientist, Keller,who had been 8to work out a very difficult problem in physics. He had 9and analyzed（分析）the problem from every angle for days, but there 10 to be no way of 11out the answer. Then one night he went to bed and dreamed. When he 12 up, he realized that he knew the answer. He had solved the problem in his 13.The hypnotist（催眠者）sat in the chair opposite him and spoke 14：I want you to concentrate on my voice. Think about 15.You know nothing but my voice. And as you pay attention to my voice, your16 will get heavier. Soon you'll be asleep. You will hear my voice and17my words, but your body will be asleep, your eyes are too heavy. You are18 asleep, and when you wake up you will 19nothing. You will forget everything. Now I am going to20slowly from one to five. One, two, three, four, five.
Directions: For each blank in the following passages there are four words or phrases marked A, B, C, and D. Fill in each blank with the word or phrase that best fits the context.
Microsoft Corp founder Bill Gates caught people's eye in a recent interview, when he suggested that robots should be taxed in, order to help humans keep their jobs. Gates is only one of many people in the tech world who have worried about automation and its 1 to workers.
It's easy to see why the tech world is 2. The rise of machine learning has increased the fear that 3 humans could simply become out of date--4, 3.5 million American truck drivers might soon find their jobs threatened by driverless trucks. Though in the past, technology usually complemented workers 5 replacing them, there's no law of nature saying the technology of the future will work the same. A few economists even claim that cheap automation has already 6 income from workers to company owners.
Another 7 is that even if the mass of humanity ultimately does find new ways to add value by complementing new technology—to “race with the machines,” as economist Erik Brynjofsson puts it—this transition could take a long time and hurt a lot of people. As Bloomberg View's Tyler Cowen has noted, wages in Britain fell for four decades at the start of the Industrial Revolution. More 8, we've seen very slow and painful adjustment to the impact of globalization. If the machine learning revolution hurts workers for 40 years before ultimately helping them, it might be worth it to 9 that revolution and give them time to adjust.
The main argument against taxing the robots is that it might hold back 10. Growth in rich countries has slowed markedly in the past decade, suggesting that it's getting harder and harder to find new ways of doing things. Stagnating productivity, combined with falling business investment, suggests that 11 of new technology is currently too slow rather than too fast—the biggest problem right now isn't too many robots, it's too few. Taxing new technology, however it's done, could make that slowdown worse.
The problem with Gate's basic proposal is that it's very hard to tell the difference between new technology that12 humans and new technology that replaces them. This is especially true over the long term. Power looms（织布机）replaced human weavers back in the Industrial Revolution. 13, people eventually became more productive, by learning to operate those looms. If taxes had slowed the development of power looms, the eventual improvements would have come later.
This is a powerful argument 14 the taxation of automation. Gates is right to say that we should start thinking ahead of time about how to use policy to mitigate（缓和）the unintended consequences of automation. But given the importance of sustaining innovation, we should look at 15 policies.
Wildlife has been greatly threatened in the modem age. There are species (物种) that are 1 every day. The white-naped crane is a typical example. So scientists are trying their best to 2 the species from going out of existence.
Chris and Tim work at a zoo, helping endangered cranes with their 3. Emma, a female crane, has been in their 4 since she arrived in 2004.
Born at an international crane foundation, Emma was 5 by human caretakers. This led to an unexpected 6, though she had a wonderful time there. Emma had 7 taken herself as a crane and become deeply attached to humans. She 8 to live with male cranes, and even had a 9 for killing some of them, which made it 10 for her to become a mother.
11, the two zookeepers didn't want to see the extinction (灭绝) of this precious species. With their patience and efforts, they successfully developed a 12 of artificial breeding (人工繁殖) and natural reproduction. This 13 Emma to give birth to five baby cranes.
The two keepers are proud of their productive work. But before they can be 14, more efforts must be made, because the population of the crane in the wild is on the 15, and many other species appear headed toward extinction. 16, not everyone has realized that wildlife has thoughts, feelings, and most importantly, equal rights to survive.
How can we 17 the ever-widening gap that separates us from other animals? Chris and Tim offered us the 18: human beings took it for granted that their 19 held all the solutions, but maybe their hearts can be a better 20.
Inventions lead to the creation of new knowledge. Knowledge is created to 1 the needs of the human beings. How does the desire of people2 knowledge? The answer lies in the ability of human beings to 3 something new.
Albert Einstein said, "Imagination is more 4 than knowledge. Knowledge is limited, but imagination includes the 5 world, promoting progress and giving birth to evolution(进化、发展). It is, strictly speaking, a 6 factor in scientific research." There is no doubt that it is through the human imagination that knowledge is 7. Knowledge can be represented in any 8 like words, pictures, diagrams or audio-visual media. People's knowing of knowledge again causes imagination as the force to keep on evolving, which 9 produces new knowledge.
The following is the example of how imagination leads to 10. As an artist, mathematician and architect, Leonardo da Vinci sketched(勾勒) plans of underwater crafts. According to this, author Jules Veme created a 11, one about a submarine(潜水艇) 12 Twenty Thousand Leagues Under the Sea. With his book, Jules Veme fueled(供给燃料) the imagination of 13 including inventors, later, real submarines were created. Jules Veme 14 his imagination about underwater 15 when he wrote his book. 16 readers admired the author's imagination when they read it, 17 inventors turned this imagination into realities.
Imagination exists within all of us. 18 yourself to imagine freely. Stir your brain to 19 inspiration while imagining. Because it is in the imagination that mysteries or wonders 20.
Earthquakes are common; thousands of them happen each day. But most are too 1 to feel. During a 2 earthquake, there is often a great noise first. Then the earth 3 terribly and many houses 4 down. Railway tracks break and trains go 5 lines; a great many factories are 6; thousands of deaths are caused, and many more lose homes… 7 the great damage and deaths caused by the earthquake 8, other disasters such as fires often 9. More buildings are destroyed and more 10 caused.
Man knows the 11 of a possible earthquake, and for centuries man has been making researches on earthquakes. More than 2, 000 years ago, 12, a Chinese scientist named Zhang Heng 13 a machine which could find out from which 14 the seismic waves had come, and this machine is still 15 by scientists today. Now we know much more about earthquakes and 16 they happen, but we still cannot 17 exactly when and where an earthquake will happen, and cannot 18 it from happening. So earthquakes are among the 19 disasters in the world.
No one can stop natural earthquakes. 20, scientists can help stop earthquakes destroying whole cities and causing too many deaths.
Computer hackers have now got their hands on mobile phones. "A phone virus programme can 1 your phone do things you have no control over", computer security experts 2. It might 3 the White house or the police. or forward your personal address book to a marketing company. Or it could simply cat into the phone's operating software, turning it 4and erasing your personal information. Similar viruses have already made mobile phone owners 5in Japan and Europe. Ari Hypponcn, chief technical officer of a computer security company in Finland, said a virus "can get your 6 and send them elsewhere. And it can record your password". Mobiles are now able to surf the Net, send emails and 7 software. So they are an easy target for the same hackers who have sent viruses to computers over the past decade.
"It's technically 8 now. "said Stephen Trilling. director of research at anti -virus software maker Symantec Corp based in the US. "If the phone is connected to the 9, it can be used to transmit threats and attack targets, just as any computer can."
In Japan, if you opened a certain email message on your mobile, it would cause the phone to repeatedly dial the national emergency number. So phone operators had to cancel emergency calls until the fault was removed. In Europe. mobiles' short message service, or SMS, has been used to send codes that could damage phones. Mobile users can 10 viruses, of course, by sticking to their traditional phones without Web links, some experts said.
Nipah, Hendra, Ebola, SARS... These are some of the world's scariest viruses, which are all carried by bats. This, to be clear, rally isn't bats' fault: The recent 1 . in outbreaks is likely due to humans and our animals 2 ever farther bats' habitat.
In Malaysia, for example, the spread of commercial pig farms into bat-inhabited forests 3 the first human outbreak of Nipah via pigs. In Australia, human Hendra cases 4 as the destruction of native forests forced fruit bats to feed in suburban 5.
One big reason is that most bats love 6 , which contributes to viruses spreading not just among individuals, but also among 7 species. What's more, most infected 8 don't die—they live normal bat lives, flying around and giving viruses the 9 to spread. Research suggests flight 10be the reason bats are so resilient (迅速恢复的) to infection.
As a rule, when flying animals produce the 11amount of energy needed for flight, they also make a lot of reactive waste products that 12 their DNA. But when bats take to the air, they 13 their in-flight DNA damage repair ability and other defenses, including 14 cells that keep viral invaders in check.
So bats can 15 deadly viruses. But what may matter even more to humans is 16 viruses survive bats. When bats are flying, their body temperature can reach around 40℃. It's far too hot for the 17 viruses, but a few hardy viruses have 18 to tolerate the heat. This means they can definitely pull through a human 19when they are transmitted to humans, which is horrible to us.
So what should we do? We'd better just leave bats 20.
These days, cars arc designed using computers. Let's look at how a new car is created.
First, several1talk about the new car and any good ideas that they have. Then they sit down at their computers and2many sketches. The best two or three drawings are chosen and then more detailed drawings of3are developed on the computer. You can change the size, shape or colour of any part on the computer to see4the car would look and then you can choose the best design.
Both the inside and the outside of the car have to be designed. Part of the inside of the car is 5so that the designers can sit in it. They can feel if there is enough6inside and if they can reach7 Then some cars are built-there are more than 15, 000 parts of a car to8
When everything is known to be9 the cars are made in the factory. Again, computers are used to make sure that all the parts are10as they are needed. The factory usually stays open all through the night so that the car production never stops.
Electric vehicle basics
Just as there are a variety of technologies available in conventional vehicles, plug-in electric vehicles (also known as electric cars or EVs) have different capabilities that can1different drivers' needs. A major 2 of EVs is that drivers can plug them in to charge from an off-board electric power source. This distinguishes them from hybrid electric vehicles, which3 an internal combustion engine with battery power but cannot be plugged in.
There are two basic types of EVs: all-electric vehicles (AEVs) and plug-in hybrid electric vehicles (PHEVs). AEVs include Battery Electric Vehicles (BEVs) and Fuel Cell Electric Vehicles (FCEVs). 4 charging from the electrical grid, both types are charged in part by 5 braking, which generates electricity from some of the energy normally6 when braking. Which type of vehicle will fit your lifestyle 7 your needs and driving habits.
All-electric vehicles (AEVs) run only on electricity. Most have all-electric ranges of 80 to 100 miles, 8 a few luxury models have ranges up to 250 miles. When the battery is 9, it can take from 30 minutes (with fast charging) up to nearly a full day (with Level 1 charging) to recharge it, depending on the type of charger and battery.
If this range is not 10, a plug-in electric vehicle (PHEV) may be a better choice. PHEVs run on electricity for shorter ranges (6 to 40 miles), then 11 over to an internal combustion engine running on gasoline when the battery is depleted. The 12 of PHEVs allows drivers to use electricity as often as possible while also being able to fuel up with gasoline if needed. Apart from reducing tailpipe emissions, powering the vehicle with electricity from the grid, compared with conventional vehicles, 13 fuel costs. When driving distances are longer than the all-electric range, PHEVs act like hybrid electric vehicles, consuming less fuel and producing fewer emissions than similar conventional vehicles. Depending on the model, the internal combustion engine may also power the vehicle at other times, such as during rapid acceleration or when using heating or air conditioning. PHEVs could also use hydrogen in a fuel cell, biofuels, or other alternative fuels as a back-up 14 gasoline.
Following some best practices can help you 15 your all-electric range and vehicle efficiency whether you have an AEV or PHEV.
You don't have to be a gardener, a farmer, or a vegetarian to appreciate how much we all depend on plants. Plants 1 us with food, shelter, clothing, medicine, and even the air we breathe! Here are just some of the ways that people rely on plants, 2 those native to the United States.
CLEAN AIR AND WATER: Plants are the basis of healthy ecosystems that 3 many functions, including purifying air and water. Green plants harness energy from sunlight through the 4 of photosynthesis (光合作用). With every breath we take, we depend on the oxygen that is given off as a by-product of that reaction. Plants also 5the water cycle. More than 90% of the water that is taken in through a plant's roots is eventually 6 back to the atmosphere in a process called transpiration.
FOOD: Plants provide the basis of most food webs on Earth. Even the 7 meat eaters, such as lions, need plants because the prey they 8 are plant eaters. The wild relatives of our own food plants are becoming increasingly important for breeding to make healthier and more productive crops. 9 the Texas wild rice, known from only one river in Texas, is being bred with northern wild rice to develop a new strain suitable for mild climates.
SHELTER: Plants provide not only food and oxygen, but also10 and shelter. The wood from trees is used in the construction of many of our homes. Plants also 11 habitats for many other animals. A single tree in the tropics can be 12 to more than 1,000 different insect species alone.
ENERGY: Every time we 13 the lights in a room, we use plants that lived a long time ago. Over 350 million years ago, giant relatives of today's ferms (蕨类) 14 mud as they died and so were prevented from decaying. Over the years, they were compressed (压缩) to 15 coal and other fossil fuels upon which most of the world now relies for energy.
I fell in love with Yosemite National Park the first time I saw it, when I was 13. My parents took us there for camping. On the way out, I asked them to wait while I ran up to EI Capitan, a 1 rock of 3, 300 feet straight up. I touched that giant rock and knew immediately I wanted to climb it. That has been my life's passion (钟爱) ever since— 2 the rocks and mountains of Yosemite. I've long made Yosemite my 3.
About 15 years ago I started seeing a lot of 4, like toilet paper, beer cans, and empty boxes, around the area. It's beyond me why visitors started respecting the place 5 and treated such a beautiful homelike place this way.
I tried 6 trash(垃圾)myself, but the job was too big. I would spend an hour or two on the job, only to find the area trashed all over again weeks later. Finally, I got so 7 it that I decided something had to change.
As a rockclimbing guide, I knew nothing about organizing any big event. But in 2004, together with some climbers, I set a date for a 8. On that day, more than 300 people 9. Over three days we collected about 6, 000 pounds of trash. It was amazing how much we were able to 10. I couldn't believe the 11 we made—the park looked clean!
Each year volunteers come for the cleanup from everywhere. In 2007 alone, 2, 945 people picked up 42, 330 pounds of trash and 12132 miles of roadway.
I often hear people 13 about their surroundings. If you are one of them, I would say the only way to change things is by 14 rather than complaining. We need to teach by 15. You can't blame others unless you start with yourself.
In 1994, the Brazilian photographer Salgado went back to his homeland in Minas Gerais, Brazil. He was1to see the land run by his family. The thick forest there was once a paradise (乐园) for him and his friends, bringing them 2 memories.
To his horror, he saw a totally different 3. Only 0. 5% of the land was covered with trees. "The land was as sick as a serious patient—everything was 4 due to deforestation (砍伐森林)," Salgado said 5 during a meeting on climate change in Paris.
Salgado 6 that he should do something about it. Then he 7 the bold idea of replanting trees on the land, which beyond his expectations, received 8 from his wife and relatives. Soon the whole family 9 and the results are remarkable. 10, the land is changing: It is carpeted with green trees again and some of the insects, birds and animals living in the land before 11. The land has been brought back to life. The 12 family's hard work also impressed people around them. They 13 cutting down trees and began to protect the environment.
"The work over the years is quite difficult but well worth the 14 and I think every little bit of work 15," said Salgado. Therefore, everyone should play a part in protecting the environment.
The victims were carried in one by one, their paws and fur burned, suffering from dehydration (脱水) and fear. Their caretakers1their wounds, and 2them in baskets with the only thing that was3—the leaves of eucalyptus (桉树) tree. As miserable fires have4more than 2 million acres in Australia, only dozens of koalas have been 5from the smoky trees and 6 ground.
Koalas, unlike kangaroos, birds or snakes, do not7from fires but instead climb trees to the top, where they can curl themselves into a ball for 8 and wait for the danger to 9.
But during big fires, such as those that have burned in recent weeks, the animals are far less likely to10. Even if the fire itself does not reach the tree11 , the animals may overheat and fall to the ground, where they can be burned to death.
The tough situation of the koala has raised12among scientists and conservationists (保护主义者). While koalas have developed to exist alongside the wildfires, they are facing new 13, not just from climate change but also from human development, which has dislocated koalas' populations, 14their ability to survive fires.
We have these15 animals not found anywhere else on this planet, and we are killing them. This is a big wake-up call.
The Thai government intends to further deepen its digital cooperation with Chinese technology company Huawei, senior Thai officials said at a cloud event held in Bangkok this week.
During the Powering Digital Thailand 2022 on Nov 17-19, Thai deputy Prime Minister Prawit Wongsuwon said digital infrastructure (基础设施), such as5G, is crucial to Thailand's 1 and social development, especially for the country's post-pandemic economic 2.
Badly hit by the COVID-19 pandemic, the tourism-reliant nation registered an economic reduction of 6. 1 percent last year, the worst in more than 20 years. However, the pandemic has significantly sped the 3 of digital technologies in Thailand, where Chinese tech companies have 4 advantages.
During the pandemic, Huawei used its technology to help local hospitals implement systems for automated medical supply, AI-backed 5 and remote treatment, which greatly improved the 6 of hospitals and made healthcare more 7.
Fueled by Thailand's digital roadmap, Huawei has focused on helping the country build 20,000 5G stations in the past two years. 8. Thailand has more than 4. 2 million 5G subscribers leading in 5G adoption among ASEAN (Association of Southeast Asian Nations) countries.
Another strength of Huawei has been its cloud capabilities. Deng Feng, general manager of Huawei Thailand, said Huawei Cloud is the only cloud service 9 with local data centers in Thailand, considering that data localization is a key trend of global enterprises due to government regulations as well as security concerns.
He emphasized the Huawei will support Thailand's low-carbon and digital development in the future in four areas, including expanding 5G coverage and usage, providing cloud services, creating low-carbon development with digital energy, and 10 industry talents.
Thai Minister of Digital Economy and Society Chaiwut Thanakamanusorn expressed his hopes for 11cooperation between the Thai government and Huawei to 12 the country's digital economy, which is targeted to1330 percent of the GDP by 2030.
According to a joint report released by Google, Temasek and Bain & Company earlier this month Thailand's digital economy is expected to 14 $30 billion this year, up 51 percent, making it the second-largest market in Southeast Asia after Indonesia.
Huawei's Rotating Chairman Guo Ping said the company will continue 15and building a tech ecosystem to facilitate faster digitalization in Asia-Pacific, and invest $100 million over the next three years to build a startup ecosystem in the region.
Different things usually stand for different feelings. Red, for example, is the color of fire, heat, blood and life. People say red is an exciting and1 color. They associate（使发生联系） red with a strong feeling like 2. Red is used for signs of 3, such as STOP signs and fire engines. Orange is the bright, warm color of 4 in autumn. People say orange is a 5 color. They6orange with happiness. Yellow is the color of7. People say it is a cheerful color. They associate yellow too, with happiness. Green is the cool color of grass in8. People say it is a refreshing color.
In general, people9two groups of colors: warm colors and10colors. The warm colors are red, orange and11. Where there are warm color and a lot of light, people usually want to be12. Those who like to be with 13like red. The cool colors are14 and blue. Where are these colors, people are usually15. Some scientists say that time seems to16 more slowly in a room with warm colors. They suggest that a warm color is a good 17 for a living room or a 18. People who are having a rest or are eating do not want time to pass quickly. Cool colors are better for some offices if the people19 there want time to20 quickly.
Young children across the globe enjoy playing games of hide and seek. For them, there's something highly exciting about 1 someone else's glance and making oneself unable to be seen.
However, we all witness that preschool children are remarkably 2 at hiding. They often cover only their eyes with their hands, leaving the rest of their bodies 3 .
For a long time, this ineffective hiding method was 4 as evidence that children are hopelessly "egocentric"（自我中心的）creatures. But our 5 research results in child developmental psychology 6 that idea.
We brought young children aged 2-4 into our Minds in Development Lab at USC. Each 7 sat down with an adult who covered her own eyes or 8 . We then asked the child if she could 9 or hear the adult. Surprisingly, children replied that they couldn't. The same 10 happened when the adult covered her own mouth: 11 children said that they couldn't 12 to her.
A number of 13 ruled out that the children misunderstood what they were being asked. The results were clear: Our young subjects 14 the questions and knew 15 what was asked of them. Their 16 to the questions reflected their true 17 that "I can see you only if you can see me, too." They simply 18 mutual（相互的）recognition and regard. Our 19 suggest when a child "hides" by putting a blanket over her head, it is not a result of egocentrism. In fact, children consider this method 20 when others use it.
In 200 Years Cows May Be the Biggest Land Mammals (哺乳动物) on the Planet
Around 13,000 years ago North America had a wider variety of mammals than modern Africa.
There were multiple horse species, camels and some now-extinct animals. And such1creatures were not just found in North America. On every continent mammals on average were a lot larger from around 2.5 million until about 11,700 years ago.
Scientists have long debated what caused all these large creatures to go extinct while many of the smaller ones2. A team of researchers led by biologist Felisa Smith analyzed evidence from millions of years' worth of mammalian extinctions and found that on each continent large mammals started to3around the same time humans first showed up.
If the extinction trend continues, many more large mammals will soon disappear as well, as the primary threats from humans have4from overhunting to indirect processes such as habitat loss. The largest land mammal 200 years from now could well be the domestic cow, Smith's research suggests. In their new study Smith and her team analyzed a database of all land mammals that lived from 65 million years ago until today. "We found5no effect of climate on mammalian extinction over 65 million years," she says. But starting around 125,000 years ago and continuing until today, large mammals have been more likely to go extinct than smaller ones, the researchers found.
The average6of surviving mammals has decreased as a result. And those large-mammal extinctions are tightly coupled with the7of humans. For most of mammalian8history, an animal's size was not predictive of its extinction risk. That9only appeared once humans began to live alongside large mammals.
This finding does not mean climate-related changes could not have10some wildlife populations, enabling humans to more easily bring about their eventual downfall.11, it suggests the greater likelihood of large mammals going extinct is tied to human activities. The animals that evolved without the risk of hunting from humans were suddenly faced with a new12. They simply could not13fast enough to survive the invasion of humans.
Smith says the lesson to be learned from the new findings is that our ancestors prepared us to be extremely skillful killers. "What's14now," she says, "is that some of us are comfortable enough, have a high enough standard of living, that we can start thinking about our use of the Earth." Rather than simply behaving as15, many of us are now in a position to become environmental protectors.
