Are we getting more stupid? According to Gerald Crabtree, a scientist at Stanford University in the US, we are.  You may not want to hear this, but Crabtree believes that human intelligence reached its peak more than 2,000 years ago and ever since then has been going downhill. “If an average Greek from 1,000 BC were transported to modern times, he or she would be one of the brightest among us,” Crabtree told The Guardian.

    At the heart of Crabtree's thinking is a simple idea. In the past, intelligence was critical for survival when our ancestors had to avoid dangerous animals and hunt for food. The difference of being smart or stupid is often life or death. However, after the spread of agriculture, when our ancestors began to live in dense ( 稠密的）farming communities, the need to keep their intelligence in peak condition gradually reduced. This is not hard to understand. Most of the time,pressure is what keeps us going – you need the pressure from your teachers to finish your homework; the pressure of looking pretty prompts(促使) you to lose weight when summer comes. And the same is also true of our intelligence – if we think less, we become less smart.

    These mutations(变) are harmful to our intelligence and they were all developed in the past 3,000 years. The other evidence that Crabtree holds is in our genes. He found that among the 2,000 to 5,000 genes that we have that determine human intelligence , there are two or more mutations in each of us. However, Crabtree's theory has been criticized by some who say that early humans may have better hunting and surviving abilities, but people today have developed a more diverse intelligence. For example, spearing a tiger doesn't necessarily require more brainpower than playing chess or writing a poem. Moreover, the power of modern education means a lot more people have the opportunity to learn nowadays. “You wouldn't get Stephen Hawking 2,000 years ago. He just wouldn't exist,” Thomas Hills of the University of Warwick, UK, told Live Science. “But now we have people of his intellectual capacity doing things and making insights(洞察力) that we would never have achieved in our environment of evolutionary adaptation.”

    Deserts are found where there is little rainfall or where rain for a whole year falls in only a few weeks' time. Ten inches of rain may be enough for many plants to survive if the rain is spread throughout the year. If it falls within one or two months and the rest of the year is dry, those plants may die and a desert may form.

    Sand begins as tiny pieces of rock that get smaller and smaller as wind and weather wear them down. Sand dunes (沙丘) are formed as winds move the sand across the desert. Bit by bit, the dunes grow over the years, always moving with the winds and changing the shape. Most of them are only a few feet tall, but they can grow to be several hundred feet high.

There is, however, much more to a desert than sand. In the deserts of the southwestern United States, cliffs (悬崖) and deep valleys were formed from thick mud that once lay under a sea more than millions of years ago. Over the centuries, the water dried up. Wind, sand, rain, heat and cold all wore away at the remaining rocks. The faces of the desert mountains are always changing –-very, very slowly —as these forces of nature continue to work on the rock.

    Most deserts have a surprising variety of life. There are plants, animals and insects that have adapted to life in the desert. During the heat of the day a visitor may see very few signs of living things, but as the air begins to cool in the evening, the desert comes to life. As the sun begins to rise again in the sky, the desert once again becomes quiet and lonely.

    The brain of an insect isn't very big. But insects are somehow still able to make lots of important decisions. Bees, ants and roaches(蟑螂) build hives(巢穴)with thousands of workers doing specialized work. The jobs are done without a head or even a plan. How do insects manage this?

    To solve the mystery, scientists in Belgium spent months building robotic roaches and then putting them among real roaches. The final goal of the research is to find out how the simple behavior of individuals gives rise to a collective decision. The roach is a good starting point for trying to answer the big question because its social system is simple enough for scientists to study.

    The first step was to build robots that real roaches would accept as their own. Although the robotic roaches don't look much like the real thing, they have similarities with them in three key ways: they naturally head toward dark areas, they are influenced by the behavior of other roaches, and even more importantly, they smell like roaches.

    The next step was getting the robotic and real roaches to work together on common tasks. In experiments, the robots would collectively head towards a dark place, copying the behavior of natural roaches. That got the researchers wondering: if you program the robotic roaches to go woward the lighted place, would the real roaches follow, going against their natural instincts.(本能) ?

    They will – it turned out. Many of the real roaches followed the robots to a lighter shelter. But influence turned out to be a two- way street. On occasion, the real roaches were able to override the programming of the robot roaches and get them to turn into dark hiding places. Being social creatures, both the robotic and natural roaches were paying attention to and following the example set by others.

    In theory, it would be possible to create a robot that could influence collective decision-making in humans. To do this, researchers would have to invent a robot that people would accept. Fortunately, the technology isn't there yet.

    Educational APP Store

    Busuu

    Busuu helps you learn English language on the go and the lesson's quality is guaranteed as it is based on CEFR language framework. Lessons range from beginners to advanced learners. Busuu is actually a great English app if you want to improve your spoken English by talking with native speakers.

    Duolingo

    Duolingo is one of the best English language apps today and highly recommended for English beginners. The system of the app helps you learn English quickly by spending twenty minutes a day. Duolingo structures your lessons that teach you about seven new words based on a topic and skill points being awarded for completing the lessons.

    Memrise

    Memrise uses some creative and easy ways to remember English words. The focus of this app is to help the users expand their vocabulary by learning English words in an effective way. Memrise also offers an offline mode to continue learning without Internet connection.

    Rosetta Stone

    Rosetta Stone is designed differently from average language apps on the marketplace today. It's trying to teach us English the way we'd learn it if we were children starting to learn the language, it has exercises designed to help you learn basic words. A variety of lessons are offered that Rosetta Stone has been using for years.

    A European Union program is letting blind people experience famous paintings for the first time. It uses three dimensional (3-D) printing to re-create famous paintings so that they can be touched.

    One painting printed with the new technology is Gustav Klimt's "The Kiss." It is a popular attraction at the Belvedere Museum in Vienna, Austria. The painting shows a man and a woman standing in a field filled with flowers. They are wearing gold robes and have their arms around each other. The man leans down to kiss the woman.

Klimt finished the painting in 1908. Until now, people who have trouble seeing can not enjoy the artwork. But thanks to the reproduction (复制品) they can touch the piece and feel the ridges (隆起) and depressions (凹地). Andreas Reichinger started making 3-D versions of artwork in 2010. He said this reproduction was his most difficult project because the couple's robes are so detailed (精细的).

    Dominika Raditsch is a blind museum visitor. She touched the reproduction. As she moved her hands around it, she said, "Exactly, can you see these? There are so many details." Raditsch said she can imagine what the original painting looks like when she touches the reproduction. "It's somehow round. You can feel it. It comes with it. And in many places it's so smooth. And then I think to myself: it probably shines too!" Raditsch said.

    The Belvedere is not the only museum to have 3-D versions of its artwork. Some of the pieces at the Prado, in Madrid, Spain, have reproductions that can be touched. But the piece in Vienna has one special part: it is made with widely available 3-D printing technology. That means one day, blind art fans anywhere in the world could download the source files and print the reproductions themselves.

Elephants might be the most well－known and well－loved animal in African wildlife. But conservation (保护) of the African elephant faces special difficulties. While the elephant population is half of what it was 40 years ago, some areas of Africa have more elephants than populated areas can support. That's why AWF scientists are studying elephant behavior, protecting habitats and finding ways for humans to live peacefully with elephants in Africa.

Years ago, overhunting and the ivory trade were the biggest threats to elephants' survival. Luckily, ivory bans (禁令), hunting rules and protected areas protect elephants from these dangers today.

The 21st century brings a different challenge to elephant conservation—land－use. Elephants walk across borders and outside parks and other protected areas. So they often destroy crops, causing conflicts (冲突) between local farmers and these big animals.

Successful conservation strategies (策略) must allow elephants to walk freely in their natural habitats while reducing conflicts between elephants and local people.

AWF researchers are searching for a way to give both elephants and people the space they need. The AWF is collecting information on elephant habitats and behavior. The information they gather will help to develop the widest possible space for elephants.

The AWF is helping elephants by protecting their habitats. And they also work with local farmers to improve their life in order to encourage them to protect rather than destroy elephants.