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.”

    Best Travel Guides by Continent

    We've broken down (分类)the best travel guides, by continent, to help you find student discounts and travel like a local on your next adventure.

    Europe—let's Go Europe 2019: The Students Travel Guide

    Let's Go was founded about 56 years ago when a Harvard student had an idea to provide accessible, budget travel tips for young people. Students love its amusing pages. let's Go Europe 2018 has everything you need for your trip—from the best beer in Brussels to how to avoid the lines at the Louvre.

    Africa—The Rough Guide to Cape Town, the Winelands, and the Garden Route

    With its colorful photos and detailed tips on how to make the most of South Africa, The Rough Guide is the book to get when visiting Africa. You may not have access to Google Maps when you're out exploring but that's OK. The Rough Guide also comes with easy use to maps. It can be purchased as an eBook, or as a paperback (平装本).

    Asia—Lonely Planet: South –East Asia on a Shoestring

    This guide is perfect for those backpacking through the hidden treasures of South-East Asia. With detailed recommendations from experts in the area, this guide helps first-times as well as experienced backpackers. This book can be purchased as a paperback travel guide. A download for an eBook or separate chapters can be purchased to serve as a guide to specific cities.

    North America—Lonely Planet USA Travel Guide

    With detailed reviews of the best places to eat, sleep, and explore, Lonely Planet is linked with budget-friendly attractions and that is why it makes our best travel guides list. This travel guide is available in paperback.

    Teenagers around the world can be happy with the news that the brain will ignore parents' order when they tap on their smartphones. A new scientific study from the University College London has shown that humans may temporarily go deaf when they're focusing on something visual at the same time.

    The researchers played the normal-volume sounds in the background. And 13 volunteers experienced inattentional deafness as their visual tasks became increasingly difficult. “We found that when volunteers were performing the demanding visual task, they were unable to hear sounds that they would normally hear,” Maria Chait said in a statement. “The brain scans showed that people didn't filter out the sounds on purpose. They were not actually hearing them in the first place.”

    The findings, published in the Journal of Neuroscience, suggest that the centre of sights and the center of sounds share limited resources. Inattentional deafness is a common everyday experience and the study explains why, according to UCL Institute of Cognitive Neuroscience Professor Nili Lavie.

    If you try to talk to someone focusing on a book, game, or television program and don't receive a response, they aren't necessarily ignoring you. They simply might not hear you at all. This could also explain why you might not hear your bus or train stop being announced if you're absorbed in your phone, book or newspaper. However, some loud sounds will still be able to break through.

    Some situations could become potentially dangerous when the quieter ones go unheard. As you can imagine, in the operating room, when a doctor concentrates on his work, he might not hear the equipment beeping. It also applies to drivers who concentrate on complex directions. Fortunately, experts have given us some useful tips on preventing such situations.

    How to eat healthfully can be especially complex for working women who often have neither the desire nor the time to cook for themselves (or for anyone else).Registered dietitian(营养专家) Barbara Morrissey suggests that a few simple rules can help.

"Go for nutrient dense foods that contain a multiple of nutrients," she suggests, "For example, select whole wheat bread as a breakfast food, rather than coffee and cake. Or drink orange juice rather than orange drink, which contains only a small percentage of real juice——the rest is largely colored sugar water. You just can't compare the value of these foods, the nutrient dense ones are so superior," she emphasizes.

    Morrissey believes that variety is not only the spice of life; it's the foundation of a healthful diet. Diets which are based on one or two foods are not only virtually impossible to keep up the strength, they can be very harmful, she says, because nutrients aren't supplied in sufficient amounts or balance.

    According to Morrissey, trying to find a diet that can cure your illnesses, or make you a super woman is a fruitless search. As women, many of us are too concerned with staying thin, she says, and we believe that vitamins are some kind of magic cure to replace food.

"We need carbohydrates(碳水化合物) protein and fat—they are like the wood in the fireplace. The vitamins and minerals are like the match, the spark, for the fuel," she explains, "We need them all, but in a very different proportion. And if the fuel isn't there, the spark is useless.”

When faced with the decision to get out of bed or have a few more minutes of sleep, which do you choose? Believe it or not, that decision could make a world of difference in the rest of your day.

About 85 percent of Americans use an alarm clock to wake up in the mornings, according to sleep researcher Till Roennenber. And while there are no official numbers on snoozing (打盹), a quick survey of social media makes it clear that hitting the snooze button is a popular pastime.

As to how the snooze button will affect your day, scientists have mixed opinions. Some scientists think people who hit the snooze button in the mornings are actually clever, creative and happy while some said that hitting the snooze button will ruin your life, or at the very least your day. "I feel that hitting the snooze button has got to be one of the worst things that ever happened to human sleep," researcher Jonathan Horowitz said. "The chances of you 'snoozing' and actually experiencing a meaningful rest are close to zero."

According to some sleep experts, when hitting the snooze button, you are in fact confusing your body and mind, and throwing yourself into a deep state of being sleepy. The body needs some time to wake up, so, when returning to what will be a light sleep for a brief period of time, you are putting your body back into a sleep mode before waking it again. At that point your body won't know what it wants, resulting in a sort of half awaken state.

If you really want to take advantage of an alarm clock, the key is to form a healthy sleep cycle. Focus your efforts on getting enough sleep each night and waking up at the same time each day so that when your alarm goes off you feel rested.

With more recognition than Halloween and less than Christmas, Valentine's Day as an imported festival faces a dangerous situation in China, where it's caught between forces of tradition and fashion. Valentine's Day has a natural enemy in China. And it is not the Chinese equivalent, which falls on the seventh day of the seventh month on the lunar calendar, usually around half a year away from Feb. 14. It is the Spring Festival, also known as the Chinese New Year, that will influence the Feast of Saint Valentine.

The real disagreement between East and West probably took place over a century ago, when China's door was forced open by Western powers and Chinese scholars supported westernization as a means to strengthen our nation's ability to compete.

The introduction of the solar calendar and Western measurements was both an acknowledgment of their influence and an effort to be accepted by the world order.

For a full century, we have had two systems running in parallel. When it comes to the eventual outcome, practicality usually beats all other concerns. Laws can help, such as the three traditional festivals of Tomb Sweeping, Dragon Boat and Mid­Autumn gaining legal status in 2008 and giving every Chinese citizen a day off, but laws cannot push what people have no feelings for. So, the celebration or boycott of imported holidays or homegrown ones should be no cause for worry. If they are irrelevant, no social media will change the public's mind; and if they are accepted, there must be a need which they happen to satisfy.

Since we have no global Qin Shihuang to force one system on every country, we can always rely on a dual (双重的) approach by which we share with the outside world on the one hand but preserve our own ways of life on the other.