An artist in Oakland, California isusing his skills to help the homeless. Greg Kloehn builds very small shelters that make life on the streets a little more comfortable. The structures offer the homeless some safety and protection from bad weather. Each little house also has wheels on the bottom so it can go wherever its owner goes.

    Greg Kloehn has given away at least 20 tiny houses. Several are on the roadside near an active railroad. On a recentday, Mr. Kloehn stops at one to visit Oscar Young. The two men hug. Inside his little shelter Mr. Young gets relief from cold nights on the streets. Mr. Kloehn also visits Sweet-Pea, another friend who also lives in one of the little homes the artist built. She says it keeps her safe and protects herbelongings.

    In the mornings, Mr. Kloehn searches the streets for building materials. He gathers what he can and takes it to his studio. There, he puts the houses together. Empty coffee bags become roofmaterial. A washing machine door and refrigerator part become windows. Nails, screws and the sticky glue hold all the pieces together. The artist also attaches a small electrical device to the house. The device is powered by the sun.

    Some of the people living on the streets once had normal houses of their own. But some of the people say they have learned to live with less and they are thankful to that man.

    Mr. Kloehn says his work is not a social project. He says he is just someone using his skills to help his homeless neighbors.

    What's your dream vacation? Watching wildlife in Kenya? Boating down the Amazon? Sunbathing in Malaysia? New chances are opening up all the time to explore the world.So we visit travel agents, compare packages and prices, and pay our money.

    We know what our vacation costs us.But do we know what it might cost someone else?It's true that many poorer countries now depend on tourism for foreign income.Unfortunately,though.tourism often harms the local people more than it helps them

    It might cost their homes and lands.In Myanmar.5.200 people were forced to leave their homes among the pagodas(佛塔）in Bagan so that tourists could visit the pagodas.

    Tourism might also cost the local people their livelihood（生计）and dignity（尊严）.Local workers often find only jobs with slim salaries in the tourist industry.And most of the profits（利润）do not help the local economy. Instead,profits return to the tour operators in wealthier countries,When the Maasai people in Tanzania were driven（驱赶）from their lands,some moved to city slums.Others now make a little money selling souvenirs or posing(摆姿势）for photos.

    Problems like these were observed more than 20 years ago.But now some non-government organizations,tour operators and local governments are working together to begin correcting them.Tourists,too,are putting on the pressure.

    The result is responsible tourism,or ethical tourism.Ethical tourism has people at its heart.New international agreements and codes of conduct（行为准则）can help protect the people's lands homes,economies and cultures.The beginnings are small,though,and the problems are complex.

    But take heart. The good news is that everyone,including us,can play a part to help the local people in the places we visit Tour operators and companies can help by making sure that local people work in good conditions and earn reasonable wages.

    They can make it a point to use only locally owned hotel restaurants and guide services.They can share profits fairly to help the local economy And they can involve the local people in planning and managing tourism.

    What can tourists do? First, we can ask tour companies to provide information about the conditions of local citizens.We can then make our choices and tell them why. And while we're abroad, we can: Buy local foods and products, not imported ones.

    Pay a fair price for goods and services and not bargain for the cheapest price.

    Avoid flaunting wealth.

    Ask before talking photographs of people.They are not just part of the landscape!

    Let's enjoy our vacation and make sure others do,too.

    The arm bones of women who lived 7-000 years ago show a surprising level of strength-even higher than today's professional athletes. That's according to a first-ever study comparing prehistoric(史前的)bones to those of living people. The finding suggests a revision of history — the everyday lives of prehistoric women were filled with hard labor, rather than just sitting at home doing lighter tasks while the men struggled and fought for life.

    “Before the study, there are no clear records describing how our ancient ancestors lived. It can be easy to forget that bone is a living tissue, one that responds to the difficulties we put our bodies through,” said lead author Alison Macintosh. “Physical force and muscle activity both put pressure on the bone. The bone reacts by changing in shape, thickness and other aspects over time. ”

    Previous studies only compared female bones to contemporary male bones, the researchers said — and that's a problem, because the response of male bones to stress and change is much bigger than that of women. For instance, as humans moved from a hunter-gatherer lifestyle constantly on the move to a more settled agrarian (农耕的)one, changes can be observed in the structure of the shinbone (胫骨) — and these changes were much more evident in men.

    However, a comparison of the bones of prehistoric women to the bonos of living female athletes can help us work out a more accurate picture of what those prehistoric women were doing. “By analyzing the bones of living people and comparing them to the ancient hones, we can start to explain the kinds of labor our ancestors were performing,” Macintosh said. What they found was that women's leg strength hasn't changed a great deal, but their arms used to be very powerful. Prehistoric women, the researchers found, had arm strength 11〜16 percent stronger than those of modern rowers, and 30 percent stronger than those of non-athletes.

    Unlike modern animal scientists, dinosaur scientists cannot sit on a hillside and use telescopes to watch dinosaurs in order to know how they lived and whether they were good parents. Instead, they have to search hard for information from dinosaurs' fossils(恐龙化石) because dinosaurs died out millions of years ago.

    It's very difficult for the scientists to reach an agreement because different results can be got from the same fossils. Many fossils of the same kind of dinosaurs have been dug out from one place. They might have formed when an entire group of dinosaurs got stuck(陷入)all at once. Or they might have been the result of dinosaurs getting stuck one after another over a course of a few centuries. Thus we can say that dinosaurs might have in the first case lived in big groups and in the second lived alone.

    Though there are two different results, dinosaur scientists now generally agree that at least some kinds of dinosaurs lived in big groups. “That's pretty much settled at this point.” Says Paul Sereno. A kind of dinosaurs called Sauropods left behind tracks in the western United States that appear to run north and south, suggesting that they even moved long distances together.

    As to whether dinosaurs cared for their young, dinosaur scientists have turned to the closest living relatives of dinosaurs, birds and crocodiles for possible models. Birds give a lot of care to their young, while crocodiles just help their young to the water. The discovered fossils of dinosaurs sitting on their eggs and staying with their young suggest the parents were taking care of their babies, but we still cannot say that all dinosaurs did the same.

    There is still a long way to go before the above questions could be answered. Dinosaur scientists will have to find more proof to reach an agreement.

    Crossing your legs is an extremely common habit. While you may find it comfortable to sit with one knee crossed over the other, it might be causing health problems that you are not aware of.

    A study published in Blood Pressure Monitoring stated that sitting with your legs crossed can increase your blood pressure. The reason this happens is because the blood in your legs has to work against gravity to be pumped back to your heart, crossing one leg over the other increases resistance, making it even harder for the blood to circulate. You won't feel any immediate effects, but sitting for long periods of time will hurt you forever.

    Crossing your legs can also lead to neck and back pain. Ideally, it's best for our bodies to sit with our feet planted flat, hip width apart, on the floor, but it's not easy to maintain perfect posture all day at the office. When you sit with your legs crossed your hips are in a twisted position, which can cause one of your pelvic bones(骨盆) to rotate. Since your pelvic bone supports your neck and spine（脊椎）, this can cause pressure on your lower and middle back and neck.

    You also might notice that when you sit with your legs crossed for long periods of time your feet and legs get painful or have the feeling of being asleep. This is because when one leg sits on top of the other it causes pressure on the veins（静脉） and nerves in your legs and feet. It can cause numbness and/or temporary paralysis in the legs, ankles, or feet. While the feeling of discomfort may only last a minute or two, repeatedly crossing your legs until they feel numb can cause permanent nerve damage.

    So next time you sit down, try to get yourself in the habit of sitting with both of your feet on the floor. Not only will it help your posture and stability, but it will also save your health in the long run.

    According to official government figures, there are more than twice as many kangaroos as people in Australia, and many Australians consider them pests(有害动物). Landholding farmers say that the country's estimated 50 million kangaroos damage their crops and compete with livestock for scarce resources. Australia's insurance industry says that kangaroos are involved in more than 80 percent of the 20,000-plus vehicle-animal collisions reported each year. In the country's underpopulated region, the common belief is that kangaroo numbers have swollen to “plague proportions."

    In the absence of traditional hunters, the thinking goes, killing kangaroos is critical to balancing the ecology and boosting the rural economy. A government-sanctioned(政府认可的) industry, based on the commercial harvest of kangaroo meat and hides, exported $29 million in products in 2017 and supports about 4,000 jobs. Today meat, hides, and leather from kangaroos have been exported to 56 countries. Global brands such as Nike, Puma, and Adidas buy strong, supple “k-leather" to make athletic gear. And kangaroo meat is finding its way into more and more grocery stores.

    Advocates point out that low-fat, high-protein kangaroo meat comes from an animal more environmentally friendly than greenhouse gas-emitting sheep and cattle. John Kelly, former executive director of the Kangaroo Industry Association of Australia, says, “Harvesting our food and fibers from animals adapted to Australia's fragile rangelands is extremely wise and sustainable. Many ecologists will tell you that there is no more humane way of producing red meat."

    Opponents(反对者) of the industry call the killing inhumane, unsustainable, and unnecessary. Population estimates are highly debatable, they say, but “plague proportions" are biologically implausible. Little kangaroos grow slowly, and many die, so kangaroo populations can expand by only 10 to 15 percent a year, and then only under the best of circumstances. Dwayne Bannon-Harrison, a member of the Yuin people of New South Wales, says the idea that kangaroos are destroying the country is laughable. “They've been walking this land a lot longer than people have," he says. “How could something that's been here for thousands of years be 'destroying' the country? I don't understand the logic in that."

    Can Australians' conflicting attitudes toward kangaroos be reconciled(和解)? George Wilson says that if kangaroos were privately owned, then graziers(放牧人)—working independently or through wildlife conservancies—would protect the animals, treating them as possessions. They could feed them, lease them, breed them and charge hunter a fee for access. “If you want to conserve something," Wilson says, “you have to give it a value. Animals that are considered pests don't have value."

    Privatization could also help reduce grazing pressures. If kangaroos were more valuable than cattle or sheep, farmers would keep less live-stock, which could be good for the environment. Under this scheme, landholders would work with the kangaroo industry on branding, marketing and quality control. The government's role would be oversight and regulation.