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National Geographic Magazine

National Geographic Magazine October 2017

The latest news in science, exploration, and culture will open your eyes to the world’s many wonders. Get a National Geographic digital magazine subscription today and experience the same high-quality articles and breathtaking photography contained in the print edit.

국가:
United States
언어:
English
출판사:
National Geographic Society
빈도:
Monthly
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2
sustainability key for cities

In 1950 less than a third of the world’s people lived in cities. Today more than half do. By 2050 two-thirds of humanity is expected to reside in urban areas. Many sprawling, densely populated areas are all about “un”: unplanned, unhealthy, unsustainable. I remember feeling the “un” when my husband and I were in New Delhi in November 2016: In the capital city of the second most populous nation on Earth, the pollution was so bad that schools had to close because it wasn’t safe for kids to be outdoors. The growth of cities has produced some of the most complex issues of our time. It’s a phenomenon that creates disruption— but also great reason for hope. At National Geographic we’re known for telling stories about vast and open places. Increasingly, however, we’re…

1
calories count

The world’s farmers grow enough food to end global hunger, but 795 million people remain undernourished. Poverty keeps many from meeting the UN Food and Agriculture Organization’s recommended average intake of 2,353 calories a day. Access is the primary problem, says the FAO’s Carlo Cafiero. Political unrest, economic crises, and natural disasters can snarl food distribution, creating pockets of scarcity that exacerbate people’s struggle to access food. The world has made progress against hunger. Undernourishment has declined from 23 to 13 percent in developing countries over the past quarter century. Even so, what a country eats reflects its economic status: People in less prosperous nations get more calories from grains or starchy roots; in industrialized countries, animal protein, fats, and sugar make up a larger portion of meals. ALBERTO LUCAS LÓPEZ, NGM…

2
do you really know your cat?

For those who’ve long wondered if their cats regard them merely as kibble dispensers, a report in the journal Behavioural Processes should be reassuring. In a study that exposed adult cats to four categories of stimuli—food, toy, scent, and human social interaction—the majority of cats preferred human interaction over all other options, even food. This type of research “was done on dogs in the ’90s” but not on cats until now, says Oregon State University’s Kristyn Vitale Shreve, a co-author of the study. “We’re trying to catch up.” Cats are stereotyped in the U.S. as untrainable and unsocial, she says, but they can be taught using the same general principles as dogs—so long as the incentives are right. Vitale’s next study will research how to use cats’ preferences to train them. What…

1
how vertebrates got their coats

From scales to feathers to fur, vertebrates clothe themselves in a dazzling variety of textures and hues. But scientists have shown that many of those coverings emerge from the same anatomical hardware. Biologists have long known that feathers and hairs both start as structures called placodes. In reptiles, however, biologists had found distinct skin areas that yielded scales but no placodes. The absence proved puzzling, since birds are more closely related to reptiles than to mammals. Had birds and mammals evolved placodes independently? Or had today’s reptiles discarded them? Then University of Geneva biologist Michel Milinkovitch visited an Italian animal fair, found scaleless, “naked” bearded dragons for sale—and a third scenario emerged. When he compared the naked lizards and their scaly kin, he saw to his shock placode-like bumps dotting the skin…

2
getting inside fido’s head

When a dog leaped from a helicopter to accompany the U.S. SEAL team on the raid of Osama bin Laden’s complex in 2011, Gregory Berns was inspired. “I thought, If dogs can jump out of helicopters, we can train them to go into an MRI,” he recalls. The next year the neuroscientist launched the Dog Project at Emory University, which was the first to teach dogs to lie still without sedation in an MRI scanner so their brains can be studied. By peering into a dog’s brain, researchers are able to see how it reacts to stimuli like hand signals, sounds, and smells. Activity in the reward center can show whether dogs prefer human affection to food (most like both equally), and which ones may not be fit for duty as…

2
spots and stripes are not so black-and-white

Think of flamboyance in the animal kingdom, and a colorful menagerie springs to mind: a parrot’s rainbow plumage or the showy scales of a tropical fish. Mammals tend to be less colorful than other animal groups, but some are strikingly attired in black-and-white. What purpose do such high-contrast patterns serve? The color scheme’s utility isn’t always apparent. Deciphering what zebras gain from having stripes has puzzled scientists for more than a century. To try to solve the mystery, wildlife biologist Tim Caro of UC Davis spent more than a decade studying zebras in Tanzania. He ruled out theory after theory—stripes don’t keep them cool, stripes don’t confuse predators—before finding an answer. In 2013 in the savanna, he set up flytraps covered in zebra skin and, for comparison, others draped in wildebeest skin.…