Innehållsförteckning för March 2016 från Discover

A simple question yields a wealth of answers. Back in our December issue, I posed a simple question: Is there a science topic we don’t cover in one of our columns that you’d like to see in future issues? I’ve been asking questions like this for a few years now, and I never know how (or even if) readers will respond. But my December query garnered one of the largest responses ever — nearly 40 letters in one afternoon alone, and they’re still coming in! Some of you wanted to see the return of long-lost departments, such as the mystery photos we used to ask readers to identify, or the brain games column that Discover once published several years back. (Guess what? One of these will return, sooner than you…

The disappearance of mammoths and giant sloths has defied explanation since the turn of the 19th century, when Thomas Jefferson sent Lewis and Clark on an expedition to, among other things, find the lost megafauna in the heart of America. Many researchers have blamed the extinction of most large mammals on the hunting excesses of nomadic humans. But could a changing climate be the culprit? In Science Smackdown, we let experts argue both sides. Too Darn Hot Hunt-crazy humans weren’t the main cause, says geneticist Alan Cooper of the University of Adelaide in Australia. Severe climate change throughout the Late Pleistocene, going back at least 125,000 years, was “perfectly capable of causing major problems,” he says. “Some extinctions occurred before humans even showed up.” In a paper in Science last…

1 Thanks to evolution, your back is a marvel of load-bearing support and flexibility — and kind of a mess. Our species is prone to back pain, for example, because our ancestors’ imperfect transition to upright walking essentially took a spine similar to that of our nearest living relatives, knuckle-walking chimpanzees, and forced it vertical with piecemeal adaptations. 2 A 2015 study found that some people are, well, chimpier than others. Humans prone to certain back problems have vertebrae closer in shape to those of a chimpanzee than those of pain-free humans. 3 Regardless of shape, you might have more (or fewer) of the bones than your neighbor. Not everyone has the standard 33 vertebrae: From top to tail, that’s seven cervical, 12 thoracic, five lumbar, five sacral and four…

It’s a question we’ve all faced: When you find a cache of longforgotten meat in the back of the refrigerator, do you throw it out and waste money, or eat it and risk intestinal distress? MIT researchers think they have the answer. Chemistry professor Timothy Swager and colleagues ran a minute electrical current through tiny cylinders of carbon atoms called nanotubes to detect compounds that rotting meat exudes — chemicals with evocative names like putrescine and cadaverine. As microbial activity increased, so did the compounds’ levels, changing the electrical signals and indicating the meat was past its prime. The company C2Sense, which licensed the technology, is working on creating portable prototypes that will encapsulate the nanotubes and a tiny battery in semipermeable, food-safe material. With C2Sense beginning field tests later…

A bedridden patient complains of lower back pain. Within days, her skin’s outer layer reddens with irritation until it blisters. Tissue begins dying, and eventually more skin layers are damaged, exposing fat, muscle and bone — the patient has a full-blown bedsore. Bedsores, or pressure ulcers, affect over 2.5 million Americans, cost $11 billion annually and can lead to debilitating and deadly infections. But that could change, thanks to collaboration between University of California, Berkeley engineers and UC San Francisco doctors. The team created a “smart” bandage that detects skin tissue damage before it’s visible. Healthy cells have nearly impermeable membranes. But when a cell starts to die, its membrane deteriorates, allowing electrical signals to pass through. The researchers took advantage of this to map electrical changes that occur when…

If you want to explore our origin story, keep an eye out for the white stinkwood trees. That, at least, is what paleoanthropologist Christine Steininger says as we push our way up a gentle incline covered in waist-tall, brown and green grasses near Maropeng, a town about 45 minutes from Johannesburg, South Africa. The land here is arid and open, except for hardy stinkwood and wild olive trees, which cling to existence in small patches. Their survival depends on putting down roots deep enough to sup on what little water collects in scattered depressions and crevices — the same spots where the fossils of our earliest ancestors have been found. Indeed, at the first stand of trees is a fissure so thick with fossils that they protrude from the breccia,…

“Is your spaceship going to be manned?” Pamela Contag once asked a rocket scientist at a symposium of the 100 Year Starship (100YSS) project, a NASA- and DARPAfunded group whose goal is to make interstellar travel possible in a century. Yes, he said, his rocket would have a crew. Contag smiled, then lowered the boom: Microbes could ruin the whole mission, she told him. While other scientists at the 2014 symposium gave hopeful presentations about antimatter propulsion and moon mining, Contag, a microbiologist, began hers with, “Warning: I’m going to bring the mood down.” We know almost nothing, she continued, about how long-term spaceflight affects the microorganisms inside us. These microbes outnumber “our” cells 10 to 1, and we’re only beginning to learn how much influence they wield. Depending on…

A fossil smaller than a sesame seed has revealed the invisible early history of animals on Earth and could reconcile a major evolutionary paradox. Previous phylogenetic studies, which model the evolution of groups of related organisms, have suggested that the animals that gave rise to sea sponges, sea anemones, worms and crustaceans first appeared 600 million to 700 million years ago. But until now, scientists had no undisputed fossil evidence of any animals at all prior to about 575 million years ago. The new fossil, apparently an ancestor of the Precambrian sea sponge, was found in 600-millionyear-old rocks in China. Its hundreds of thousands of microscopic cells are spectacularly preserved in phosphate minerals. The body consists of three vaselike openings, the walls perforated by tiny pores — just like modern…

Mine, me, I. Conventional thinking holds that narcissists overuse these first-person pronouns. Au contraire, says research from the University of Arizona. The common association between narcissism and the high use of those pronouns, known as I-talk, is rooted in a 1988 study from the University of California, Berkeley. Back then, researchers tested just 48 participants, and subsequent similar experiments haven’t replicated the finding. So Matthias Mehl, an associate psychology professor at Arizona, launched the most robust examination to date of the relationship between I-talk and narcissism. Mehl and his team collaborated with researchers from six universities — four in the U.S. and two in Germany — and asked more than 4,800 people to complete a communication task in which participants either talked or wrote about themselves. Participants also completed a…

The fight against antibiotic resistance seems like an uphill battle: Bacteria outsmart our drugs, and our slow discovery of new antibiotics can’t keep pace with their constant evolution. Although part of President Barack Obama’s recent $1.2 billion allocation for fighting antibiotic resistance does involve drug discovery, some scientists and companies are repurposing existing therapies, which can save time and money. For antibiotics to kill bacteria, bacterial cells must ingest them, and they need energy to do that. In 2011, James Collins, a systems biologist at the Howard Hughes Medical Institute, found that some bacteria unfazed by antibiotics are actually just less metabolically active than their sensitive counterparts and aren’t energized enough to ingest the drugs. He called them persisters — different from genetically resistant bacteria that mutate to survive antibiotic…

“He won’t eat anything but cornflakes,” complained the mother of a boy I used to know. Breakfast, lunch, dinner — always a bowl of cornflakes and milk. Even at other people’s houses, he made no concessions. To his mother, his extreme diet was a source of worry and exasperation. To the rest of us, he was a fascinating case study. Where did it come from, this bizarre cornflake fixation? It just seemed to be part of his personality, something no one could do anything about. Whether you’re a child or a parent, the question of “likes and dislikes” is one of the great mysteries. Human tastes are astonishingly diverse and can be mulishly stubborn. Even within the same family, likes can vary dramatically from person to person. Some prefer the…

Powered by Astronomy magazine AN OBSERVATORY’S NEW LIFE After more than four decades of service, the aging Mayall Telescope atop Arizona’s Kitt Peak will soon see farther than ever into space, thanks to a novel camera that will pinpoint the location of 25 million galaxies up to 10 billion light-years away. Turn the page to read more about how new technology will help old observatories keep their eyes on the skies for years to come.…

One spring six decades ago, in the ponds and marshes along a western arm of Lake Michigan, about 25 miles north of the city of Green Bay, Wis., the northern leopard frog Lithobates pipiens was busy breeding. The males trumpeted sex calls that vaguely sounded like, “ ’ere I am,” followed by croaks of “rah-rah-rah” when they sensed females nearby. The females responded with their own throaty grunts. The outcome of this noisy annual ritual was a lot — an awful lot — of fertilized eggs attached to plants or afloat in the waters of the marshes. During a normal breeding season, the lake would recede and the water would dry up or grow shallow, allowing only about 1 percent of the spawn to survive and mature. A different scenario…