Table of contents for December 2017 in Discover

I’ve been doing what I call slow-mo running for many months now. The idea is to keep your heart rate under a specific threshold on your “easy” run days — even walking if you have to. Then on your “hard” days, you kick it up a notch and push even faster on your sprints. It’s all about building aerobic capacity, which can be awfully frustrating on the easy days, when you just want to go. At the heart of this athletic strategy? Persistence. This issue features stories of persistence, stories of researchers trying something, watching it miss its target, and trying again. Alan Stern and a team of fellow planetary scientists chased a shadow around the globe this summer, in pursuit of the perfect spacecraft course. It’s just one example…

AN ARMS RACE is playing out inside your body. It’s part of an invisible war that’s raged for billions of years. When viruses hunt and infect bacteria, the bacterial survivors store pieces of their vanquished foes — DNA snippets — within their genomes so that next time, they can detect and defend against the attack. In response, viruses evolve their own counterattack. The bacteria’s natural defense system is called CRISPR-Cas9. And in 2012, biochemist Jennifer Doudna, together with French microbiologist Emmanuelle Charpentier, upended genetics with an ingenious idea. What if scientists could exploit CRISPR as a gene-editing tool? Since then, Doudna and others have hacked these cellular weapons in an effort to treat diseases and create stronger crops. Now scientists are attempting another task: avoiding unintended mutations resulting from their…

10,000,000 The number of new genetic variants researchers pinpointed across the Swedish population. They sequenced the complete genomes from 1,000 people, which will serve as a resource for other geneticists and could help diagnose diseases. 7 The number of genes scientists recently linked to insomnia risk. After combing through genetic data from over 100,000 individuals, researchers found the genes were more common in people who had trouble getting enough shut-eye. 1 MINUTE The amount of time, on average per night, that a group of modern Tanzanian hunter-gatherers were all asleep at the same time. Experts say the minuscule overlap supports the notion that humans evolved different sleep patterns as a way to ensure someone was up to alert others of nighttime threats, such as predators. 1.5 % The average reduction…

1 THE PLANET FACTORY Exoplanets and the Search for a Second Earth By Elizabeth Tasker Want to understand how scientists find these distant worlds and what they might mean for our future? Astrophysicist Tasker delivers all the answers in this fastpaced primer. 2 THE ZOOMABLE UNIVERSE An Epic Tour Through Cosmic Scale, From Almost Everything to Nearly Nothing By Caleb Scharf What do a common cold-causing virus, an adult blue whale and the red supergiant star Betelgeuse have in common? They’re all examples that Scharf uses to walk readers through matters of size. 3 THE ANIMALS AMONG US How Pets Make Us Human By John Bradshaw From the dawn of domestication to pampered modern pets, anthrozoologist Bradshaw, author of the best-selling Cat Sense and Dog Sense, traces the evolution of…

The ideal medical science experiment has: • A defined disease.• An easily measured outcome.• A simple animal model.• Sick people happy to volunteer.• Funding. On this scorecard, mental illnesses get a 0. There’s no clearly identified gene or genes for mental illnesses, no blood test, no outward physical signs and no simple technical fix. Diagnosis generally relies on people being willing to give honest answers to personal questions about their mood or the voices in their heads. Thoughts, emotions, behavior — “We are dealing with the most sensitive areas of human beings,” says Shekhar Saxena of the World Health Organization. “These are complex issues, and measurement techniques are still not good enough.” Measuring treatment success isn’t any easier. It’s the same questionnaires, with subjective answers. Cultural stigma against diseases that…

Last summer, a team of astronomers tried three times to catch the tiny shadow of a distant world as it raced across our planet, like a tiny eclipse, at 60,000 mph. On June 3, they deployed an array of telescopes at sites in Africa and South America, but never saw the 14- to 25-mile-wide shadow. On July 10, the scientists chased the shadow across the South Pacific aboard NASA’s SOFIA Boeing 747, which packs a Hubble-sized ‘scope. They got within 1 mile and one second of its predicted time and place, but still missed. Yet those attempts, paired with space telescope observations, let them refine their predictions. On their third and final chance, the team caught MU69 from Argentina. Their results are now helping plot New Horizons’ course.…

→ When tourists visited Egypt in the late 19th century, they often came home carrying animal mummies. The ancient creatures were considered excellent souvenirs, compactly embodying the exotic rituals of an ancient society. The mummies were also abundant. On basements. That’s where a curatorial assistant at the Brooklyn Museum found 30 uncataloged animal mummies in 2009, neatly shelved in a storage vault. Times had changed since they were set aside in the 1930s and ’40s. “Early on, museums were specifically interested in displaying luxurious objects,” says associate curator Yekaterina Barbash. “Now more and more curators are interested in displaying the real life of ancient Egyptians.” The Brooklyn mummies were neither rare nor glamorous. On the contrary, as the most commonplace artifacts of ancient Egypt, they clearly relate to everyday cultural…

FOR MORE THAN A CENTURY, the Natural History Museum of Los Angeles County has exhibited exotic specimens from around the world. But recently that global focus has shifted, as biologists recognize that LA itself is among the planet’s most diverse ecosystems. A new Urban Nature Research Center is enlisting citizen scientists to catalog species that they find in their backyards, from spiders to squirrels. Their goal is to better understand how biodiversity is affected by urbanization and globalization. Documenting the city’s urban wildlife is revealing patterns in migration and adaptation that may inform similar studies in other cities. Indo-Pacific Gecko Hemidactylus garnotii ✗ Indigenous to southeast Asia, these geckos are now found in Florida and Hawaii. Both those states supply non-native nursery plants to Los Angeles. ✗ The critter’s populations…

“Do the children view the marshmallows as puffy clouds that are abstract, or do they view the marshmallows as something gooey and sweet and yummy and tasty? The way you view the marshmallow is a very strong predictor of whether you wait or not.” — Cornell University associate psychology professor Vivian Zayas, on the classic marshmallow test that investigates children’s ability to regulate their behavior. River floods can have a huge impact on the surrounding lands. Overflows can be harmful not just to local wildlife populations, but to human communities across the globe. Effects from climate change are on the rise, making it more important than ever to understand changes in seasonal flooding patterns. A study recently published in Science looked at data from more than 4,200 observational hydrometric stations…

Ceres and Pluto don’t seem to have much in common. Nestled in the asteroid belt between Mars and Jupiter, Ceres is a tiny loner, while Pluto — in the Kuiper Belt at the edge of the solar system — is nearly three times as big and hosts a handful of moons. A mixture of rock and water ice dominates Ceres’ landscape, while methane and nitrogen ices cover Pluto. A thin, hazy atmosphere hangs over Pluto, while astronomers have seen only faint traces of gas above Ceres. The worlds are so dissimilar that planetary scientist Steve Desch says he is one of only a handful of researchers familiar with both. But look a little closer, and it turns out the dwarf planets aren’t all that different. New traces of ammonia on…

More than 10,000 years ago, somewhere in the Andean foothills between Argentina and Bolivia, two wild legume species mixed, probably with the help of some pollinating bees. Their offspring was atypical — a freak of nature that couldn’t remix with its wild ancestors and cousins. The freak plant continued to evolve, first on its own, and then by selection as farmers domesticated it for its tasty seeds that grew, not from its branches like most beans and peas, but beneath the soil. Merchants carried it throughout South America and eventually to the Caribbean islands. From there, Spanish clerics and conquistadors took the first peanuts to Europe and then on to Asia and Africa. The world learned to love the humble peanut. The transplant came to West Africa early, but it’s…

The Problem With E-Cigarettes Electronic cigarettes have gained a steady following in the U.S., but their health effects aren’t fully understood. University of Connecticut chemists developed a way to detect how much damage e-cigarettes may inflict on human cells. By mixing DNA with an electrochemiluminescent (ECL) agent, a mixture that lights up after electrochemical reactions take place, and exposing it to extracts from cigarette smoke and e-cigarette vapor, the chemists were able to spot DNA damage. Compared with unfiltered (nf) tobacco cigarettes, nicotine e-cigarettes are just as harmful. And non-nicotine (nn) e-cigarettes caused damage similar to that of filtered tobacco cigarettes. Here, colors approaching white on the scale indicate higher ECL levels and more damage, while colors closer to black indicate lower levels and less damage. “One hundred fifty years…

Balanced on this pencil tip is a tiny prototype of a temperature sensor, similar to those in some wearable health and fitness trackers. What’s even smaller is its need for power — just 113 picowatts, or about 10 trillionths of a watt. That’s roughly 600 times less than what current sensors use. Such minimal power needs could add years to these sensors’ lives and allow them to harvest energy from low-power sources of electricity — including the human body.…

To figure out not only how many people die from specific diseases but also how much each disease affects people’s quality of life, researchers in 1992 first estimated what’s called the global burden of disease. This takes into account lives affected — and those lives cut short — by disabilities, disease or injuries, in areas around the world. Select 2016 Results YLD, both sexes, all ages Ranking of Disabilities/Diseases, in Select Areas Top Disability Causes 1. Mental disorders & substance abuse 2. Other noncommunicable 3. Musculoskeletal disorders 4. Neurological disorders 5. Diabetes/endocrine 6. Nutritional deficiencies 7. Unintentional injury 8. Cardiovascular diseases 9. Chronic respiratory 10. Diarrhea/lower respiratory The category for mental disorders and substance abuse includes the following: • Schizophrenia• Alcohol use disorders• Drug use disorders• Depression• Bipolar disorders• Anxiety•…

Could a mutation in a cholesterolregulating gene be to blame in cases of unexplained infertility? Endocrinologist Annabelle Rodriguez thinks so. HDL not only carries cholesterol to the liver, she says, but it is also responsible for delivering cholesterol to the adrenal glands and ovaries. It’s needed there to make hormones, including progesterone, which is essential for early embryo development. Years ago, Rodriguez noted that genetically engineered “Scarb1 knockout” mice were difficult to breed; the female mice were always infertile. Rodriguez wondered if the same association might exist in humans, so she analyzed ovarian cells from women undergoing in vitro fertilization at Johns Hopkins’ infertility clinic. In a 2011 paper, she reported that female carriers of a defect in SCARB1 had lower levels of progesterone than women without the mutation. It…