Table of contents for December 2015 in Discover

In 1993, geneticist Dean Hamer co-published a study claiming male homosexuality was at least partially genetic, and he identified the chromosome segment where one of the relevant genes was located. It was just some of the research on the controversial topic that Discover unpacked in a June 2007 feature article, “Born Gay?” Since then, researchers from Northwestern University and NorthShore University HealthSystem Research Institute in Evanston, Ill., have replicated Hamer’s results in a larger, more robust paper — and they’re working on a more sophisticated study. Hamer looked at 76 pairs of gay brothers, while psychiatrist Alan Sanders recruited 409 pairs of brothers and used the same analysis Hamer used, called linkage analysis. Linkage studies use genetic markers, which act like signposts, pointing researchers to the general area on the…

Eleven years into its mission exploring Saturn and its moons, the Cassini spacecraft continues to make new kinds of discoveries. Most recently, it helped researchers map the bottom of the major seas and lakes on Titan, thanks to a new method for analyzing the venerable probe’s data. RADAR, one of Cassini’s 12 science instruments, maps the surface of Titan, Saturn’s largest moon, when it flies near it by sending down microwaves and timing their return trip. Scientists had assumed Titan’s lakes would absorb the microwaves, eliminating any chance of measuring the moon’s seafloors. But in May 2013, Cassini passed over Titan’s northern hemisphere for another view of the surface, and the sea Ligeia Mare was along the path. So Marco Mastrogiuseppe, a researcher on the Cassini team who had used…

On March 5,1979, the Voyager spacecraft hurtled past Jupiter and sent back a grainy snapshot of something previously spotted only on Earth: bursts of lightning. It was proof that our home planet isn’t alone in atmospheric spectacle. But it wasn’t surprising. After all, lightning is just a rush of electrons leading to an electric spark on an atmospheric scale — any atmosphere. In the years since, spacecraft have spotted bursts of lightning elsewhere in our solar system, from the cloud tops of Venus, to Saturn’s moon Titan, to an electrical storm so big and bright on Saturn itself that it shone even during the day. Similarly, powerful streams of electricity almost certainly crackle in the skies of thousands of exoplanets strewn throughout the galaxy. But so far, there’s no proof.…

Archaeologists and astronomers don’t seem to have much in common. One digs into the earth while the other looks at the sky, and a stone tool once wielded by Homo erectus couldn’t be more different from an exploding star at the edge of the visible universe. But the sciences are actually fundamentally similar: Both try to understand the present by looking deep into the past, whether it’s the origin of the human species or of the universe. For some astronomers, the parallels are even closer. One of the great mysteries of the cosmos is how and when and why the first stars flared into light out of the darkness that followed the Big Bang. Nobody knows for sure what those first stars looked like, or how they lived and died.…

1 Lava wasn’t called lava until Mount Vesuvius erupted in 1737. Francesco Serao used the word, derived from labes (“fall” or “slide” in Latin), to compare the hot ooze on the volcano’s slopes to mudslides after a heavy rain. 2 Lava is magma that has erupted above the planet’s surface. The most common variety of molten rock, either above ground or below, is basalt. 3 Basaltic lava the world over is classified with the Hawaiian words a’a or pahoehoe based on consistency. Pahoehoe tends to spread slowly — imagine cake batter poured into the center of a pan. 4 A’a lava, on the other hand, often advances erratically, including occasional sudden surges. The same eruption of lava can switch from pahoehoe to a’a, depending on factors such as thickness and…

SOLSTICE SUNBURN The wide-striped band that dominates this ghostly view of a southern English yard is actually the track of the sun across the sky, climbing gradually higher from the winter to summer solstices. To create this image, retired photonics professor Greg Parker made a cylindrical pinhole camera using a plastic pipe 4 inches wide. He loaded it with a sheet of light-sensitive photographic paper and left the pinhole — literally just a hole on the curved side — open from Dec. 21, 2013, to June 21, 2014. Breaks in the bright streaks indicate clouds.…

As Oscar the Grouch and garage sale aficionados know, you can uncover treasures while going through someone’s old stuff. That’s exactly how two astronomers from Seoul National University in Korea found an ancient, relatively close galaxy — by combing other researchers’ leftovers. Myung Gyoon Lee and In Sung Jang were looking for ultra faint dwarf (UFD) galaxies, remnants of the universe’s first galaxies. They scoured Hubble telescope images up to 15 years old of a nearly empty region of space just outside the Milky Way, and their search paid off: Lee and Jang reported last year that they uncovered a tiny, faint galaxy called Virgo UFD1. It’s the most distant UFD ever seen, and it formed almost 12 billion years ago. Not bad for dumped data. Scouring others’ observations for…

Q How can you get used to eating spicy food? Do your taste buds change, or is there a psychological element at play? — Alex Klunk, Chesterfield, VA A Spicy food tolerance comes from a physical change in how some of the body’s pain receptors react to capsaicin, the molecule responsible for the “hot” in spicy peppers and foods flavored with them. Psychology factors into how much we like the burn, not how we feel the burn. The spicy heat (as well as temperature heat) is registered through specific receptors on the tongue’s nerve cells. When exposed to capsaicin, these receptors open to allow in sodium and calcium ions, causing the receptors to transmit that hot signal to the brain. However, with repeated short-term exposure to capsaicin, those calcium ions…

Twenty years ago I was a resident in psychiatry and was called down to the emergency room one night to see a patient. Richard, 40, was wearing jeans, a button-down shirt and exceptionally clean white sneakers. He had neatly folded his unused patient gown and placed it at the foot of the bed. He was calm and didn’t appear to be physically injured. His pulse-oximeter, clipped around his right index finger, displayed normal vital signs on the bedside monitor. I glanced back over my shoulder to the senior emergency room physician sitting at the desk, nodded toward the patient and gave him a quizzical look. The other doctor raised an index finger and circled it around his right ear — the universal “crazy” gesture. I walked over to Richard and…

Most stellar archaeologists look for traces of the first stars in the universe, but Ivan Ramirez is interested in a more recent vintage. He wants to find the long-lost siblings of the sun — the hundreds or perhaps thousands of stars that condensed, along with our home star, from a single cloud of gas about 4.6 billion years ago. “If we can figure out the detailed properties of the place where our sun and its planets formed,” he says, “we might be able to find out if those conditions had anything to do with the fact that life exists here on Earth.” At first, he didn’t like the odds. “It was a project that was most likely to fail,” says Ramirez, an astronomer at the University of Texas at Austin.…

Going under the knife for heart surgery would make anyone anxious, but thanks to advancements in medicine, most of us can rest easy knowing that risks for complications are pretty low. In the early days of cardiac surgery, though, it wasn’t uncommon for someone to die on the operating table due to preoperative misdiagnosis. Because early surgeons and cardiologists had to base their preoperative cardiac diagnoses on their stethoscope, the heart’s X-ray silhouette and the ECG, their diagnoses were imprecise. Surgeons, thinking they were operating on a simple hole in the heart, opened it to find additional complex abnormalities of valves for which they had no surgical solution. Desperate children died on the operating table or soon thereafter as surgeons tried to explain the mistaken diagnosis to grieving parents. Cardiac…

Runoff from Greenland’s melting snow is one of the biggest potential contributors to sea level rise. Scientists usually gauge meltwater runoff by using regional climate models to compare calculations of melting at the surface with estimates of how much water refreezes — whatever water that doesn’t refreeze is considered runoff. But recent research shows that supraglacial rivers flowing over the ice sheet could swell oceans even more than massive icebergs or the drainage from Greenland’s glacial lakes. To get these findings, a NASA-funded team led by Laurence Smith, chair of the geography department at UCLA, spent six days on the ice during July 2012 — directly after a record-setting ice sheet melt. They braved dangerous, slippery conditions to gather data in some of the planet’s most hostile terrain. IN HIS…

Fifty million people have epilepsy, and many suffer brutally unpredictable seizures. If the seizures could be anticipated, electrical brain implants could stop a nascent seizure in its tracks, or at least give patients warning. For 15 years the National Institutes of Health and other agencies spent $40 million trying — and never quite succeeding — to devise algorithms that could spot a growing neurologic storm. Then a frustrated group of epilepsy physicians invited computer nerds around the world to take a shot instead, providing data sets recorded from the brains of human epilepsy patients and epileptic dogs. Three months — and $30,000 of prize money — later, the winners had produced algorithms predicting seizures with better than 84 percent accuracy.…

For more than a century, anthropologists have wondered why we possess a chin when apes and our Homo ancestors are chinless. The chin sticks out, so to speak, as a distinguishing human trait. As such, experts have numerous theories about the chin’s evolutionary purpose. We present the best in Science Smackdown. The Chin as Biomechanical Brace The biomechanical view has two camps. Human language arose around the same time as the chin. So one camp argues that the tongue muscles’ repetitive action during speech might have led to an extra anchor of bone, which became the chin. The second camp thinks it stems from the mechanical stresses of eating: the masticatory hypothesis. But earlier this year, anthropologist Nathan Holton and his University of Iowa colleagues published a paper disputing the…

For Armchair Adventurers White Eskimo Knud Rasmussen’s Fearless Journey Into the Heart of the Arctic By Stephen R. Bown Not as famous as Shackleton or Nansen, Inuit-Danish Rasmussen was arguably even more intrepid, traveling by dog sled from Greenland to Alaska in the 1920s. Bown captures both his charisma and soulful side in a biography full of wonder and peril. For Foodies First Bite How We Learn to Eat By Bee Wilson Food writer Wilson probes the psychology of food memories, dips into the chemistry of flavor and digs deep into the physiological and social roots of obesity in this smorgasbord of insights. Bread, Wine, Chocolate The Slow Loss of Foods We Love By Simran Sethi From the industrialization of chocolate to the art of turning grapes into bottles worth…

IT WAS JUST AFTER MIDNIGHT IN NEW YORK WHEN POLICE CHASED DOWN AND ARRESTED the suspect wanted in a potential hate crime. A gay man had been shot and killed with a silver revolver. The suspect was cooperative to a point. He gave them the silver revolver in his holster. He also gave them an ID. Then he clammed up. When they brought him to the precinct to book him, the ID turned out to be fake. He wouldn’t tell them his real name. They couldn’t take his fingerprints. By this time, it was just after 7 a.m. The officers called Edwin Coello, the sergeant who has led the New York Police Department’s Facial Identification Section since it was formed in late 2011. It was a Saturday, and Coello was…

On July 14, I was driving back to Johns Hopkins University’s Applied Physics Lab in Laurel, Md. — mission control for the New Horizons spacecraft — when I suddenly found myself swept up in an interplanetary race. Earlier in the day, I huddled with the science and engineering teams as the probe completed its historic Pluto flyby. Or rather, as we all hoped it had. We wouldn’t know for sure until New Horizons’ “mission accomplished” signal arrived, and because of the enormous distance involved, that signal would take a tedious 4.6 hours to reach Earth. So we all took a break while waiting for the triumphant message, due to arrive at 8:53 p.m. Just as I pulled into the parking lot, prepared to join the vigil, I realized with a…