ATLANTA — Grim discoveries in Belize’s aptly named Midnight Terror Cave shed light on a long tradition of child sacrifices in ancient Maya society.

A large portion of 9,566 human bones, bone fragments and teeth found on the cave floor from 2008 to 2010 belonged to individuals no older than 14 years, bioarchaeologist Michael Prout reported April 15 at the annual meeting of the American Association of Physical Anthropologists. Many of the human remains came from 4- to 10-year-olds. Because these bones are so fragmented, it’s difficult to estimate precisely how many individuals lay in the cave.
Prout, of California State University, Los Angeles, and colleagues suspect these children were sacrificed to a rain, water and lightning god that the ancient Maya called Chaac.

Radiocarbon dating of the bones indicates that the Maya deposited one or a few bodies at a time in the cave over about a 1,500-year-period, starting at the dawn of Maya civilization around 3,000 years ago, Prout said. At least 114 bodies were dropped in the deepest, darkest part of the cave, near an underground stream. Youngsters up to age 14 accounted for a minimum of 60 of those bodies. Ancient Maya considered inner cave areas with water sources to be sacred spaces, suggesting bodies were placed there intentionally as offerings to Chaac.

The researchers found no evidence that individuals in the cave had died of natural causes or had been buried.

Until now, an underground cave at Chichén Itzá in southern Mexico contained the only instance of large-scale child sacrifices by the ancient Maya, Prout said. Other researchers have estimated that 51 of at least 101 individuals whose bones lay scattered in Chichén Itzá’s “sacred well” were children or teens.

Researchers have often emphasized that human sacrifices in ancient Central American and Mexican civilizations targeted adults. “Taken together, however, finds at Chichén Itzá and Midnight Terror Cave suggest that about half of all Maya sacrificial victims were children,” Prout said.

Peacocks know how to twerk it to attract females.

During mating season, a flamboyant fowl will raise his iridescent train, shake his wings and vibrate his fan. Such displays can go on for hours.

Biologist Roslyn Dakin of the University of British Columbia in Vancouver teamed with physicist Suzanne Kane of Haverford College in Pennsylvania and other collaborators to break down the basic biomechanics of this shimmy show, known as rattling. The team also investigated a related peacock move called shivering — a reshuffling of feathers akin to a dandy combing his hair — that occurs before females arrive.
The researchers recorded feral peafowl (Pavo cristatus) in action with a high-speed video camera and studied feathers in the lab. Rattling birds literally shake their shorter, stiff tail feathers to strum their fanned-out train, making the train feathers vibrate at the same high frequency (25.6 hertz on average), the team reports April 27 in PLOS ONE. This frequency sweet spot generates a loud rustling noise — also part of the show. Although the scientists saw variety from bird to bird, individual peacocks tended to vibrate their feathers at a consistent frequency. Males with longer trains vibrated at slightly higher frequencies than those with shorter ones. Shivering involved lower-frequency feather vibrations than rattling.

Despite all this gyration, the eyespots stay still thanks to tiny hooks that lock the eyespot barbs together. “It isn’t just beautiful,” Kane explains. “It acts like a single mass at the top of the feather.”

Previous studies have shown that males with more iridescent eyespots have better game. High-frequency shimmying might be indicative of a male’s health or muscle power, Dakin says. But how the female perceives the total package remains to be studied. “One has to wonder what it’s like to be a female seeing this for the first time,” she says.

The historic El Niño event currently shaking up Earth’s weather rose like a phoenix from the hot remains of a failed 2014 El Niño, new research suggests.

In 2014, the scientific community buzzed about the possibility of a supersized El Niño as warm Pacific Ocean water sloshed eastward. That July, however, large winds pushed westward and halted the budding El Niño before it fully formed (SN: 11/1/14, p. 6). Those same winds also prevented the release of stored-up ocean heat, researchers report in a paper to be published in Geophysical Research Letters. In March 2015, that lingering heat gave the current El Niño a jump start toward the extreme, the researchers propose.
The ongoing El Niño is among the three strongest on record (SN Online: 7/16/15); it has boosted rainfall in California, contributed to ocean coral bleaching and helped make 2015 the hottest year on record (SN: 2/20/16, p. 13). Such a once-in-a-generation El Niño would have been less likely without the failed 2014 event, says study coauthor Michael McPhaden, a physical oceanographer at the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory in Seattle.

“In a sense, we dodged a bullet in 2014 by not having a monster El Niño,” McPhaden says. “But that was short-lived, because the conditions that shut that developing El Niño down set up the big one in 2015.”

El Niños typically form every two to seven years when Pacific winds shift a large, near-surface pool of warm water eastward. That warm water then rises to the surface and releases its heat into the atmosphere, causing global shifts in storms, precipitation and temperatures.

The fizzled 2014 El Niño followed by a colossal event in 2015 is very unusual, McPhaden says. He and climate scientist Aaron Levine, also at NOAA’s Pacific Marine Environmental Laboratory, wondered if the sequence of events was just a coincidence. So the researchers looked at decades of El Niño climate data and ran computer simulations of various hypothetical El Niño events.

Under typical ocean conditions, the chances of a 2015 El Niño of any strength are about 27 percent, the researchers estimate. The remnant heat from the failed 2014 El Niño increased those odds to roughly 40 percent. Having a failed El Niño the previous year stacks the deck in favor of an El Niño, McPhaden and Levin conclude. But it “isn’t a guarantee,” Levine says.
A similar aborted El Niño occurred in 1990, the researchers find. An El Niño formed the following year, but the event ended up being more modest than the current super El Niño. That’s in part because the eastward-blowing winds in 1991 were relatively weak, Levine says. Strong El Niños require strong winds, not just warm water, he adds.

Forecasting those winds is tricky because the winds and the warm water “are all part of the same system,” says Kevin Trenberth, a climate scientist at the National Center for Atmospheric Research in Boulder, Colo. Ocean heat can cause atmospheric changes that can in turn influence the winds. The new work provides insights, he says, “but it is far from complete.”

The planet Mercury is about to throw some shade at Earth.

For about seven hours on Monday, May 9, the innermost planet will trek across the face of the sun and cast a shadow on our planet. During its journey, a rare event known as a transit, Mercury will appear as a tiny black speck on the sun. The transit will begin at 7:12 a.m. Eastern Daylight Time and end at 2:42 p.m. It will be visible from most countries, though folks in Japan, Australia, New Zealand, and islands in the West Pacific are out of luck.

Transits of Mercury happen on average about eight times a century and only in May or November. The last one was in 2006; the next one won’t be until 2019.

Don’t stare at the sun to try and see it. Seriously. Don’t do that. Staring at the sun is dangerous. Plus, Mercury is tiny. A solar-filtered telescope with at least 50x magnification is the best and safest way to enjoy the show. Many astronomy clubs and organizations will have viewing events. And there will be many ways to see it online such as NASA TV, the Virtual Telescope Project and the Slooh Observatory.

Packing on a few pounds may not be such a bad thing.

As a group, overweight people are living the longest nowadays, suggests an almost four-decade study in Denmark published May 10 in JAMA. And obese people seem to be at no higher risk of dying than those of normal weight. The new analysis fuels ongoing debate about what’s a healthy body mass index — especially in light of rising obesity rates (SN: 5/14/16, p. 5), improved heart health treatments and other factors influencing health and longevity.
“This is a very carefully done study,” says Rexford Ahima, a physician who studies endocrine disorders at the University of Pennsylvania School of Medicine. The findings strengthen the notion that “BMI as a number alone may not be sufficient to predict health and risk of death. It has to be taken within context.” Ahima was not involved in the research but has analyzed previous studies urging a rethink of how BMI influences mortality.

Researchers screen for obesity by calculating BMI — a popular but fairly crude measurement of body fat reached by dividing a person’s weight in kilograms by the square of height in meters. People with BMIs between 18.5 and 24.9 are considered normal. A BMI between 25 and 29.9 is “overweight”; 30 and above is “obese.”

Many studies suggest that obese individuals face a higher risk of heart disease, stroke and other ills. But some analyses have found that heavier folks may not in fact be in such dire straits. In one study of type 2 diabetes patients, those with normal weight when diagnosed were more likely to die than those who were overweight or obese (SN: 9/8/12, p. 13). And a 2013 meta-analysis of 97 studies found that being overweight was associated with lower risk of death than having a normal BMI — a surprising finding that echoed a 2005 study by the same researchers.

In this new analysis, clinical biochemist Børge Nordestgaard of Copenhagen University Hospital and his team studied more than 100,000 adults. The three groups of white Danes, recruited about 15 years apart, reflected the general population in Copenhagen.

From 1976 to 2013, BMI associated with lowest risk of death increased from 23.7 to 27. That falls squarely in the overweight category. What’s more, obese individuals had the same mortality risk as people in the normal range, the analysis found. That trend held even when researchers took into account potentially confounding factors including age, sex, smoking and a history of cardiovascular disease or cancer.
While some might misinterpret the study to mean “you can eat as much as you like,” this is not what the findings suggest, Nordestgaard says. Rather, the results indicate that people who are moderately overweight might not need to worry as much as they had in the past. That might be because better treatments are now available for high blood pressure, high cholesterol and other risk factors for heart disease, Nordestgaard speculates. “So maybe you can be overweight if you have [these conditions] treated.” But the study was not designed to address whether improved heart health care actually caused “healthy” BMI values to creep up over time.

It’s also unclear whether the results apply to other ethnic groups. A substantial fraction of Asians, for instance, develop type 2 diabetes and heart disease despite having BMIs lower than the existing cutoff point for being overweight.

The findings underscore the idea that a person’s BMI does not tell the whole story. While this measure is good for comparing populations, it is not as useful for evaluating individuals and their risk for disease and death, Ahima says. Interpreting an individual’s BMI depends on many other factors, including “whether you are man or woman, how much muscle you have, how physically fit you are and what diseases you have.”

COLD SPRING HARBOR, N.Y. — Garbled signals from cellular antennas may have grounded the Galápagos cormorant.

Galápagos cormorants (Phalacrocorax harrisi) are the only cormorant species with wings too small to lift the birds’ large bodies off the ground. Broken primary cilia —antennas that cells need to receive key developmental messages — left the cormorants with stunted wings, UCLA evolutionary biologist Alejandro Burga suggested May 12 at the Biology of Genomes meeting.

Burga and colleagues compared DNA of flightless Galápagos cormorants with that of their close relatives, including double-crested cormorants (Phalacrocorax auritus), which have large wings and can fly. The researchers found more than 23,000 differences in more than 12,000 genes. Those changes have occurred within the last 2 million years, a short time by evolutionary standards.
Many of those genes probably have nothing to do with wing size. So Burga and colleagues narrowed down which genes might have had the biggest effect on cormorant evolution using a computer program that predicts whether a change in a gene will affect its function. Genes that have mutations that damage function may have big evolutionary consequences. Of the genes predicted to have altered function, the researchers selected the 3.3 percent that have changed most drastically in Galápagos cormorants.

To determine what these genes do, Burga examined whether any of the human versions of these genes cause problems when they are mutated in people. Eight of the banged-up genes were associated with limb defects caused by faulty primary cilia, hairlike structures that grow from cells. The cilia receive signals important for the development and proper functioning of cells (SN: 11/3/12, p.16). In people, genetic mutations that damage primary cilia lead to a wide variety of diseases, including developmental defects.

Normal versions of those eight genes are necessary for primary cilia to pick up signals sent by an important protein called hedgehog. Those genes are so crucial for normal development that evolution has not allowed them to change much in 300 million years. Three other genes that are mutated in the flightless cormorants affect other aspects of the primary cilia. In people, mutant versions of all 11 cilia genes can cause small limbs, extra fingers and short ribs, Burga said.

It wasn’t clear whether the cilia defects were the primary cause of the birds’ flightlessness. So Burga further narrowed his focus to 10 of the altered Galápagos cormorant genes predicted by the computer program to give the biggest functional and evolutionary disadvantages. Those genes would be the most important wing shrinkers, Burga and his colleagues reasoned.

One of those top 10 candidates is a gene called CUX1. The protein it produces helps turn on other genes. Vertebrates from primitive coelacanths to people have nearly identical versions of the gene. But in flightless cormorants, four amino acids have been lost from the protein, suggesting that it can no longer do its job or does it poorly. In chickens, a defective form of CUX1 can shrink wings. That finding indicates the Galápagos cormorant’s altered form of CUX1 might also make wings smaller because it fails to turn on limb growth genes.
Many researchers would have left the story at that point, says Ludovic Orlando, an evolutionary biologist at the University of Copenhagen. “But they didn’t simply stop there,” Orlando says. “They made an effort to validate their findings. It’s unusual.”

Burga and colleagues wondered whether CUX1 and the primary cilia changes were related. The researchers injected cells used to mimic skeletal development in lab dishes with the normal vertebrate version of CUX1. Activity levels of two cilia genes rose by about 50 percent. That is evidence that CUX1 normally helps to regulate activity of primary cilia genes.

But the Galápagos cormorant version of CUX1 barely budged activity of the cilia genes. It also was not as good at stimulating growth and development of bone cells as the normal version, the researchers found. Those findings strengthen the case that CUX1 and primary cilia together were involved in shrinking the flightless fowl’s wings.

It’s still a mystery why Galápagos cormorants have normal size legs, Burga said.

Houseflies stretch their legs to land. Bumblebees hover, then slowly descend. Now, insect-sized flying robots have a way to stick the landing, too.

A tiny aerial bot about the size of a bee (nicknamed RoboBee) uses static electricity to cling to the underside of a leaf and perch on other materials, study coauthor Robert Wood of Harvard University and colleagues report in the May 20 Science.

RoboBee, a bot with shiny, flapping wings and four pinlike legs, is the first of its size that can fly, perch on a surface and then take off again. This energy-saving feat could one day extend mission time in search and rescue operations, the researchers say.
For robots, tackling the problem of flight has been easier than figuring out how to land. “Engineers have been trying to build perching mechanisms for flying robots nearly as long as we have been creating flying robots,” Wood says.
Researchers have had success with bigger, bird-sized bots (SN: 2/7/15, p. 18), but their landing mechanisms are tricky to scale down. For the microbot, Wood and colleagues wanted something simple: lightweight and without moving parts.

The team created an “electroadhesive” patch with electrodes that can be charged, letting the patch stick to different surfaces, like a balloon sticking to the wall after being rubbed on someone’s hair.

Switch the electrodes on and the patch, a circular disc on top of the robot, helps RoboBee hang out on overhanging pieces of glass or plywood, for example. Switch the electrodes off and the bot detaches, free to fly again. The sticky contraption lets RoboBee rest between flights: The bot used about a thousandth as much energy perching than hovering, the researchers found.

The cooling effect of pollution may have been exaggerated.

Fossil fuel burning spews sulfuric acid into the air, where it can form airborne particles that seed clouds and cool Earth’s climate. But that’s not the only way these airborne particles can form, three new studies suggest. Tree vapors can turn into cooling airborne particles, too.

The discovery means these particles were more abundant before the Industrial Revolution than previously thought. Climate scientists have therefore overestimated cooling caused by air pollution, says atmospheric chemist Urs Baltensperger, who coauthored the three studies.
Simulating unpolluted air in a cloud chamber, Baltensperger and colleagues created microscopic particles from vapors released by trees. In the real world, cosmic rays whizzing into the atmosphere foster the development of these particles, the researchers propose in the May 26 Nature. Once formed, the particles can grow large enough to form the heart of cloud droplets, the researchers show in a second paper in Nature. After sniffing the air over the Swiss Alps, some of the same researchers report in the May 27 Science the discovery of the particles in the wild.

“These particles don’t just form in the laboratory, but also by Mother Nature,” says Baltensperger, of the Paul Scherrer Institute in Villigen, Switzerland.

Airborne particles, called aerosols, are microscopic bundles of molecules. Some aerosols start fully formed, such as dust and salts from sea spray, while others assemble from molecules in the atmosphere.

Since the 1970s, scientists have suspected that sulfuric acid is a mandatory ingredient for aerosols assembled in the air. Sulfuric acid molecules react with other molecules to form clusters that, if they grow large enough, can become stable. Human activities such as coal burning have boosted sulfuric acid concentrations in the atmosphere, subsequently boosting the abundance of aerosols that seed clouds and reflect sunlight like miniature disco balls. That aerosol boost partially offsets warming from greenhouse gases.

A cloud chamber at the CERN laboratory near Geneva allowed Baltensperger and his collaborators to simulate the atmosphere when sulfuric acid was scarce. The researchers added alpha-pinene, the organic vapor that gives pine trees their characteristic smell, to pristine air and watched for growing aerosols. Previous, though inconclusive, work suggested that the pine vapors might form aerosols.
Alpha-pinene molecules reacted with ozone in the air and formed molecules that reacted and bundled together to form aerosols, the researchers observed. The researchers added an extra layer of realism by using one of CERN’s particle beams to mimic ions from the cosmic rays bombarding Earth’s atmosphere. The “rays” led to the formation of as many as 100 times the number of aerosols. The added ions help stabilize the growing aerosols, the researchers propose.

Further testing showed that the newborn aerosols can rapidly grow from around 2 nanometers wide — roughly the diameter of a DNA helix — to 80 nanometers across, large enough to seed cloud droplets.

At a research station high in the Swiss Alps, researchers observed aerosol formation during atmospheric conditions with low sulfuric acid concentrations and abundant molecules akin to alpha-pinene. The researchers couldn’t confirm the rapid growth seen in the lab, though.

Quantifying the overall climate influence of fossil fuel burning in light of the new discovery will be tricky, says Renyi Zhang, an atmospheric chemist at Texas A&M University in College Station. “Atmospheric processes are complex,” he says. “They had a pure setup, but in reality the atmosphere is loaded with chemicals. It’s hard to draw direct conclusions at this point.”

Painkillers in the opium family may actually make pain last longer. Morphine treatment after a nerve injury doubled the duration of pain in rats, scientists report the week of May 30 in the Proceedings of the National Academy of Sciences.

The results raise the troubling prospect that in addition to having unpleasant side effects and addictive potential, opioids such as OxyContin and Vicodin could actually extend some types of pain. If a similar effect is found in people, “it suggests that the treatment is actually contributing to the problem,” says study coauthor Peter Grace, a neuroscientist at the University of Colorado Boulder.
Scientists have known that opioid-based drugs can cause heightened sensitivity to pain for some people, a condition called opioid-induced hyperalgesia. The new study shows that the effects linger weeks after use of the drugs is stopped. Male rats underwent surgery in which their sciatic nerves, which run down the hind legs, were squeezed with a stitch — a constriction that causes pain afterward. Ten days after surgery, rats received a five-day course of either morphine or saline.

Rats that didn’t receive morphine took about four weeks to start recovering, showing less sensitivity to a poke. Rats that got morphine took about eight weeks to show improvements — double the time. “That’s far bigger than we had anticipated,” Grace says. “We were definitely surprised by that.”

These experiments were done with male rats, but unpublished data indicate that morphine extends pain even longer in female rats, Grace says, results that fit with what’s known about differences in how males and females experience pain.

Longer-lasting pain in the rats came courtesy of an inflammatory response in the spinal cord. The immune system sees morphine as a threat, the researchers suspect, and responds by revving up inflammation through specialized cells called microglia. Experiments that shut down this process in microglia shortened the duration of the pain.

Many questions remain. Scientists don’t yet know if a similar immune reaction happens in people. Nor is it known whether all opioid-based painkillers would behave like morphine.
Understanding the details of how the process works has important implications for doctors, many of whom may be unaware of opioids’ complex relationship with pain, says internal medicine physician Jonathan Chen of Stanford University School of Medicine. Clarity on how opioids influence pain could change doctors’ prescribing habits and encourage the search for better pain treatments, he says.

Grace points out that the experiments were done in genetically similar rats, and that people may have more varied responses to opioids. That variability might mean that not everyone would be at risk for such long-lasting pain, he says. “But clearly these data suggest that there may be a subset of people who might be in trouble.”

Radiation from the 23 nuclear tests conducted near Bikini Atoll in the 1940s and ’50s has lingered far longer than previously predicted.

Radioactive material such as cesium-137 currently produces, on average, 184 millirems of radiation per year on Bikini Atoll. And some parts of the island hit 639 millirems per year, researchers report online the week of June 6 in the Proceedings of the National Academy of Sciences. Those measurements, made last year, surpass the 100 millirems per year safety standard set by the United States and the Republic of the Marshall Islands, which controls the island.

Scientists had predicted that, by now, radiation levels would have dropped to 16 to 24 millirems per year. But those estimates came from extrapolating from measurements made in the 1970s. The mismatch probably stems from incorrect assumptions about how rapidly radioactive material washes off the island, proposes study coauthor Emlyn Hughes, a physicist at Columbia University.

Whether the higher radiation levels pose a serious health risk to caretakers who live on the island for part of the year depends on how long they stay on the island and whether the local fruit they eat is safe, Hughes says.