Antarctica’s meltdown could spur sea level rise well beyond current predictions. A new simulation of the continent’s thawing ice suggests that Antarctic melting alone will raise global sea levels by about 64 to 114 centimeters by 2100, scientists report in the March 31 Nature.

Adding Antarctic melt to other sources of sea level rise, such as the expansion of warming seawater and melting Greenland ice, the scientists predict that sea levels will rise 1.5 to 2.1 meters by the end of the century. That’s as much as double previous predictions that didn’t incorporate mechanisms that can expedite the Antarctic ice sheet’s collapse, though uncertainties remain, says study coauthor David Pollard, a paleoclimatologist at Penn State.
Predicting future sea level rise requires understanding how the oceans rose in the past. Scientists often glean ancient sea level rise by reconstructing the locations of ancient coastlines. But these coastlines can be a slippery target: Forces such as tectonic activity can cause Earth’s surface to rise and fall, obscuring the effects of past sea level rise. Depending on how much uplift obfuscated ancient sea level records — ranging from no uplift to massive uplift — the new prediction of 21st century sea level rise can differ by 35 centimeters or more.

A separate study also highlights the challenges of factoring changing coastlines into sea level rise predictions. Researchers estimate online April 2 in Geophysical Research Letters that groundwater depletion has caused the coasts of California and India to rebound upward, counteracting sea level rise in those regions by about 0.4 millimeters per year.

“I really would be happier if we had the luxury of doing the research on this without bothering the public until we have 95 percent confidence in an answer,”says Penn State glaciologist Richard Alley, who was not involved in either study. “Any single forecast is notably uncertain, but if we continue warming the world rapidly, the most likely outcome is a major event of large and rapid sea level rise.”

Two warm periods, one about 125,000 years ago and another about 3 million years ago, were particularly useful for Pollard and coauthor Robert DeConto, a geoscientist at the University of Massachusetts Amherst. Those bouts of warming shrank Earth’s ice sheets and boosted sea levels by several meters. Pollard and DeConto used these sea level records to fine-tune a computer simulation of how climate change affects the Antarctic ice sheet. The researchers then applied their calibrated simulation to current climate conditions and projected sea level rise thousands of years into the future.

Assuming that society takes no actions to curb greenhouse gas emissions, the simulation predicts that Antarctic melting will accelerate around 2050 as rising temperatures destabilize several keystone glaciers in West Antarctica. After 2100, Antarctica’s contribution to sea level rise will exceed 4 centimeters a year — more than 10 times the current rate from all sources.
Such severe sea level rise would reshape most of Earth’s coastlines, and the waters would rise even higher as time goes on, Pollard predicts. “Sea levels won’t peak until around 3,000 to 4,000 years from now,”he says. At that point, Antarctica will have raised global sea levels by about 20 meters.

The consequences of this long-term sea level rise will be dire, says Maureen Raymo, a marine geologist at Columbia University’s Lamont-Doherty Earth Observatory in Palisades, N.Y., who was not involved with the work. “I haven’t seen anyone mention the long, slowly unfolding refugee crisis that will only get worse as hundreds of millions [of people] are displaced worldwide,” she says.

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.”

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.”

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.

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.”

SAN DIEGO — The long-standing mystery of the Milky Way’s missing satellite galaxies has a credible culprit, new research suggests. Supernovas, the vigorous explosions of massive stars, might have shoved much of the matter surrounding our galaxy deep into space, preventing a horde of tiny companion galaxies from forming in the first place.

Millions of teeny galaxies should be buzzing around the Milky Way, according to theories about how galaxies evolve, but observations have turned up only a few dozen (SN: 9/19/15, p. 6). And the brightest of those that have been found are lightweights compared with what theorists expect to find. But new computer simulations designed to track the growth of galaxies down to the level of individual stars reveal the critical role that supernovas might play in resolving these conundrums.
Philip Hopkins, an astrophysicist at Caltech, presented the results June 13 during a news briefing at a meeting of the American Astronomical Society.

“Galaxies don’t just form stars and sit there,” Hopkins said. “If you [add] up all the energy that supernovae emitted during a galaxy’s lifetime, it’s greater than the gravitational energy holding the galaxy together. You cannot ignore it.”

Simulations are typically limited by computing power, and efforts to simulate galaxy evolution have to brush over some details. For instance, rather than capture everything that’s going on in a galaxy, simulations slap on the additive effects of supernovas in an ad hoc fashion. These limitations don’t fully capture all the physics of stellar winds and supernova shocks that ripple through a galaxy.

Hopkins’ simulations grow a galaxy organically within a computer, tracing the evolution of a system such as the Milky Way over 13 billion years. Within a massive virtual blob of dark matter — the elusive substance thought to bind galaxies together — gas collects and fragments into stellar nurseries. Stars are born and die in this digital universe. A volley of life-ending explosions from the most massive of these stars lead to a turbulent galactic history, Hopkins finds.

“As these stars form rapidly in the early universe, they also live briefly and explode and die violently, ejecting material far from the galaxy,” he said. “They’re not just getting rid of gas.” They’re stirring up the dark matter as well, preventing a multitude of satellite galaxies from forming, and whittling away at those few that survive. “It’s not until quite late times … that [the galaxy] settles down and forms what we would call a recognizable galaxy today,” Hopkins said.
The idea that stellar tantrums could chip away at the gas and dark matter around a galaxy is not new, says Janice Lee, an astronomer at the Space Telescope Science Institute in Baltimore. But Hopkins’ simulations bring a lot more detail to that story and show that it’s a plausible reason for our galaxy’s satellite shortfall.

Before declaring that the mystery of the missing satellite galaxies is solved, however, astronomers need to run a few more checks against reality, says Lee. There are still assumptions in the calculations about how energy from dying stars interacts with interstellar gas, for example. The precise details of that interaction can affect how many stellar runts versus behemoths form in star clusters.

NASA’s James Webb Space Telescope, scheduled to launch in 2018, could probe star clusters in several relatively nearby galaxies, she says. Those observations could be compared with virtual clusters that appear in the simulations to see how close they match the real universe.

Even Amelia Earhart couldn’t compete with the great frigate bird. She flew nonstop across the United States for 19 hours in 1932; the frigate bird can stay aloft up to two months without landing, a new study finds. The seabird saves energy on transoceanic treks by capitalizing on the large-scale movement patterns of the atmosphere, researchers report in the July 1 Science. By hitching a ride on favorable winds, the bird can spend more time soaring and less time flapping its wings.

“Frigate birds are really an anomaly,” says Scott Shaffer, an ecologist at San Jose State University in California who wasn’t involved in the study. The large seabird spends much of its life over the open ocean. Both juvenile and adult birds undertake nonstop flights lasting weeks or months, the scientists found. Frigate birds can’t land in the water to catch a meal or take a break because their feathers aren’t waterproof, so scientists weren’t sure how the birds made such extreme journeys.

Researchers attached tiny accelerometers, GPS trackers and heart rate monitors to great frigate birds flying from a tiny island near Madagascar. By pooling data collected over several years, the team re-created what the birds were doing minute-by-minute over long flights — everything from how often the birds flapped their wings to when they dived for food.
The birds fly more than 400 kilometers, about equivalent to the distance from Boston to Philadelphia, every day. They don’t even stop to refuel, instead scooping up fish while still in flight.

And when frigate birds do take a break, it’s a quick stopover.

“When they land on a small island, you’d expect they’d stay there for several days. But in fact, they just stay there for a couple hours,” says Henri Weimerskirch, a biologist at the French National Center for Scientific Research in Villiers-en-Bois who led the study. “Even the young birds stay in flight almost continually for more than a year.”

Frigate birds need to be energy Scrooges to fly that far. To minimize wing-flapping time, they seek out routes upward-moving air currents that help them glide and soar over the water. For instance, the birds skirt the edge of the doldrums, a windless region near the equator. On either side of the region, consistent winds make for favorable flying conditions. Frigate birds ride a thermal roller coaster underneath the bank of fluffy cumulus clouds frequently found there, soaring up to altitudes of 600 meters.

Airplanes tend to avoid flying through cumulus clouds because they cause turbulence. So the researchers were surprised to find that frigate birds sometimes use the rising air inside the clouds to get an extra elevation boost — up to nearly 4,000 meters. The extra height means the birds have more time to gradually glide downward before finding a new updraft. That’s an advantage if the clouds (and the helpful air movement patterns they create) are scarce.

It’s not yet clear how frigate birds manage to sleep while on the wing. Weimerskirch suggests they might nap in several-minute bursts while ascending on thermals.

“To me, the most fascinating thing was how incredibly far these frigate birds go in a single flight, and how closely tied those flight patterns are to the long-term average atmospheric condition,” says Curtis Deutsch, an oceanographer at the University of Washington in Seattle. As these atmospheric patterns shift with climate change, frigate birds might change their path, too.

Aging happens to each of us, everywhere, all the time. It is so ever-present and slow that we tend to take little notice of it. Until we do. Those small losses in function and health eventually accumulate into life-changers.

Despite its constancy in our lives, aging remains mysterious on a fundamental level. Scientists still struggle to fully explain its root causes and its myriad effects. Even as discoveries pile up (SN: 12/26/15, p. 20), a clear picture has yet to emerge. Debates continue about whether individual life spans and the problems associated with aging are programmed into our bodies, like ticking time bombs we carry from birth. Others see the process as a buildup of tiny failures, a chaotic and runaway deterioration that steals vim and vigor, if not health and life itself. There is no unified theory of aging. That means that there is no one way to stop it. As longtime aging researcher Caleb Finch put it in an interview with Science News: Aging is still a black box.
The issue is an urgent one. The globe’s population has never been older. According to the U.S. Census Bureau’s 2015 An Aging World report, by 2020 the number of people 65 and older worldwide will outnumber children 5 and under for the first time in history. Seniors will make up 22.1 percent of the U.S. population in 2050, and nearly 17 percent globally (a whopping 1.6 billion people), the demographers predict. Worldwide, the 80-and-above crowd will grow from 126 million to 447 million. It’s a population sea change that will have ripple effects on culture, economics, medicine and society.

Scientists working at the frontiers of the field do agree that there are probably many ways to slow aging, Tina Hesman Saey reports in this special issue. Saey sums up current thinking on the actors of aging, as well as a number of intriguing approaches that might well tame aging’s effects. The goal, most agree, is not to find a fountain of youth but the keys to prolonging health.

It turns out that healthy aging in people does occur naturally. It is, however, in the words of Ali Torkamani, “an extremely rare phenotype.” Torkamani leads a genetic study of people 80 and older who are living free of chronic disease, described by Saey in her story. He and his team failed to find a single set of genes that protect these “wellderly.” Instead, the people studied carry a plethora of different genetic variants. They do share a lower risk of heart disease and Alzheimer’s. And, he says, the data hint that gene variants linked to key cognitive areas may be at play, leading him to ask: “Is cognitive health just one of the components of healthy aging? Or is there something about having a healthy brain that protects against other signs of aging?”

Exactly what happens in the brain as we age is a question Laura Sanders takes up in “The mature mind.” An intriguing idea is that the brain begins to lose the specialization that makes it so efficient in its prime, she reports. Further afield, Susan Milius considers a hydra and a weed, examining what these outliers of aging can tell us about how aging evolved and how flexible it truly is. Her answer: Very. The sheer diversity in life cycles and declines gives credence to arguments that while death may come for all of us, a robust old age could well be in the cards for more of us.

Those little piles of dirt that ant colonies leave on the ground are an indication that ants are busy underground. And they’re moving more soil and sediment than you might think. A new study finds that, over a hectare, colonies of Trachymyrmex septentrionalis fungus-gardening ants in Florida can move some 800 kilograms aboveground and another 200 kilograms below in a year.

The question of how much soil and sand ants can move originated not with entomologists but with geologists and archaeologists. These scientists use a technique called optically stimulated luminescence, or OSL, to date layers of sediment. When minerals such as quartz are exposed to the sun, they suck up and store energy. Scientists can use the amount of energy in buried minerals to determine when they last sat on the surface, taking in the sun.

But ants might muck this up. To find out, a group of geologists and archaeologists reached out to Walter Tschinkel, an entomologist at Florida State University. Figuring out how much sand and soil ants dig up and deposit on the surface — called biomantling — is relatively easy, especially if the color of the soil they’re digging up is different from that found on the ground. But tracking movement underground, or bioturbation, is a bit more complicated.
Tschinkel and his former student Jon Seal, now an ecologist at the University of Texas at Tyler, turned to an area of the Apalachicola National Forest in Florida dubbed “Ant Heaven” for its abundant and diverse collection of ants. Tschinkel has worked there since the 1970s, and for the last six years, he has been monitoring some 450 colonies of harvester ants, which bring up plenty of sandy soil from underground. But he was also curious about the fungus-gardening ants.

Tschinkel and Seal had already shown that the fungus-gardening ant “is extremely abundant, that it moves a very large amount of soil, and that as the summer warms up, it digs a deeper chamber and deposits that soil in higher chambers without exposing it to light,” Tschinkel says. “In other words, it appeared to do a very large amount of soil mixing of the type [that had been] described in harvester ants.”

No one had ever quantified an ant colony’s subterranean digging before. Tschinkel and Seal started by digging 10 holes a meter deep and filling them with layers of native sand mixed with various colors of art sand — pink, blue, purple or yellow, green and orange, with plain forest sand at the top. Each hole was then topped with a cage, and an ant colony was transferred with the fungus that the ants cultivate like a crop. Throughout the experiment, the researchers collected sand that the ants deposited on the surface and provided the colonies with food for their fungus, including leaves, small flowers and oatmeal. Seven months later, Tschinkel and Seal carefully excavated the nine surviving ant colonies and quantified grains of sand moved from one sand layer to another. The team reports its findings July 8 in PLOS ONE.

By the end of the study, each ant colony had deposited an average of 758 grams of sand on the surface and moved another 153 grams between one colored layer and another underground, mostly upward. The ants dug chambers to farm their fungus, and they sometimes filled them up with sand from deeper layers as they dug new chambers in areas with temperature and humidity best suited for cultivation.
With more than a thousand nests per hectare, the ants may be moving about a metric ton of sand each year, covering the surface with 6 centimeters of soil over the course of a millennium, the researchers calculated.

All of this mixing and moving could prove a challenge for geologists and archaeologists relying on OSL. “When ants deposit sand from deeper levels at higher levels (or the reverse), they are mixing sand with different light-emitting capacity, and therefore with different measured ages,” Tschinkel notes. “People who use OSL need to know how much such mixing occurs, and then devise ways of dealing with it.” Now that scientists know that ants could be a problem, they should be able to develop ways to work around the little insects.