Light is two-faced: Sometimes it behaves like a wave, sometimes like a particle. Now, scientists have shown that light’s shifty disposition persists even after trekking thousands of kilometers into space and back again, researchers report October 25 in Science Advances.

Depending on how light is measured, it can either be particle-like, lighting up a camera pixel, for example, or wavelike, interfering with other waves like ripples on the surface of water. It’s one of the many oddities of quantum mechanics. Before light is measured, quantum theory suggests, it is in a particle-wave limbo, neither purely one nor the other.

Physicists have tested this idea by performing “delayed-choice” experiments in the lab, in which researchers send light into a device and randomly choose whether or not to flip a switch that seems to retroactively change the light’s behavior (SN: 5/30/15, p. 9). In one configuration, the light travels down two paths at once and acts like a wave, interfering with itself. In the other, the light acts like a particle, taking a single path. That choice of configuration can be made even after the light has already traveled through the device but before being measured, revealing that light remains in quantum limbo until it is finally detected.

For the first time, physicist Paolo Villoresi of the University of Padua in Italy and colleagues took the technique into space. The researchers sent light through a lab apparatus and up to a satellite equipped with reflectors, which bounced the light back down to the device. While the light was in transit, the scientists used a random number generator to determine whether to configure their apparatus so that the light would behave like a particle or a wave. The light performed as expected, verifying that quantum mechanics holds even over the round trip into space and back.

Remote Bouvet Island, a tiny, glacier-smothered landmass in the South Atlantic rimmed by 500-meter-tall cliffs, has a notable distinction: It’s the only known spot on Earth, scientists say, that has zero invasive species. Every other place, and every person, on the planet is at least indirectly affected by one or more species that has been transported — either intentionally or inadvertently — to new lands from the ecosystems in which the species evolved.
In The Aliens Among Us, biologist and science journalist Leslie Anthony chronicles the detrimental effects of invasive species, as well as how these organisms spread and how they can be fought. In the United States, such interlopers — everything from zebra mussels in the Great Lakes to Burmese pythons in the Everglades — damage crops, infrastructure or otherwise cost taxpayers about $145 billion annually.

Invasive species, Anthony writes, are “children born of globalization and consumerism.” Their numbers increase as international trade widens and accelerates. Some species surreptitiously hitch a ride to their new homes on human transport: Think seeds and burrs on hikers’ clothing, or fish in ballast water of cargo ships. Others have been deliberately released, like earthworms or baitfish set loose by fishermen, or exotic lizards and snakes set free by careless pet owners. Rats, the world’s foremost invasive species, have traveled the world with explorers and traders; so have tropical fire ants, which genetic studies suggest have hitchhiked from southwestern Mexico to Asia and beyond starting in the 16th century in soil used as ballast in Spanish ships.

The Aliens Among Us is a thoroughly engaging book that draws from Anthony’s fieldwork and interviews with scientists, community volunteers, government researchers and policy makers. These groups are struggling to intercept species before they establish a beachhead on new shores, as well as eradicate those that have already gained a foothold. Discussion of people fighting the spread of Zika virus and other exotic diseases — big threats despite their minuscule size — makes the book especially timely.
Some battles against invasives seem almost doomed to fail. Besides the inexorable increase of trade, the inescapable specter of climate change continues to open new vistas for species to colonize (SN: 12/24/16, p. 23).

An Alzheimer’s-related protein can move from the blood to the brain and accumulate there, experiments on mice show for the first time.

The results, published online October 31 in Molecular Psychiatry, suggest that the protein amyloid-beta outside the brain may contribute to the Alzheimer’s disease inside it, says Mathias Jucker, a neurobiologist at the University of Tübingen in Germany. This more expansive view of the disease may lead scientists to develop treatments that target parts of the body that are easier than the brain to access.

The experiments don’t suggest that people could contract Alzheimer’s from another person’s blood. “The bottom line is that this study is thought-provoking but shouldn’t cause alarm,” says neurologist John Collinge of University College London. “There really isn’t any evidence that you can transmit Alzheimer’s disease by blood transfusion.”

But researchers wondered whether, over time, A-beta might build up in the brain by moving there from the blood, where it’s normally found in small quantities. Earlier animal studies have shown that A-beta can move into the brain if it’s injected into the bloodstream, but scientists didn’t know whether A-beta from the blood can be plentiful enough to form plaques in the brain.
To test this, researchers used a form of extreme blood-sharing in the experiment. Six pairs of mice — with one mouse engineered to produce gobs of human A-beta and one normal — were surgically joined for a year, causing blood mingling that’s far more extensive than that of a blood transfusion. After a year, the brains of the mice carrying the mutations were full of A-beta plaques, as expected. But these plaques were also inside the brains of the normal mice in the joined pairs.
In those normal mice, A-beta levels weren’t as high as they were in the mutated mice, but the fact that they existed was notable, says study coauthor Weihong Song of the University of British Columbia in Vancouver. Unjoined control mice without the mutation showed no A-beta accumulation.

The brains of the joined mice also showed other signs of deterioration. The researchers observed inflammation, tiny areas of bleeding and a dangerous type of the protein tau in the brains of normal mice that had been exposed to blood full of A-beta. In people, Alzheimer’s is often marked by both A-beta plaques and tangles of tau.
The results don’t mean that Alzheimer’s is predominantly caused by factors in the blood. “We still think of Alzheimer’s as a brain disorder,” Song says. But factors in the blood, in some cases, might have the power to nudge the disease along, the results suggest.

A-beta is made by cells in the brain, but also by blood platelets, skin cells, muscles and other parts of the body. Normally, “there is a balance between A-beta inside and outside the brain,” Song says. But when this balance is thrown off, such as when the body is chock-full of the protein, or when the blood-brain barrier — the blockade that keeps potential dangers out of the brain — deteriorates with age, the brain may get an extra dose, Song proposes. By tweaking this balance, it’s possible that drugs or therapies that reduce A-beta in the body might help slow or prevent Alzheimer’s disease.

Evidence has been accumulating that A-beta can behave as a prion, a misfolded protein that can incite normally folded proteins to go rogue (SN: 10/17/15, p. 12). Song says that the experiments don’t address whether A-beta from the blood can behave as a prion and prompt already existing A-beta in the brain to form plaques. The normal mice’s brain plaques seemed to be built from human A-beta protein, and the only source of that was the blood of the mutated partner mouse.

DENVER — An invasive beetle has unexpected — and potentially troublesome — tastes in trees. Now two new studies are clarifying the insects’ dining habits, researchers reported at the annual Entomological Society of America meeting.

Metallic-green Asian beetles called emerald ash borers (Agrilus planipennis) have devastated wide swaths of forest in North America. For years, researchers believed that only various kinds of ash trees were at risk. But in 2014, researchers noticed infestations in white fringe trees (Chionanthus virginicus), a multi-stemmed tree native to the southeastern United States with flowers like a cluster of streamers. And after looking at trees related to ashes, researchers reported lab evidence in 2017 that the beetle larvae can grow to adulthood in the Manzanilla variety of commercial olive trees (Olea europaea). Whether the beetle poses a serious or slight risk to the overlooked targets is still being researched.
Emerald ash borers, accidentally imported probably in wood packing materials during the 1980s or 1990s, have killed hundreds of millions of ash trees in 31 states and two Canadian provinces. Larvae chewing tunnels through trees’ internal nutrient channels can doom a tree. It’s “a major, major pest,” says entomologist Jackie Hoban of the University of Maryland in College Park. “It’s so sad — you see entire patches of trees just dead.”
Lab tests of the recently discovered threat to olive trees show that adult borers don’t eat as much of these leaves as they do of ash leaves, forest entomologist Donnie Peterson of Wright State University in Dayton, Ohio, reported November 6 at the meeting. These adults also die prematurely if those leaves are the only food option. But adult borers’ distaste for this variety of olive doesn’t yet mean the trees are safe. Female beetles feeding on ash trees might, in theory, fly to a nearby olive to lay eggs.
To compare beetles’ preferences for laying eggs on olive versus ash will take a larger study. But Peterson’s first results are a little worrying. When he put olives and green ashes in a known infested zone, one of the few eggs he found was on an olive tree.

Free-flying beetles do lay eggs on white fringe trees, attacks that long went unreported. But the trees may not be as healthful a feeding site for beetle larvae as ash trees. In indoor tests, fewer larvae survived to their later stages on the fringe trees compared with larvae on white ashes, David Olson of the University of Kentucky in Lexington reported November 5.
Olson works on whether biocontrol strategies developed for ash trees might also work on white fringe trees. So far, it doesn’t look encouraging. In outdoor tests, the most successful of four tiny parasitic wasp species released in North America did what they’re supposed to: Tetrastichus planipennisi doomed some beetle larvae in ash trees by using the youngsters as living food for baby wasps. Beetle larvae in nearby fringe trees, however, escaped wasp attacks.

Even if fringe trees don’t turn out to suffer massive damage, they could still present a very real threat if nurseries shipping trees from infested areas accidentally transport beetle larvae, too, Hoban says. Besides spreading the pests, that could make it tougher for ashes to weather existing invasions. The hope for ashes is that wasps will help keep beetles in check, and some exceptional ash trees will prove resistant enough to rebuild some sort of population.

Editor’s note: This story was updated November 23 to change the photo at the top of the story. The original photo was not an emerald ash borer.

Self-driving vehicles passed a major milestone in November when Waymo’s minivans hit the streets of Phoenix without backup human drivers — reportedly making them the first fleet of fully autonomous cars on public roadways. Over the next few months, people will get a chance to take these streetwise vehicles for a free spin as the company tries to drum up excitement — and a customer base — for its launch of a driverless taxi service.

But even as these cars are ditching human supervisors, many people doubt the safety of machine motorists. A whopping 85 percent of baby boomers and even 73 percent of millennials confess to being afraid to ride in self-driving cars, according to a recent AAA survey. And while Waymo claims its vehicles are designed to be the world’s most experienced drivers — based on road tests as well as clocking millions of virtual miles — there’s still no consensus among experts about how safe is “safe enough” when it comes to street-smart cars.
It’s especially difficult to tell whether self-driving cars have earned their licenses when scientists are still writing the driver’s test.

Besides the sheer convenience of being able to take your hands off the wheel, the major appeal of self-driving cars is safer roadways. After all, mechanical chauffeurs can’t get drunk or distracted — factors involved in 29 and 10 percent of fatal accidents, respectively. But the only surefire way to evaluate autonomous cars’ reliability is test-driving them in real traffic, explains Nidhi Kalra, an information scientist at the RAND Corporation in San Francisco. “I think a lot of people were thinking, ‘Oh, we’ll just wait until the companies do enough test-driving,’” she says. “You could wait until the next millennium until that happens.”

In a 2016 study, Kalra and a colleague showed that self-driving cars would have to trek hundreds of millions or perhaps billions of miles to demonstrate with comfortable certainty that they caused fewer fatalities than the average person (about 1.1 per 100 million miles driven). Based on the current number of self-driving cars, that task could take decades or centuries to complete.

Tech developers hardly have that kind of time, so companies like Waymo assess their vehicles’ safety by pairing real driving time with practice on a private track and millions of miles a day in computer simulations.
Still, simulations can’t replace the value of actual road experience, says Philip Koopman, an electrical and computer engineer at Carnegie Mellon University in Pittsburgh. “What about the scenarios they didn’t know [to simulate]?” he says. “Weird, weird, weird stuff happens out on the roadways.”

Since current self-driving safety assurances aren’t exactly airtight, Koopman argues that self-driving cars should be held to a way higher standard than human drivers — say, 10 times safer than the average human — before they’re given the green light. That would provide enough wiggle room in the margin of error to assume that the driverless car actually is safer, Koopman reasons.

But getting to that point could take a long time, and miss the opportunity to save many lives, Kalra says. She’s confident because her team forecast a future — actually lots of different futures — where self-driving cars hit the road when they were 10, 75 or 90 percent safer than the average human driver. At 10 percent, fatalities drop to one death per 100 million miles. Maybe that doesn’t seem like a lot, but with those cars much closer to being ready to roll, some 500,000 lives could be saved between 2020 and 2050, the team forecasts, compared with the imagined futures where people hold out for way higher safety standards.

But just aiming for 10 percent safer doesn’t provide much margin for error, Koopman argues. “You’re cutting it pretty close.”

And a lower safety standard could mean more accidents at first — and a public backlash, says Azim Shariff, a psychologist at the University of California, Irvine. People may be less inclined to accept mistakes made by machines than humans, and research has shown that people are more risk-averse when it comes to risks that they can’t control.

“What happens when a 4-year-old in the back of a car that’s operated by her mother gets killed by an autonomous car?” Shariff asks.

Success depends on buy-in. “So public opinion is really going to matter,” Shariff says.

Right now, most Americans may not be lining up to hop aboard fully autonomous cars. But “once people start knowing people who have been in them and lived to tell the tale, so to speak, I think it will change quickly,” says David Groves, a policy analyst at the RAND Corporation in Santa Monica, Calif.

Kalra also suspects that people will fear autonomous cars less when the National Highway Traffic Safety Administration establishes a self-driving car safety rating, like its crash test ratings for traditional cars. That kind of rating system “will probably come after the technology is on the road, just as it did for regular cars,” she says. “We didn’t have a safety rating system when the Model T came out. It sounds like it’s the cart before the horse to have cars before safety ratings, but that’s often how it happens.”

Liquid methane and ethane flow through a subterranean plumbing system on Titan, which drains lakes and connects seas. That’s one of the first scientific results from the latest, most complete map of the Saturnian moon’s topography.

Planetary scientist Paul Corlies of Cornell University and colleagues released the map — based on all the data from NASA’s Cassini mission, which ended in September (SN Online: 9/15/17) — in Geophysical Research Letters on December 2.

Titan, Saturn’s largest moon, hosts seas, lakes, clouds and rain — all composed of hydrocarbons such as methane and ethane instead of water. The elevations of seas and mountains across 9 percent of Titan’s surface were directly recorded by Cassini as it flew past Titan over 13 years. The researchers had to infer altitudes for the rest of the globe.
Compared with previous maps, the new one adds mountains in the southern hemisphere and shows that Titan is more of a squashed sphere than previously thought. Researchers can now use the map to build computer simulations of everything from Titan’s atmosphere to its interior structure. “Within hours of the paper actually being available online, people we’ve never collaborated with started contacting [Corlies] to ask how to get the data,” says study coauthor Alexander Hayes, a planetary scientist also at Cornell.

But the first study to use the map, also published December 2 in Geophysical Research Letters, is research that Hayes has been working on for a decade. The work shows that Titan has a sea level as well as the hydrocarbon equivalent of groundwater — pores in subsurface rock are filled with liquid that can seep into and between the lakes and seas.

“Looking for actual evidence that the lakes could be communicating was a fundamental question from Cassini,” Hayes says. “This is the final paper that gives the best evidence that it exists.”
His team analyzed the altitudes of Titan’s liquid bodies and found that the three largest seas — Ligeia Mare, Kraken Mare and Punga Mare— are all about the same elevation, just like Earth’s oceans. In other words, Titan has a sea level, Hayes says. To maintain that uniformity, the seas must be connected through channels that could be above or below ground.
The moon’s poles are dotted with small lakes and depressions that are shaped like lakes but contain no liquid. Hayes and colleagues found that the liquid levels of the filled lakes are above sea level, so they are potentially isolated from the seas. If the lakes and seas were connected, the lakes’ liquid could drain into the seas, and the liquids’ surface heights would all match — or the lakes would be empty.

The floors of the dry lake beds are at a higher elevation still. Hayes thinks that may indicate that their liquid flowed into the filled polar lakes. Those hydrological connections probably occur underground because there do not appear to be enough connections on the surface. If scientists could dig deeper into a dry lake, he predicts, they would hit liquid at the level of the filled lakes’ surfaces.

A remaining mystery is how the small polar lakes formed. Both the dry and filled lakes have steep walls, flat floors and rims that rise above the surrounding ground — features that lakes on Earth tend not to have. “They look like you went around Titan’s polar region with a cookie cutter and cut out little shapes,” Hayes says.

His best guess is that the lakes are sinkholes (SN: 1/25/14, p. 14), which collapsed when the bedrock material was dissolved out from under them. If true, then Titan’s poles may be covered with a thick layer of a kind of solid that hydrocarbons can dissolve, like acetylene. But sinkholes shouldn’t have raised rims, so that theory doesn’t explain everything.

The researchers hope other investigators will have some new ideas. “We’re just saying, these are all the observations. Please tell us how they fit together,” Hayes says.

Planetary scientist Jani Radebaugh of Brigham Young University in Provo, Utah, thinks the odd lakes could be the remnants of icy volcanoes. Explosive eruptions could create the raised rims, and the depressions could be empty magma chambers that collapsed. “I think we should consider it,” she says.

But she agrees that Hayes’ groundwater theory makes sense. Seeing hydrological systems on Titan that are similar to Earth’s “is satisfying, and helps to validate that what we understand from the Earth should work on other bodies, regardless of what the liquid is made of,” she says.

A new antibacterial ointment could help take down drug-resistant bacteria.

In human skin samples and mice, the medicine completely cleared wounds of MRSA, the strain of Staphylococcus aureus that is resistant to methicillin and other antibiotics, and antibiotic-resistant Acinetobacter baumannii. Both microbes are known to cause serious infections in hospital patients. Researchers in the Netherlands created the gel’s key ingredient, a chain of amino acids called SAAP-148, by improving on a bacteria-fighting peptide found in humans.
The synthetic peptide prevents pathogens from forming biofilms — colonies of microbes enveloped in a protective slime that shields them from antibiotics, the researchers report online January 10 in Science Translational Medicine. Bacteria living in a biofilm can be 10 to 1,000 times as hard to kill as their free-floating counterparts. SAAP-148 also wiped out microbes that hunker down in a dormant, drug-tolerant state during an antibiotic assault, then lead the bacterial resurgence after treatment ends.

“This peptide could provide a much-needed boost to our arsenal of antibiotics,” says David Weiss, a microbiologist at Emory University School of Medicine in Atlanta, who wasn’t involved in the work.

Unlike S. aureus and A. baumannii bacteria exposed to conventional antibiotics in the study, the microbes didn’t develop strong resistance to SAAP-148 after at least a couple weeks’ exposure to the compound. These results are “quite promising,” says Weiss, who would like to see the peptide tested against other bacteria as well. Studies of the gel in humans will begin this year.

Death: A Graveside Companion makes for an unusual coffee-table book, with its coppery etched Grim Reaper on the cover. Yet you may be surprised by how much fun it is to pore through the book’s lavish artwork of skulls, cadavers and fanciful imaginings of the afterlife.

There is, after all, a reason for the term “morbid curiosity.” It’s only natural for people to try to understand and come to terms with their inevitable demise, and as the book reveals, it is only in modern Western society that the topic of death has become so taboo. Even as recently as Victorian times, the book notes, the dead were laid out in the family parlor, their hair cut off and twisted to make decorative mementos to hang on the wall.
As a founder of New York City’s now-closed Morbid Anatomy Museum, Joanna Ebenstein has set out to help change modern attitudes, by giving us permission to let our morbid curiosity loose. “It is my hope that this book might act as a gesture towards redeeming death, to invite it back into our world in some small way,” she writes. “It is precisely by keeping death close at hand and coming to terms with its inevitability that we are able to lead full rich lives.”
She brings together 1,000 images of historical artwork, illustrations and artifacts showcasing humankind’s ongoing quest to imagine and find meaning in death, along with 19 essays by a diverse set of writers, art experts and scientific thinkers. The writings cover spiritual and symbolic aspects of death, such as the origins of Mexico’s Day of the Dead, and the surprising variety of death-themed amusements over the years. An early Coney Island attraction, for instance, re-created the experience of being buried alive. Some essays delve into scientific history, such as miniature crime scenes used in forensic science and the history of cadavers in the study of anatomy.
While the essays are illuminating, the illustrations and photographs, along with informative captions, provide most of the book’s substantial heft, as well as its heart. Only by browsing through still life paintings called vanitas, popular in the 16th and 17th centuries, for instance, will you truly grasp what these symbolic masterpieces are meant to convey: the transience of beauty and earthly pursuits.
If I have any quibble with this compendium, it’s that the essays (but thankfully not captions) are printed in sepia tones that make them hard to read without good lighting. But given the subject, this book may be best read while sitting next to a sunny window anyway.

Brain scientists have filmed a first-of-a-kind birth video. It reveals specialized cells in the brains of mice dividing to create newborn nerve cells.

The images, published in the Feb. 9 Science, show intricacies of how certain parts of the adult mouse brain can churn out new nerve cells. These details may help lead to a deeper understanding of the role of this nerve cell renewal in such processes as memory.

Deep in the brains of mice, a memory-related structure called the hippocampus is known to be flush with new nerve cells. But because this buried neural real estate is hard to study, the circumstances of these births weren’t clear.
Using living mice, Sebastian Jessberger, a neuroscientist at the University of Zurich, and colleagues removed the outer layers of brain tissue that obscure the hippocampus. The scientists marked 63 cells called radial stem cells, which can divide to create new nerve cells. Researchers then watched these stem cells for up to two months, taking pictures every 12 or 24 hours.
During that time, 42 of these stem cells underwent a spurt of division, churning out two kinds of cells: intermediate cells that would go on to produce nerve cells as well as mature nerve cells themselves. Once this burst of activity ended, the radial stem cells disappeared by dividing themselves into mature nerve cells that could no longer split.

Many of these newly formed nerve cells had brief lives, dying either within the first four days, or 13 to 18 days after birth. It’s not clear what kills these newborn cells. Interspersed among the dying cells, survivors go on to knit themselves into the brain.

PORTLAND, Ore. — Penguins preserve records of Antarctic environmental change. The birds’ feathers and eggshells contain the chemical fingerprints of variations in diet, food web structure and even climate, researchers reported February 12 at the American Geophysical Union’s 2018 Ocean Sciences Meeting.

The Antarctic environment has changed dramatically in recent decades. Overfishing has led to a decline in krill, small swimming crustaceans that are a key food source for birds, whales, fish and penguins in the Southern Ocean. Climate change is altering wind directions, creating open water regions in the sea ice that become hot spots for life.
These changes have cascading effects on food webs and on the cycling of nutrients. “Penguins are excellent bioarchives of this change,” says Kelton McMahon, an oceanic ecogeochemist at the University of Rhode Island in Kingston.

Penguins are at the heart of the Antarctic food web, and their tissues are known to capture details about what they’ve eaten. Different food sources contain different proportions of carbon and nitrogen isotopes, forms of the elements with different numbers of neutrons. For example, food sources such as krill and fish have different amounts of nitrogen-15 relative to nitrogen-14. The tissues of penguins, such as feathers and eggshells, preserve these proportions.
Previous studies had already noted a large shift in isotopic values in penguin tissues in the last 80 years, but those studies couldn’t distinguish between shifts in the penguins’ diet versus climate-related shifts in the isotopic values of the microscopic creatures at the very bottom of the food web. So McMahon and his colleagues created a tool to make this distinction — and ultimately to track Antarctic environmental changes through time.
The team focused on the isotopic values of individual amino acids, the building blocks of proteins. Those values reveal “a lot about the biochemistry happening inside the body,” McMahon says. Some of these values are significantly altered as food is digested and incorporated into an animal’s body; others are little changed.

To understand what the wild penguins had been eating through time, the team first developed a set of “chemical fingerprints” for the isotopic values of a dozen different amino acids by mapping how the values found in Atlantic herring, a dietary staple, changed in the penguins’ bodies after digestion. The researchers acquired these data through a controlled feeding study in collaboration with the Omaha Henry Doorly Zoo and Aquarium in Nebraska that monitored precisely what, when and how much a population of Gentoo penguins ate. Comparing the chemical fingerprints with wild Gentoo penguin tissues revealed what the wild penguins must have eaten in the past.

Over the past 80 years, the penguins have shifted from eating mostly fish to eating primarily krill and then back to fish, the team reported. There is probably a straightforward historical explanation, McMahon said: In the late 1800s to the mid-1900s, whalers extensively hunted marine mammals that tend to dine on krill. Penguins likely took advantage of the resulting krill surplus. But from the 1970s to 1990s, krill harvesting ramped up, and penguins shifted back to a fish-dominated diet.

But there’s more to the story. Certain amino acids in the penguins’ food are known to pass through the body with their isotopic values essentially unchanged. In fact, the isotopes in those amino acids are thought to reflect the original isotopic values of the creatures at the very base of the Antarctic food web: phytoplankton floating in the Southern Ocean. Because climate drives the isotopic values of those phytoplankton, the isotopes in those amino acids are a record of climate change.

In the case of nitrogen, higher nitrogen-15 values relative to nitrogen-14 in phytoplankton are likely linked to more open water spaces within the sea ice, McMahon said. Such open spaces, called polynyas, have appeared in recent decades around Antarctica due to changes in wind directions linked to climate change.

This study highlights the power of this amino acid isotope technique to track environmental change through animal tissues, says Seth Newsome, an animal ecologist at the University of New Mexico in Albuquerque who was not involved in the study. The technique is becoming popular because it can detect both diet and baseline changes in the food web from the same tissue, he says.

“This 80-year record is just part of a much broader record of change,” McMahon said. The team plans next to look further back in time. Excavations have revealed penguin eggshells as old as 10,000 years that have a story to tell.