Monday, April 13, 2020

The Rich Meals That Keep Wild Animals on the Menu

Samoa’s population of “little dodos” is dwindling down to nothing, but the appetites of wealthy people keep putting these rare birds at risk.


Melanie Lambrick

Story by J. B. MacKinnon

MARCH 19, 2020 SCIENCE


The biggest bird-hunting day of the year in the island nation of Samoa, it turns out, is not a great day to start searching for one of the world’s rarest birds. It is the eve of White Sunday, a national holiday during which many wild birds are eaten as a favorite traditional food, and 12-gauge shotguns have been ringing out in the forests for days. Even the most common birds are in hiding.

I have joined Gianluca Serra, an Italian ecologist and conservationist who specializes in creatures at the furthest edge of extinction, on a week-long quest for a bird that probably numbers no more than 200. We begin on an airy jungle ridge above a village called Uafato, in a hut designed to conceal us in shadows. Uafato is remote by the standards of Upolu, the more heavily populated of Samoa’s two main islands, and it has turned its communal forest into a no-hunting zone. The birds don’t appear to be aware of this fact. Apart from the ocean winds, which periodically drag in a squall so heavy that it triggers instant symptoms of the common cold, the landscape is remarkably still and silent.

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I would like to tell you the name of the bird we are pursuing, but even that is not easy. In Samoan, it is called either manumea (which can mean “red bird” or “precious bird”) or manuma (“shy bird”). The first scientific report on the species was published in 1845, and the bird soon became known to English speakers as the tooth-billed pigeon, because its lower bill features bizarre sawlike serrations. Early naturalists also tossed around names such as “dodo pigeon” and “dodlet,” because it resembles a miniature version of the dodo, that famously flightless bird driven extinct in the 1600s. Because genetic testing has now shown that the tooth-billed pigeon really is related to the dodo, and because it, too, may be facing extinction, some are again calling it the “little dodo.”

Let us agree, here, to call it the manumea. By any name, it is a dark blue-green and chestnut pigeon, large enough to be mistaken for a chicken, with a hooked, outsize, sunset-colored beak, as though it had ambitions of becoming a parrot. It lives only in Samoa, where it is the national bird, found on the nation’s currency and in murals throughout the capital city of Apia. Hardly any Samoans have seen the living bird.

Ironically, on those rare occasions when a manumea reveals itself, the bird has presence. Since the 19th century, observers have described it as beautiful, dignified, special. Serra has had one clear sighting and sketched his impression immediately afterward. His drawing shows an electric-blue phantasm on the wing, more like an angel or a pegasus than any earthly being. He saw it from the same hiding spot we are using above Uafato.

After five and a half hours, we are still, with apologies to Samuel Beckett, waiting for dodo. “It’s a ghost species,” says Serra, whose swept-back silver hair and perpetually sunburned face give him the look of a European consul gone tropical. “How can we conserve something we can’t see?”

Giving up for the day, we descend to Uafato, whose white sand and palm trees are overseen by a tall, tumbling waterfall. Cooking for the White Sunday feast has begun, and the air smells like burning coconut husks.

“Where are the manumea?” Serra asks one giggling 10-year-old. He pats the boy’s stomach. “Are they all in Samoan bellies?”

It’s a joke, but a dark-humored one: When a species is reduced to very low numbers, hunters can easily pick off the last individuals. For decades, everyone from conservationists and economists to much of the general public has assumed that the culprits are the world’s desperate, hungry poor, for whom filling an empty stomach is a higher priority than biodiversity. But in Samoa, a more complicated story has emerged, one that doesn’t so easily let the rich world off the hook. We human beings aren’t just eating endangered species any more. We’re consuming them.


Aday later, Serra and I are standing on an ancient structure in the jungle of Savai’i, the larger and wilder of Samoa’s main islands. It is a place of endings. We are just inland from the nation’s western limit, a point of black rock that seems to descend, stepwise, into the sea. In Polynesian tradition, this is O Le Fāfā, entrance to the underwater world of the dead.

The pyramidal edifice we have clambered to the top of is one of dozens in Samoa’s forests. The mound is not small: It’s wider than a basketball court and as tall as a one-story building. The jungle has nearly taken it over, but eight rounded lobes stemming off a central platform are still discernible. The mysterious structure is known as a “star mound,” and it was used, at least at times, to hunt pigeons.

When the ancestors of today’s Samoans arrived by boat about 3,000 years ago, the islands were home only to creatures that could swim, fly, or drift to their shores. Among these, pigeons, including the manumea, were the largest and tastiest wildlife on hand. Under Samoa’s strongly hierarchical social system, hunting them was reserved for chiefs, in the same way that deer hunting in England was once the preserve of aristocrats.

When a village hosted a pigeon hunt, invited chiefs, or matai, are thought to have been assigned to the lobes on the star mound, and would then compete to capture the most wild pigeons using long-handled nets. The hunts were a divine ritual, a spectator sport, a reason for communities to gather and feast, and they disappeared rapidly under the influence of European missionaries in the early 19th century. Or rather, they were transmuted.


In 2014, Samoa’s statistics bureau wrapped up a survey of what Samoans were eating and drinking. The nation has the third-highest prevalence of obesity in the world, and the research, carried out in partnership with the Food and Agriculture Organization of the United Nations, was comprehensive. Nearly 10 percent of households turned in detailed accounts of their daily diet.

Read: Is it safe to eat bushmeat?

Rebecca Stirnemann, an ecologist from New Zealand who was living in Samoa, saw an opportunity to sort out who, exactly, was eating Samoan wildlife. She didn’t expect to catch people eating manumea. Hunters who specialized in manumea could still be found as late as the 1980s, but soon afterward the bird became too rare to target. Instead, Stirnemann worried that hunters pursuing the more common Pacific pigeon, or lupe (pronounced loop-ay), were killing manumea opportunistically or by accident. Interviews with Samoan hunters carried out by Stirnemann and Samoa’s environment ministry indicated that more than a quarter of them had shot multiple manumea by mistake. In later interviews with a smaller group of highly experienced hunters, Serra learned that 41 percent had shot at least one manumea.

“If you hear a pigeon-like call and shoot up in the air, you could get either of them,” Stirnemann told me. She hoped the dietary survey would reveal how many lupe Samoans were eating, as a measure of the threat that hunting posed to manumea. In keeping with prevailing wisdom, she assumed that many of the hunted pigeons were ending up in the pots of the poorest people—a consequence of the subsistence hunting that endangers wildlife worldwide.


Analyzing the results of the household survey, Stirnemann found that Samoans were collectively eating more pigeon than anyone had anticipated: at least 22,000 birds each year. That’s 22,000 chances to accidentally shoot a manumea. But the poor weren’t eating the most: Nearly 45 percent of those pigeons had been eaten in the homes of the richest 10 percent. Expand that to the wealthiest 40 percent of households, and the share climbed to a stunning 80 percent.

“We were all surprised by the results,” Stirnemann said. “People didn’t realize they were having such a big impact on the population of pigeons, let alone manumea. And they also didn’t realize who was predominantly eating them.”

As stirnemann soon learned, her findings added to a growing body of research that is shattering assumptions about who eats threatened species, and why. In the same year as the Samoan survey, pioneering research from the Brazilian Amazon showed that people may be eating more wildlife, not less, as they escape rural poverty for the cities. Poorer households were still hunting wild animals to put food on the table, but also to sell to richer people. The wealthy were the greatest consumers of threatened and “prestige” species—including a monkey, a large rodent called the lowland paca, and a fish that can weigh as much as a German shepherd.

Because mainly poor, rural people had killed wild animals in the past for food or medicine, conservationists and development experts alike had predicted that people raised out of poverty would buy industrial food and pharmaceuticals at the store, the way most of us do in the West. Presto chango, the world’s wildlife would be saved.


But worrying studies kept trickling in. In Peru’s rain-forest cities, some of the heaviest consumers of wild meat proved to be visiting military personnel, industry executives, and tourists. In Vietnam, rhinoceros horn is still used as medicine, but the illness might best be described as affluenza: Almost half of users were treating hangovers, and another third were attempting to detoxify their body, in some cases mixing the powdered horn directly into wine to make a cocktail described in news articles as “the alcoholic drink of millionaires.” The story is much the same in China, where officials suspect that the coronavirus first passed to humans through an as-yet-unidentified wild animal. If you picture impoverished Chinese people eating any living thing they can get their hands on, think again. In today’s China, wild meat is frequently a delicacy and other animal products, like fur and traditional medicine, are luxuries; the trade has sharply increased, rather than decreased, with the nation’s rising wealth. (In February, China banned the sale of wild meat, with a loophole for medicinal products, but a lot of the trade was already underground.) Even in a country as impoverished as Zimbabwe, researchers found that hunters ate only a quarter of the meat they harvested, selling the rest to “people with cash incomes” who were “generally older and wealthier.”

Read: The price of protecting rhinos


CITES, the treaty body that governs international trade in wild plants and animals, first picked up on the trend in 2014. “We are seeing a disturbing shift in demand for some species from health to wealth,” John Scanlon, the secretary-general of the organization at the time, said. Wild meat, which had long been a dietary staple for many of the world’s poorer people, was morphing into a modern consumer luxury—a “positional good” that, like a Louis Vuitton handbag or Cartier watch, is used far less for its functional purpose than to signal identity, social belonging, and status. Threatened species were being eaten as a flash of conspicuous consumption by businessmen bonding on drunken sprees, by wealthy families showing respect to visitors, by urbanites hoping to reconnect with their rural roots.

Part of the reason Western conservationists expect countries with rising incomes to go easier on threatened species is that they believe their own countries did so in the past. But in the late 19th and early 20th centuries, commercial “market hunters” were still supplying mainly upper-class Americans with wild delicacies such as diamondback terrapin and canvasback duck even as—especially as—those species’ populations were being decimated. The trade slowed only with the advent of strictly enforced conservation laws. Rosaleen Duffy, a political ecologist at the University of Sheffield, argues that, again, the consumption of wildlife didn’t stop; it was transmuted. The United States and the United Kingdom are major importers of wildlife products; a study of eBay purchases found that the U.S. is the end destination for more than two-thirds of the traffic in protected species.


Even legal wild foods reflect a shift from strictly caloric to “elite” consumption. A 2018 study by an international team of fishery scientists looked at where fish caught in the world’s high seas—outside any nation’s jurisdiction—were going to market. Conservationists are concerned that the high seas are being overfished; fishery defenders reply that their fishing helps feed the hungry. In the end, the researchers found that the catch ranged from big-game species like tuna and swordfish (some of which have been reduced to 10 percent or less of their historical abundance) to an assortment of smaller fish, squid, and other sea creatures. The majority was feeding upscale consumers in places such as the United States, the European Union, and Japan. Several species were used almost entirely as feed for fish farms or pets (again, mainly in rich nations), while others were turned into nutraceuticals aimed not at combatting hunger or disease, but at optimizing the performance of already healthy people—to make us, as we say today, “better than well.”Melanie Lambrick

“All of us are consumers of wildlife in one way or another,” Duffy says. “We eat wildlife, we wear it as clothing and accessories, we consume it as medicine, and we buy ornaments made from it.”

The reasons for the manumea’s disappearance in Samoa are less rapacious: The bird is no longer deliberately hunted, but killed unintentionally. Yet it, too, is entangled in matters of prestige and identity. And the little dodo is on the verge—the very brink of the cusp—of extinction.


“Let me paint a picture of why it is so hard for people to say no to pigeon dishes,” Jesse Lee, a young chef with an interest in Samoan foodways, told me. “It’s a memory food; it’s the peak of all dishes. It’s the ultimate chicken soup.”

We were seated in his restaurant, Mi Amor, a farm-to-table joint in Apia that smells of lime leaves, coconut, tuna, and fresh lemongrass. Lee has eaten pigeon only a few times. In every case, it has been because his parents—his father is a matai—have received them as gifts. “It’s a mark of respect.”

Nearly every Samoan I spoke with had eaten pigeon, but a clear pattern emerged: How often and how recently they had eaten it tended to correlate with their wealth, power, and status. Fiame Naomi Mata’afa is about as prestigious as a figure can be in Samoa: Besides being the deputy prime minister and minister of natural resources and environment, Fiame holds a high matai title and is the daughter of the man whose hands literally lowered the flag of colonial rule to launch Samoa’s independence. (Note that in Samoa, matai titles are used in place of individuals’ surnames.) Fiame is also a spokesperson for a new campaign to save the manumea led by the Samoa Conservation Society and her ministry; in the campaign’s strategy document, she publicly applauds “all Samoans who have made the voluntary decision to forego the purchase, gifting, or eating of all pigeon until we can ensure that our Manumea is out of danger.” Yet when I asked where and when she had last eaten pigeon, she replied with candor. “Probably in cabinet. Probably last month,” she said. “The minister who usually brings it, he has a restaurant, so usually it arrives cooked.” The minister in question is Sala Fata Pinati, the minister of tourism.


Similarly, Seumaloisalafai Afele Faiilagi, who oversees manumea conservation at the environment ministry, acknowledges that he used to receive “a lot of lupe” because his father is the high matai of Uafato—the village where Serra and I first searched for manumea. “Because it is rare, people recognize that it is for the high chief,” Seumaloisalafai said. In Samoa, that can add up to a lot of pigeons: The country has 18,000 matai. Church leaders, too, often receive pigeon as gifts, or even request it as a favorite food. As Stirnemann put it, the well-to-do consumers in Samoa are typically a far cry from the global elite. “It’s not like wealthy-with-swimming-pools wealthy. It would just be your richer people in the average population.”

By comparison, Tu Alauni, a young woman raised in Apia, said that the only time she had tasted pigeon was when her mother, very ill, had arranged to buy a single bird, hoping it might improve her health. “It was the most important food in their times,” Alauni told me. She expected that the small piece of pigeon her mother shared with her would be a “once in a lifetime” experience—all the more so now that Alauni has actually seen a live manumea. In 2017, one perched alongside the terrace of her workplace, the Forest Cafe, which overlooks a jungle ravine in the mountains above the city. Alauni now feels personally invested in the fate of the manumea, and the café’s owners, who also saw the bird, are reforesting the area with native trees. Still, hunting takes place so close to the property that bird shot once fell out of the sky onto the café’s roof.


Poor people in Samoa have practical reasons for eating less pigeon. A single bird costs 15 Samoan tālā—enough money to buy a week’s worth of meals for a family. A box of shotgun shells costs 65 tālā, which could otherwise purchase four dress shirts, three backpacks for schoolchildren, or 13 whole chickens. Hunters I spoke with said that even their shells are now often paid for by wealthy buyers.

To be clear, hunting pigeons has been against the law in Samoa for more than 25 years. The law has not been enforced, however, and most Samoans consider it inoperative to the point that hunting and eating pigeon are spoken of freely. I encountered secrecy only once: After a professor told me he had dined on lupe the previous week at a resort, the hotel’s staff insisted they had never served the bird.

Wild pigeon is food in Samoa, but no one needs to eat pigeon. Sitting at Mi Amor, its doors and windows open in the evening heat, Lee said the perception of wild pigeon as something consumed, not merely eaten, could one day be the manumea’s salvation. “The next generation is not as interested in food, actually. They’re more interested in the next iPhone or the next Samsung—whatever the new technology is going to be,” Lee said. “If the next generation will prefer to get a gift of an iPhone instead, or some shoes, the pigeons probably won’t be too bothered.”

Of course, the manumea has to survive that long—which is anything but a sure bet.


Serra tells me that searching for the rarest of rare creatures takes not only perseverance, but faith. After days of fruitless trekking through Samoa’s wildest forests, I understand what he means. The idea that a manumea might appear just around the next corner begins to seem ridiculous, as though we were watching for shooting stars in the tiny clear patch of a night sky otherwise obscured by clouds. Every second seems essential—you can’t step off the trail to relieve yourself without keeping your eyes peeled—but at the same time hopeless. Carrying on, then, takes faith, or obsession. Serra’s favorite book, he tells me, is Moby-Dick.

So we ascend for hours into the clouds above the village of A’opo, on the north slope of Savai’i. The jungle is alive, teeming with birds, and in that single day we see or hear nearly all of the forest species in Samoa’s slim birdwatching guide. “All except one,” says Serra, as we finally descend in drenching, blood-warm rain. “Maybe we are documenting the extinction.”

The extinction. Most of us understand those words only in the abstract. To Serra, they’re personal. Serra, who currently lives in Florence, Italy, moved to Samoa in 2012 to run conservation projects with the United Nations’ Environment Programme and Global Environment Facility across the South Pacific. After four years, he returned to the field as a freelance manumea researcher, working for Samoa’s ministry of the environment, among others. But his immersion in critically endangered species began nearly 20 years ago with the northern bald ibis, when he traced ghostly sightings by Bedouin nomads and local hunters to a small colony in Syria. At the time, the black, cranelike bird—once widespread across North Africa, southeastern Europe, and the Middle East—was known to nest only in Morocco; there hadn’t been a verified sighting in Syria since the 1930s. Serra and his Syrian and Bedouin colleagues found seven birds. He then watched as all these remaining ibises were lost in subsequent years, mainly to hunting.


The idea that Serra may witness another disappearance—the global extinction of the manumea—weighs on him. Yet he doesn’t even know, really, where to look for the bird. Contradictory reports have been the norm since the earliest written accounts. Sometimes the manumea is described as a bird of the high cloud forests, sometimes of the coastal lowlands; the last known photograph of the species was taken in 2013, in the parking lot of a resort near the busiest town on Savai’i. Some have said the manumea prefers, like its cousin the dodo, to peck about on the ground; others, that it never leaves the treetops. “Who knows?” Serra says. “Total speculations.”

Because manumea are hard to see, estimates of how many remain have depended in part on where they’ve been heard. But when Serra tested 10 expert bird hunters, he found that even most of them could not consistently identify the bird by its recorded call. (The manumea’s only known call is a softly rising and falling sound—mmmMMMmmm—like a cow on a foggy morning; it is thought to be slightly lower in pitch and subtly different in rhythm than a similar call made by the lupe.) The idea that 200 birds remain is, Serra says, little more than a guess. The number could be higher, or much, much lower. “We may be searching for the last 10, or 15.”

If the manumea does go extinct, the last one could die something like this: On a hunt when he was 17 years old, a man named Norman Paul saw the silhouette of a pigeon on a telephone wire, and shot at it. He was startled to discover that what he had gunned down was not a lupe, but a bird he had never seen before. Immediately, he regretted the kill—something special had died by his hand. Today, some 45 years later, he runs a hotel on the mountainside where he shot the bird. It is called Le Manumea, in memoriam, and tourists there gather in an atmosphere of thatch and tiki, unaware of the lingering sadness captured by the resort’s name. A sign at the entrance promises happy hour all day.


On the basis of confirmed sightings, Serra now estimates that a person looking for the manumea could expect to spot one only every three to five years. “There is a Tasmanian-tiger aspect to the manumea,” he says, referring to the wolflike marsupial that probably went extinct in Tasmania in 1936, but is still regularly, if unreliably, reported to exist in the wild. “As people become aware of the manumea, they desire to see it.” A radio station once contacted the environment ministry to report that a listener had brought a manumea into the studio. It proved to be the fiaui, or white-throated pigeon, a bird often mistaken for the manumea. Serra and I have seen plenty of them.

The first campaign to save the manumea was launched in 1993. It was funded by Rare, an American organization that promotes local pride in endangered species, but otherwise took a grassroots approach—including school puppet shows and a manumea-friendly sermon for Samoa’s many, many churches—led by government environmental staff. Fourteen years passed before the next big conservation drive, followed again by a long lapse.

Today’s effort to save the manumea, then, is beginning almost from scratch. Samoa has dedicated conservationists (the head parks and reserves officer, Moeumu Uili, teared up as she recounted capturing the manumea on film in 2013), but money and resources are hard to come by in a nation with the same population as Yonkers, New York—and in a world replete with endangered species that need help. This time, international partners include BirdLife, the Auckland Zoo, and the New Zealand government.


Hunting is certainly not the only threat facing the bird. Most evidence points to manumea preferring lowland forests, 80 percent of which have been logged, built over, or cleared for the family farms that Samoans call plantations. Then there are invasive species such as rats and cats, which count the manumea among their prey. The first documented observations of manumea in the wild, written in gorgeously hurried cursive by the naturalist and explorer Titian Peale in the late 1840s, were also the first to predict the bird’s extinction:


A few years since a passion arose for cats, and they were obtained by all possible means from the whale ships visiting the islands … Pussy (a name generally adopted by the Polynesians for cats), not liking yams and taro, the principal food of the islanders, preferred Manu-mea, and took to the mountains in pursuit of them. There the cats have multiplied and become wild, and live upon our Didunculus, or Little Dodo, the Manu-mea of the natives, which, it is believed, will, in a very few years, cease to be known.

The manumea has outlived expectations by more than 170 years—but barely. In 2014, its global conservation status was downgraded from endangered to critically endangered, meaning “intensive conservation actions” are needed to prevent its extinction.

Read: The quiet disappearance of birds in North America

The international team met in Samoa in October 2019 to decide on those actions, all of which were abruptly postponed when a deadly measles outbreak was declared a national emergency in November. The Samoan government’s top priority for the manumea’s recovery, according to Seumaloisalafai, will be to pursue Serra’s research into the bird’s call. If the manumea’s vocal imprint can be distinguished from the lupe’s through digital analysis, scientists could distribute sensors throughout the islands and collect the best data yet on where the birds are and how many remain.


Also key to the recovery plan is developing and supporting a network of manumea-friendly villages (there are already six) that commit to protecting their forests and banning hunting. The Auckland Zoo, meanwhile, is prepared to provide training and support for rat-killing programs in village forests. The zoo will also study the feasibility of a captive-breeding facility in Samoa, its first great challenge being the fact that, as one manumea researcher put it, “the difficulty throughout the present century has been to find even single representatives of the species.”

Pigeon hunting is a practice that can be addressed cheaply and immediately—at least in theory. With Samoa’s measles crisis now over, a marketing campaign starting in April will first draw attention to the manumea’s plight before calling on Samoans to ban the shooting, trading, and eating of pigeon. The goal is to reduce pigeon consumption by a quarter this year. “I don’t think the bird will be saved by the hunting issue alone,” said James Atherton, who is of British and Samoan descent and helped found the Samoa Conservation Society seven years ago, “but it’s the one thing that every Samoan can do to save the manumea.”

Still, asking Samoans to stop eating pigeon is as fraught with complexity as asking the world’s wealthy consumers to give up their favorite seafood. Seiuli Vaifou Aloalii Temese, head of the Centre for Samoan Studies at the National University of Samoa, pulled back the layers of meaning associated with pigeons. She told me about memories of her father hunting for lupe before White Sunday when she was a girl, and always giving one bird to the pastor before preparing the rest. They would share those meals with neighbors who had no lupe to eat, dishing out the best portions to the chiefs. Pigeon hunting has even been woven into the language. A meeting might open with a phrase like Ua malumaunu le fogatia, which translates as “The star mound is made sacred by the lupe that gather there,” or an attractive woman might be described in casual conversation as a “lupe.”


“They feel very Samoan when they eat the lupe. It is also nice to eat the lupe. They will think of those proverbs when they eat the lupe,” Seiuli Vaifou said. “This is why the lupe hunting is so important.”

I heard another story that put it more bluntly. After a workshop for the save-the-manumea campaign, one visiting conservationist, feeling buoyant about the bird’s future, went to a nearby market and told a vendor about the plan to discourage people from eating pigeon. “But,” the vendor said in disbelief, “it’s like cocaine to some people!”

Serra and i may have possibly, finally, caught a glimpse of the manumea. We had traveled to Tafua-tai, a brightly painted village laid out beneath the emerald saddle of a volcanic crater. As one story would have it, the entire village was won by the ancestors of its current inhabitants—in a pigeon-catching contest.

Tafua-tai offers reasons for optimism. For one, it is a manumea-friendly village. For another, the famous 2013 photo of the bird was taken nearby. Also, we are guided by Tuluiga Ulu Anoa’i, whose grandfather, as a high matai in the late 1980s, convinced the community to protect its forest from development. Ulu Anoa’i, who has a keen eye for forest wildlife, might be the person to have most recently sighted a manumea—just two months ago, at the crater’s edge. Because she had never seen one before, however, she can’t be absolutely certain.


During an extended trip to the volcano, we see wonderful things—the many-colored fruit dove is as beautiful as its name suggests—but not our little dodo. Then Ulu Anoa’i takes us to hear the remarkable claims of her uncle, Tiaalii Matauaina. He is a barrel of a man, with the dramatic, wide-eyed facial expressions of a mustachioed Rodney Dangerfield. Sitting in a yellow lavalava sarong and polo shirt in front of his home, he tells us he sees manumea in the forest frequently—sometimes even in his garden. His most recent sighting was three or four days ago. “If I kill a manumea, we can give it to you,” he says. It’s hard to tell whether he’s joking.

Tiaalii agrees to take us to the places where he sees manumea most often. First, though, we have to wait out the heat of the afternoon. “In the morning, the light here is magnificent; it is like the dawn of creation,” Serra says. “At midday, it is hostile. It is hell.” At last, with the lowering sun, the birding hour arrives: As we set out, patches of forest are trilling and cooing with pigeons and doves. Once, Tiaalii thinks he hears the manumea’s call, but he isn’t sure. At last, we turn up a narrow path through a green delirium.

“One day, here—four, five manumea,” Tiaalii says, gesturing as though his hands were birds bursting from the bush. We carry on toward a towering tree.

“Manumea!” Tiaalii cries. His powerful right hand seizes me by the scruff of my neck and directs my head to a spot in the sky. There, a pigeon-size bird hurtles overhead, a black silhouette against the blue. A moment later it’s gone.


Serra, coming up from behind, caught only the briefest glimpse. “What a difficult bird,” he says, and proceeds to ask Tiaalii for details about what he had seen.

“The color!” says Tiaalii, eyes bulging. “Blue, red, and bit of black!” With his hands he makes a large, hooked beak, opening and closing. “Psh psh psh.”

So there you have it: An experienced local with an eye for birds has found us our manumea. Also possible, though, is that he wants rather badly to be the one to help us find the bird, or that he feels our longing, and the fast approach of twilight, and wants us to go home happy. It is hard to imagine that there had been time, in the brief moment when the bird flushed from the tree and crossed overhead, for Tiaalii to see the color and detail he claimed. Even he, ultimately, seems unconvinced.

To see a manumea, or to save one, is bound up in memory and desire. “My left brain doesn’t believe him, but my right brain wants to believe him,” Serra says. He is not prepared to add this to his list of probable sightings in the field.

A few days later, our search over, we sit at the edge of Apia’s harbor with James Atherton, of the Samoa Conservation Society. Reviewing our efforts, Serra concludes they had been “quite representative” and “quite depressing.”

“This bird,” Serra says, “it’s impossible to see.”

“Well, that’s why we’re working so hard to save this very rare bird,” Atherton replies.

Serra looks out to where the waves break over the twilight reef with a dull and constant roar, like the engine of the world. “I think we’d better hurry up a little,” he says.

J. B. MACKINNON is a writer based in Vancouver, Canada. His work has appeared in The New Yorker, National Geographic, and Nautilus. He is the author of The Once and Future World.

Discovery challenges nuclear theory

Researchers test the way we understand forces in the universe

Date:April 1, 2020
Source:University of Massachusetts Lowell

A discovery by a team of researchers led by UMass Lowell nuclear physicists could change how atoms are understood by scientists and help explain extreme phenomena in outer space.

The breakthrough by the researchers revealed that a symmetry that exists within the core of the atom is not as fundamental as scientists have believed. The discovery sheds light on the forces at work within the atoms' nucleus, opening the door to a greater understanding of the universe. The findings were published today in Nature, one of the world's premier scientific journals.

The discovery was made when the UMass Lowell-led team was working to determine how atomic nuclei are created in X-ray bursts -- explosions that happen on the surface of neutron stars, which are the remnants of massive stars at the end of their life.

"We are studying what happens inside the nuclei of these atoms to better understand these cosmic phenomena and, ultimately, to answer one of the biggest questions in science -- how the chemical elements are created in the universe," said Andrew Rogers, UMass Lowell assistant professor of physics, who heads the research team.

The research is supported by a $1.2 million grant from the U.S. Department of Energy to UMass Lowell and was conducted at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. At the lab, scientists create exotic atomic nuclei to measure their properties in order to understand their role as the building blocks of matter, the cosmos and of life itself.

Atoms are some of the smallest units of matter. Each atom includes electrons orbiting around a tiny nucleus deep within its core, which contains almost all its mass and energy. Atomic nuclei are composed of two nearly identical particles: charged protons and uncharged neutrons. The number of protons in a nucleus determines which element the atom belongs to on the periodic table and thus its chemistry. Isotopes of an element have the same number of protons but a different number of neutrons.

At the NSCL, nuclei were accelerated to near the speed of light and smashed apart into fragments creating strontium-73 -- a rare isotope that is not found naturally on Earth but can exist for short periods of time during violent thermonuclear X-ray bursts on the surface of neutron stars. This isotope of strontium contains 38 protons and 35 neutrons and only lives for a fraction of a second.

Working around the clock over eight days, the team created more than 400 strontium-73 nuclei and compared them to the known properties of bromine-73, an isotope that contains 35 protons and 38 neutrons. With interchanged number of protons and neutrons, bromine-73 nuclei are considered "mirror partners" to strontium-73 nuclei. Mirror symmetry in nuclei exists because of the similarities between protons and neutrons and underlies scientists' understanding of nuclear physics.

Roughly every half-hour, the researchers created one strontium-73 nucleus, transported it through the NSCL's isotope separator and then brought the nucleus to a stop at the center of a complex detector array where they could observe its behavior. By studying the radioactive decay of these nuclei, the scientists found that strontium-73 behaved entirely differently from bromine-73. The discovery raises new questions about nuclear forces, according to Rogers.

"Strontium-73 and bromine-73 should appear identical in structure, but surprisingly do not, we found. Probing symmetries that exist in nature is a very powerful tool for physicists. When symmetries break down, that tells us something's wrong in our understanding, and we need to take a closer look," Rogers said.

What the scientists saw will challenge nuclear theory, according to Daniel Hoff, a UMass Lowell research associate who was the lead author of the article published in Nature.

"Comparing strontium-73 and bromine-73 nuclei was like looking in a mirror and not recognizing yourself. Once we convinced ourselves that what we were seeing was real, we were very excited," Hoff said.

Along with Rogers, a Somerville resident, and Hoff of Medford, the UMass Lowell team included Physics Department faculty members Assistant Prof. Peter Bender, Emeritus Prof. C.J. Lister and former UMass Lowell research associate Chris Morse. Physics graduate students Emery Doucet of Mason, N.H., and Sanjanee Waniganeththi of Lowell also contributed to the project.

As part of the team's study, state-of-the-art theoretical calculations were carried out by Simin Wang, a research associate at Michigan State, and directed by Witold Nazarewicz, MSU's John A. Hannah Distinguished Professor of Physics and chief scientist at the Facility for Rare Isotope Beams (FRIB), which will open next year.

The researchers' work "offers unique insights into the structure of rare isotopes," Nazarewicz said. "But much still remains to be done. New facilities coming online, such as FRIB at MSU, will provide missing clues into a deeper understanding of the mirror symmetry puzzle. I am glad that the exotic beams delivered by our facility, unique instrumentation and theoretical calculations could contribute to this magnificent work."

Plans for more experiments are already underway, as the researchers seek to refine and confirm their observations and study these isotopes further.

Story Source:
Materials provided by University of Massachusetts Lowell.

Journal Reference:
D. E. M. Hoff, A. M. Rogers, S. M. Wang, P. C. Bender, K. Brandenburg, K. Childers, J. A. Clark, A. C. Dombos, E. R. Doucet, S. Jin, R. Lewis, S. N. Liddick, C. J. Lister, Z. Meisel, C. Morse, W. Nazarewicz, H. Schatz, K. Schmidt, D. Soltesz, S. K. Subedi, S. Waniganeththi. Mirror-symmetry violation in bound nuclear ground states. Nature, 2020; 580 (7801): 52 DOI: 10.1038/s41586-020-2123-1


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University of Massachusetts Lowell. "Discovery challenges nuclear theory: Researchers test the way we understand forces in the universe." ScienceDaily. ScienceDaily, 1 April 2020. .
MUTUAL AID
Black rhinos eavesdrop on the alarm calls of hitchhiking oxpeckers to avoid hum
ans

Date:April 9, 2020
Source:Cell Press
Black rhinos eavesdrop on the alarm calls of hitchhiking oxpeckers ...
In Swahili, red-billed oxpeckers are called Askari wa kifaru, or "the rhino's guard." Now, a paper appearing April 9 in the journal Current Biology suggests that this indigenous name rings true: red-billed oxpeckers may act as a first line of defense against poachers by behaving like sentinels, sounding an alarm to potential danger. By tracking wild black rhinos, researchers found that those carrying oxpeckers were far better at sensing and avoiding humans than those without the hitchhiking bird.

While conservation efforts have rebounded the critically endangered black rhino's numbers, poaching remains a major threat. "Although black rhinos have large, rapier-like horns and a thick hide, they are as blind as a bat. If the conditions are right, a hunter could walk within five meters of one, as long as they are downwind," says Roan Plotz (@RoanPlotz), a lecturer and behavioral ecologist at Victoria University, Australia., who co-authored the paper with ecological scientist Wayne Linklater (@PolitEcol) of California State University -- Sacramento. Oxpeckers, which are known to feed on the ticks and lesions found on the rhino's body, may make up for the rhino's poor eyesight by calling out if they detect an approaching human.

To study the role that oxpeckers might play, Plotz and his team recorded the number of oxpeckers on two groups of the rhinos they encountered. Rhinos tagged with radio transmitters -- which allowed researchers to track them while evading detection from oxpeckers -- carried the bird on their backs more than half the time. The untagged black rhinos they found, on the other hand, carried no oxpeckers most of the time -- suggesting that other untagged rhinos that carried the birds might have avoided encountering the researchers altogether. "Using the differences we observed between oxpeckers on the tagged versus untagged rhinos, we estimated that between 40% and 50% of all possible black rhino encounters were thwarted by the presence of oxpeckers," says Plotz.
☆SMARTCLUB☆ News : Bird alarm calls help rhinos avoid ...

Even when the researchers were able to locate the tagged rhinos, the oxpeckers' alarm calls still appeared to play a role in predator defense. The field team ran a "human approach" experiment, where one researcher would walk towards the rhino from crosswind while a colleague recorded the rhino's behavior. The field team recorded the number of oxpecker carried, the rhinos' behavior upon approach, and the distance of the researcher when either the rhinos became vigilant or, if undetected, it became unsafe to get any closer.

"Our experiment found that rhinos without oxpeckers detected a human approaching only 23% of the time. Due to the bird's alarm call, those with oxpeckers detected the approaching human in 100% of our trials and at an average distance of 61 meters -- nearly four times further than when rhinos were alone. In fact, the more oxpeckers the rhino carried, the greater the distance at which a human was detected," he says. He adds that these improved detection and distance estimates may even be conservative, because they don't take into account the untagged rhinos carrying oxpeckers that the team could not detect.

When a rhino perceived the oxpecker alarm call, it nearly always re-oriented itself to face downwind -- their sensory blind spot. "Rhinos cannot smell predators from downwind, making it their most vulnerable position. This is particularly true from humans, who primarily hunt game from that direction," says Plotz.

Taken together, these results suggest that oxpeckers are effective companions that enable black rhinos to evade encounters with people and facilitate effective anti-predator strategies once found. Some scientists even hypothesize that oxpeckers evolved this adaptive behaviour as a way to protect their source of food: the rhinos.

"Rhinos have been hunted by humans for tens of thousands of years, but the species was driven to the brink of extinction over the last 150 years. One hypothesis is that oxpeckers have evolved this cooperative relationship with rhinos relatively recently to protect their food source from human overkill," says Plotz.

Despite this closely tied relationship, oxpecker populations have significantly declined, even becoming locally extinct in some areas. As a result, most wild black rhino populations now live without oxpeckers in their environment. But based on the findings in this study, reintroducing the bird back into rhino populations may bolster conservation efforts. "While we do not know that reintroducing the birds would significantly reduce hunting impacts, we do know oxpeckers would help rhinos evade detection, which on its own is a great benefit," says Plotz.

Plotz says that these findings, inspired by a Swahili name, also highlight the importance of local knowledge. "We too often dismiss the importance of indigenous people and their observations. While western science has been incredibly useful, there are many insights we can learn from indigenous communities."

Story Source:
Materials provided by Cell Press

Journal Reference:
Roan D. Plotz, Wayne L. Linklater. Oxpeckers Help Rhinos Evade Humans. Current Biology, 2020; DOI: 10.1016/j.cub.2020.03.015

Cite This Page:
Cell Press. "Black rhinos eavesdrop on the alarm calls of hitchhiking oxpeckers to avoid humans." ScienceDaily. ScienceDaily, 9 April 2020. .
New fossil from Brazil hints at the origins of the mysterious tanystropheid reptiles
New fossil from Brazil hints at the origins of the mysterious ...
New species named after Tolkien's Aragorn hints at early southern evolution for these reptiles

A new species of Triassic reptile from Brazil is a close cousin of a mysterious group called tanystropheids

Date:April 8, 2020
Source:PLOS

A new species of Triassic reptile from Brazil is a close cousin of a mysterious group called tanystropheids, according to a study published April 8, 2020 in the open-access journal PLOS ONE by Tiane De-Oliviera of the Federal University of Santa Maria, Brazil and colleagues.

After the Permian mass extinction, 250 million years ago, reptiles took over global ecosystems. Among the early groups to appear after this extinction event were the tanystropheids, a group of long-necked animals whose lifestyles are still mysterious, but who were nonetheless successful in the Triassic Period. However, the early evolution of this group is poorly understood, as their remains are very rare from the Early Triassic.

In this study, De-Oliviera and colleagues describe a new specimen of reptile from Early Triassic rocks of the Sanga do Cabral Formation in southern Brazil. Skeletal comparison indicates this specimen, known from remains of the hind leg, pelvis, and tail, is the closest known relative of tanystropheids. The researchers identified these remains as belonging to a new species, which they named Elessaurus gondwanoccidens. The name derives in part from the Elvish name (Elessar) of a character from Lord of the Rings also known as Aragorn or Strider, chosen as a reference to the fossil animal's long legs.

Most tanystropheid fossils are found in Middle to Late Triassic rocks of Europe, Asia, and North America, and often in marine sediments. The presence of Elessaurus in continental deposits of Early Triassic South America suggests that the origins of this group may lie in the southern continents, and that their ancestors may have lived on land before later species adapted to aquatic life. A clearer view of the group's origins will rely on more rare fossils from this early time in their evolution.


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Materials provided by PLOS. Note: Content may be edited for style and length.

Journal Reference:
Tiane M. De-Oliveira, Felipe L. Pinheiro, Átila Augusto Stock Da-Rosa, Sérgio Dias-Da-Silva, Leonardo Kerber. A new archosauromorph from South America provides insights on the early diversification of tanystropheids. PLOS ONE, 2020; 15 (4): e0230890 DOI: 10.1371/journal.pone.0230890


Cite This Page:
PLOS. "New fossil from Brazil hints at the origins of the mysterious tanystropheid reptiles: New species named after Tolkien's Aragorn hints at early southern evolution for these reptiles." ScienceDaily. ScienceDaily, 8 April 2020. .
Smartphone videos produce highly realistic 3D face reconstructions

Method foregoes expensive scanners, camera setups, studios

Date:April 1, 2020
Source:Carnegie Mellon University

Normally, it takes pricey equipment and expertise to create an accurate 3D reconstruction of someone's face that's realistic and doesn't look creepy. Now, Carnegie Mellon University researchers have pulled off the feat using video recorded on an ordinary smartphone.

Using a smartphone to shoot a continuous video of the front and sides of the face generates a dense cloud of data. A two-step process developed by CMU's Robotics Institute uses that data, with some help from deep learning algorithms, to build a digital reconstruction of the face. The team's experiments show that their method can achieve sub-millimeter accuracy, outperforming other camera-based processes.

A digital face might be used to build an avatar for gaming or for virtual or augmented reality, and could also be used in animation, biometric identification and even medical procedures. An accurate 3D rendering of the face might also be useful in building customized surgical masks or respirators.

"Building a 3D reconstruction of the face has been an open problem in computer vision and graphics because people are very sensitive to the look of facial features," said Simon Lucey, an associate research professor in the Robotics Institute. "Even slight anomalies in the reconstructions can make the end result look unrealistic."

Laser scanners, structured light and multicamera studio setups can produce highly accurate scans of the face, but these specialized sensors are prohibitively expensive for most applications. CMU's newly developed method, however, requires only a smartphone.

The method, which Lucey developed with master's students Shubham Agrawal and Anuj Pahuja, was presented in early March at the IEEE Winter Conference on Applications of Computer Vision (WACV) in Snowmass, Colorado. It begins with shooting 15-20 seconds of video. In this case, the researchers used an iPhone X in the slow-motion setting.

"The high frame rate of slow motion is one of the key things for our method because it generates a dense point cloud," Lucey said.

The researchers then employ a commonly used technique called visual simultaneous localization and mapping (SLAM). Visual SLAM triangulates points on a surface to calculate its shape, while at the same time using that information to determine the position of the camera. This creates an initial geometry of the face, but missing data leave gaps in the model.

In the second step of this process, the researchers work to fill in those gaps, first by using deep learning algorithms. Deep learning is used in a limited way, however: it identifies the person's profile and landmarks such as ears, eyes and nose. Classical computer vision techniques are then used to fill in the gaps.

"Deep learning is a powerful tool that we use every day," Lucey said. "But deep learning has a tendency to memorize solutions," which works against efforts to include distinguishing details of the face. "If you use these algorithms just to find the landmarks, you can use classical methods to fill in the gaps much more easily."

The method isn't necessarily quick; it took 30-40 minutes of processing time. But the entire process can be performed on a smartphone.

In addition to face reconstructions, the CMU team's methods might also be employed to capture the geometry of almost any object, Lucey said. Digital reconstructions of those objects can then be incorporated into animations or perhaps transmitted across the internet to sites where the objects could be duplicated with 3D printers.


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Carnegie Mellon University. "Smartphone videos produce highly realistic 3D face reconstructions: Method foregoes expensive scanners, camera setups, studios." ScienceDaily. ScienceDaily, 1 April 2020. .
Astronomers use slime mould to map the universe's largest structures
The behaviour of one of nature's humblest creatures and archival data from the NASA/ESA Hubble Space Telescope are helping astronomers probe the largest structures in the Universe

Date:March 26, 2020
Source: ESA/Hubble Information Centre

The single-cell organism known as slime mould (Physarum polycephalum) builds complex web-like filamentary networks in search of food, always finding near-optimal pathways to connect different locations.

In shaping the Universe, gravity builds a vast cobweb-like structure of filaments tying galaxies and clusters of galaxies together along invisible bridges of gas and dark matter hundreds of millions of light-years long. There is an uncanny resemblance between the two networks, one crafted by biological evolution, the other by the primordial force of gravity.

The cosmic web is the large-scale backbone of the cosmos, consisting primarily of dark matter and laced with gas, upon which galaxies are built. Even though dark matter cannot be seen, it makes up the bulk of the Universe's material. Astronomers have had a difficult time finding these elusive strands, because the gas within them is too dim to be detected.

The existence of a web-like structure to the Universe was first hinted at in galaxy surveys in the 1980s. Since those studies, the grand scale of this filamentary structure has been revealed by subsequent sky surveys. The filaments form the boundaries between large voids in the Universe. Now a team of researchers has turned to slime mould to help them build a map of the filaments in the local Universe (within 100 million light-years of Earth) and find the gas within them.

They designed a computer algorithm, inspired by the behaviour of slime mould, and tested it against a computer simulation of the growth of dark matter filaments in the Universe. A computer algorithm is essentially a recipe that tells a computer precisely what steps to take to solve a problem.

The researchers then applied the slime mould algorithm to data containing the locations of over 37,000 galaxies mapped by the Sloan Digital Sky Survey. The algorithm produced a three-dimensional map of the underlying cosmic web structure.

They then analysed the light from 350 faraway quasars catalogued in the Hubble Spectroscopic Legacy Archive. These distant cosmic flashlights are the brilliant black-hole-powered cores of active galaxies, whose light shines across space and through the foreground cosmic web. Imprinted on that light was the telltale signature of otherwise invisible hydrogen gas that the team analysed at specific points along the filaments. These target locations are far from the galaxies, which allowed the research team to link the gas to the Universe's large-scale structure.

"It's really fascinating that one of the simplest forms of life actually enables insights into the very largest-scale structures in the Universe," said lead researcher Joseph Burchett of the University of California (UC), U.S.A. "By using the slime mould simulation to find the location of the cosmic web filaments, including those far from galaxies, we could then use the Hubble Space Telescope's archival data to detect and determine the density of the cool gas on the very outskirts of those invisible filaments. Scientists have detected signatures of this gas for over half a century, and we have now proven the theoretical expectation that this gas comprises the cosmic web."

The survey further validates research that indicates intergalactic gas is organised into filaments and also reveals how far away gas is detected from the galaxies. Team members were surprised to find gas associated with the cosmic web filaments more than 10 million light-years away from the galaxies.

But that wasn't the only surprise. They also discovered that the ultraviolet signature of the gas gets stronger in the filaments' denser regions, but then disappears. "We think this discovery is telling us about the violent interactions that galaxies have in dense pockets of the intergalactic medium, where the gas becomes too hot to detect," Burchett said.

The researchers turned to slime mould simulations when they were searching for a way to visualise the theorised connection between the cosmic web structure and the cool gas, detected in previous Hubble spectroscopic studies.

Then team member Oskar Elek, a computer scientist at UC Santa Cruz, discovered online the work of Sage Jenson, a Berlin-based media artist. Among Jenson's works were mesmerizing artistic visualisations showing the growth of a slime mould's tentacle-like network of structures moving from one food source to another. Jenson's art was based on scientific work from 2010 by Jeff Jones of the University of the West of England in Bristol, which detailed an algorithm for simulating the growth of slime mould.

The research team was inspired by how the slime mould builds complex filaments to capture new food, and how this mapping could be applied to how gravity shapes the Universe, as the cosmic web constructs the strands between galaxies and galaxy clusters. Based on the simulation outlined in Jones's paper, Elek developed a three-dimensional computer model of the buildup of slime mould to estimate the location of the cosmic web's filamentary structure.

This analysis of the cosmic web in the local Universe also dovetails with observations published last autumn in the journal Science of the Universe's filamentary structure much farther away, about 12 billion light-years from Earth, near the Universe's beginning. In that study, astronomers analysed the energetic light from a young galaxy cluster illuminating the filaments of hydrogen gas connecting it.

The team's paper will appear in the Astrophysical Journal Letters.

Story Source:
Materials provided by ESA/Hubble Information Centre. Note: Content may be edited for style and length.

Journal Reference:
Joseph N. Burchett, Oskar Elek, Nicolas Tejos, J. Xavier Prochaska, Todd M. Tripp, Rongmon Bordoloi, Angus G. Forbes. Revealing the Dark Threads of the Cosmic Web. The Astrophysical Journal, 2020; 891 (2): L35 DOI: 10.3847/2041-8213/ab700c

ESA/Hubble Information Centre. "Astronomers use slime mould to map the universe's largest structures." ScienceDaily. ScienceDaily, 26 March 2020. .
Nuclear Tests Marked Life on Earth With a Radioactive Spike

Even as it disappears, the “bomb spike” is revealing the ways humans have reshaped the planet.

ART BY Zoe van Djik

Story by Carl Zimmer MARCH 2, 2020 THE ATLANTIC SCIENCE

On the morning of March 1, 1954, a hydrogen bomb went off in the middle of the Pacific Ocean. John Clark was only 20 miles away when he issued the order, huddled with his crew inside a windowless concrete blockhouse on Bikini Atoll. But seconds went by, and all was silent. He wondered if the bomb had failed. Eventually, he radioed a Navy ship monitoring the test explosion.

“It’s a good one,” they told him.


Then the blockhouse began to lurch. At least one crew member got seasick—“landsick” might be the better descriptor. A minute later, when the bomb blast reached them, the walls creaked and water shot out of the bathroom pipes. And then, once more, nothing. Clark waited for another impact—perhaps a tidal wave—but after 15 minutes he decided it was safe for the crew to venture outside.

The mushroom cloud towered into the sky. The explosion, dubbed “Castle Bravo,” was the largest nuclear-weapons test up to that point. It was intended to try out the first hydrogen bomb ready to be dropped from a plane. Many in Washington felt that the future of the free world depended on it, and Clark was the natural pick to oversee such a vital blast. He was the deputy test director for the Atomic Energy Commission, and had already participated in more than 40 test shots. Now he gazed up at the cloud in awe. But then his Geiger counter began to crackle.


“It could mean only one thing,” Clark later wrote. “We were already getting fallout.”

That wasn’t supposed to happen. The Castle Bravo team had been sure that the radiation from the blast would go up to the stratosphere or get carried away by the winds safely out to sea. In fact, the chain reactions unleashed during the explosion produced a blast almost three times as big as predicted—1,000 times bigger than the Hiroshima bomb.

Within seconds, the fireball had lofted 10 million tons of pulverized coral reef, coated in radioactive material. And soon some of that deadly debris began dropping to Earth. If Clark and his crew had lingered outside, they would have died in the fallout.

Clark rushed his team back into the blockhouse, but even within the thick walls, the level of radiation was still climbing. Clark radioed for a rescue but was denied: It would be too dangerous for the helicopter pilots to come to the island. The team hunkered down, wondering if they were being poisoned to death. The generators failed, and the lights winked out.

“We were not a happy bunch,” Clark recalled.

They spent hours in the hot, radioactive darkness until the Navy dispatched helicopters their way. When the crew members heard the blades, they put on bedsheets to protect themselves from fallout. Throwing open the blockhouse door, they ran to nearby jeeps as though they were in a surreal Halloween parade, and drove half a mile to the landing pad. They clambered into the helicopters, and escaped over the sea.

Read: The people who built the atomic bomb

As Clark and his crew found shelter aboard a Navy ship, the debris from Castle Bravo rained down on the Pacific. Some landed on a Japanese fishing boat 70 miles away. The winds then carried it to three neighboring atolls. Children on the island of Rongelap played in the false snow. Five days later, Rongelap was evacuated, but not before its residents had received a near-lethal dose of radiation. Some people suffered burns, and a number of women later gave birth to severely deformed babies. Decades later, studies would indicate that the residents experienced elevated rates of cancer.

The shocking power of Castle Bravo spurred the Soviet Union to build up its own nuclear arsenal, spurring the Americans in turn to push the arms race close to global annihilation. But the news reports of sick Japanese fishermen and Pacific islanders inspired a worldwide outcry against bomb tests. Nine years after Clark gave the go-ahead for Castle Bravo, the United States, Soviet Union, and Great Britain signed a treaty to ban aboveground nuclear-weapons testing. As for Clark, he returned to the United States and lived for another five decades, dying in 2002 at age 98.

Among the isotopes created by a thermonuclear blast is a rare, radioactive version of carbon, called carbon 14. Castle Bravo and the hydrogen-bomb tests that followed it created vast amounts of carbon 14, which have endured ever since. A little of this carbon 14 made its way into Clark’s body, into his blood, his fat, his gut, and his muscles. Clark carried a signature of the nuclear weapons he tested to his grave.

I can state this with confidence, even though I did not carry out an autopsy on Clark. I know this because the carbon 14 produced by hydrogen bombs spread over the entire world. It worked itself into the atmosphere, the oceans, and practically every living thing. As it spread, it exposed secrets. It can reveal when we were born. It tracks hidden changes to our hearts and brains. It lights up the cryptic channels that join the entire biosphere into a single network of chemical flux. This man-made burst of carbon 14 has been such a revelation that scientists refer to it as “the bomb spike.” Only now is the bomb spike close to disappearing, but as it vanishes, scientists have found a new use for it: to track global warming, the next self-inflicted threat to our survival.

Sixty-five years after Castle Bravo, I wanted to see its mark. So I drove to Cape Cod, in Massachusetts. I was 7,300 miles from Bikini Atoll, in a cozy patch of New England forest on a cool late-summer day, but Clark’s blast felt close to me in both space and time.

I made my way to the Woods Hole Oceanographic Institute, where I met Mary Gaylord, a senior research assistant. She led me to the lounge of Maclean Hall. Outside the window, dogwoods bloomed. Next to the Keurig coffee maker was a refrigerator with the sign that read store only food in this refrigerator. We had come to this ordinary spot to take a look at something extraordinary. Next to the refrigerator was a massive section of tree trunk, as wide as a dining-room table, resting on a pallet.

The beech tree from which this slab came from was planted around 1870, by a Boston businessman named Joseph Story Fay near his summer house in Woods Hole. The seedling grew into a towering, beloved fixture in the village. Lovelorn initials scarred its broad base. And then, after nearly 150 years, it started to rot from bark disease and had to come down.

“They had to have a ceremony to say goodbye to it. It was a very sad day,” Gaylord said. “And I saw an opportunity.”

Gaylord is an expert at measuring carbon 14. Before the era of nuclear testing, carbon 14 was generated outside of labs only by cosmic rays falling from space. They crashed into nitrogen atoms, and out of the collision popped a carbon 14 atom. Just one in 1 trillion carbon atoms in the atmosphere was a carbon 14 isotope. Fay’s beech took carbon dioxide out of the atmosphere to build wood, and so it had the same one-in-a-trillion proportion.

When Gaylord got word that the tree was coming down in 2015, she asked for a cross-section of the trunk. Once it arrived at the institute, she and two college students carefully counted its rings. Looking at the tree, I could see a line of pinholes extending from the center to the edge of the trunk. Those were the places where Gaylord and her students used razor blades to carve out bits of wood. In each sample, they measured the level of radiocarbon.

“In the end, we got what I hoped for,” she said. What she’d hoped for was a history of our nuclear era.

What Lies Beneath

For most of the tree’s life, they found, the level had remained steady from one year to the next. But in 1954, John Clark initiated an extraordinary climb. The new supply of radiocarbon atoms in the atmosphere over Bikini Atoll spread around the world. When it reached Woods Hole, Fay’s beech tree absorbed the bomb radiocarbon in its summer leaves and added it to its new ring of wood.

As nuclear testing accelerated, Fay’s beech took on more radiocarbon. A graph pinned to the wall above the beech slab charts the changes. In less than a decade, the level of radiocarbon in the tree’s outermost rings nearly doubled to almost two parts per trillion. But not long after the signing of the Partial Test Ban Treaty in 1963, that climb stopped. After a peak in 1964, each new ring of wood in Fay’s beech carried a little less radiocarbon. The fall was far slower than the climb. The level of radiocarbon in the last ring the beech grew before getting cut down was only 6 percent above the radiocarbon levels before Castle Bravo. Versions of the same sawtoothlike peak Gaylord drew had already been found in other parts of the world, including the rings of trees in New Zealand and the coral reefs of the Galapagos Islands. In October 2019, Gaylord unveiled an exquisitely clear version of the bomb spike in New England.

When scientists first discovered radiocarbon, in 1940, they did not find it in a tree or any other part of nature. They made it. Regular carbon has six protons and six neutrons. At UC Berkeley, Martin Kamen and Sam Ruben blasted carbon with a beam of neutrons and produced a new form, with eight neutrons instead of six. Unlike regular carbon, these new atoms turned out to be a source of radiation. Every second, a small portion of the carbon 14 atoms decayed into nitrogen, giving off radioactive particles. Kamen and Ruben used that rate of decay to estimate carbon 14’s half-life at 4,000 years. Later research would sharpen that estimate to 5,700 years.

Soon after Kamen and Ruben’s discovery, a University of Chicago physicist named Willard Libby determined that radiocarbon existed beyond the walls of Berkeley’s labs. Cosmic rays falling from space smashed into nitrogen atoms in the atmosphere every second of every day, transforming those atoms into carbon 14. And because plants and algae drew in carbon dioxide from the air, Libby realized, they should have radiocarbon in their tissue, as should the animals that eat those plants (and the animals that eat those animals, for that matter).

Libby reasoned that as long as an organism is alive and taking in carbon 14, the concentration of the isotope in its tissue should roughly match the concentration in the atmosphere. Once an organism dies, however, its radiocarbon should decay and eventually disappear completely.

To test this idea, Libby set out to measure carbon 14 in living organisms. He had colleagues go to a sewage-treatment plant in Baltimore, where they captured the methane given off by bacteria feeding on the sewage. When the methane samples arrived in Chicago, Libby extracted the carbon and put it in a radioactivity detector.. It crackled as carbon 14 decayed to nitrogen.

Read: Global warming could make carbon dating impossible

To see what happens to carbon 14 in dead tissue, Libby ran another experiment, this one with methane from oil wells. He knew that oil is made up of algae and other organisms that fell to the ocean floor and were buried for millions of years. Just as he had predicted, the methane from ancient oil contained no carbon 14 at all.

Libby then had another insight, one that would win him the Nobel Prize: The decay of carbon 14 in dead tissues acts like an archaeological clock. As the isotope decays inside a piece of wood, a bone, or some other form of organic matter, it can tell scientists how long ago that matter was alive. Radiocarbon dating, which works as far back as about 50,000 years, has revealed to us to when the Neanderthals became extinct, when farmers domesticated wheat, when the Dead Sea Scrolls were written. It has become the calendar of humanity.

Word of Libby’s breakthrough reached a New Zealand physicist named Athol Rafter. He began using radiocarbon dating on the bones of extinct flightless birds and ash from ancient eruptions. To make the clock more precise, Rafter measured the level of radiocarbon in the atmosphere. Every few weeks he climbed a hill outside the city of Wellington and set down a Pyrex tray filled with lye to trap carbon dioxide.


Rafter expected the level of radiocarbon to fluctuate. But he soon discovered that something else was happening: Month after month, the carbon dioxide in the atmosphere was getting more radioactive. He dunked barrels into the ocean, and he found that the amount of carbon 14 was rising in seawater as well. He could even measure extra carbon 14 in the young leaves growing on trees in New Zealand.

The Castle Bravo test and the ones that followed had to be the source. They were turning the atmosphere upside down. Instead of cosmic rays falling from space, they were sending neutrons up to the sky, creating a huge new supply of radiocarbon.

In 1957, Rafter published his results in the journal Science. The implications were immediately clear—and astonishing: Man-made carbon 14 was spreading across the planet from test sites in the Pacific and the Arctic. It was even passing from the air into the oceans and trees.

Other scientists began looking, and they saw the same pattern. In Texas, the carbon 14 levels in new tree rings were increasing each year. In Holland, the flesh of snails gained more as well. In New York, scientists examined the lungs of a fresh human cadaver, and found that extra carbon 14 lurked in its cells. A living volunteer donated blood and an exhalation of air. Bomb radiocarbon was in those, too.

Bomb radiocarbon did not pose a significant threat to human health—certainly not compared with other elements released by bombs, such as plutonium and uranium. But its accumulation was deeply unsettling nonetheless. When Linus Pauling accepted the 1962 Nobel Peace Prize for his campaigning against hydrogen bombs, he said that carbon 14 “deserves our special concern” because it “shows the extent to which the earth is being changed by the tests of nuclear weapons.”

Photos: When we tested nuclear bombs

The following year, the signing of the Partial Test Ban Treaty stopped aboveground nuclear explosions, and ended the supply of bomb radiocarbon. All told, those tests produced about 60,000 trillion trillion new atoms of carbon 14. It would take cosmic rays 250 years to make that much. In 1964, Rafter quickly saw the treaty’s effect: His trays of lye had less carbon 14 than they had the year before.

Only a tiny fraction of the carbon 14 was decaying into nitrogen. For the most part, the atmosphere’s radiocarbon levels were dropping because the atoms were rushing out of the air. This exodus of radiocarbon gave scientists an unprecedented chance to observe how nature works.

Today scientists are still learning from these man-made atoms. “I feel a little bit bad about it,” says Kristie Boering, an atmospheric chemist at UC Berkeley who has studied radiocarbon for more than 20 years. “It’s a huge tragedy, the fact that we set off all these bombs to begin with. And then we get all this interesting scientific information from it for all these decades. It’s hard to know exactly how to pitch that when we’re giving talks. You can’t get too excited about the bombs that we set off, right?”

Yet the fact remains that for atmospheric scientists like Boering, bomb radiocarbon has lit up the sky like a tracer dye. When nuclear triggermen such as John Clark set off their bombs, most of the resulting carbon 14 shot up into the stratosphere directly above the impact sites. Each spring, parcels of stratospheric air gently fell down into the troposphere below, carrying with them a fresh load of carbon 14. It took a few months for these parcels to settle on weather stations on the ground. Only by following bomb radiocarbon did scientists discover this perpetual avalanche.

Once carbon 14 fell out of the stratosphere, it kept moving. The troposphere is made up of four great rings of circulating air. Inside each ring, warm air rises and flows through the sky away from the equator. Eventually it cools and sinks back to the ground, flowing toward the equator again before rising once more. At first, bomb radiocarbon remained trapped in the Northern Hemisphere rings, above where the tests had taken place. It took many years to leak through their invisible walls and move toward the tropics. After that, the annual monsoons sweeping through southern Asia pushed bomb radiocarbon over the equator and into the Southern Hemisphere.
ILLUSTRATION Zoe van Djik

Eventually, some of the bomb radiocarbon fell all the way to the surface of the planet. Some of it was absorbed by trees and other plants, which then died and delivered some of that radiocarbon to the soil. Other radiocarbon atoms settled into the ocean, to be carried along by its currents.

Carbon 14 “is inextricably linked to our understanding of how the water moves,” says Steve Beaupre, an oceanographer at Stony Brook University, in New York.

In the 1970s, marine scientists began carrying out the first major chemical surveys of the world’s oceans. They found that bomb radiocarbon had penetrated the top 1,000 meters of the ocean. Deeper than that, it became scarce. This pattern helped oceanographers figure out that the ocean, like the atmosphere above, is made up of layers of water that remain largely separate.

The warm, relatively fresh water on the surface of the ocean glides over the cold, salty depths. These surface currents become saltier as they evaporate, and eventually, at a few crucial spots on the planet, these streams get so dense that they fall to the bottom of the ocean. The bomb radiocarbon from Castle Bravo didn’t start plunging down into the depths of the North Atlantic until the 1980s, when John Clark was two decades into retirement. It’s still down there, where it will be carried along the seafloor by bottom-hugging ocean currents for hundreds of years before it rises to the light of day.

Some of the bomb radiocarbon that falls into the ocean makes its way into ocean life, too. Some corals grow by adding rings of calcium carbonate, and they have recorded their own version of the bomb spike. Their spike lagged well behind the one that Rafter recorded, thanks to the extra time the radiocarbon took to mix into the ocean. Algae and microbes on the surface of the ocean also take up carbon from the air, and they feed a huge food web in turn. The living things in the upper reaches of the ocean release organic carbon that falls gently to the seafloor—a jumble of protoplasmic goo, dolphin droppings, starfish eggs, and all manner of detritus that scientists call marine snow. In recent decades, that marine snow has become more radioactive.

In 2009, a team of Chinese researchers sailed across the Pacific and dropped traps 36,000 feet down to the bottom of the Mariana Trench. When they hauled the traps up, there were minnow-size, shrimplike creatures inside. These were Hirondellea gigas, a deep-sea invertebrate that forages on the seafloor for bits of organic carbon. The animals were flush with bomb radiocarbon—a puzzling discovery, because the organic carbon that sits on the floor of the Mariana Trench is thousands of years old. It was as if they had been dining at the surface of the ocean, not at its greatest depths. In a few of the Hirondellea, the researchers found undigested particles of organic carbon. These meals were also high in carbon 14.

Read: A troubling discovery in the deepest ocean trenches

The bomb radiocarbon could not have gotten there by riding the ocean’s conveyor belt, says Ellen Druffel, a scientist at UC Irvine who collaborated with the Chinese team. “The only way you can get bomb carbon by circulation down to the deep Pacific would take 500 years,” she says. Instead, Hirondellea must be dining on freshly fallen marine snow.

“I must admit, when I saw the data it was really amazing,” Dreffel says. “These organisms were sifting out the very youngest material from the surface ocean. They were just leaving behind everything else that came down.”

More than 60 years have passed since the peak of the bomb spike, and yet bomb radiocarbon is telling us new stories about the world. That’s because experts like Mary Gaylord are getting better at gathering these rare atoms. At Woods Hole, Gaylord works at the National Ocean Sciences Accelerator Mass Spectrometry facility (NOSAMS for short). She prepares samples for analysis in a thicket of pipes, wires, glass tubes, and jars of frothing liquid nitrogen. “Our whole life is vacuum lines and vacuum pumps,” she told me.

At NOSAMS, Gaylord and her colleagues measure radiocarbon in all manner of things: sea spray, bat guano, typhoon-tossed trees. The day I visited, Gaylord was busy with fish eyes. Black-capped vials sat on a lab bench, each containing a bit of lens from a red snapper.

The wispy, pale tissue had come to NOSAMS from Florida. A biologist named Beverly Barnett had gotten hold of eyes from red snapper caught in the Gulf of Mexico and sliced out their lenses. Barnett then peeled away the layers of the lenses one at a time. When she describes this work, she makes it sound like woodworking or needlepoint—a hobby anyone would enjoy. “It’s like peeling off the layers of an onion,” she told me. “It’s really nifty to see.”

Eventually, Barnett made her way down to the tiny nub at the center of each lens. These bits of tissue developed when the red snapper were still in their eggs. And Barnett wanted to know exactly how much bomb radiocarbon is in these precious fragments. In a couple of days, Gaylord and her colleagues would be able to tell her.

Gaylord started by putting the lens pieces into an oven that slowly burned them away. The vapors and smoke flowed into a pipe, chased by helium and nitrogen. Gaylord separated the carbon dioxide from the other compounds, and then shunted it into chilled glass tubes. There it formed a frozen fog on the inside walls.

Later, the team at NOSAMS would transform the frozen carbon dioxide into chips of graphite, which they would then load into what looks like an enormous, crooked laser cannon. At one end of the cannon, graphite gets vaporized, and the liberated carbon atoms fly down the barrel. By controlling the magnetic field and other conditions inside the cannon, the researchers cause the carbon 14 atoms to veer away from the carbon 12 atoms and other elements. The carbon 14 atoms fly onward on their own until they strike a sensor.

Ultimately, all of this effort will end up in a number: the number of carbon 14 atoms in the red-snapper lens. For Barnett, every one of those atoms counts. They can tell her the exact age of the red snapper when the fish were caught.

That’s because lenses are peculiar organs. Most of our cells keep making new proteins and destroying old ones. Cells in the lens, however, fill up with light-bending proteins and then die, their proteins locked in place for the rest of our life. The layers of cells at the core of the red-snapper lenses have the same carbon 14 levels that they did when the fish were in their eggs.

Using lenses to estimate the ages of animals is still a new undertaking. But it’s already delivered some surprises. In 2016, for example, a team of Danish researchers studied the lenses from Greenland sharks ranging in size from two and a half to 16 feet long. The lenses of the sharks up to seven feet long had high levels of radiocarbon in them. That meant the sharks had hatched no earlier than the 1960s. The bigger sharks all had much lower levels of radiocarbon in their lenses—meaning that they had been born before Castle Bravo. By extrapolating out from these results, the researchers estimated that Greenland sharks have a staggeringly long life span, reaching up to 390 years or perhaps even more.

Barnett has been developing an even more precise clock for her red snapper, taking advantage of the fact that the level of bomb radiocarbon peaked in the Gulf of Mexico in the 1970s and has been falling ever since. By measuring the level of bomb radiocarbon in the center of the snapper lenses, she can determine the year when the fish hatched.

Knowing the age of fish with this kind of precision is powerful. Fishery managers can track the ages of the fish that are caught each year, information that they can then use to make sure their stocks don’t collapse. Barnett wants to study fish in the Gulf of Mexico to see how they were affected by the Deepwater Horizon oil spill of 2010. Their eyes can tell her how old they were when they were hit by that disaster.

When it comes to carbon, we are no different than red snapper or Greenland sharks. We use the carbon in the food we eat to build our body, and the level of bomb radiocarbon inside of us reflects our age. People born in the early 1960s have more radiocarbon in their lenses than people born before that time. People born in the years since then have progressively less.

For forensic scientists who need to determine the age of skeletal remains, lenses aren’t much help. But teeth are. As children develop teeth, they incorporate carbon into the enamel. If people’s teeth have a very low level of radiocarbon, it means that they were born well before Castle Bravo. People born in the early 1960s have high levels of radiocarbon in their molars, which develop early, and lower levels in their wisdom teeth, which grow years later. By matching each tooth in a jaw to the bomb curve, forensic scientists can estimate the age of a skeleton to within one or two years.

Even after childhood, bomb radiocarbon chronicles the history of our body. When we build new cells, we make DNA strands out of the carbon in our food. Scientists have used bomb radiocarbon in people’s DNA to determine the age of their cells. In our brains, most of the cells form around the time we’re born. But many cells in our hearts and other organs are much younger.

We also build other molecules throughout our lives, including fat. In a September 2019 study, Kirsty Spalding of the Karolinska Institute, near Stockholm, used bomb radiocarbon to study why people put on weight. Researchers had long known that our level of fat is the result of how much new fat we add to our body relative to how much we burn. But they didn’t have direct evidence for exactly how that balance influences our weight over the course of our life.

Spalding and her colleagues found 54 people from whom doctors had taken fat biopsies and asked if they could follow up. The fat samples spanned up to 16 years. By measuring the age of the fat in each sample, the researchers could estimate the rate at which each person added and removed fat over their lives.

The reason we put on weight as we get older, the researchers concluded, is that we get worse at removing fat from our bodies. “Before, you could intuitively believe that the rate at which we burn fat decreases as we age,” Spalding says, “but we showed it for the first time scientifically.”

Unexpectedly, though, Spalding discovered that the people who lost weight and kept it off successfully were the ones who burned their fat slowly. “I was quite surprised by that data,” Spalding said. “It adds new and interesting biology to understanding how to help people maintain weight loss.”

Children who are just now going through teething pains will have only a little more bomb radiocarbon in their enamel than children born before Castle Bravo did. Over the past six decades, the land and ocean have removed much of what nuclear bombs put into the air. Heather Graven, a climate scientist at Imperial College London, is studying this decline. It helps her predict the future of the planet.


Graven and her colleagues build models of the world to study the climate. As we emit fossil fuels, the extra carbon dioxide traps heat. How much heat we’re facing in centuries to come depends in part on how much carbon dioxide the oceans and land can remove. Graven can use the rise and fall of bomb radiocarbon as a benchmark to test her models.

In a recent study, she and her colleagues unleashed a virtual burst of nuclear-weapons tests. Then they tracked the fate of her simulated bomb radiocarbon to the present day. Much to Graven’s relief, the radiocarbon in the atmosphere quickly rose and then gradually fell. The bomb spike in her virtual world looks much like the one recorded in Joseph Fay’s beech tree.

Graven can keep running her simulation beyond what Fay’s beech and other records tell us about the past. According to her model, the level of radiocarbon in the atmosphere should drop in 2020 to the level before Castle Bravo.

“It’s right around now that we’re crossing over,” Graven told me.

Graven will have to wait for scientists to analyze global measurements of radiocarbon in the air to see whether she’s right. That’s important to find out, because Graven’s model suggests that the bomb spike is falling faster than the oceans and land alone can account for. When the ocean and land draw down bomb radiocarbon, they also release some of it back into the air. That two-way movement of bomb radiocarbon ought to cause its concentration in the atmosphere to level off a little above the pre–Castle Bravo mark. Instead, Graven’s model suggests, it continues to fall. She suspects that the missing factor is us.

We mine coal, drill for oil and gas, and then burn all that fossil fuel to power our cars, cool our houses, power our factories. In 1954, the year that John Clark set off Castle Bravo, humans emitted 6 billion tons of carbon dioxide into the air. In 2018, humans emitted about 37 billion tons. As Willard Libby first discovered, this fossil fuel has no radiocarbon left. By burning it, we are lowering the level of radiocarbon in the atmosphere, like a bartender watering down the top-shelf liquor.

If we keep burning fossil fuels at our accelerating rate, the planet will veer into climate chaos. And once more, radiocarbon will serve as a witness to our self-destructive actions. Unless we swiftly stop burning fossil fuels, we will push carbon 14 down far below the level it was at before the nuclear bombs began exploding.

To Graven, the coming radiocarbon crash is just as significant as the bomb spike has been. “We're transitioning from a bomb signal to a fossil-fuel-dilution signal,” she said.

The author Jonathan Weiner once observed that we should think of burning fossil fuels as a disturbance on par with nuclear-weapon detonations. “It is a slow-motion explosion manufactured by every last man, woman and child on the planet,” he wrote. If we threw up our billions of tons of carbon into the air all at once, it would dwarf Castle Bravo. “A pillar of fire would seem to extend higher into the sky and farther into the future than the eye can see,” Weiner wrote.

Bomb radiocarbon showed us how nuclear weapons threatened the entire world. Today, everyone on Earth still carries that mark. Now our pulse of carbon 14 is turning into an inverted bomb spike, a new signal of the next great threat to human survival.


CARL ZIMMER is a columnist at The New York Times. His latest book is She Has Her Mother’s Laugh: The Powers, Perversions, and Potential of Heredity.
Cold War nuclear bomb tests reveal true age of whale sharks
Whale Shark Scares The Sh%t Out Of Me!!! - YouTube

The radioactive legacy of the arms race solves a mystery about the world's largest fish

Atomic bomb tests conducted during the Cold War have helped scientists for the first time correctly determine the age of whale sharks.

Date:April 6, 2020

Source:Australian Institute of Marine Science

Atomic bomb tests conducted during the Cold War have helped scientists for the first time correctly determine the age of whale sharks.

The discovery, published in the journal Frontiers in Marine Science, will help ensure the survival of the species -- the largest fish in the world -- which is classified as endangered.

Measuring the age of whale sharks (Rhincodon typus) has been difficult because, like all sharks and rays, they lack bony structures called otoliths that are used to assess the age of other fish.

Whale shark vertebrae feature distinct bands -- a little like the rings of a tree trunk -- and it was known that these increased in number as the animal grew older. However, some studies suggested that a new ring was formed every year, while others concluded that it happened every six months.

To resolve the question, researchers led by researchers led by Joyce Ong from Rutgers University in New Jersey, USA, Steven Campana from the University of Iceland, and Mark Meekan from the Australian Institute of Marine Science in Perth, Western Australia, turned to the radioactive legacy of the Cold War's nuclear arms race.

During the 1950s and 1960s, the USA, Soviet Union, Great Britain, France and China conducted tests of nuclear weapons. Many of these were explosions detonated several kilometres in the air.

One powerful result of the blasts was the temporary atmospheric doubling of an isotope called carbon-14.

Carbon-14 is a naturally occurring radioactive element that is often used by archaeologists and historians to date ancient bones and artefacts. Its rate of decay is constant and easily measured, making it ideal for providing age estimates for anything over 300 years old.

However, it is also a by-product of nuclear explosions. Fallout from the Cold War tests saturated first the air, and then the oceans. The isotope gradually moved through food webs into every living thing on the planet, producing an elevated carbon-14 label, or signature, which still persists.

This additional radioisotope also decays at a steady rate -- meaning that the amount contained in bone formed at one point in time will be slightly greater than that contained in otherwise identical bone formed more recently.

Using bomb radiocarbon data prepared by Steven Campana, Ong, Meekan, and colleagues set about testing the carbon-14 levels in the growth rings of two long-dead whale sharks stored in Pakistan and Taiwan. Measuring the radioisotope levels in successive growth rings allowed a clear determination of how often they were created -- and thus the age of the animal.


New Study Estimates Whale Sharks' Lifespan - YouTube

"We found that one growth ring was definitely deposited every year," Dr Meekan said.

"This is very important, because if you over- or under-estimate growth rates you will inevitably end up with a management strategy that doesn't work, and you'll see the population crash."

One of the specimens was conclusively established as 50 years old at death -- the first time such an age has been unambiguously verified.

"Earlier modelling studies have suggested that the largest whale sharks may live as long as 100 years," Dr Meekan said.

"However, although our understanding of the movements, behaviour, connectivity and distribution of whale sharks have improved dramatically over the last 10 years, basic life history traits such as age, longevity and mortality remain largely unknown.

"Our study shows that adult sharks can indeed attain great age and that long lifespans are probably a feature of the species. Now we have another piece of the jigsaw added."

Whale sharks are today protected across their global range and are regarded as a high-value species for eco-tourism. AIMS is the world's leading whale shark research body, and the animal is the marine emblem of Dr Meekan's home state, Western Australia.

Drs Ong, Meekan, and Campana were aided by Dr Hua Hsun Hsu from the King Fahd University of Petroleum and Minerals in Saudi Arabia, and Dr Paul Fanning from the Pakistan node of the UN Food and Agricultural Organisation.

Story Source:
Materials provided by Australian Institute of Marine Science. Note: Content may be edited for style and length.

Journal Reference:
Joyce J. L. Ong, Mark G. Meekan, Hua Hsun Hsu, L. Paul Fanning, Steven E. Campana. Annual Bands in Vertebrae Validated by Bomb Radiocarbon Assays Provide Estimates of Age and Growth of Whale Sharks. Frontiers in Marine Science, 2020; 7 DOI: 10.3389/fmars.2020.00188


Cite This Page:
Australian Institute of Marine Science. "Cold War nuclear bomb tests reveal true age of whale sharks: The radioactive legacy of the arms race solves a mystery about the world's largest fish." ScienceDaily. ScienceDaily, 6 April 2020. .
Discovery of life in solid rock deep beneath sea may inspire new search for life on MarS

Bacteria live in tiny clay-filled cracks in solid rock millions of years old


Newly discovered single-celled creatures living deep beneath the seafloor have provided clues about how to find life on Mars. 

These bacteria were discovered living in tiny cracks inside volcanic rocks after researchers perfected a new method cutting rocks into ultrathin slices to study under a microscope. 

Researchers estimate that the rock cracks are home to a community of bacteria as dense as that of the human gut, about 10 billion bacterial cells per cubic centimeter.

Date:April 2, 2020
Source:University of Tokyo

Newly discovered single-celled creatures living deep beneath the seafloor have given researchers clues about how they might find life on Mars. These bacteria were discovered living in tiny cracks inside volcanic rocks after researchers persisted over a decade of trial and error to find a new way to examine the rocks.


Researchers estimate that the rock cracks are home to a community of bacteria as dense as that of the human gut, about 10 billion bacterial cells per cubic centimeter (0.06 cubic inch). In contrast, the average density of bacteria living in mud sediment on the seafloor is estimated to be 100 cells per cubic centimeter.

"I am now almost over-expecting that I can find life on Mars. If not, it must be that life relies on some other process that Mars does not have, like plate tectonics," said Associate Professor Yohey Suzuki from the University of Tokyo, referring to the movement of land masses around Earth most notable for causing earthquakes. Suzuki is first author of the research paper announcing the discovery, published in Communications Biology.

Magic of clay minerals

"I thought it was a dream, seeing such rich microbial life in rocks," said Suzuki, recalling the first time he saw bacteria inside the undersea rock samples.

Undersea volcanoes spew out lava at approximately 1,200 degrees Celsius (2,200 degrees Fahrenheit), which eventually cracks as it cools down and becomes rock. The cracks are narrow, often less than 1 millimeter (0.04 inch) across. Over millions of years, those cracks fill up with clay minerals, the same clay used to make pottery. Somehow, bacteria find their way into those cracks and multiply.

"These cracks are a very friendly place for life. Clay minerals are like a magic material on Earth; if you can find clay minerals, you can almost always find microbes living in them," explained Suzuki.

The microbes identified in the cracks are aerobic bacteria, meaning they use a process similar to how human cells make energy, relying on oxygen and organic nutrients.

"Honestly, it was a very unexpected discovery. I was very lucky, because I almost gave up," said Suzuki.

Cruise for deep ocean samples

Suzuki and his colleagues discovered the bacteria in rock samples that he helped collect in late 2010 during the Integrated Ocean Drilling Program (IODP). IODP Expedition 329 took a team of researchers from the tropical island of Tahiti in the middle of the Pacific Ocean to Auckland, New Zealand. The research ship anchored above three locations along the route across the South Pacific Gyre and used a metal tube 5.7 kilometers long to reach the ocean floor. Then, a drill cut down 125 meters below the seafloor and pulled out core samples, each about 6.2 centimeters across. The first 75 meters beneath the seafloor were mud sediment and then researchers collected another 40 meters of solid rock.

Depending on the location, the rock samples were estimated to be 13.5 million, 33.5 million and 104 million years old. The collection sites were not near any hydrothermal vents or sub-seafloor water channels, so researchers are confident the bacteria arrived in the cracks independently rather than being forced in by a current. The rock core samples were also sterilized to prevent surface contamination using an artificial seawater wash and a quick burn, a process Suzuki compares to making aburi (flame-seared) sushi.

At that time, the standard way to find bacteria in rock samples was to chip away the outer layer of the rock, then grind the center of the rock into a powder and count cells out of that crushed rock.

"I was making loud noises with my hammer and chisel, breaking open rocks while everyone else was working quietly with their mud," he recalled.

How to slice a rock

Over the years, continuing to hope that bacteria might be present but unable to find any, Suzuki decided he needed a new way to look specifically at the cracks running through the rocks. He found inspiration in the way pathologists prepare ultrathin slices of body tissue samples to diagnose disease. Suzuki decided to coat the rocks in a special epoxy to support their natural shape so that they wouldn't crumble when he sliced off thin layers.

These thin sheets of solid rock were then washed with dye that stains DNA and placed under a microscope.

The bacteria appeared as glowing green spheres tightly packed into tunnels that glow orange, surrounded by black rock. That orange glow comes from clay mineral deposits, the "magic material" giving bacteria an attractive place to live.

Whole genome DNA analysis identified the different species of bacteria that lived in the cracks. Samples from different locations had similar, but not identical, species of bacteria. Rocks at different locations are different ages, which may affect what minerals have had time to accumulate and therefore what bacteria are most common in the cracks.

Suzuki and his colleagues speculate that the clay mineral-filled cracks concentrate the nutrients that the bacteria use as fuel. This might explain why the density of bacteria in the rock cracks is eight orders of magnitude greater than the density of bacteria living freely in mud sediment where seawater dilutes the nutrients.

From the ocean floor to Mars

The clay minerals filling cracks in deep ocean rocks are likely similar to the minerals that may be in rocks now on the surface of Mars.

"Minerals are like a fingerprint for what conditions were present when the clay formed. Neutral to slightly alkaline levels, low temperature, moderate salinity, iron-rich environment, basalt rock -- all of these conditions are shared between the deep ocean and the surface of Mars," said Suzuki.

Suzuki's research team is beginning a collaboration with NASA's Johnson Space Center to design a plan to examine rocks collected from the Martian surface by rovers. Ideas include keeping the samples locked in a titanium tube and using a CT (computed tomography) scanner, a type of 3D X-ray, to look for life inside clay mineral-filled cracks.

"This discovery of life where no one expected it in solid rock below the seafloor may be changing the game for the search for life in space," said Suzuki.


Story Source:
Materials provided by University of Tokyo. Note: Content may be edited for style and length.

Journal Reference:
Yohey Suzuki, Seiya Yamashita, Mariko Kouduka, Yutaro Ao, Hiroki Mukai, Satoshi Mitsunobu, Hiroyuki Kagi, Steven D’ Hondt, Fumio Inagaki, Yuki Morono, Tatsuhiko Hoshino, Naotaka Tomioka, Motoo Ito. Deep microbial proliferation at the basalt interface in 33.5–104 million-year-old oceanic crust. Communications Biology, April 2, 2020 DOI: 10.1038/s42003-020-0860-1


Cite This Page: 
University of Tokyo. "Discovery of life in solid rock deep beneath sea may inspire new search for life on Mars: Bacteria live in tiny clay-filled cracks in solid rock millions of years old." ScienceDaily. ScienceDaily, 2 April 2020. .