Making North America: Life Hero

<p></p><p>How did life emerge on our primeval continent? Why was North America home to so many iconic dinosaurs like <i>T. rex</i>? And how did a huge sea filled with giant marine reptiles end up covering Kansas? We tell the surprising intertwined story of life and the landscape in North America.</p>

<p>How did massive volcanic eruptions, inland seas, and land bridges pave the way for life?</p>

Making North America: Life

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<p>A new study provides compelling evidence that children can inherit mitochondrial DNA from both their parents.</p>

Not your mom’s genes: Mitochondrial DNA can come from Dad

NOVA Wonders Can We Make Life? Hero

<p></p><p>&quot;It&#x27;s alive!&quot; Since Dr. Frankenstein spoke those famous words, we&#x27;ve been alternately enthralled and terrified by the idea of creating life in the lab. Now, a revolution in genetic engineering and thrilling innovations in synthetic biology are bringing that dream—or nightmare, as the case may be—closer to reality. New tools allow researchers to use cells to create their own DNA and edit it into existing genomes with more ease and less cost than ever before. Along with renewed hopes for treating some genetic diseases, there&#x27;s serious talk of using the newest technologies to bring long-extinct animals back from the dead – like the team hoping to resurrect the woolly mammoth. Science fiction is quickly becoming science fact. Another daring genetic experiment to bioengineer animals could prevent Lyme disease. But the power to make life comes with deep ethical questions. What are the potential rewards—and dangers—of tinkering with nature? <i>NOVA Wonders</i> explores the benefits and the burden of risk surrounding the controversial new technology.</p><p></p><p></p>

<p>A revolution in gene editing enables scientists to create and edit DNA like never before.</p>

Can We Make Life?

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Evolution

Koch Foundation

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      <div class="rich-text"><p>The electric eel is the closest thing nature’s got to a living, breathing battery.</p><p>Running up to eight feet in length, these serpentine swimmers (which actually aren’t true eels, but <a href="https://www.nationalgeographic.com/animals/fish/e/electric-eel/">a type of knifefish</a>) are packed with thousands of cells that can generate their own electricity. Some of their homemade jolts are low-voltage, radar-like pulses that help the fish navigate. When prompted, however, electric eels can also serve up shocks powerful enough to <a href="https://www.nytimes.com/2017/09/14/science/electric-eels-shock.html">incapacitate a horse</a>.</p></div>
  

  
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      <div class="rich-text"><p>Beneath this electrifying exterior, things get even funkier. Unlike most other fish, electric eels don’t rely on their gills to breathe, instead periodically peeking above water to <a href="https://nationalzoo.si.edu/animals/electric-eel">suck air into their lung-like mouths</a>. During the dry season, females will lay thousands of eggs into nests forged out of their mates’ saliva. And—because DIY electricity just isn’t enough—when they’re f(eel)ing threatened, these suckers can <a href="https://science.sciencemag.org/content/346/6214/1231.abstract"><i>launch themselves</i> at attackers</a> to deliver targeted parcels of pain.</p><p>There’s a lot that makes the electric eel unique. And for centuries, scientists thought they all comprised a single species—<i>Electrophorus electricus—</i>occupying its own lonely branch on the knifefish family tree. But it turns out electric eels harbor quite the shocking secret: These fish are so nice, they speciated twice.</p>
            <figure class="richtext-image full-width"><img alt="2A - Carlos David de Santana - Electrophorus voltai Xingu River_4 Picture by L. Sousa.jpg" class="richtext-image full-width" height="520" width="800"
            src="/wgbh/nova/media/images/2A_-_Carlos_David_de_Santana_-_Electrophorus_v.width-800.jpg"/><figcaption><p>Electric eels like <i>Electrophorus voltai</i> are especially fond of slow, shallow waters. “That’s prime real estate,” says Kory Evans, a fish biologist at Brown University. Image Credit: L. Sousa</p><div class="credit"><p></p></div></figcaption>
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            <p>An international team of scientists has found that at least three species of electric eel slither the rivers of South America. One of them, <i>Electrophorus voltai</i>, packs an unexpectedly powerful punch, discharging shocks up to 860 volts. That’s a 30 percent uptick over the previous record—and a stat that earns <i>E. voltai</i> the title of the strongest known living source of electricity.</p><p>“That’s bonkers,” says <a href="https://koryevans.weebly.com/about.html">Kory Evans</a>, an evolutionary biologist who studies electric fish at Brown University, but was not involved in the study. “The fact that there’s a living organism that has the ability to generate this kind of violent electricity is really shocking, no pun intended.”</p></div>
  

  
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      <div class="rich-text"><p>The <a href="https://www.nature.com/articles/s41467-019-11690-z">study</a>, published today in the journal <i>Nature Communications</i>, triples the membership of the genus <i>Electrophorus</i>, which now includes the OG <i>E. electricus</i>, as well as newcomers <i>E. voltai</i> and <i>E. varii.</i> (Does this make electric eels less special? Maybe it boosts their appeal by a factor of three.)</p><p>In truth, though, the discovery has been a long time coming. Since their discovery in 1766 by Swedish zoologist Carl Linnaeus, electric eels have been found all over Greater Amazonia, lurking wherever the water’s fresh, calm, and chock full of invertebrate snacks.</p><p>That’s an enormous range for a single species—essentially the top half of a continent, Evans says. Animals that spread into such diverse geographical regions tend to split off into separate species, especially if disparate groups lose contact with one another along the way. That <i>should</i> have been the case for electric eels, which, with their penchant for shallow, slow-moving waters, aren’t exactly the most cosmopolitan of fish.</p><p>Researchers have been trying to “break up” <i>E. electricus</i> for years, says Evans, who praised the new paper. “My first thought was, ‘Oh, they finally did it!’”</p>
            <figure class="richtext-image full-width"><img alt="4A - Carlos David de Santana - Aerial view_typical electric eel Upland habitat_Coppename River_Suriname Picture by de Santana.jpeg" class="richtext-image full-width" height="600" width="800"
            src="/wgbh/nova/media/images/4A_-_Carlos_David_de_Santana_-_Aerial_view_typ.width-800.jpg"/><figcaption><p>The highland regions of Greater Amazonia, the stomping grounds of <i>Electrophorus electricus</i> and<i> Electrophorus voltai.</i> Image Credit: C. David de Santana</p><div class="credit"><p></p></div></figcaption>
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            <p>There’s a few reasons it took 250 years to get to this point, says study author <a href="https://electriceel2013.wixsite.com/electric-fishes">David de Santana</a>, a zoologist and fish biologist at the Smithsonian’s National Museum of Natural History. For one, the trio of species his team teased apart all look remarkably similar, save for a few subtle discrepancies, like the shapes of their skulls. Even now, with three clear-cut bins to sort them into, picking apart their physical differences takes an exacting eye. According to de Santana, who studies fish morphology for a living, “this was my hardest work yet.”</p><p>The crux of the matter came down to a combination of intensive field work and modern genetic sequencing. De Santana and his colleagues spent the better part of four years traipsing through the river basins of Greater Amazonia, wrangling fish out of muddy streams, swamps, and plains throughout Brazil, French Guiana, Guyana, and Suriname.</p><p>Back in the lab, DNA extracted from 107 specimens revealed three distinct groups of animals. While the trio appear to share a common ancestor, they ultimately split from each other in two bouts: once about 7.1 million years ago, when <i>E. varii</i> branched off, and again 3.6 million years ago, when <i>E. electricus</i> and <i>E. voltai</i> went their separate ways.</p><p>Nowadays, the three species don’t have much to do with one another. While <i>E. electricus</i> was once thought to dominate the entire Amazonian region, de Santana’s team has narrowed its range to the Guiana Shield, a northerly geological formation home to highlands with rapids and waterfalls. South of this is a similar region called the Brazilian Shield, which appears to be the main stomping grounds of <i>E. voltai.</i> De Santana thinks the fast-flowing waters may have helped shape the two closely-related species’ relatively flat heads.</p><p>The geographic outlier of the bunch, then, is <i>E. varii,</i> a more bulb-headed fish that lurks in the lowlands of the Amazon Basin, where the waters are murky and sluggish.</p>
            <figure class="richtext-image full-width"><img alt="4B - Carlos David de Santana - typical electric eel Lowland habitat Picture by D. Bastos.png" class="richtext-image full-width" height="529" width="800"
            src="/wgbh/nova/media/images/4B_-_Carlos_David_de_Santana_-_typical_electri.width-800.png"/><figcaption><p>The lowland regions of Greater Amazonia, where <i>Electrophorus varii</i> is known to lurk. Image Credit: D. Bastos</p><div class="credit"><p></p></div></figcaption>
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            <p>Not to be outdone, <i>E. voltai</i> managed to distinguish itself in its own way. When the researchers hooked electrodes up to some of the fish to suss out their shock factor, one <i>E. voltai</i> specimen managed to pump out a whopping 860 volts of electricity.</p><p>The team only hooked six fish up to their oscilloscope, and de Santana suspects researchers have yet to crown the world’s most electrifying eel. (De Santana, who’s received his fair share of shocks, adds that the jolts are brief, and “not so bad.” That said, you would <i>not</i> want to get cornered by a dozen or so pissed off electric eels at once—a real concern, considering the team believes the fish sometimes hunt in packs.)</p><p>It’s still not totally clear what originally drove the three <i>Electrophorus</i> species apart, de Santana says. But his team is now hard at work disentangling more of the differences that exist between them—and it’s very possible that a few more species have yet to be uncovered.</p><p>Evans suspects the new species designations won’t slither down smoothly for everyone. “Usually when you split up species...it gets controversial,” he says. “But genetically, [these electric eels] sort out nicely, and it’s hard to argue with that.”</p><p><a href="https://kmallenneuro.com/">Kate Allen</a>, a neuroscientist and fish biologist at Johns Hopkins University who was not involved in the study, agrees, pointing out that at least 250 species of electric fish exist in South America (though <i>Electrophorus</i> are the only ones that weaponize their zap). “It’s kind of weird that there would only be one species of electric eel given the diversity in the rest of their group,” she says.</p>
            <figure class="richtext-image full-width"><img alt="3A - Carlos David de Santana - Electrophorus varii Rio Negro 2 Picture by D. Bastos.jpg" class="richtext-image full-width" height="228" width="800"
            src="/wgbh/nova/media/images/3A_-_Carlos_David_de_Santana_-_Electrophorus_v.width-800.jpg"/><figcaption><p>The newly described electric eel species <i>Electrophorus varii</i> swims through murky, slow-flowing lowland waters. Image Credit: D. Bastos</p><div class="credit"><p></p></div></figcaption>
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            <p>Regardless of where species lines are drawn, though, simply having a more comprehensive catalog of these funky fish could be a boon for scientists in a variety of fields, de Santana says. Electric eels inspired Italian physicist Alessandro Volta to design the first battery in 1799; centuries later, researchers are still studying them to develop <a href="https://www.ncbi.nlm.nih.gov/pubmed/26766594">more efficient</a> <a href="https://www.ncbi.nlm.nih.gov/pubmed/29239354">power sources</a>. Other <i>Electrophorus</i> aficionados are exploring applications in the <a href="https://onlinelibrary.wiley.com/doi/abs/10.1002/cmdc.201500104">treatment of neurodegenerative disease</a>, or <a href="https://jeb.biologists.org/content/216/13/2501">designing robots</a> modeled on the fish’s elongated anal fin, which allows it to swim backward or forward, or simply hover in place.</p><p>For these reasons and more, de Santana stresses the importance of preserving biodiversity in the Amazon, where <a href="https://www.theguardian.com/environment/2019/aug/23/amazon-fires-what-is-happening-anything-we-can-do">thousands of fires</a> currently rage amidst widespread deforestation. The electric eels’ species surprise, he says, is just the latest piece of evidence that many of the region’s biological riches remain unexplored.</p><p>After all, there’s nothing more conspicuous than an 8-foot-long electric eel leaping out of the water to shock you, Allen adds. If we’re still finding diversity “in such a big, charismatic species,” she says, “that means there’s a lot out there we don’t yet know about.”</p></div>
  

  
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<p>That earns this fish, <i>Electrophorus voltai</i>, the title of the strongest known living source of electricity.</p>

Newly described species of electric eel serves up shocks of 860 volts





  
      <div class="rich-text"><p>Being white can make it tough to blend in—if you’re a nocturnal bird, that is.</p><p>For years, researchers have puzzled over the snowy plumage of some <a href="https://www.allaboutbirds.org/guide/Barn_Owl/id">barn owls</a> (<i>Tyto alba</i>), which makes them stick out like sore thumbs against the black backdrop of night. This lack of camouflage becomes even more apparent when these pearly predators take to the skies beneath a full moon, which can backlight the birds as they descend upon their rodent prey.</p><p>But these frost-feathered creatures may have good reason not to shirk this lunar spotlight. It turns out that white barn owls actually hunt <i>best</i> when the moon looms large—not in spite of their conspicuous coloration, but because of it.</p></div>
  

  
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      <div class="rich-text"><p>The driving force behind this counterintuitive trend, described in a <a href="https://www.nature.com/articles/s41559-019-0967-2">study</a> published today in the journal <i>Nature Ecology &amp; Evolution</i>, is a neat visual trick: As light bounces off of bright plumage, it has a deer-in-headlights effect on rodents, triggering a freezing response that makes them easier to catch.</p><p>In other words, the ghostly plumage of the white barn owl is so visible, it’s scary—and that can mean curtains for its super-skittish prey.</p><p>“This is a really exciting paper,” says <a href="https://eeb.princeton.edu/people/monica-carlson">Monica Carlson</a>, who studies avian plumage at Princeton University, but was not involved in the study. “Given that we [humans] are a diurnal species...we’re biased toward studying the species we see the most. But this forges new territory in the study of how animals’ colors have evolved.”</p>
            <figure class="richtext-image full-width"><img alt="IMG_1403.jpeg" class="richtext-image full-width" height="597" width="800"
            src="/wgbh/nova/media/images/IMG_1403.width-800.jpg"/><figcaption><p>Barn owls (Tyto alba) are one of the most widespread birds in existence. They&#x27;re recognizable by their heart-shaped faces, and come in varying shades of auburn and white. Image Credit: Alexandre Roulin, University of Lausanne</p><div class="credit"><p></p></div></figcaption>
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            <p>In a world where predators often rely on camouflage to sneak up on their prey, most nocturnal hunters have evolved coats, scales, hairs, and feathers in hues of brown, gray, or black that match the sunless landscape. Barn owls, whose feathers range from deep russet to luminous white, fly in the face of this trend—and until now, it’s been totally unclear why, says study author <a href="https://www.unil.ch/dee/en/home/menuinst/people/group-leaders/prof-alexandre-roulin.html">Alexandre Roulin</a>, a behavioral biologist at the University of Lausanne in Switzerland. (A quick aside: Though snowy owls <a href="https://www.audubon.org/field-guide/bird/snowy-owl">are also white</a>, that’s more to help them blend into their native Arctic tundra, where they often hunt during the day.)</p><p>But inklings of inspiration began to dawn on Roulin during the evening jaunts he’d take to capture barn owls for study. On nights when the moon was full, the whitest of the birds would appear to him “like stars crossing the sky,” he says. “They [were] just so visible.”</p></div>
  

  
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      <div class="rich-text"><p>Dazzling though the birds were to human eyes, Roulin suspected that white barn owls’ ghostly pallor might betray their presence to prey, saddling the birds with a hunting handicap on moonlit nights. But when he and his colleagues dug into their barn owl database—which contained nearly 30 years’ worth of meticulous recordings from 360 nest-boxes in western Switzerland—and overlaid some of the measurements onto the lunar cycle, they discovered the exact opposite to be true.</p><p>On new moon nights, when the moon was least visible in the sky, white and red owls were equally efficient hunters, and hauled the same number of prey back to the owlets in their nests. As the moon waxed, however, the red owls began to falter. And by the time the full moon rolled around, their nestlings weighed less than those raised by white parents—who, in contrast, seemed entirely unphased by the extra light.</p><p>To suss out the secrets of the white birds’ relative success, the team rounded up several dozen common voles (<i>Microtus arvalis</i>), a favorite food among barn owls, and placed each rodent in a brightly or dimly lit room that mimicked either the beginning or end of the lunar cycle. Then, because live birds would have been too difficult to test, the team acquired a set of red and white taxidermied barn owls—all immortalized in postures of flight—and flung them at the voles via a 7-foot zipline.</p><p>Of course, the stuffed birds posed no <i>real</i> threat. But these vulnerable voles were none the wiser. As the owls hurtled down the zipline, most of the rodents froze in fear for several seconds—a common response to an approaching predator, Roulin says. Under new moon conditions, the voles reacted similarly to all the owls the researchers sent their way. But when the room’s “moon” was full, the voles’ paralysis lasted five seconds longer if their assailants were white instead of red.</p>
            <figure class="richtext-image full-width"><img alt="41559_2019_967_MOESM1_ESM.jpg" class="richtext-image full-width" height="300" width="800"
            src="/wgbh/nova/media/images/41559_2019_967_MOESM1_ESM.width-800.jpg"/><figcaption><p>One of the white (left) and one of the red (right) taxidermied owls used in the study. Image Credit: San-Jose et al., Nature, 2019</p><div class="credit"><p></p></div></figcaption>
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            <p>The stuffed white owls also seemed to draw predatory power from the faux moonlight: The better lit the room was, the brighter the birds glowed—and the longer the voles remained immobile.</p><p>Motionless prey is much easier to catch, which is great news for (living) white barn owls, Roulin says. In the wild, this terrifying tactic may buy the birds a few extra seconds to swoop in for the kill—explaining, perhaps, their hunting prowess on moonlit nights, when they’re basically “ghosts,” Roulin jokes.</p><p>“The beautiful thing about this study is that it doesn’t just aim to describe [how the owls’ color affects survival]—it also describes the mechanism behind the process,” says <a href="https://mariadelgado.org/">Maria Delgado</a>, a behavioral ecologist at the University of Oviedo in Spain who was not involved in the study.</p><p>From a color-challenged rodent’s point of view, there’s one big difference between a red owl and a white one: brightness, generated by light reflecting off their feathers. On a small scale, a predator’s beacon-like glow might compromise its stealth. Taken to an extreme, however, this weakness becomes a strength that exploits rodents’ natural aversion to strong light.</p>
            <figure class="richtext-image full-width"><img alt="News &amp; Views_ 41559_2019_Article_977.jpg" class="richtext-image full-width" height="568" width="800"
            src="/wgbh/nova/media/images/News__Views__41559_2019_Article_977.width-800.jpg"/><figcaption><p>Given their glimmer, you might expect the whitest barn owls to be terrible hunters when moon looms large. But it turns out that quite the opposite is true. Image Credit: Isabelle Henry</p><div class="credit"><p></p></div></figcaption>
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            <p>That’s exactly what seems to be going on here, Roulin says. In a follow-up experiment, the researchers introduced another taxidermied white owl to the voles—only this time, they coated the bird’s feathers with duck preen wax, a substance that dulls their natural sheen. Faced with this more muted bird, the voles seemed far less flummoxed, and were quicker to unfreeze. “It’s almost like [these waxed birds] were red,” he says.</p><p>Still, we shouldn’t feel <i>too</i> badly for the browner birds, Roulin adds. The melanin behind their red plumage reinforces feather strength, bolstering the birds against abrasion and fluctuations in temperature. And although white barn owls may shine when the moon is full, their cloak of visibility could come with costs under other circumstances, such as when they’re trying to avoid detection by competitor bird species like carrion crows.</p><p>Tradeoffs like these are probably why the species hasn’t gone monochromatic. In the wild, the plumage of barn owls spans the spectrum between red and white, and each subtle variation may be ideally suited to its own time and place. Roulin and his team are now surveying barn owl populations worldwide to see if some habitats—such as those with more cloud or tree cover—might favor birds of certain shades.</p>
            <figure class="richtext-image full-width"><img alt="IMG_1346.jpeg" class="richtext-image full-width" height="597" width="800"
            src="/wgbh/nova/media/images/IMG_1346.width-800.jpg"/><figcaption><p>Depending on the color of their plumage, barn owls might have their own time of the month. Image Credit: Alexandre Roulin, University of Lausanne</p><div class="credit"><p></p></div></figcaption>
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            <p>Plenty of questions remain, with few researchers to answer them, Roulin says. Studying nocturnal animals as a diurnal human isn’t easy: When nighttime field work gets particularly intense, some of Roulin’s students get just four hours of sleep a night.</p><p>Still, studies like these are crucial for expanding our understanding of the many factors that drive the evolution of plumage, Carlson says. From our perspective, it may seem like there’s little to see after the sun has set. But for nocturnal predators like the barn owl, that couldn’t be further from the truth.</p><p>“We need to conduct these studies while taking into consideration the ecological niche of the species we’re studying,” she says. After all, taking a different perspective—even one that’s often in the dark—can be pretty illuminating.</p></div>
  

  
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<p>The feathery glint startles their rodent prey, making them easier to catch.</p>

Moonlight turns white barn owls into terrifying ‘ghosts’





  
      <div class="rich-text"><p>The world has lost a very good—and very clever—girl.</p><p>Chaser, the border collie who garnered international attention for her impressive vocabulary of more than 1,000 words, died last week at her home in Spartanburg, South Carolina. She is survived by members of the Pilley family, her owners since 2004—and an enduring legacy of language learning many once thought impossible for canines.</p><p>During her 15 years of life, Chaser displayed a remarkable knack for nouns, learning to distinguish between all the members of a massive collection of well-worn toys. But her gift extended beyond one of rote memorization, says Pilley Bianchi, daughter of owner Sally Pilley. Chaser didn’t just pick up words and remember them. She mastered them conceptually, distinguishing verbs from adjectives, and categorizing objects she’d never seen—not unlike, Bianchi says, a human toddler learning to speak.</p></div>
  

  
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      <div class="rich-text"><p>The late psychologist John Pilley, Chaser’s original owner and Bianchi’s father, first began training the pup in 2004. At the time, experts in the field were abuzz about another dog in Germany who’d been taught to tell apart 200 items. But Pilley, then 76, had a hunch Chaser might be capable of more. Over the course of the next three years, he patiently coached Chaser on a daily basis, showing her objects like squeaky toys, stuffed animals, and even pieces of clothing, while repeating their names over and over.</p><p>Some of the monikers were straightforward—a dolphin plush called “porpoise,” a duck dubbed “mallard”—while others, like a monkey referred to as “Uncle Fuzz,” were a little more whimsical. In total, Pilley showed Chaser <a href="https://www.sciencedirect.com/science/article/abs/pii/S0376635710002925#!">1,022 objects</a>. And she remembered them all.</p>
            <figure class="richtext-image full-width"><img alt="Robin Pilley Toy Pile.JPG" class="richtext-image full-width" height="600" width="800"
            src="/wgbh/nova/media/images/Robin_Pilley_Toy_Pile.width-800.jpg"/><figcaption><p>Chaser with her pile of 1,000-plus toys, each of which she knows by name. Image Credit: Courtesy of Robin Pilley</p><div class="credit"><p></p></div></figcaption>
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            <p>That was just the beginning, Bianchi says. As Pilley continued to push the limits of Chaser’s language learning abilities, the boundaries only seemed to expand. Chaser didn’t just retain the names of objects: She could sort them into categories, like balls or sticks, based on their common characteristics, even if she’d never encountered the items before.</p><p>The same logic applied to tasks of inference. Presented with a group of familiar objects with one foreign interloper, Chaser could nose out the new item, presumably through process of elimination. If she heard an unfamiliar word, she attached it to an unfamiliar thing—an advanced deduction for even a primate. (Watch Chaser do this with <a href="https://www.pbs.org/wgbh/nova/video/how-smart-are-dogs/">NOVA scienceNOW</a>.)</p><p>She could also tell the difference between verbs (fetch, take, chase) and adjectives (long, short, big, small). Chaser even seemed to heed the rules of sentence structure—a hint that she had some <a href="https://www.sciencedirect.com/science/article/abs/pii/S002396901300026X?via%3Dihub">grasp of grammar</a>.</p><p>It became clear that Pilley had stumbled upon something very unexpected. For Chaser, words had meaning, Bianchi says. They weren’t just repertoires of sounds; they were <i>concepts.</i></p></div>
  

  
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      <div class="rich-text"><p>All the while, Chaser remained an eager and facile student. Like the rest of her border collie breed, she was an indefatigable worker for one simple reason: It was fun.</p><p>“It was actually very simple for Chaser,” Bianchi says. “She learned everything through play. [Learning vocabulary and grammar] sounds very complicated, but for Chaser it was very organic. Her joy of repetition was only exceeded by our exhaustion of it.”</p><p>Perhaps this isn’t surprising. For generations, border collies have been bred to maintain a certain professional intimacy with the shepherds they originally served. “Watch a collie work with a sheepherder, and you will come away amazed how small a gesture the person can do to communicate with his dog,” Alexandra Horowitz, a dog behavior expert at Barnard College, <a href="https://www.nytimes.com/2011/01/18/science/18dog.html?pagewanted=all&amp;_r=1&amp;">told Nicholas Wade at <i>The New York Times</i> in 2011</a>.</p><p>But Chaser’s particular talents were enough to garner some attention, and Pilley ended up publishing two <a href="https://www.sciencedirect.com/science/article/abs/pii/S0376635710002925#!">peer-reviewed</a> <a href="https://www.sciencedirect.com/science/article/abs/pii/S002396901300026X?via%3Dihub">papers</a> on her accomplishments. The pair continued their partnership up until Pilley’s death in June 2018—an event that left the then 14-year-old collie in the hands of Pilley’s wife, Sally, and daughter, Robin, in their home in South Carolina.</p><p>Earlier this month, Chaser began to deteriorate from what veterinarians confirmed to be natural causes, Bianchi says. She died on Tuesday, July 23, at the age of 15—a little beyond the typical lifespan of her breed. Following Chaser’s burial in the backyard of the family home, the Pilleys sprinkled some of John’s ashes on her grave.</p>
            <figure class="richtext-image full-width"><img alt="Mark Olencki (2).jpg" class="richtext-image full-width" height="531" width="800"
            src="/wgbh/nova/media/images/Mark_Olencki_2.width-800.jpg"/><figcaption><p>Chaser with John Pilley. Image Credit: Mark Olencki, Wofford College</p><div class="credit"><p></p></div></figcaption>
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            <p>Chaser was special, but not necessarily unique, Bianchi says, and there’s no reason other dogs can’t preserve and build upon the legacy she’s left. “My father’s goal was to shift the paradigm,” she says. “Dogs are smarter than we give them credit for. He believed there will be a <i>world</i> of Chasers. Humans aren’t at the top of the intellectual ladder.”</p><p>For the Pilleys, though, Chaser’s memory is cherished for far more than her mental acumen. She was a study subject, but also a loyal companion and beloved family member, with an infectious enthusiasm that charmed <a href="https://www.chaserthebordercollie.com/the-research">researchers</a> and <a href="https://www.popsci.com/science/article/2013-07/i-met-worlds-smartest-dog/">journalists</a> alike. And not all her commands were for business: Chaser eventually learned that the word “hug” was a request for her to leap into the arms of the beseecher.</p><p>Despite her penchant for knowledge, Chaser wasn’t exactly an <i>obedient</i> dog, Bianchi says. “She was a character,” she recalls with a laugh, pointing to the collie’s sense of sass. If Chaser wasn’t a fan of someone—human or canine—she made it known. All you had to do, Bianchi explains, was say their name and see if it elicited a growl. “She knew the names of all the dogs and people [she went on walks with], and she had an attitude about each of them,” she says.</p>
            <figure class="richtext-image full-width"><img alt="chaser red ball courtesy Pilley Bianchi.JPG" class="richtext-image full-width" height="800" width="800"
            src="/wgbh/nova/media/images/chaser_red_ball_courtesy_Pilley_Bianchi.width-800.jpg"/><figcaption><p>Chaser with a red ball. Image Credit: Courtesy of Pilley Bianchi</p><div class="credit"><p></p></div></figcaption>
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            <p>Chaser’s mischief also marks one of Bianchi’s fondest memories of the collie—a time when she bolted from Bianchi’s side during a visit to NBC Studios in February 2011. Winter storms had all but shuttered the city, Bianchi says, leaving poor Chaser cooped up in her apartment. The expanse of the studio was the first open space the collie had seen in days. After racing gleefully around the studio, she reappeared with a beach ball she’d filched from a storage room and began to bark and bounce the ball on her nose.</p><p>“That ball never touched the ground,” Bianchi says. “We’d never seen her do that.”</p><p>“My father really encouraged her to solve problems and just think for herself,” she says. “The studio hands were like, ‘Wow, that’s so awesome! How did you teach her to do that?’ And we just said, ‘We didn’t. She’s just doing it.’”</p></div>
  

  
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<p>The border collie achieved international fame for her remarkable grasp on vocabulary and sentence structure.</p>

Chaser, the language-learning dog with a 1,000-word vocabulary, has died





  
      <div class="rich-text"><p>For animals without eyelids, fish are surprisingly capable of catching some serious shut-eye.</p><p>When zebrafish (<i>Danio rerio</i>) doze off, they catch their z’s much like people do, <a href="https://www.nature.com/articles/s41586-019-1336-7">new research</a> shows. These striped swimmers even appear to experience the piscine equivalent of REM sleep, the stage in which humans dream—and something that, until now, has only been reported in mammals, birds, and reptiles.</p><p>That doesn’t necessarily mean that fish are dreaming, or even that their version of sleep is completely identical to ours. Even so, the study, published today in the journal <i>Nature,</i> suggests that multistage snoozing could be common among vertebrates—the group of animals that includes mammals, birds, reptiles, amphibians, and fish—and may have arisen more than 450 million years ago.</p><p>“This paper is a long time coming,” says <a href="https://faculty.sites.uci.edu/audreychenlew/">Audrey Chen Lew</a>, a neurobiologist at the University of California, Irvine who was not involved in the study. “It’s really nice work that...demonstrates similarities between fish and humans and other mammals that we haven’t seen before.”</p></div>
  

  
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      <div class="rich-text"><p>That sleep is more or less ubiquitous among complex animals such as vertebrates, which all have the neural circuitry that makes up the spinal cord, might sound like a no-brainer. But in the world of neurobiology, things aren’t so black and white.</p><p>One issue is that sleep isn’t always easy to measure or identify. In some creatures, it’s an easy behavior to pick out: As they doze off, many animals will settle into a relaxed posture, stop most of their movements, and become less aware of their surroundings for an extended period of time (without entering a coma or other difficult-to-reverse state of being).</p><p>Other organisms, however, don’t abide by these criteria, prompting researchers to search for a more cellular definition of sleep—something that might be universally detectable among all those who do, in fact, engage in regular slumber.</p>
            <figure class="richtext-image full-width"><img alt="Zebrafish95-300.jpg" class="richtext-image full-width" height="260" width="800"
            src="/wgbh/nova/media/images/Zebrafish95-300.width-800.jpg"/><figcaption><p>Zebrafish are transparent during their first few weeks of life. Shown here is a larva, or juvenile. Image Credit: Shawn Burgess, NHGRI, Wikimedia Commons</p><div class="credit"><p></p></div></figcaption>
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            <p>That’s actually something that scientists have more or less nailed down in mammals, birds, and reptiles, all of which exhibit similar patterns of electrical activity in the brain when hitting the hay. Fish, on the other hand, have remained mostly mysterious, due in part to the fact that many sleep research methods are tailored to humans and other land-based species.</p><p>But even though they’re separated by at least 400 million years of evolution, fish and humans <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3703927/">aren’t all that different</a>. Throughout the piscine body are familiar hallmarks of human physiology, down to the genes written into their DNA. When it comes to fish, all the right machinery is there for human-like sleep, says study author <a href="https://profiles.stanford.edu/philippe-mourrain">Philippe Mourrain</a>, a neurobiologist at Stanford University. It’s just that no one had yet found a way to check if it was doing the same thing.</p><p>So a team of scientists led by Mourrain decided to invent a method of their own. In <a href="https://www.mayoclinic.org/tests-procedures/polysomnography/about/pac-20394877">human sleep studies</a>, sensors hooked up to a person’s body record their brain activity, heart rate, breathing, and muscle movements. Taking inspiration from this comprehensive suite of measurements, the researchers developed what was, in effect, a whole-body scan for a zebrafish—a striped, inch-long minnow that develops with a transparent body during its first few weeks of life.</p><p>This see-through skin was key to the experiment’s success, as it allowed the researchers to peer directly into the fish’s organs without the need for surgeries or other invasive procedures, says study author <a href="https://profiles.stanford.edu/louis-leung">Louis Leung</a>, who conducts research under Mourrain’s supervision. In humans, many sleep study measurements are collected by recording electrical signals by way of electrodes on the skin. But the fish’s transparency allowed the researchers to gather the same kinds of data by simply putting fluorescent markers into cells, which then lit up in the presence of electrical signals, yielding a pictorial play by play of individual cells’ behavior over time.</p></div>
  

  
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      <div class="rich-text"><p>When the team analyzed the brain waves of a school of juvenile zebrafish in repose, they discovered two familiar patterns of electrical activity. The first bore a striking resemblance to what’s known in humans as deep or slow-wave sleep, so named because it produces a series of synchronized, low-frequency brain waves. In people, deep sleep is marked by low brain activity, and is thought to give the body the opportunity to recuperate. It may also play a role in memory consolidation.</p><p>If that’s also true in fish, Mourrain says, it makes a lot of sense. Even in animals for whom life goes along swimmingly, there’s always a need for some R&amp;R. And fish, too, need to learn. But Mourrain was far more taken aback to see another hallmark of human sleep echoed in zebrafish: the state in which people dream.</p><p>So-called rapid-eye movement (REM) sleep is actually bursting with brain activity, on par with measurements taken during waking hours. The big difference, of course, is that the rest of the body <i>isn’t</i> awake, and is actually mostly immobilized (except for the eyes, which, in humans, jerk back and forth).</p><p>Much of this also appears to be true for zebrafish, except for their eyes, which kept quiet along with the rest of the body, Mourrain says. (Many other animals also keep their eyes still during REM sleep.)</p><p>Neither deep sleep nor REM sleep was completely identical between humans and fish, points out <a href="https://www.ucl.ac.uk/~ucbtjr3/People.html">Guliz Ozcan</a>, a neurobiologist and zebrafish expert at University College London who was not involved in the study. For one thing, the zebrafish equivalent of slow-wave sleep was a lot, well, <i>slower.</i> Despite these differences, Ozcan says, the neural “signatures” of both states are clearly recognizable—implying that the human version of sleep might be far less human than once thought.</p><p>With these new findings, Leung says, zebrafish can now join the growing list of vertebrates in which sleep has been pinpointed on a more molecular level. Without testing every single vertebrate in existence, it’s hard to say whether multistage sleep is <i>universal</i> in this group<i>,</i> he adds. But as a representative for fish—which comprise around half of all known vertebrate species—the zebrafish and its startling slumber hint that multistage sleep may have been present in a common ancestor of mammals, birds, reptiles, and fish, which lived at least 450 million years ago.</p><p>Amphibians are likely to share the trait as well, since they’re more closely related to us than fish are, Mourrain says. The next step, he adds, will be to see if the same signatures extend even further back in evolutionary time.</p>
            <figure class="richtext-image full-width"><img alt="combo.jpg" class="richtext-image full-width" height="668" width="800"
            src="/wgbh/nova/media/images/combo.width-800.jpg"/><figcaption><p>Top: A zebrafish larva with a fluorescent central nervous system. Cells light up as they become active. Bottom: The central nervous system and muscles of the zebrafish, illuminated with the same fluorescence. Using this system, researchers were able to record cellular signatures of sleep without invasive procedures. Image Credit: Courtesy of Louis Leung, Stanford University</p><div class="credit"><p></p></div></figcaption>
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            <p>Such deep-rooted implications make this paper “a total breakthrough,” says <a href="https://www.neuro.duke.edu/people/faculty/eva-naumann">Eva Naumann</a>, a neurobiologist at Duke University who was not involved in the study. “I can’t overstate it: [Finding these patterns of brain activity] was the missing piece of the puzzle...I’ve been waiting for a study like this to come out ever since I started working in this field.”</p><p>The big picture here doesn’t paint humans as primitive, though. Rather, these results should “elevate the zebrafish as a model system to study neural phenomena like sleep,” Naumann adds.</p><p>The study’s results also showed that, when deprived of sleep or treated with sleeping pills, zebrafish react similarly to humans both behaviorally and physiologically, hinting that they could also be useful in screening drugs to treat irregular or disordered sleep, Ozcan says.</p><p>There’s still, however, the elephant in the room: Despite being so widespread, sleep and all its stages continue to puzzle researchers trying to suss out their true purpose. But whatever it is that dozing is doing, if it really did evolve this long ago, and stuck around in so many species, “that points to something really essential,” Leung says.</p><p>As for whether zebrafish dream during their version of REM, that’s still an open question. If dreaming is a product of learning and memorization, it’s certainly possible, Mourrain says.</p><p>After all, most breakthroughs come from the most unexpected places, he says. Including the ones people (or any other species, perhaps) never even dreamed of.</p></div>
  

  
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<p>Deep sleep and REM sleep could be universal among vertebrates, stretching 450 million years back in evolutionary time.</p>

Like us, fish experience the ‘dreaming’ stage of sleep





  
      <div class="rich-text"><p>In November of 1978, an observer in a Boston institution hurriedly scrawled down a short note that, unbeknownst to them, would eventually send waves through the research field of language development.</p><p>“He says ‘Hoover’ in plain English,” the page read. “I have witnesses.”</p><p>That sentence wouldn’t have been remarkable, save for one detail: The “he” in question—Hoover—was a harbor seal.</p></div>
  

  
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      <div class="rich-text"><p>Over the next several months, Hoover’s trainers at Boston’s New England Aquarium discovered that their unusual flippered friend could do far more than speak his own name. Rewarded with treats of fish whenever he spoke, the seal quickly began verbally greeting aquarium employees and patrons alike.</p><p>On these occasions, Hoover would adopt a straight-backed posture and square his shoulders (or, at least, the seal equivalent of shoulders) before <a href="https://www.youtube.com/watch?v=prrMaLrkc5U">yelping out phrases</a> like “hello there, how are you,” “come over here,” or “get out of here” in a thick, rumbling New England accent, punctuated by raucous barks. He also appeared to be capable of “laughter,” scientists <a href="https://www.nrcresearchpress.com/doi/abs/10.1139/z85-157#.XRJIPGJKjOQ">noted in a 1985 study</a>, and once emitted a “blood-curdling scream” so alarming that an observer logged it as a data point in Hoover’s file.</p><div style="padding-bottom: 74.94553376906318%;" class="responsive-object">
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<p>Researchers later realized that Hoover had picked up several of these quirks from the Maine fisherman who had rescued him from the shores of Cundys Harbor when he was a pup. “Hoover sounds much like a male human with a Boston accent,” they <a href="https://www.nrcresearchpress.com/doi/abs/10.1139/z85-157#.XRJIPGJKjOQ">wrote</a>. Others, however, seemed to be Hoover-specific idiosyncrasies: “He often sounds somewhat inebriated,” the paper reads, “probably because of his tendency to slur together sounds representing separate human words.”</p><p>Unsurprisingly, Hoover’s remarkable ability to mimic human speech made him a hit—and people from all over flocked to Massachusetts to visit and converse with the world’s one and only “talking seal.” Hoover seemed to enjoy the spotlight, even staging the occasional fit, complete with “raspy breathing” and “strange cries,” to garner the attention of exasperated aquarium staff.</p><p>Even after Hoover died in 1985, scientists continued to puzzle over his startling verbosity. While Hoover was clearly producing the sounds of human speech, it was unclear <i>how</i> exactly he’d managed the feat—and researchers weren’t sure if this uncanny ability was just a fishy fluke.</p><p>Now, decades later, new research might finally help seal the deal. Reporting last week in the journal <i>Current Biology,</i> a team of scientists at the University of St. Andrews in the United Kingdom provides a fresh batch of evidence that <a href="https://www.cell.com/current-biology/fulltext/S0960-9822(19)30685-2?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0960982219306852%3Fshowall%3Dtrue">seals can indeed learn and imitate many of the complex sounds fundamental to human speech</a>. Not only can pups belt out clear vowels—a skill that many of our closest primate relatives can’t achieve—but they can also <a href="https://www.youtube.com/watch?v=-ahW_f5Sd3Q">recognizably “sing”</a> the first few notes of tunes like the <i>Star Wars</i> theme song and “Twinkle, Twinkle, Little Star.”</p><p>“This is the proof we’ve been waiting for,” says <a href="http://www.cbd.cmu.edu/directory/fellows/postdoctoral-researchers/">Morgan Wirthlin</a>, a computational biologist studying language development at Carnegie Mellon University who was not involved in the study. “It’s long been thought that [seals and their relatives] have this incredible capacity for vocal learning...but this paper is the first to demonstrate it in a really clearly defined way.”</p><div style="padding-bottom: 56.25%;" class="responsive-object">
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<p>In the study, University of St. Andrews biologists Amanda Stansbury and <a href="https://risweb.st-andrews.ac.uk/portal/en/persons/vincent-janik(72f80aa4-1961-44bb-8923-27832001f7d7).html">Vincent Janik</a> trained three young gray seals named Zola, Janice, and Gandalf to copy tones played from a computer by rewarding them with fish. At first, the researchers focused on notes that were within their species’ vocal repertoire, or something a seal might normally hear from a herdmate in the wild.</p><p>Once the seals were comfortable with this task, Stansbury upped the ante, and began including sounds at high, unfamiliar frequencies, as well as sequences that incorporated vowels from human speech. Stansbury even remixed some combinations to recall common jingles and songs that no seal would be expected to produce under natural circumstances.</p><p>The renditions were imperfect, and they might not sound as wicked smart as a Mainer from the 1970s. But the accuracy the seals achieved with unfamiliar melodies and human vowel sounds was impressive—especially considering that this is something that non-human primates tend to struggle with, says Stansbury, who is now at the El Paso Zoo in Texas. “Seals are the closest non-human analog we’ve found this behavior in,” she says.</p></div>
  

  
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      <div class="rich-text"><p>“This is really the first example of a non-human animal that seems to be using vocal learning in the same way we are,” adds <a href="https://directory.whoi.edu/profile/lsayigh/">Laela Sayigh</a>, an animal behaviorist studying dolphin communication at the Woods Hole Oceanographic Institution who was not involved in the study. “The ability to produce these [vowel sounds]...is so central to our own speech as humans. It’s incredibly fascinating to see that seals have this capability, and that it’s so closely aligned with our own.”</p><p>On the whole, animals with vocal capabilities flexible enough to expand in this way are rare. Seals, however, have a rare combination of traits that many other creatures lack, including a key anatomical advantage: a larynx, or voice box—much like the one found in humans.</p><p>“The top of the larynx is what allows people to change between vowels, which linguists will tell you is the most basic building block of language,” says <a href="https://babylab.cornell.edu/people/samantha-carouso/">Samantha Carouso-Peck</a>, a behavioral biologist studying songbirds at Cornell University who was not involved in the study. <a href="https://www.smithsonianmag.com/science-nature/zebra-finches-dream-little-dream-melody-180969925/">Songbirds</a>, she adds, can accomplish something similar with an analogous structure called a syrinx. But a true larynx affords an animal more precise control over the production of sound.</p><p>Of course, hardware alone doesn’t make an adept vocal learner—the neural software needs to be in place, too, Wirthlin explains. “What’s impressive...isn’t really that they [can make these vowel sounds], but that they’re able to copy the structure of a human vowel that isn’t part of their normal repertoire,” she says. “That’s about having the right kinds of neural connections and being able to control the vocal apparatus in a way that other animals can’t.”</p>
            <figure class="richtext-image full-width"><img alt="Janice.JPG" class="richtext-image full-width" height="373" width="800"
            src="/wgbh/nova/media/images/Janice.width-800.jpg"/><figcaption><p>Janice, one of the gray seals trained in the study. After a year of working with the researchers, Janice (as well as the other two seals, Zola and Gandalf) was released to the wild. Image Credit: Courtesy of Amanda Stansbury, El Paso Zoo (formerly University of St. Andrews)</p><div class="credit"><p></p></div></figcaption>
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            <p>It’s still unclear why seals in particular have this exceptional ability, but Carouso-Peck thinks it’s likely got something to do with their dynamic social structure. “There’s a very interesting lesson here about how being highly social, being intelligent, and being a vocal learner seem to be a package deal,” she says. Combined with a keen ear, a sharp tongue and flexible learning style may help mothers and pups find each other over the cacophony of large pods, or give bachelor(ette) seals an edge during mating season.</p><p>Whatever the reason behind the chatter, the new findings reinforce the idea that humans are far from the only ones with the gift of the gab—and, at long last, validate Hoover’s loquacious legacy.</p><p>“Before this, Hoover’s story was an anecdote,” Sayigh says. “This study really cements the reality that seals are capable of modifying their own vocal production based on new sounds they’ve heard...and Hoover was definitely doing that.”</p><p>It’s only fitting, then, that the star of this story gets the last word. Now <i>get outta here!</i></p></div>
  

  
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<p>In the late 1970s, a harbor seal named Hoover began catcalling passersby at the New England Aquarium in a thick Maine accent. A new study confirms seals’ uncanny ability to copy human speech.</p>

‘Talking’ seals mimic sounds from human speech, and validate a Boston legend





  
      <div class="rich-text"><p>You know the look. Everyone does. The wide, winsome eyes; the forlorn, furrowed brow. It’s enough to melt your heart—and send your hand reaching for the treat bag.</p><p>But the next time your dog fixes you with that sorrowful stare, take comfort (or chagrin) in the knowledge that she—and the rest of the world’s pet pooches—could owe their expressive eyes entirely to us.</p></div>
  

  
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      <div class="rich-text"><p>According to <a href="https://www.pnas.org/cgi/doi/10.1073/pnas.1820653116">new research</a> published today in the journal <i>PNAS</i>, the allure of puppy dog eyes may be a product of domestication, acquired as a lineage of charismatic canines split off from wolves. While their wild ancestors lack the necessary facial anatomy to raise their inner eyebrows, dogs possess certain muscles that, when put to use, make their mugs resemble ours—something that may have piqued the interest of ancient peoples.</p><p>These brow-raising results hint that, on the road to becoming our closest companions, dogs may have evolved a way to hijack, or at least mimic, a core tenet of human communication: eye contact.</p>
            <figure class="richtext-image full-width"><img alt="iStock-871215928.jpg" class="richtext-image full-width" height="534" width="800"
            src="/wgbh/nova/media/images/iStock-912167862.width-800.jpg"/><figcaption><p>It&#x27;s hard to stay mad at a face like this. Image Credit: RalchevDesign, iStock</p><div class="credit"><p></p></div></figcaption>
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            <p>“Eye contact is central to human communicative skills,” says <a href="https://www.aleahbowie.com/">Aleah Bowie</a>, a conservation psychologist at Duke University who was not involved in the study. “So it makes sense if we’re selecting for non-human animals [like dogs], we’re going to look for the same kind of traits.”</p><p>In other words, the power of puppy dog eyes is rooted not so subtly in a bit of egocentrism: Wide, expressive eyes <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0082686">remind us of human babies</a>, or a person on the verge of tears—emotive extremes of ourselves.</p></div>
  

  
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      <div class="rich-text"><p>And dogs, it seems, have reaped the benefits of this facial familiarity. There’s even evidence to suggest mutts who raise their inner eyebrows more often even <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0082686">get adopted more quickly from shelters</a>.</p><p>Of course, shelters didn’t exist tens of thousands of years ago, when people first cozied up with a subset of unusually friendly wolves. But that doesn’t mean a similar process wasn’t happening in the early days of domestication: In gravitating toward friendlier canines, humans might have inadvertently reshaped an entire lineage, altering traits both physical and psychological.</p><p>If that’s the case, then wolves might be expected to show less puppy-eyed prowess—or even lack some of the anatomical accoutrements necessary to maneuver their brows.</p><p>To put this theory to the test, a team of researchers led by <a href="http://www2.port.ac.uk/department-of-psychology/staff/dr-juliane-kaminski.html">Juliane Kaminski</a> and <a href="http://www2.port.ac.uk/department-of-psychology/staff/dr-bridget-waller.html">Bridget Waller</a>, both comparative psychologists at the University of Portsmouth in the United Kingdom, compared the facial muscles of six modern mutts and four gray wolves—a stand-in for domestic dogs’ long-gone wild ancestor. Though the two species’ faces were almost identical, almost all dogs tested possessed two extra muscles around their eyes that helped them raise their brows and pull their eyelids in certain directions—both movements that are, scientifically speaking, adorable.</p><p>“To see this kind of soft tissue change in the timespan of [dog domestication] is remarkable,” Waller says. The wolves, however, weren’t a “completely blank slate,” she adds. While the wolves didn’t have fully developed muscles, a few sparse muscle fibers existed in their place—just enough, she says, for evolution to “grab hold and make bigger, more uniform, and more stable in the dogs.”</p><p>Soft tissue like muscle doesn’t fossilize well, and a face-off between two modern species is just an approximation for gazing backwards in time. But already, the study presents a tantalizing hint of how these muscles may have beefed up over time. Only one dog breed studied lacked one of the two critical eye muscles: the Siberian Husky, which is more closely related to wolves than most other dog breeds. “This is suggestive of [an intermediate stage], but we need to follow up on this with other breeds,” Waller says.</p>
            <figure class="richtext-image full-width"><img alt="203461.jpg" class="richtext-image full-width" height="888" width="800"
            src="/wgbh/nova/media/images/203461.width-800.jpg"/><figcaption><p>Most dogs appear to possess two muscles that wolves lack: the levator anguli oculi medialis muscle (LAOM) and the retractor anguli oculi lateralis muscle (RAOL). The pair help dogs maneuver their eyebrows and eyelids. Image Credit: Juliane Kaminski et al., PNAS, 2019</p><div class="credit"><p></p></div></figcaption>
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            <p>To complement their anatomical findings, the researchers next filmed 27 shelter dogs and nine captive wolves for two minutes after a stranger approached them. As expected, dogs came out ahead in this face-off as well: On average, they raised their inner eyebrows more often, and seemed capable of producing more exaggerated movements with their eyes than their wolf cousins—findings in keeping with the team’s dissection.</p><p>“It’s really exciting to see a study exploring the connection between anatomy and behavior,” says <a href="https://dogs.arizona.edu/people/gitanjali-gnanadesikan">Gitanjali Gnanadesikan</a>, a cognitive biologist studying dog domestication at the University of Arizona who was not involved in the study. “In the process of domestication, both have changed in remarkable ways...and many of these changes are intertwined. Trying to understand how these different pieces fit together is extremely important.”</p><p>As eye-opening as the findings are, however, Gnanadesikan cautions that they raise “just as many questions as they answer...we still don’t know if these gazes contain information, or if dogs are intentionally trying to communicate with them.”</p>
            <figure class="richtext-image full-width"><img alt="iStock-871215928.jpg" class="richtext-image full-width" height="533" width="800"
            src="/wgbh/nova/media/images/iStock-871215928.width-800.jpg"/><figcaption><p>Wolves can twitch their brows, but those subtle movements are nothing compared to the heartwrenching stares of dogs. Image Credit: Nastasic, iStock</p><div class="credit"><p></p></div></figcaption>
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            <p>Figuring that out, she says, will require more studies on how these heart-wrenching stares are used in different contexts. Dogged gazes may tug on our heartstrings, but it’s important not to attribute <i>too</i> much to our canine comrades.</p><p>Even so, the study underscores the importance of facial expressions in communication, Waller says. That seems obvious. But it’s nonetheless notable, she says, just how much humans’ penchant for emotion has shaped our interactions—with both our own species and others.</p><p>It may not have been intentional on our part, or theirs. Either way, these pooches’ expressive eyes continue to get them out of the doghouse. And for anyone who’s ever fed Fido scraps under the table, or forgiven the massacre of an unlucky shoe, it’s clear that these looks of longing have yet to lose their luster.</p><p>You sly dog, you.</p></div>
  

  
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<p>Wolves lack the facial muscles required to raise their eyebrows—a feature that makes dogs especially endearing to people.</p>

Canines evolved puppy dog eyes to woo human companions





  
      <div class="rich-text"><p>With its loose, bunchy skin and sun-starved complexion, the naked mole-rat (<i>Heterocephalus glaber</i>) recalls an uncooked bratwurst dried on permanent press—and it might be one of the last creatures you’d expect to have superpowers.</p><p>But scientists have known for years that these wrinkly wonders boast an astounding set of death-defying qualities: They live decades longer than other rodents, <a href="https://www.pbs.org/wgbh/nova/article/once-thought-immune-to-cancer-naked-mole-rats-found-with-tumors/">almost never get cancer</a>, and can <a href="https://www.pbs.org/wgbh/nova/article/naked-mole-rats-make-like-a-plant-to-survive-in-zero-oxygen/">survive without oxygen for more than 18 minutes</a>. They’re even impervious to certain types of pain.</p><p>Now, new research suggests that some of these rodents’ oddball characteristics may not be as unusual as once thought. According to a <a href="https://science.sciencemag.org/cgi/doi/10.1126/science.aau0236">study</a> published today in the journal <i>Science,</i> the inability to feel pain is something of a family trait—one that runs rampant across the mole-rat phylogenetic tree.</p></div>
  

  
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      <div class="rich-text"><p>But for these rodents, the evolution of a pain-free existence comes with a twist. Rather than being passed down in carbon copy as mole-rats split off into separate species, resistance to pain seems to have arisen independently in separate lineages—and it doesn’t always manifest in the same way. While some species of these subterranean critters live in blissful ignorance of the sting of acid burns, others are immune only to acrid substances commonly found in plants.</p><p>“This is a fabulous study and a very thorough investigation,” says <a href="https://www.calicolabs.com/team-member/rochelle-shelley-buffenstein/">Rochelle Buffenstein</a>, a biologist studying naked mole-rats at Calico Labs in San Francisco who was not involved in the study. “The researchers have provided a little window into how these animals are able to shut down different kinds of pain in different situations.”</p>
            <figure class="richtext-image full-width"><img alt="6257899504_ac3b1b7070_o.jpg" class="richtext-image full-width" height="546" width="800"
            src="/wgbh/nova/media/images/6257899504_ac3b1b7070_o.width-800.jpg"/><figcaption><p>The naked mole-rat (<i>Heterocephalus glaber</i>), a super-social burrowing rodent native to parts of East Africa. These sausage-shaped critters are impervious to chemical pain from acid and capsaicin. Image Credit: Smithsonian&#x27;s National Zoo, flickr</p><div class="credit"><p></p></div></figcaption>
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            <p>For all its simplicity, the word “pain” encompasses an awful lot. Many different flavors of unpleasantness exist, but one of the body’s most important pain-sensing systems exists solely to detect the types of dangerous chemicals that tend to lurk in snake venom or poisonous shrubs.</p><p>This makes it all the weirder that the naked mole-rat <a href="https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.0060013">can’t feel two pretty universally agonizing kinds of chemicals</a>: acid and capsaicin (the spicy substance that gives chili peppers their heat). Though the reason behind these insensitivities hasn’t been completely worked out, it probably has something to do with these rodents’ underground habitats, where they’re exposed to a bevy of extreme conditions. Here, adaptations that eased the nuisance of pain could be a way to make a tough life more bearable.</p></div>
  

  
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      <div class="rich-text"><p>Naked mole-rats, however, aren’t the only rodents tunneling in the sands of sub-Saharan Africa. Dozens of other African mole-rat species exist, each with its own unique environmental quirks—but no one had ever tested whether the naked mole-rat’s closest cousins shared its insensitivity to pain.</p><p>So a team of researchers led by <a href="https://www.mdc-berlin.de/lewin">Gary Lewin</a>, a molecular physiologist at the Max Delbrück Center, decided to construct a family tree of mole-rat pain tolerance. After amassing nine evolutionarily distant species of African rodents (including the OG naked mole-rat), the team injected the rodents with three odious chemicals: dilute hydrochloric acid, capsaicin, and allyl isothiocyanate (AITC)—the sinus-clearing compound that gives wasabi and horseradish their pungent taste.</p><p>Right off the bat, it was clear that pain tolerance was not a universal mole-rat attribute. Like their distant mouse relatives (and humans, for that matter), four out of nine rodent species expressed discomfort in the presence of all three chemicals. Of the five remaining, two species, the Cape mole-rat (<i>Georychus capensis</i>) and the East African root rat (<i>Tachyoryctes splendens</i>), had no response to hydrochloric acid, while another, the Natal mole-rat (<i>Cryptomys hottentotus natalensis</i>), was insensitive to capsaicin. As before, the naked mole-rat was indifferent to both. Oddly, pain sensitivity combinations didn’t match up by relatedness, suggesting that several lineages had found their own way to the same pain-free outcome.</p><p>Every species tested, however, had a strong reaction to AITC—a compound known for its destructive powers in most animal bodies—except for one: the highveld mole-rat (<i>Cryptomys hottentotus pretoriae</i>), which became “the star of this particular study,” Lewin says. “This insensitivity [to AITC] is, as far as we know, completely unique in the animal kingdom.”</p><p>To track down the basis of this enigmatic trait, Lewin and his team extracted and compared genetic material from all nine species. The analysis revealed two subtle differences in the highveld mole-rat. One was a mutation in a gene that made AITC tougher to detect. Another boosted the expression of a protein that jettisoned signaling molecules out of pain receptive cells, compromising their ability to relay the presence of AITC.</p>
            <figure class="richtext-image full-width"><img alt="iStock-172383652.jpg" class="richtext-image full-width" height="533" width="800"
            src="/wgbh/nova/media/images/iStock-172383652.width-800.jpg"/><figcaption><p>Horseradish is among the many plant roots that contain allyl isothiocyanate (AITC), a pungent, spicy chemical that burns when eaten. Image Credit: blowbackphoto, iStock</p><div class="credit"><p></p></div></figcaption>
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            <p>But neither of these alterations had completely removed the AITC detection system from the highveld mole-rat. The genetic hardware was still in place—the lines of communication had just been gummed up. When the researchers next treated the rodents with a chemical that plugged up the protein that made pain receptive cells leaky, they became just as sensitive to AITC as their horseradish-hating cousins.</p><p>A drug that did the exact opposite of this and <i>increased</i> the leakiness of the protein could someday have value as a therapy for chronic pain, Lewin says.</p><p>It’s still unclear why only the highveld mole-rat has adopted AITC insensitivity, but as with its cousins, the trait is probably a product of its unusual lifestyle, says study author <a href="https://www.linkedin.com/in/ole-eigenbrod/?originalSubdomain=de">Ole Eigenbrod</a>, who completed his PhD in Lewin’s lab. It’s possible these rodents have become tolerant to AITC to cope with the spicy roots in their diets, or the stinging bites of the Natal droptail ants that frequent highveld hovels.</p><p>A pain-free coexistence with ants could confer “a huge advantage” on highveld mole-rats, which would be able to populate areas without any challenge from other rodent species, which are presumably sensitive to the insects’ nips and nibbles, Lewin says. It’s even possible that highveld mole-rats have expanded the typical vegetarian palate of their kin to include these ants, which could be a serious perk in times of scarcity.</p>
            <figure class="richtext-image full-width"><img alt="iStock-1124742136.jpg" class="richtext-image full-width" height="533" width="800"
            src="/wgbh/nova/media/images/iStock-1124742136.width-800.jpg"/><figcaption><p>A common mole-rat (<i>Cryptomys hottentotus hottentotus</i>). This species of burrowing African rodent can feel all three types of chemical pain. Image Credit: avstraliavasin, iStock</p><div class="credit"><p></p></div></figcaption>
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            <p>That said, there are trade-offs to any kind of pain tolerance—and it remains to be seen what cost the highveld mole-rat may be paying for these ant-ics. There’s probably a reason researchers haven’t yet found a mole-rat—or any other animal—that’s completely impervious to all three of these painful chemicals, says <a href="https://medicine.yale.edu/bbs/people/elena_gracheva.profile">Elena Gracheva</a>, a neuroscientist at Yale University who was not involved in the study. (Were that hypothetical animal to be discovered, though, it would still presumably be vulnerable to myriad other types of pain, including cold burns and the agony of flesh wounds.) Pain, after all, is a memorable tutor—and a life without clear signs of danger <a href="https://ghr.nlm.nih.gov/condition/congenital-insensitivity-to-pain">would probably be a short one</a>.</p><p>But the work done on this family of stoic rodents just goes to show that “pain, while important, can still be very fluid,” says <a href="http://www.childrenshospital.org/research/labs/woolf-laboratory/people/post-doctoral-research-fellows/simmie-foster">Simmie Foster</a>, a neuroscientist and pain expert at Harvard Medical School and Boston Children’s Hospital who was not involved in the study. “Pain responds to a changing environment...and there are instances in which it’s beneficial to adapt.”</p><p>Given what these critters have to deal with on a daily basis, pain tolerance might just be another notch in the mole-rat superpower belt. After all, it’s in the harshest environments that the most creative solutions for survival often arise. “[These rodents] have been forced to defy dogmas and figure out how to live in these circumstances,” Buffenstein says. “They don’t read the textbooks on how a mammals should behave...they’ve figured out their <i>own</i> best way.”</p><p>Naked or not, mole-rats can clearly take the heat.</p></div>
  

  
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<p>Some African mole-rats seem to tolerate the burn of spicy plants or biting insects that cause most other animals excruciating pain.</p>

Topic: Evolution

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