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

baby-2436661_1920.jpg

<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?

topic-evolution.jpg

Evolution

Koch Foundation

Draper





  
      <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>
  

  
      <div class="ad"></div>
  

  
      <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>
            </figure>
            <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>
  

  
      <div class="related"></div>
  

  
      <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>
            </figure>
            <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>
            </figure>
            <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>
  

  
      <div class="newsletter"></div>
  



<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>
  

  
      <div class="ad"></div>
  

  
      <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>
            </figure>
            <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>
  

  
      <div class="related"></div>
  

  
      <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>
            </figure>
            <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>
            </figure>
            <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>
  

  
      <div class="newsletter"></div>
  



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

The naked mole-rat is impervious to certain kinds of pain. It’s not alone





  
      <div class="rich-text"><p>Seeing someone else suffer a big disappointment can have a pretty damaging effect on your own morale. That’s definitely the case with people—and it may be true for ravens, too.</p><p>New research suggests that, like humans and many other mammals, common ravens (<i>Corvus corax</i>) can read and internalize the emotional states of others. In the <a href="https://www.pnas.org/cgi/doi/10.1073/pnas.1817066116">study</a>, published today in the journal <i>PNAS,</i> ravens watch their friends grapple with a frustrating task in which they’re denied a tasty treat. Though the onlookers aren’t deprived of anything, they then seem to mirror their partners’ discontent, and start behaving pessimistically themselves.</p></div>
  

  
      <div class="ad"></div>
  

  
      <div class="rich-text"><p>Unlike people, ravens can’t speak freely about their emotional distress. But these results hint at the tantalizing possibility that humans aren’t alone in their interconnectedness, and could provide early evidence of something akin to empathy in birds.</p><p>“This paper is a tremendous step forward in being able to understand the evolutionary roots of empathy,” says <a href="https://corvidresearch.blog/">Kaeli Swift</a>, an animal behaviorist and corvid expert at the University of Washington who was not involved in the study. “I think it would be too far to say that [this paper shows] ravens are empathetic…but this work could be foundational in eventually arriving at that conclusion.”</p>
            <figure class="richtext-image full-width"><img alt="iStock-1081629534.jpg" class="richtext-image full-width" height="533" width="800"
            src="/wgbh/nova/media/images/iStock-1081629534.width-800.jpg"/><figcaption><p>In many ways, raven intelligence rivals that of primates. These birds are adept at problem solving, deception, and even mimicking human speech. Image Credit: Tom Meaker, iStock</p><div class="credit"><p></p></div></figcaption>
            </figure>
            <p>Showing that non-human animals have empathy—the ability to understand and share the feelings of others—is no easy task. A big part of the challenge is obvious: Researchers can’t ask their subjects how they’re feeling, says <a href="https://sites.lsa.umich.edu/prestos-lab/">Stephanie Preston</a>, a neuroscientist studying emotion and behavior at the University of Michigan who was not involved in the study.</p><p>But some researchers argue that empathy can be broken down and tested through its more manageable components. For instance, you can’t have empathy without emotional contagion, or the tendency of the feelings and behaviors of an emotional reaction to hop from individual to individual even in the absence of what triggered them. Emotional contagion is, in a sense, a way to experience by proxy—and it can come with serious perks.</p></div>
  

  
      <div class="related"></div>
  

  
      <div class="rich-text"><p>“This gives you the ability to learn information about something without having to experience it yourself,” Preston says. “There’s an advantage to not having to experience pain, or realize food makes you sick, or see that someone is threatening...it can also give you the information you need to provide help to another in distress. It’s an efficient way to learn in a social environment.”</p><p>Emotional contagion is a fixture of the human experience, but it’s also been demonstrated in other species, including rats and pigs, thought to be both clever and social. Though ravens have <a href="https://science.sciencemag.org/content/357/6347/202">both</a> <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3064662/">these</a> qualities in spades, no one had yet investigated whether these black-feathered birds could mirror the feelings of their friends. So a team of researchers led by <a href="https://cogbio.univie.ac.at/people/phd-candidates/jessie-adriaense/">Jessie Adriaense</a>, a cognitive biologist at the University of Vienna, put a group (technically, an “unkindness”) of eight ravens raised at the Haidlhof Research Station in Austria to the test.</p><p>The researchers first sorted the most buddy-buddy birds into pairs. Then, one member of each raven duo, dubbed the “observer,” was placed in front of a closed, unfamiliar box—an ambiguous situation designed to probe the bird’s baseline emotional state. While an optimistic raven may eagerly toy with the container, expecting a reward, a pessimistic bird would more likely to regard it with skepticism. At the start of the experiment, the ravens curiously pecked at the box after only momentary hesitation.</p><p>Then, each observer raven looked on as its partner bird, the “demonstrator,” was emotionally manipulated by a scientist. Demonstrator ravens were shown two different food items of different appeal: scrumptious morsels of dried dog food and an unappealing nubbin of raw carrot. Then, a researcher took one food away and handled the remaining treat as if the bird was about to be fed. Those left ogling the kibble behaved enthusiastically, while those saddled with the unappetizing vegetable quickly lost interest. Though the spectating ravens couldn’t see the foods themselves, they remained privy to their friends’ reactions.</p><p>Immediately after watching this ordeal play out, each observer raven was presented once again with a mystery box. Not much changed for the birds who had just seen their friends zealously react to kibble. But the ravens who had witnessed their partners’ carroty chagrin waited much longer than before to start tinkering with the box—as if they had already resigned themselves to disappointment. (The birds later switched roles so that each raven in the study got to experience its own emotional rollercoaster.)</p>
            <figure class="richtext-image full-width"><img alt="201010.jpg" class="richtext-image full-width" height="530" width="800"
            src="/wgbh/nova/media/images/201010.width-800.jpg"/><figcaption><p>A raven in an experimental compartment at Haidlhof Research Station in Austria. Image Credit: Jessie E. C. Adriaense, University of Vienna</p><div class="credit"><p></p></div></figcaption>
            </figure>
            <p>It’s not entirely clear why the effects of pessimism were stronger, but this finding isn’t entirely surprising, says <a href="https://www.lomapendergraft.com/">Loma Pendergraft</a>, a corvid cognition expert at the University of Washington who was not involved in the study. After all, there’s probably an evolutionary advantage to being a little more sensitive to negative outcomes. “If something is ambiguous...it’s better to tend towards caution, because the potential cost could include death,” he says.</p><p>But it seems something about the reactions of jilted demonstrators was, in fact, contagious. Had their partners “caught” their disillusionment?</p><p>It’s possible, but the study can’t guarantee that infectious element was <i>emotion,</i> says <a href="https://www.jennifervonk.com/">Jennifer Vonk</a>, a cognitive psychologist at Oakland University who was not involved in the study. The researchers weren’t able to test the emotional state of the demonstrator ravens, making it tough to confirm if the observers were actually picking up on feelings, or a set of behaviors associated with them. Behaviors, too, can be contagious—just step into a room full of people and yawn.</p>
            <figure class="richtext-image full-width"><img alt="Paul (53).JPG" class="richtext-image full-width" height="533" width="800"
            src="/wgbh/nova/media/images/Paul_53.width-800.jpg"/><figcaption><p>A raven at the Haidlhof Research Station in Austria. Image Credit: Jessie E. C. Adriaense, University of Vienna</p><div class="credit"><p></p></div></figcaption>
            </figure>
            <p>Still, in many cases, emotions tend to come packaged up with a reliable set of behaviors, Preston says. “Each species has its own repertoire of behaviors that are common...you have to start somewhere.”</p><p>Going from emotional awareness to empathy remains a big jump, however. One crucial part of the equation that still needs to be addressed is whether infectious feelings come paired with concern and care for another individual in distress, Preston says. For that, an observer bird may be expected to soothe a disappointed demonstrator. (There is, however, separate evidence that ravens are capable of <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2868892/">consoling</a> and <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3064662/">reconciling</a> with each other after fights.)</p><p>None of that takes away from how exciting this find is, she adds—especially in birds. “These building blocks of empathy are present in diverse species,” she says. “Empathy is not something that defines us as humans. There is a long evolutionary history leading up to our ability to empathize.”</p></div>
  

  
      <div class="newsletter"></div>
  



<p>These crafty birds might be capable of interpreting and internalizing the emotions of others.</p>

Seeing friends disappointed bums us out. The same may be true for ravens





  
      <div class="rich-text"><p>Don’t be fooled by their charming name: <a href="http://medent.usyd.edu.au/fact/bedbugs.html">Bed bugs</a> don’t need beds to set up shop. These intrepid insects will colonize pretty much any place where people pile up, including hotels, movie theaters, libraries, even the <a href="http://gothamist.com/2014/08/06/bed_bugs_on_the_n_train.php">occasional subway</a>—ready and waiting to ruin a human life with their bloodsucking mouthparts and death-defying durability.</p><p>It’s easy to dismiss bed bugs as loathsome pests that exist to make humans miserable. But in reality, bed bugs predate humans by leaps and bounds, making <i>us</i> the unwanted interlopers that first crossed into their turf.</p></div>
  

  
      <div class="ad"></div>
  

  
      <div class="rich-text"><p>According to a newly mapped bed bug family tree, these puny pests have been guzzling the blood of other animals for more than 100 million years, long before the rise of both modern humans and bats, their most common host. The <a href="https://www.cell.com/current-biology/fulltext/S0960-9822(19)30477-4?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0960982219304774%3Fshowall%3Dtrue">research</a>, published today in the journal <i>Current Biology,</i> shows that the bed bug timeline stretches further back than even the <a href="https://www.pbs.org/wgbh/nova/article/new-fossils-mass-extinction-wiped-out-dinosaurs/">mass extinction</a> that wiped out 75 percent of Earth’s plant and animal species, including all dinosaurs, 66 million years ago.</p><p>The surprising longevity of bed bugs means we’re no longer certain of the identity of these bloodthirsty buggers’ first host. But the study’s findings could still offer clues on how bed bugs once made the jump to humans, and if that transition will have an encore act in the future.</p><p>“Bed bugs didn’t evolve on humans,” says study author <a href="https://www.sheffield.ac.uk/aps/staff-and-students/acadstaff/siva-jothy">Michael Siva-Jothy</a>, an entomologist and evolutionary biologist at the University of Sheffield in the United Kingdom. “We just happen to be their current host at the moment—which means they’re very good at what they do.”</p>
            <figure class="richtext-image full-width"><img alt="iStock-165162859.jpg" class="richtext-image full-width" height="600" width="800"
            src="/wgbh/nova/media/images/iStock-165162859.width-800.jpg"/><figcaption><p>Bed bug bites are caused primarily by two species—Cimex lectularius and Cimex hemipterus—which pierce human skin and drink blood with their sucking mouthparts. Luckily, neither is thought to transmit disease. Image Credit: smuay, iStock</p><div class="credit"><p></p></div></figcaption>
            </figure>
            <p>The scourge of bed bugs on humankind is believed to stretch back to the very dawn of our species. But only three species—<i>Cimex lectularius</i>, <i>Cimex hemipterus</i>, and, less commonly, <i>Leptocimex boueti</i>—routinely spend their nights supping on human blood. At least 100 other types of bed bugs exist worldwide, feeding mostly on bats and, to a lesser extent, birds, and researchers still don’t have a good understanding of these insects’ origins, and how species have split and diversified over time.</p><p>To generate a more complete bed bug catalog, an international team of scientists led by <a href="http://www.dresden-ipp.de/research/research-groups/klaus-reinhardt/">Klaus Reinhardt</a>, a molecular and evolutionary biologist at the Dresden University of Technology in Germany, set out to amass insects from around the world.</p><p>A handful of specimens weren’t too hard to come by, arriving via the generosity of natural history museums, or scientific colleagues who had seen the team’s requests for help on Twitter. Collecting the lion’s share of the data, however, required some pretty gnarly field trips that featured amateur cliff scaling, treks through knee-deep guano, and hikes into remote mountaintop caves—all in search of nondescript insects just millimeters long.</p><p>In all, sample collection alone took the study’s 15 authors the better part of 15 years. But the result was an unprecedented collection of pristine bed bug DNA, representing 34 species hailing from 62 localities around the globe.</p><p>“It’s really difficult to collect these specimens,” says <a href="https://heteroptera.ucr.edu/index.php/people/christiane-weirauch">Christiane Weirauch</a>, a systematic entomologist at the University of California, Riverside who was not involved in the study. “It’s just so cool that this team has pulled this together.”</p></div>
  

  
      <div class="related"></div>
  

  
      <div class="rich-text"><p>By comparing DNA sequences across species, Reinhardt, Siva-Jothy, and their colleagues were able to trace the evolutionary relationships between the bed bugs they’d collected. The researchers then combined their data with evidence from known insect fossils to pinpoint when bed bug lineages had split in the past. And when the bed bug family tree was finally mapped, the team was met with a set of findings that flew in the face of almost everything they’d expected.</p><p>Because bats remain the most common host of bed bugs (technically, bat bugs) today, Siva-Jothy says, most researchers have assumed that the first bed bugs to scuttle the Earth also gorged on the blood of these winged mammals. Cozied up to cave-dwelling bats, bed bugs would’ve then had an easy time making the hop to our human ancestors seeking shelter some 2 million years ago, and evolved alongside the genus <i>Homo</i> ever since.</p><p>Neither of these theories panned out.</p><p>The researchers’ analysis now places the origin of bedbugs around 115 million years ago, during the Cretaceous—a whopping 30 to 50 million years before bats are believed to have come onto the scene. It’s not yet clear what species first drew the bed bug straw, but a good candidate might be a small, social, cave-dwelling mammal, Reinhardt says.</p><p>Others, however, aren’t ready to completely rule out bats, or at least an early bat-like ancestor. “The fossil records for [both bed bugs and mammals] are patchy...that makes it hard to make definitive statements,” says <a href="http://runewarkbiology.rutgers.edu/ware%20lab/Welcome.html">Jessica Ware</a>, an entomologist and evolutionary biologist at Rutgers University who was not involved in the study. “It’s possible bats are older, and we’ve just underestimated.”</p><p>Some 70 more bed bug species have yet to be analyzed in this way, and the family tree could still change with the addition of new data, Ware says. “That being said, this is the first and maybe most comprehensive analysis people have done for [this group of insects].”</p><p>Regardless of where, and on whom, bed bugs got their start, it appears these insects were hardy enough to weather a mass extinction—and have remained alarmingly adaptable ever since. The researchers’ findings suggest that, throughout their evolutionary history, several bed bug species went from bothering bats to terrorizing birds and vice versa. Along the way, at least three species dipped their spindly legs into human stock. Surprisingly, all three species appear to have evolved independently, with each making a separate jump to human hosts.</p><p>In other words, we humans didn’t actually do much to shape the evolution of one of our most iconic pests, who were perfectly content binging on the blood of bats and birds. It just so happened that, when an unlucky member of the genus <i>Homo</i> stumbled onto their path, certain bed bugs were flexible enough to expand their palates.</p>
            <figure class="richtext-image full-width"><img alt="Bat and bed bug - credit Mark Chappell, Univ Cailf, Riverside.jpg" class="richtext-image full-width" height="555" width="800"
            src="/wgbh/nova/media/images/Bat_and_bed_bug_-_credit_Mark_Chappell_Univ_Ca.width-800.jpg"/><figcaption><p>Bats were once thought to be the first host of bed bugs. But a newly mapped family tree shows that bed bugs predate bats by 30 to 50 million years. Image Credit: Mark Chappell, University of California, Riverside</p><div class="credit"><p></p></div></figcaption>
            </figure>
            <p>There’s even a chance <i>another</i> bed bug species might one day develop a taste for human blood, Reinhardt says (in fact, it may <a href="https://academic.oup.com/ae/article-pdf/58/1/58/18756174/ae58-0058.pdf">already be happening</a>). Based on the historical data, these transitions happen roughly every half a million years.</p><p>But the more pressing concern may be the enemies we already know, Siva-Jothy says. “With human populations expanding, and our reliance on animals, and the way cities grow and communicate…there will be more opportunities for the species we’ve already got to become more widespread.”</p><p>Given the stubbornness of bed bug infestations, that’s not great news. It’s enough to make us wonder if bed bugs have the apocalyptic armor to outlive us all.</p><p>We may not have made our bed bugs. But we still have to lie with them.</p></div>
  

  
      <div class="newsletter"></div>
  



<p>The rise of bed bugs preceded modern humans by at least 100 million years. They survived the extinction that killed the dinosaurs. Could they outlive us all?</p>

Bed bugs don’t need beds, or humans, to survive. They never did





  
      <div class="rich-text"><p>Some 5,000 years ago, <i>Homo</i> domesticated <i>Equus</i>—and the histories of human and horse intertwined.</p><p>In the millennia since, peoples worldwide have leveraged the speed and power of these once-wild creatures to plow fields, stage hostile takeovers, and carry everything from goods to diseases across contentious borders. Even a good number of modern human languages owe their roots to equines: Before the ancestral tongue of Proto-Indo-European splintered into hundreds of linguistic descendants still spoken today, it was ferried throughout the Eurasian continent on horseback.</p></div>
  

  
      <div class="ad"></div>
  

  
      <div class="rich-text"><p>Horses have dramatically shaped the human civilization—but researchers still know surprisingly little about how we have shaped them. To this day, even the identity of the wild ancestor of the modern domestic horse remains mysterious.</p><p>But now, thanks to a new analysis of ancient DNA, an international team of scientists has constructed the <a href="https://www.cell.com/cell/fulltext/S0092-8674(19)30384-8">largest collection of horse genomes to date</a>, spanning tens of thousands of years of equine history across Europe and Asia. Their <a href="https://www.cell.com/cell/fulltext/S0092-8674(19)30384-8">study</a>, published today in the journal <i>Cell,</i> suggests that the genetic diversity of domestic horses has deteriorated only in the last few hundred years, underscoring the toll recent animal husbandry practices have taken on modern breeds.</p><p>“This study is brilliant,” says <a href="https://scholar.harvard.edu/vagheesh/home">Vagheesh Narasimhan</a>, a mathematical genomicist at Harvard University who was not involved in the study. “Just to see data of this scale being produced for a species other than humans is spectacular.”</p>
            <figure class="richtext-image full-width"><img alt="iStock-865176640.jpg" class="richtext-image full-width" height="532" width="800"
            src="/wgbh/nova/media/images/iStock-865176640.width-800.jpg"/><figcaption><p>Today, only two lineages of horses remain: the modern domestic horse and its small, stocky cousin, the endangered Przewalski&#x27;s horse. Image Credit: LifeJourneys, iStock</p><div class="credit"><p></p></div></figcaption>
            </figure>
            <p>To map out a timeline of equines past, a team of researchers led by <a href="http://amis.cnrs.fr/?Orlando-Ludovic&amp;lang=fr">Ludovic Orlando</a>, a molecular archaeologist and geneticist at the French National Center for Scientific Research, the University of Toulouse, and the University of Copenhagen, turned to the best source of information it had: ancient DNA, extracted from 250 fossils strewn across sites from Spain to Mongolia.</p><p>“DNA is nature’s own written history,” says <a href="http://animal.ifas.ufl.edu/faculty/brooks/index.shtml">Samantha Brooks</a>, a horse geneticist at the University of Florida who was not involved in the study. “Horses can’t write or speak their side of their story, but we can read a little bit about the events based on their DNA.”</p></div>
  

  
      <div class="related"></div>
  

  
      <div class="rich-text"><p>To deduce how humans may have sculpted the biology of their hoofed companions, the researchers compared ancient genomes from across time and space, and explored how they stacked up against modern breeds. This large-scale approach allowed them to both track the rise and fall of certain traits within the equine gene pool and link those shifts to events throughout human history.</p><p>Horses were first bridled by humans sometime between the fourth and third millennium BCE. Through their analysis, the researchers found that breeding priorities have undergone several revolutions in the centuries since. For instance, around 1,000 years ago, strong, sturdy builds came into fashion, ushering in the lasting age of the Arabian horses, which still frequent many a stable today. Traits like speed and the ability to amble—a medium-speed gait that’s considered more comfortable for riders—also became common fixtures in the equine lineage.</p><p>Despite these reproductive restrictions, the genomic time series showed that domesticated horses remained relatively genetically diverse for the first 4,000 years or so of their close coexistence with humans. It was only around 200 or 300 years ago that these levels took a sharp downturn.</p><p>“This is the moment that genetic diversity started to collapse,” says study author <a href="http://amis.cnrs.fr/?Fages-Antoine&amp;lang=fr">Antoine Fages</a>, a paleogenomicist at the University of Toulouse. “It’s quite amazing that it happened so quickly and so recently.”</p><p>The turning point coincides neatly with the latter half of the 18th century, when horse racing began in earnest, paring down the list of “desirable” equine traits, Fages says. As agility and power skyrocketed in importance, breeders began to select only a handful of stallions to sire future generations, keeping large parts of the population from throwing their genetic hats into the ring.</p><p>The dip isn’t shocking, though, and it parallels what humans have seen in other domesticated species, like dogs and livestock, Brooks says. The timing, she says, also coincides with cultural and technological evolutions in our history. As humans became less dependent on horses for farming and transportation, the relationship between the two species began to change. Eventually, equines settled into a newer, more specialized niche—recreation—giving breeders less incentive to keep their stables stocked with a diverse set of animals.</p><p>Even today, the genetic diversity of horses is in decline, says <a href="https://www.equine.umn.edu/bio/equine-genomics-genetics-team/molly-mccue">Molly McCue</a>, a horse geneticist at the University of Minnesota who was not involved in the study. This is “critically important” to keep in mind, she says, because populations with less genetic variation are more vulnerable to accumulating mutations, some of which may lead to disease.</p><p>Still, this downward trajectory isn’t a foregone conclusion, Fages says. It’s worth remembering the fact that humans were able to manage horses for thousands of years without negatively impacting their genetics.</p>
            <figure class="richtext-image full-width"><img alt="Horse-racing-1.jpg" class="richtext-image full-width" height="533" width="800"
            src="/wgbh/nova/media/images/Horse-racing-1.width-800.jpg"/><figcaption><p>The best of today&#x27;s thoroughbreds can race at speeds up to 55 miles per hour, and have a substantially different genetic makeup than the horses that thundered across the steppes and plains of Eurasia thousands of years ago. Image Credit: Softeis~commonswiki, Wikimedia Commons</p><div class="credit"><p></p></div></figcaption>
            </figure>
            <p>Regardless of what awaits horses in the future, though, one key gap in their past has yet to be filled. While Przewalski’s horses—the only other lineage of horse still alive today—are known to hail from <a href="https://science.sciencemag.org/content/360/6384/111">Botai horses</a>, the ancestors that once gave rise to our modern domesticates remain anonymous.</p><p>Even with so many genomes at their disposal, the researchers were surprised to find themselves no closer to an answer. Their search, however, did rule out two previously unknown candidates: two long-gone lineages that once independently roamed Iberia and Siberia. While both were still thriving during some of the early days of domestication, the DNA in their remains bore little resemblance to that of today’s horses, suggesting that neither lineage directly gave rise to modern breeds before they died out. “These are sort of the horse equivalent of what Neanderthals and Denisovans are to humans,” Orlando says.</p><p>Several branches, it seems, are still missing from the equine family tree. But in the meantime, these new lineages add some much-needed complexity to the enigmatic tale of the horse—and, in turn, our own storied past.</p><p>“Human cultures and civilizations are what they are today in part because some people had horses, and others did not,” Brooks says. “Knowing more about their history tells us a lot about ourselves.”</p><p><i>To learn more about the rich history of horse domestication, watch “</i><a href="https://www.pbs.org/wgbh/nova/video/first-horse-warriors/"><i>First Horse Warriors</i></a><i>,” premiering at 9 p.m. EDT/8 p.m. CDT on Wednesday, May 15 on PBS.</i></p></div>
  

  
      <div class="newsletter"></div>
  



<p>A sweeping genomic study expands the equine family tree and pinpoints how humans might have reshaped the equine gene pool.</p>

Domestic horses have existed for millennia. Modern breeding reduced their genetic diversity in just a few hundred years





  
      <div class="rich-text"><p>Given the choice between a wolf and a dog for a companion, you might be more inclined to choose a floppy-eared mutt.</p><p>For what it’s worth, that’s probably the right choice—as long as you’re human.</p><p>According to a <a href="https://doi.org/10.1371/journal.pone.0215444">study</a> published today in the journal <i>PLOS ONE</i>, wolves appear to be more inclined than dogs to be generous with their pack mates. When given the choice, wolves deliver food to their friends, even if they don’t benefit themselves. Dogs, on the other hand, quickly lose interest in the absence of personal payoff.</p><p>So far, these differences have only been noted with dogs raised in packs, and can’t be extrapolated to any pooches that live as pets. But the results hint at a surprising possibility: To become humans’ best friends, dogs may have had to reroute their loyalties—and snub their own species in the process.</p><p>“[These results] should encourage the scientific community to reexamine the hypotheses about the purpose of domestication,” says <a href="https://www.nps.gov/yell/learn/nature/wolves.htm">Kira Cassidy</a>, a wolf research at Yellowstone National Park who was not involved in the study. “[While] wolves have evolved to cooperate in order to survive...perhaps, after many generations of domestication, dogs now see humans as their family.”</p></div>
  

  
      <div class="ad"></div>
  

  
      <div class="rich-text"><p>All domestic dogs can trace their genetic roots back to a fierce, wolf-like ancestor—but today, few dog breeds still look or act the part. Over the course of human-driven domestication, this once-wild lineage grew tame, eventually accumulating enough genetic changes that an entirely new species arose. Now, modern mutts lounge in our living rooms and nibble at scraps from the edges of our plates; they’ve even learned to <a href="https://science.sciencemag.org/content/298/5598/1634.long">tune in to the subtleties</a> of <a href="https://www.smithsonianmag.com/science-nature/why-most-helpful-dogs-keep-calm-and-carry-180969731/">human emotion</a>.</p><p>Dogs’ persisting partnership with people may make it tempting to give humans all the credit for canine congeniality. But gray wolves, the other direct descendants of that long-gone lupine ancestor, aren’t exactly slouches at cooperation. In the wild, wolves rely on their pack mates for everything from food to caring for their young. The charitable nature of domestic dogs may be a product of human intervention—but it could just as easily be an age-old trait passed down from their pack-living predecessors.</p><p>To suss out whether dogs or wolves had the upper paw, a team of researchers led by <a href="https://www.wolfscience.at/en/aboutus/team/racheldale/">Rachel Dale</a> decided to see if two groups of canines would be willing to perform the ultimate act of altruism: give without getting in return.</p></div>
  

  
      <div class="related"></div>
  

  
      <div class="rich-text"><p>But the cushy, human-centric lifestyle of pet dogs can be hard to compare to the the close-knit, pack culture of wolves. To level the playing field, Dale and her team conducted their experiments using captive wolves and dogs raised in cohorts of their own species at the Wolf Science Center in Austria.</p><p>Nine wolves and six dogs were given the opportunity to deliver a tasty treat to a pack mate by pressing their noses to a “giving” symbol on a touchscreen. (To make sure the wolves weren’t just having fun nosing the touchscreens, the researchers also included a “withhold” option on the interface.) None of the donors were able to access the food themselves, but if they behaved selflessly, they could watch their friends chow down in their place.</p><p>To Dale’s surprise, the wolves repeatedly bested their domestic canine cousins in the realm of generosity. While the wolves booped the “giving” option time and time again to reward their pack mates, dogs were less likely to be team players.The wolves also showed an obvious preference for familiar faces, quickly losing interest in the tasks when they didn’t recognize the recipient. Dogs, on the other hand, didn’t seem eager to gift grub to other members of their species, regardless of whether they’d spent time with them or not.</p><p>These results were “surprising at first,” but in hindsight, there are several reasonable explanations, says <a href="https://www.ripon.edu/faculty/julia-meyers-manor/">Julia Meyers-Manor</a>, a dog behavior expert at Ripon College who was not involved in the study. In the wild, teamwork is often a matter of life and death—but within the cozy confines of human civilization, independence might be a more useful strategy. As dogs exchanged a lifestyle of hunting for scavenging human scraps, there may have been less pressure for groups of canines to act as cohesive units, and instead fend for themselves.</p>
            <figure class="richtext-image full-width"><img alt="199204.jpg" class="richtext-image full-width" height="325" width="800"
            src="/wgbh/nova/media/images/199204.width-800.jpg"/><figcaption><p>Because the wolf on the right pressed the &quot;giving&quot; symbol, its partner on the left was rewarded with a piece of sausage while the donor watched. Image Credit: Rachel Dale, Wolf Science Center</p><div class="credit"><p></p></div></figcaption>
            </figure>
            <p>“Domestication hasn’t necessarily made dogs more tolerant of, or cooperative with, each other,” Dale says. “Some people have assumed this…but just because they’ve been selected to work so well with humans, that doesn’t mean they’ll do it with each other as a byproduct.” In fact, Dale says, it’s possible that the <i>inverse</i> may be true: Through domestication, humans could have inadvertently encouraged canines to choose person over pup.</p><p>For now, that’s still a theory. Additionally, because the dogs in the study grew up in packs, the results don’t have any bearing on how pet dogs, which spend most of their time around humans, might behave. In fact, Dale’s previous work suggests that dogs raised in the presence of people will happily share resources with <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0167750#pone.0167750.ref005">their own kind</a>.</p><p>It’s not yet clear why dogs may differ as pets or pack mates, but Dale has a theory. While pack dogs live by their own set of rules, most of the mutts that hang out with humans are rewarded for being chummy, she says. That sort of positive reinforcement could bring out the best in these dogs under all kinds of circumstances.</p><p>In other words, there’s nothing to show that dogs have lost the ability to lend a helping paw. After all, plenty of canines can still be counted on to have each other’s backs—and they were doing it long before we humans entered the picture.</p><p>“Sometimes we think, ‘Humans can cooperate, and it’s something other animals don’t have,’” says <a href="https://dogs.arizona.edu/people/gitanjali-gnanadesikan">Gitanjali Gnanadesikan</a>, who studies social behavior in dogs at the University of Arizona, but was not involved in the study. “But we see examples of this behavior throughout the animal kingdom...it’s naive to think other animals wouldn’t have ways of collaborating.”</p></div>
  

  
      <div class="newsletter"></div>
  



<p>Dogs might be less inclined to be generous to their pack mates, hinting that domestication hasn’t necessarily improved canine social skills.</p>

Wolves boop their snoots to touch screens to feed their friends. Dogs? Not so much.

<p></p>
<p>Fossilized fish uncovered in North Dakota appear to preserve the catastrophic fallout of the asteroid impact that wiped out the dinosaurs.</p>
<p>Newly uncovered fossils in North Dakota appear to be the victims of one of the most catastrophic days in Earth’s history—the day the dinosaurs died 66 million years ago. A team of researchers led by paleontologist Robert DePalma reports chaotic debris created by two huge waves that surged up a river from an ancient inland sea. They say the site holds much more evidence that will keep them busy for years to come.</p>
<p><b>Stunning Fossil Discovery Could Offer Glimpse into Day the Dinosaurs Died</b></p><p>Published: April 22, 2019</p><p></p><p><b>Onscreen:</b> Newly uncovered fossils in North Dakota appear to be the victims of the most catastrophic day in Earth’s history… the day the dinosaurs died.</p><p><b>Jay Melosh:</b> You basically get a snapshot at the time that all these critters were dying. I think of this as the paleontological discovery of the century.</p><p><b>Onscreen</b>: A team of researchers led by paleontologist Robert DePalma says they uncovered chaotic debris created by two huge waves that surged up a river from an ancient inland sea.</p><p><b>Robert DePalma:</b> Essentially what you are looking at is a cross-section of what was alive at the time and you’re looking at a moment-by-moment record of conditions right after impact.</p><p><b>Onscreen</b>: Sixty-six million years ago, an asteroid smashed into Earth along the coast of Mexico setting off a chain reaction of apocalyptic events.</p><p><b>David Kring:</b> Massive earthquakes, immense landslides, and tsunamis or tidal waves that radiated across the Gulf of Mexico basin and for those of us in the United States, incursions of flood waters up onto the continent.</p><p><b>Onscreen</b>: Scientists think the impact also launched molten rock into the atmosphere where it formed little beads, called tektites, that rained back down to Earth.</p><p><b>Jan Smit:</b> DePalma pried out a region of the gills, and there was a collection of tektites stuck in the gills right there on the spot. From then I was totally convinced that he had something fantastic in that area.</p><p><b>DePalma:</b> What we see is these ejecta beads, these ejecta spherules caught in the gills of the fish. So that shows that these fish were alive right up until the time they were buried in the mud. They were entombed relatively instantaneously that’s why they are so well preserved. They are three-dimensionally preserved. That’s how we know that this was a very rapid event.</p><p><b>Onscreen</b>: Team members say the site holds much more evidence that will keep them busy for years to come.</p><p><b>DePalma:</b> This site and the research actually directly applies to what we’ve got going on today because this impact is one of our only test beds to see how the world ecology responds to major natural hazards and extinction-level events.</p><p><b>Smit:</b> There are lots of open questions to answer all the beautiful observations we have. We are just at the beginning.</p>
<p></p>
<p></p>
<p></p>

<p>Fossilized fish uncovered in North Dakota appear to preserve the catastrophic fallout of the asteroid impact that wiped out the dinosaurs.</p>

Topic: Evolution

Hero Feature