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2024 Stories
Mummified saber-toothed kitten discovered in Siberia
In 2020, prospectors hunting for ancient mammoth tusks in Siberia made a surprise discovery. The frozen clump of hair they noticed sticking out of a riverbank turned out to be a literal and figurative furball: a saber-toothed cat cub, desiccated and preserved in permafrost. Last month, scientists reported on their research on this first-of-its-kind specimen. The 37,000-year-old kitten mummy, complete with whiskers, fur, and claws, died when it was three weeks old. While the remains have not yet revealed how this individual cat died, they are providing insight into saber-toothed cats in general, including details that are hard to glean from bones alone. For example, the preserved kitten’s fur was dark brown, not spotted, as in many modern big cats, its neck was unusually thick and muscly, and its long upper lip might suggest that its famous canines would have been covered as an adult. Read on to learn more about the evolution of this charismatic group of mammals.
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Mpox: What’s a clade got to do with it?
Viral evolution makes the news again (in its usual, cruel way) as mpox cases surge in Africa. The outbreak, centered in the Democratic Republic of the Congo (DRC), threatens to spill over to other continents, constituting a global health emergency according to the World Health Organization. In 2022, mpox began to spread widely for the first time outside of Africa, where the virus naturally infects animals and sometimes makes the jump to human hosts. Most people infected with mpox fully recover without treatment. Although the 2022 outbreak eventually spread to 116 countries, it killed only around 220 people. The viral strain behind the current outbreak, however, appears to be deadlier. The DRC has already reported more than 1000 deaths. The difference seems to come down to the evolutionary origins of the two viral strains.
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One small step for ancient dinos, one long plane ride for modern humans
Last month scientists announced that they’d identified a close match for dinosaur tracks found in the rocks of northern Cameroon…in Brazil, almost 4000 miles across the Atlantic Ocean! The footprints are about 120 million years old and include tracks from theropods (relatives of Tyrannosaurus), ornithopods (relatives of Hadrosaurus), and sauropods (relatives of Apatosaurus). Both sets of tracks, made when dinosaurs traversed the muddy surfaces near ancient streams and lakes, are preserved in the same sorts of sediments. In fact, the African and South American tracks are so similar that scientists think that they represent two halves of the same path, along which dinosaurs dispersed. How could a walking route that began in Africa ever wind up in South America? A look at Earth’s geologic history provides the answer…and illustrates the nature of scientific theories like evolution.
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Wildfires drive evolutionary change, but can California ecosystems keep up?
In recent decades, fires have increased in size and frequency throughout California. The most recent of these record-breaking wildfires, named Park Fire, is the fourth-largest recorded wildfire in the state’s history. Park Fire started in Bidwell Park in Chico, California, as the result of arson. So far, it has burned through over 429,000 acres, destroyed more than 600 structures and burned through protected ecosystems, like Bidwell Park, the Big Chico Creek Ecological Reserve, and over 113,000 acres of Lassen National Forest. Many factors contribute to California’s ever larger and more frequent fires, but two big ones are climate change – with its resultant dry spells and record-breaking temperatures – and shifts in fire management strategies. In the last century, fire suppression practices, as opposed to controlled burns, have become the norm. Smaller, more frequent controlled burns decrease excess vegetation, reducing a fire’s ability to spread, while strict fire suppression can lead to a build-up of vegetation, increasing the frequency of large-scale wildfires. Here we’ll see how fires can drive evolution, helping plants survive and thrive after fires – and how more frequent fires can make some of these fire-adapted traits a liability.
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We live in the age of humans, but it’s not the Anthropocene … yet
While you’ve probably heard of the Triassic, Jurassic, and Cretaceous periods by way of their most charismatic animals, the dinosaurs, other units of geologic time are less well known. The Siderian Period, for example, rarely makes headlines because it is, by definition, old news – 2.5-billion-year-old news. However, discussions of geologic time recently sprang up in news feeds when geologists considered shaking things up and declaring the end of the Holocene Epoch, which we’ve been living in since the last Ice Age ended more than 11,000 years ago. The idea was to cap the Holocene by sectioning off a new unit of time called the Anthropocene – the age of humans. Here we’ll dig into the geologic time scale to see why it matters and what the idea of the Anthropocene Epoch is all about.
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Measles: New outbreaks, old virus
In recent weeks, measles cases have popped up across the U.S in Ohio, Florida, Washington, Michigan, Indiana, Minnesota, and beyond. This highly contagious virus often leads to hospitalization and occasionally to serious complications and death, especially in children under five. While the vaccine is safe and effective, declining vaccination rates have left pockets of people vulnerable. Measles might sound like ancient history compared to COVID-19, mpox, Zika, and other outbreaks that have made headlines in recent years – but how long has measles really been around? Evolutionary biology has the answer.
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Why species stay the same
The word evolution is nearly synonymous with change. One species diversifies into many. A disaster triggers a mass extinction among marine life. A microbe becomes resistant to our drugs. Each of these changes, large or small, is a classic example of evolution in action. But what about lack of change? Most of the species we observe around us today look about the same as they did in our grandparents’ time. And the fossil record includes many species that seem hardly to have changed at all for millions of years. How does this conspicuous stability square with evolutionary theory? New research supports one explanation.
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Menacing mosquitoes: Nature or nurture?
Last month, a California resident was infected with dengue fever after a bite from a local mosquito. This case made the news because it was the first, but it may not be last. Dengue and another mosquito-transmitted disease, malaria, are on the rise around the world. Several factors are behind this trend. Climate change allows mosquitoes to live in broader geographic regions. A city-dwelling mosquito species has been transported across continents and established itself in dense urban areas. And, importantly, mosquitoes have changed.
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Are we boosting the evolutionary potential of SARS-CoV-2?
It’s baaack! COVID-19 is surging again, but this time, its symptoms are milder. That’s probably because vaccines and previous infections have led to some degree of immunity. And even when symptoms aren’t mild, we now have treatments to help those most at risk of severe disease. However new evidence suggests that one of those treatments, the medication molnupiravir, causes mutations in the virus and that these mutant viruses can be passed from person to person. Should we be worried?
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Familiar sparks for ancient extinctions
Around 10,000 years ago, two-thirds of Earth’s large mammals blipped out of existence. Mammoths, mastodons, sabertoothed cats, and many other species from all over the world went extinct. Despite investigating many possible causes, biologists have yet to find a smoking gun revealing the culprit behind the disappearances. But that doesn’t necessarily mean that we are missing something. Extinction can be, well … complicated. Perhaps we haven’t been able to identify a single main trigger for the extinctions because several causes acted together. A new study takes this possibility seriously and untangles the interacting factors behind large mammal extinctions in Southern California at the end of the last Ice Age.
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Meteorite impact no picnic for sharks either
Around 66 million years ago, a massive meteorite struck Earth, triggering a series of ecological disasters that wiped out T. rex along with all the other non-bird dinosaurs. For most of us, that’s old news – and might be as much as we know about this dramatic time. But scientists, of course, dig much deeper into the past, investigating exactly how mass extinctions played out and how they affected different groups of organisms. Now, new research explores this same extinction event from the view of another ancient and famously toothy group: sharks, skates, and rays.
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How did dinos get so big…and so little?
Dinosaurs come in all sizes. The lumbering Argentinosaurus probably reached 115 feet, the winged Microraptor less than 4 feet. And today, the sole surviving lineage of dinosaurs – modern birds – includes both miniscule hummingbirds and leggy ostriches. (Learn more about why birds are actually a type of dinosaur here.) Scientists have long been interested in how non-bird dinosaurs, which include the largest land-dwelling animals that ever lived, came to have such different body sizes. The answer, of course, is through evolution, but what evolutionary changes were involved? New research helps answer that question.
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Nature or nurture? In tiger snake evolution it’s complicated…
Seeing differences in the biological world often leads to questions about nature and nurture. Did I outperform my sibling in basketball because I inherited my mom’s quick reaction time (nature) or because I practiced more (nurture)? Is this golden delicious apple really old (nurture) or are they just a mealy apple type (nature)? Is our dog well behaved because she’s part golden retriever (nature) or because of all that puppy training (nurture)? Often the answers to such questions are not either/or. New research on venomous tiger snakes highlights just how intertwined nature and nurture can be – and how evolution has a hand in both!
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