UC Berkeley
2023 Stories
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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Human evolution in response to an ancient pandemic
Bubonic plague and ancient DNA are having a media moment. Evo in the News most recently covered a search for DNA from the plague bacterium, Yersinia pestis, in graves from the 1300s. Last month, we celebrated Svante Pääbo’s Nobel prize for his work on ancient DNA. And this month, we dig into another investigation that excavated DNA from the time of the Black Death, a particularly deadly plague outbreak, to illuminate how that epidemic shaped the course of human evolution.
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Evolution of the plague pandemic
Over the summer, researchers announced that they’d identified the source of a deadly pandemic. This might sound like another story on COVID-19 – but in fact, the research did not focus on bats in China circa 2019, but on tombstones in Kyrgyzstan circa 1340. The Black Death, an outbreak of bubonic plague, killed perhaps as much as 60% of the population of Western Europe and Asia in less than 10 years. Bubonic plague is caused by the bacteria Yersinia pestis, which can spread through flea bites that transmit the microbe from one infected animal to another, as well as directly from person to person. This pandemic pestilence still lurks in rodents and other small animals around the world today, but now we treat the disease with antibiotics and understand its transmission well enough to tamp down outbreaks. However, many questions about the plague’s deadliest epidemic in the Late Middle Ages remain – mysteries to which ancient graves seemed to hold clues…
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Shrinking salmon
You can’t tell when it’s on your dinner plate, but wild salmon have been shrinking. Salmon from populations around the world now have smaller body sizes than they did 30 to 60 years ago. While the causes of this shift aren’t always clear, potential culprits include fishing, climate change, and competition for food (e.g., from hatchery-bred salmon). Now, new research untangles the probable causes of reduced body size in one population of wild Atlantic salmon – and demonstrates how the impacts of human activities can ripple through ecosystems.
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Preventing the evolution of a vaccine-resistant COVID strain
Many of us breathed a sigh of relief when COVID-19 vaccines rolled out. For those with the good luck of living in places with easy access, getting a shot or two could mean a fast track back to normal life — no more masks or social distancing. As vaccination rates went up, new cases fell, and social restrictions followed the same trend. It made sense to relax the rules we’d been living with once new virus cases slowed. However, recent research reveals potential evolutionary pitfalls in this approach.
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On the evolutionary trail of MRSA
The bacterium MRSA (shorthand for methicillin-resistant Staphylococcus aureus) resists several antibiotics and can cause super-charged staph infections, leading to difficult-to-treat skin infections, pneumonia, and sepsis. Antibiotic resistant bacteria like MRSA caused more than a million deaths in 2019. Now an international team of researchers has discovered what they think is the source of one variety of MRSA – and it didn’t come about through incremental evolution in people being treated with the antibiotic methicillin. It came from…hedgehogs.
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Omicron and the case of the hidden evolution
Over the past month, the SARS-CoV-2 Omicron strain has dominated world news. This fast-spreading coronavirus variant has led to travel restrictions, cancelled holiday plans, sold-out test kits, reimposed lockdowns, and of course, a staggering number of new COVID-19 cases. Scientists quickly pivoted to study Omicron, trying to learn how easily it spreads, how sick it makes us, and whether it resists our treatments, vaccines, and antibodies from previous COVID infections. We need to revisit all these questions because Omicron is very different from other coronavirus strains. Omicron has accumulated more than 50 new mutations in comparison to the strain that started the pandemic. Furthermore, Omicron is not descended from the Delta strain, which was responsible for the previous wave of infections. In fact, Omicron is so different from other variants that it seems like it’s been evolving on its own for many months. And that leads us to another mystery that scientists are puzzling over: where has Omicron been hiding while all this evolution was occurring?
Read more »Omicron y el caso de la evolución escondida
Durante el último mes, las cepas del SARS-CoV-2 Omicron han dominado los noticiarios del mundo. Esta variante de rápida transmisión ha llevado a limitar viajes, a cancelar planes de vacaciones, al agotamiento de los kits de pruebas, a la vuelta de los confinamientos, y además a un asombroso número de nuevos casos de COVID-19. Los científicos rápidamente se han puesto a estudiar Omicron, intentando entender qué tan rápido se transmite, qué tanto nos enferma, y si es resistente a los tratamientos, a las vacunas, y a los anticuerpos de infecciones de COVID previas. Necesitamos revisar todas estas cuestiones porque Omicron es muy diferente de otras cepas de coronavirus. Omicron ha acumulado más de 50 nuevas mutaciones en comparación con la cepa que empezó la pandemia. Además Omicron no es un descendiente de la cepa Delta, responsable de la anterior ola de infecciones. De hecho, Omicron es tan diferente de otras variantes que parece que ha estado evolucionando por su cuenta durante muchos meses. Y esto nos conduce a otro misterio que los científicos están tratando de resolver: ¿dónde estaba Omicron escondido mientras toda esta evolución tenía lugar?
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