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Post by Joanna on Jul 27, 2015 18:55:14 GMT -5
Global-Warming Killed Woolly Mammoths, Other Large AnimalsThe mighty megafauna of the last ice age, including the woolly mammoths, short-faced bears and cave lions, largely went extinct because of rapid climate-warming events, a new study finds. During the unstable climate of the Late Pleistocene, about 60,000 to 12,000 years ago, abrupt climate spikes, called interstadials, increased temperatures between 7 and 29 degrees Fahrenheit (4 and 16 degrees Celsius) in a matter of decades. Large animals likely found it difficult to survive in these hot conditions, possibly because of the effects it had on their habitats and prey, the researchers said. Interstadials “are known to have caused dramatic shifts in global rainfall and vegetation patterns,” the study’s first author Alan Cooper, director for the Australian Centre for Ancient DNA at the University of Adelaide in Australia, said in a statement emailed to Live Science.
Temperature drops during the Late Pleistocene showed no association with animal extinctions, Cooper said. Instead, only the hot interstadial periods were associated with the large die-offs that hit populations (local events) and entire species of animals (global events), he said. Ancient humans also played a role in the megafaunal extinction, albeit a smaller one, he said. By disrupting the animals’ environments, human societies and hunting parties likely made it harder for megafauna to migrate to new areas and refill areas once populated by animals that had gone extinct, he said.
Extinction analysis. The study is the latest in a long string of research examining what caused megafauna, or animals weighing more than 99 pounds, to die off during the Late Pleistocene. George Cuvier, the French paleontologist who first recognized the mammoth and the giant ground sloth, started the speculation in 1796 when he suggested that giant biblical floods were to blame for the animals’ demise. The extinctions also baffled Charles Darwin after he encountered megafaunal remains in South America. Since then, various studies have placed the bulk of responsibility on ice age humans, temperature swings and a perfect storm of events.
However, advances in examining ancient DNA and ancient climate allowed Cooper and his colleagues to get to the bottom of the issue. They examined DNA from dozens of megafaunal species that lived during the Late Pleistocene, combing through more than 50,000 years of DNA records for extinction events. The ancient DNA not only told them about global extinction events, but also local population turnovers, which occur when a group of animals dies and another population of animals moves in to replace them. They then compared the data on megafauna extinction with detailed records of severe climate events, which they gathered from Greenland ice cores and the sedimentary record of the Cariaco Basin off Venezuela. “By combining these two records, we can place the climate and radiocarbon dating data on the same timescale, thereby allowing us to precisely align the dated fossils against climate,” Cooper said. “The high-resolution view we gained through this approach clearly showed a strong relationship between warming events and megafaunal extinctions.” The findings also show that extinction events were staggered over time and space, likely because the interstadial warming events had different effects on different regions, Cooper said.
Modern connections. Earth’s climate is much more stable today than it was during the Late Pleistocene, making the world’s current warming trends a “major concern,” the researchers said. “In many ways, the rise of atmospheric carbon dioxide levels and resulting warming effects are expected to have a similar rate of change to the onset of past interstadials, heralding another major phase of large mammal extinctions,” Cooper said. In addition, humans have disrupted the habitats and surrounding areas of many wild animals, making it challenging for species to migrate or shift ranges to places where they would be better adapted to deal with climate change, he said.
Other researchers called the new study an important one. It shows “that the extinction and population turnover of many megafauna was associated with rapid warming periods, rather than the last glacial maximum [when the ice sheets reached their maximum during the last glacial period] or Younger Dryas as has previously been suggested,” said Eline Lorenzen, an assistant professor of paleogenetics at the University of Copenhagen in Denmark. In fact, understanding how the past climate change affected extinction rates may help people be better prepared for future rapid global warming events, she said. “This study is a bit of a wake-up call,” Lorenzen said. “Here we have empirical evidence – based on data from a lot of species – that rapid climate warming has profoundly impacted megafauna communities, negatively, during the past 50,000 years. “It doesn’t bode well for the future survival of the world’s megafauna populations,” she concluded. Source: Laura Geggel, LiveScience, July 23, 2015.
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Post by aprillynn93 on Jul 28, 2015 12:50:57 GMT -5
You can't blame that one on humans!
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Post by Joanna on Mar 12, 2019 22:15:08 GMT -5
Scientists Try to Bring Back Woolly MammothsCells from a woolly mammoth that died 28,000 years ago, implanted in mouse cells, have begun to show “signs of biological [activity].” However, researchers caution it’s unlikely the extinct creatures will walk the Earth again anytime soon. The research, published in Scientific Reports, details how a well-preserved woolly mammoth, found in 2011 in the Siberian permafrost, has begun to show some activity. “This suggests that, despite the years that have passed, cell activity can still happen and parts of it can be recreated,” Kei Miyamoto, a member of the team that conducted the work, said in an interview with AFP. “Until now, many studies have focused on analyzing fossil DNA and not whether they still function,” he added.
The study’s abstract reveals “in the reconstructed oocytes, the mammoth nuclei showed the spindle assembly, histone incorporation and partial nuclear formation; however, the full activation of nuclei for cleavage was not confirmed.” Unfortunately, there were varying levels of DNA damage, which the researchers said “were comparable to those of frozen-thawed mouse sperm and were reduced in some reconstructed oocytes.”
While some evidence of biological processes were seen, the damage the elements had on the cells are not enough for bringing the mammoth back to life, eschewing any kind of “Jurassic Park-style resurrection” that many have hoped for, Miyamoto explained. “We have also learned that damage to cells was very profound. We are yet to see even cell divisions. I have to say we are very far from recreating a mammoth.”
Woolly mammoths became extinct more than 4,000 years ago, with some scientists believing they died off from a combination of the changing climate and human hunters. The hairy creatures were part of the elephant family, sharing a common ancestor with Asian and African elephants – the only two species that exist today – that lived about 4 million years ago. There were approximately 20 species of mammoths, of which the woolly mammoth is just one. Mammoth remains are found in most parts of the northern hemisphere, where they once thrived. Frozen remains have been found in Siberia and Alaska.
Despite Miyamoto’s comments, some researchers are attempting to bring back the mammoth with the use of gene editing, including the controversial CRISPR gene editing tool. George Church, a Harvard and MIT geneticist and co-founder of CRISPR, is the head of the Harvard Woolly Mammoth Revival team, a project that is attempting to introduce mammoth genes into the Asian elephant for conservation purposes. “The elephants that lived in the past – and elephants possibly in the future – knocked down trees and allowed the cold air to hit the ground and keep the cold in the winter, and they helped the grass grow and reflect the sunlight in the summer,” Church told Live Science in May 2018. “Those two [factors] combined could result in a huge cooling of the soil and a rich ecosystem.”
Mammoth remains have been found all over the globe in recent months. In June, a mysterious mammoth bone was discovered on a beach in Loch Ryan in southwestern Scotland. In August, a frozen woolly mammoth was found in Siberia, with researchers theorizing that because of its small stature, it may be a new type species. It has been dubbed a “Golden mammoth” and could be as much as 50,000 years old. In September, a mammoth kill site was discovered in Austria, where Stone Age people slaughtered the might animals.
The ‘Humpty Dumpty’ Problem. Breathing life into the extinct woolly mammoth is a different, possibly impossible, operation. During life, the damage to fragile DNA is repaired naturally. After death, the genetic code quickly breaks down. Robert DeSalle, a curator at the American Museum of Natural History, calls this the “Humpty Dumpty” problem. These genetic fragments would likely be 10,000 to 100,000 times smaller than the DNA pieces the researchers in the human genome project are working with, DeSalle said. According to the curator, with the exception of a simple flu virus, “no organisms have been manipulated this way.” Then there are the ethical issues, even if a cloned herd could survive in places like Canada or the Dakotas. “In principle,” Greenwood argues, “they don’t belong here anymore.” Sources: Chris Ciaccia and James Rogers, Fox News, March 12, 2019, and Willow Lawson, ABC News.
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Post by JoannaL on Sept 17, 2021 19:18:17 GMT -5
Company Plans to Recreate the Woolly Mammoth
With $15 million in private funding, a team of scientists and entrepreneurs have announced they have found a company called Colossal for the purpose of genetically resurrecting the woolly mammoth. “This is a major milestone for us,” said George Church, a biologist at Harvard Medical School, who for eight years has been leading a small team of moonlighting researchers developing the tools for reviving mammoths. “It’s going to make all the difference in the world.”
Other researchers, however, have their doubts concerning Colossal’s ability to pull off such a feat. But even if they are proven wrong and the company succeeds in its endeavor, they question whether it is ethical to produce an animal about which we know so little. They also question who would be in charge of deciding to set such animals free on the Siberian tundra of the 21st century and could they potentially alter the ecosystems of the locations where they are released? “There’s tons of trouble everyone is going to encounter along the way,” admitted Beth Shapiro, a paleogeneticist at the University of California Santa Cruz and the author of “How to Clone a Mammoth.”
The idea behind Colossal first emerged in 2013, when Dr. Church sketched it out in a talk at the National Geographic Society.
Source: Carl Zimmer, The New York Times, September 17, 2021.
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