According to a theory proposed in 2007, the explosion of a comet over North America killed off the Clovis people and many of the continent’s largest mammals nearly 13,000 years ago. Not so fast, says a new study published in the Proceedings of the National Academy of Sciences, fueling a WWE-style stare down between the opposing camps.
The new report explains that archaeologists have examined sediments at seven Clovis-age sites across the United States, and found that the concentration of magnetic debris was insufficient to confirm an extraterrestrial impact at that time [Nature News]. The original theory’s evidence came from magnetic microspherules, or cosmic debris, discovered in sediments at 25 locations. However, one of the new study’s authors, Todd Surovell, said that even after 18 months of sedimentary analysis and hundreds of hours peering into a microscope, he could find no evidence of microspherules to support the the exploding comet theory. Snap.
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The giant, prehistoric kangaroo that once hopped over the Australian landscape may have been wiped out by the first human settlers on that continent, a new study argues. In making this claim, the researchers are entering into a long-running debate over whether Australia’s “megafauna,” which also included marsupial lions and hippo-sized wombats, were driven extinct by the changing climate or by overzealous hunting. And while the new study, which will be published in the Proceedings of the National Academy of Sciences, makes an interesting case for the latter hypothesis, some researchers are not convinced.
Researchers analyzed the teeth of the nearly seven-foot-tall kangaroo, known as Procoptodon goliah, to determine what it ate and drank. Different sources of water and food leave trace amounts of particular types, or isotopes, of hydrogen and carbon atoms, which are deposited in the teeth like a recorded diet. Additionally, tiny patterns of wear give clues about the type of food a given creature chewed. The team concluded that the giant kangaroos fed mainly on saltbush shrubs [BBC News]. These hardy bushes thrive in arid conditions, which makes it less likely that the kangaroos ran out of food as the continent’s climate got hotter and drier.
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For six years, psychiatrists thought they had found a genetic clue as to what makes some people more prone to depression when they’re hit with an emotional blow: a single gene. A 2003 study created a sensation among scientists and the public because it offered the first specific, plausible explanation of why some people bounce back after a stressful life event while others plunge into lasting despair [The New York Times]. But now a broader analysis of 14 studies has found no link between the gene and the risk of depression, and researchers argue that the 2003 findings were prematurely heralded as a breakthrough. “I think what happened is that people who’d been working in this field for so long were desperate to have any solid finding” [The New York Times], says Kathleen R. Merikangas, one of the authors of the new study.
The so-called “depression gene” that researchers focused on in the 2003 study helps regulate levels of serotonin, a brain chemical that plays a major role in depression and is a key target of antidepressant drugs. Researchers … found from a long-term study of 847 people in New Zealand that those with a short version, or allele, of the serotonin transporter gene were more likely to become depressed by adverse life events than were those with only long alleles [ScienceNOW Daily News].
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A computer analysis of symbols inscribed on stone tablets and artifacts more than 4,000 years ago has prompted a new debate on a fiercely contested question: Did the people of the Indus Valley civilization have a written language? According to the researchers who conducted the latest analysis, the answer is yes, and the next step is to search for the grammatical rules governing the language. But other researchers have harsh words for the methods used in the study. “As they say: garbage in, garbage out,” [New Scientist], one critic says.
The Indus civilisation flourished in isolation 4,500 years ago along the border of what is now eastern Pakistan, but almost no historical information exists about the people and their long-lost community. Archaeologists working in the region have unearthed a rich hoard of artifacts, including amulets, seals and ceramic tablets, many of which are embellished with the unusual symbols [The Guardian]. But some researchers contend that the symbols are simply religious or political imagery, and that they don’t add up to a language. They note that most of the inscriptions are extremely short (averaging only four or five symbols), and that few symbols are used repeatedly.
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The earthquake that hit central Italy in the middle of last night, reducing some towns to rubble and killing at least 90 people, was foretold by an Italian seismologist–but his warnings were ignored, according to news reports. However, many researchers say that the seismologist’s predictions were based on inadequate evidence, and say the Italian government was right not to publicize his predictions, as they would only have spread panic.
The region felt its first tremors in mid-January. Scientists say that tremors do not necessarily indicate that a larger quake is on the way, but seismologist Giampaolo Giuliani grew increasingly concerned. He published his warnings, which received some attention; according to Italian newspapers, vans with loudspeakers drove around the town of L’Aquila one month ago telling locals to evacuate their houses. Then Giuliani, who based his forecast on concentrations of radon gas around seismically active areas, was reported to police for “spreading alarm” and was forced to remove his findings from the Internet. “Now there are people who have to apologize to me and who will have what has happened on their conscience” [Reuters], he told an Italian newspaper.
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The blast that shook the Chernobyl nuclear power plant more than 20 years ago, sending a highly radioactive plume of fallout into the air, still affects local populations of butterflies and bees and other insects, according to a new study. The study appears to argue against the idea put forward by previous researchers that the region around the power plant, contaminated by radiation and off limits to most humans, has become a sort of post-apocalyptic Eden [The New York Times], in which animals can live unmolested. However, the new results are stirring up controversy.
A pair of researchers conducted standard surveys in forests around Chernobyl over three springs from 2006 to 2008, noting the numbers of bumblebees, butterflies, grasshoppers, dragonflies and spider webs at points with radiation levels that varied over four orders of magnitude [The New York Times]. They found that the number of bugs declined as the radiation increased, and that even relatively low levels of radiation impacted insect populations. The researchers say insects may be particularly vulnerable because radiation is usually found in the top layer of soil, where many invertebrates spend time during either their egg, larvae, or adult phases.
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The Mars Phoenix Lander conked out in November, ending the active mission of the robotic scientist, but the results of its five months of research on Martian geology are still coming in. In a late-breaking update, some Phoenix scientists now declare that they spotted several drops of liquid salt water on the lander’s legs; this would be the first time liquid water has been detected and photographed beyond Earth.
The researcher who proposed the hypothesis, Nilton Renno, was careful to say, “This is not a proof.” But he added: “I think the evidence is overwhelming. It’s not circumstantial evidence” [The New York Times]. Liquid water would boost the possibility that microbial life could survive beneath the Martian surface.
Renno bases his claim on images that show several blobs on the lander’s legs that changed between snapshots, seeming to merge and grow in size. The dramatic assertion has divided the Phoenix’s science team, with some researchers arguing that the low-resolution pictures actually show nothing more than clumps of frost. “It’s highly unlikely that [liquid water is] the explanation,” said Michael Hecht of NASA’s Jet Propulsion Laboratory…. “It’s just water vapor moving around. It’s an ordinary, unexciting explanation” [AP].
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