A fungus found within ancient mammoth dung is providing scientists with clues about how the large ancient mammals collectively known as megafauna went extinct. The fungus, Sporormiella, produces spores in the dung of large herbivores. These are then preserved in the layers of mud and can provide an index of the number of these animals, or megafauna, that roamed the environment at a particular time [BBC News]. For a new study, researcher Jacquelyn Gill collected and analyzed spores in sediment samples from an Indiana lake and several sites in New York.
From Gill’s analysis, published in the journal Science, she concluded that North American megafauna began a slow decline around 15,000 years ago and vanished about 1,000 years later. The data suggests megafauna started going extinct much earlier than previously though, which basically wipes out two theories of their extinction.
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Minuscule diamond fragments found in a sediment layer dating from thousands of years ago are bolstering the theory that a catastrophic comet impact wiped out many forms of life in North America, including what are thought to have been the first human settlers of the continent, the so-called Clovis people. The nano-diamonds are buried at a level that corresponds to the beginning 12,900 years ago of the Younger Dryas, a 1,300-year-long cold spell during which North American mammoths, saber-toothed cats, camels and giant sloths became extinct. The Clovis culture of American Indians also appears to have fallen apart during this time [Reuters].
The new study adds evidence to the controversial theory, but some skeptics are not convinced. “The whole thing still does not make sense, and there are lots of contradictions,” said Christian Koeberl, a professor of geological sciences…. His chief reservation is that there is no crater. “A body of this size does not just blow up without a trace in the atmosphere,” Dr. Koeberl said. “Physics won’t have it” [The New York Times]. In reply, supporters of the theory say that some of the comet fragments may have exploded in midair, while others may have hit an ice sheet that was several miles thick, lessening the possibility of a crater forming.
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The last woolly mammoths, who tromped around the Siberian tundra before going extinct about 10,000 years ago, had North American roots, according to a new genetic analysis. Scientists studied DNA from the remains of 160 mammoths from across North America and Eurasia, and determined that the last remaining mammoths were migrants who had come to Siberia via the Bering land bridge, and somehow replaced the endemic population.
Researchers believe that mammoths originally spread from Asia to North America via the land bridge, creating two genetically distinct populations. Now, they’re hypothesizing that some members of the North American group eventually made a return trip and proved hardier survivors than the Siberian group. “For some reason the North American guys went back over and became kings,” says [lead researcher] Hendrik Poinar [New Scientist].
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Neanderthals don’t have the best reputation. In the public mind, the heavy-browed hominids are thought of as a stupid species that couldn’t compete with brighter Homo sapiens, as the also-rans that therefore went extinct. But a newly discovered trove of Neanderthal tools in Sussex, England may help rehabilitate their image. The tools, which date from the end of the Neanderthal era at around 30,000 B.C., show surprising sophistication, archaeologists say.
“The tools we’ve found at the site are technologically advanced and potentially older than tools in Britain belonging to our own species,” said [University College London]’s Matthew Pope. “It’s exciting to think that there’s a real possibility these were left by some of the last Neanderthal hunting groups to occupy northern Europe,” he added. “The impression they give is of a population in complete command of both landscape and natural raw materials with a flourishing technology — not a people on the edge of extinction” [Discovery News].
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Woolly mammoths may all look the same in your average natural history museum display — the extinct animals are always depicted with the same curly tusks, shaggy hair, and lumbering feet. But researchers have just discovered that they were not all the same, that two genetically distinct groups of mammoths roamed the Siberian plains many millennia ago, and that one group avoided extinction for an extra 30,000 years.
Researchers first went in search of tufts of mammoth hair that had been frozen in the permafrost. They then used a new technique that allowed them to read the complete DNA sequence of an animal’s mitochondria (an energy-producing organelle within a cell) from a single hair. The DNA in mitochondria is passed only through the mother’s line, and doesn’t give information about changes in gene function, as nuclear DNA can. But it is useful because it doesn’t change from parent to offspring, making it easy to show when different animal groups are present [Nature News].
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