冰河時期北極野花消失 可能導致了巨獸滅絕# Animals - 动物园
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冰河時期北極野花消失 可能導致了巨獸滅絕
Disappearance of wildflowers may have doomed Ice Age giants
By Will Dunham2 hours ago
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By Will Dunham
WASHINGTON (Reuters) - Flower power may have meant the difference between
life and death for some of the extinct giants of the Ice Age, including the
mighty woolly mammoth and woolly rhinoceros.
Scientists who studied DNA preserved in Arctic permafrost sediments and in
the remains of such ancient animals have concluded that these Ice Age beasts
relied heavily on the protein-rich wildflowers that once blanketed the
region.
But dramatic Ice Age climate change caused a huge decline in these plants,
leaving the Arctic covered instead in grasses and shrubs that lacked the
same nutritional value and could not sustain the big herbivorous mammals,
the scientists reported in the journal Nature on Wednesday.
The change in vegetation began roughly 25,000 years ago and ended about 10,
000 years ago - a time when many of the big animals slipped into extinction,
the researchers said.
Scientists for years have been trying to figure out what caused this mass
extinction, when two-thirds of all the large-bodied mammals in the Northern
Hemisphere died out.
"Now we have, from my perspective at least, a very credible explanation,"
Eske Willerslev of the University of Copenhagen, an expert in ancient DNA
who led an international team of researchers, said in a telephone interview.
The findings contradicted the notion that humans arriving in these regions
during the Ice Age caused the mass extinction by hunting the big animals
into oblivion - the so-called overkill or Blitzkrieg hypothesis.
"We think that the major driver (of the mass extinction) is not the humans,"
Willerslev said, although he did not rule out that human hunters may have
delivered the coup de grace to some species already diminished by the
dwindling food supplies.
The Arctic region once teemed with herds of big animals, in some ways
resembling an African savanna. Large plant eaters included woolly mammoths,
woolly rhinos, horses, bison, reindeer and camels, with predators including
hyenas, saber-toothed cats, lions and huge short-faced bears.
The scientists carried out a 50,000-year history of the vegetation across
the Arctic in Siberia and North America.
They obtained 242 permafrost sediment samples from various Arctic sites and
studied the feces and stomach contents from the mummified remains of Ice Age
animals recovered in places like Siberia. They determined the age of the
samples and analyzed the
DNA.
While many scientists had thought the ecosystem had been grasslands and the
big animals were grass eaters, this study showed it instead was dominated by
a kind of plant known as forbs - essentially wildflowers.
"The whole Arctic ecosystem looked extremely different from today. You can
imagine these enormous steppes with no trees, no shrubs, but dominated by
these small flowering plants," Willerslev said.
Christian Brochmann, a botanist at the Natural History Museum at the
University of Oslo, said the permafrost contained "a vast, frozen DNA
archive left as footprints from past ecosystems," that could be deciphered
by exploring animal and plant collections already stored in museums.
(Reporting by Will Dunham, editing by G Crosse)
冰河時期北極野花消失 可能導致了巨獸滅絕
Disappearance of wildflowers may have doomed Ice Age giants
By Will Dunham2 hours ago
0shares
By Will Dunham
WASHINGTON (Reuters) - Flower power may have meant the difference between
life and death for some of the extinct giants of the Ice Age, including the
mighty woolly mammoth and woolly rhinoceros.
Scientists who studied DNA preserved in Arctic permafrost sediments and in
the remains of such ancient animals have concluded that these Ice Age beasts
relied heavily on the protein-rich wildflowers that once blanketed the
region.
But dramatic Ice Age climate change caused a huge decline in these plants,
leaving the Arctic covered instead in grasses and shrubs that lacked the
same nutritional value and could not sustain the big herbivorous mammals,
the scientists reported in the journal Nature on Wednesday.
The change in vegetation began roughly 25,000 years ago and ended about 10,
000 years ago - a time when many of the big animals slipped into extinction,
the researchers said.
Scientists for years have been trying to figure out what caused this mass
extinction, when two-thirds of all the large-bodied mammals in the Northern
Hemisphere died out.
"Now we have, from my perspective at least, a very credible explanation,"
Eske Willerslev of the University of Copenhagen, an expert in ancient DNA
who led an international team of researchers, said in a telephone interview.
The findings contradicted the notion that humans arriving in these regions
during the Ice Age caused the mass extinction by hunting the big animals
into oblivion - the so-called overkill or Blitzkrieg hypothesis.
"We think that the major driver (of the mass extinction) is not the humans,"
Willerslev said, although he did not rule out that human hunters may have
delivered the coup de grace to some species already diminished by the
dwindling food supplies.
The Arctic region once teemed with herds of big animals, in some ways
resembling an African savanna. Large plant eaters included woolly mammoths,
woolly rhinos, horses, bison, reindeer and camels, with predators including
hyenas, saber-toothed cats, lions and huge short-faced bears.
The scientists carried out a 50,000-year history of the vegetation across
the Arctic in Siberia and North America.
They obtained 242 permafrost sediment samples from various Arctic sites and
studied the feces and stomach contents from the mummified remains of Ice Age
animals recovered in places like Siberia. They determined the age of the
samples and analyzed the
DNA.
While many scientists had thought the ecosystem had been grasslands and the
big animals were grass eaters, this study showed it instead was dominated by
a kind of plant known as forbs - essentially wildflowers.
"The whole Arctic ecosystem looked extremely different from today. You can
imagine these enormous steppes with no trees, no shrubs, but dominated by
these small flowering plants," Willerslev said.
Christian Brochmann, a botanist at the Natural History Museum at the
University of Oslo, said the permafrost contained "a vast, frozen DNA
archive left as footprints from past ecosystems," that could be deciphered
by exploring animal and plant collections already stored in museums.
(Reporting by Will Dunham, editing by G Crosse)
