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Woolly Mammoth - Mammuthus primigenius
#1
Woolly Mammoth - Mammuthus primigenius

[Image: yuka-ice-age-elephant-mammuthus-primigenius_3_7412.jpg]

Scientific classification 
Kingdom: Animalia 
Phylum: Chordata 
Class: Mammalia 
Order: Proboscidea 
Family: Elephantidae 
Genus: †Mammuthus 
Species: Mammuthus primigenius 

The woolly mammoth, also called the tundra mammoth, is an extinct species of mammoth. This animal is known from bones and frozen carcasses from northern North America and northern Eurasia with the best preserved carcasses in Siberia.

This mammoth species was first recorded in (possibly 150,000 years old) deposits of the second last glaciation in Eurasia. They were derived from steppe mammoths (Mammuthus trogontherii).

Physical Description
Woolly mammoths had a number of adaptations to the cold, most famously the thick layer of shaggy hair, up to 50 cm (20 in) long, for which the woolly mammoth is named. They also had far smaller ears than modern elephants; the largest mammoth ear found so far was only a foot (30 cm) long, compared to six feet (1.8 m) for an African elephant. They had a flap of hairy skin which covered the anus, keeping out the cold.
Their teeth were also adapted to their diet of coarse tundra grasses, with more plates and a higher crown than their southern relatives. Their skin was no thicker than that of present-day elephants, but unlike elephants they had numerous sebaceous glands in their skin which secreted greasy fat into their hair, improving its insulating qualities. They had a layer of fat up to 8 cm (3 in) thick under the skin which, like the blubber of whales, helped to keep them warm.
Woolly mammoths had extremely long tusks - up to 16 feet (5 m) long - which were markedly curved, to a much greater extent than those of elephants. It is not clear whether the tusks were a specific adaptation to their environment, but it has been suggested[attribution needed] that mammoths may have used their tusks as shovels to clear snow from the ground and reach the vegetation buried below.


Extinction
While most woolly mammoths died out at the end of the Pleistocene (12,000 years ago), a small population survived on St. Paul Island, Alaska, up until 6000 BC, while another remained on Wrangel Island, located in the Arctic Ocean, up until 1700 BC. Possibly due to their limited food supply, these animals were a dwarf variety, thus much smaller than the original Pleistocene woolly mammoth. However, the Wrangel Island mammoths should not be confused with the Channel Islands Pygmy Mammoth, Mammuthus exilis, which was a different species.

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#2
Ancient DNA Traces Woolly Mammoth's Disappearance

Science Daily — Some ancient-DNA evidence has offered new clues to a very cold case: the disappearance of the last woolly mammoths, one of the most iconic of all Ice Age giants, according to a recent article. DNA lifted from the bones, teeth, and tusks of the extinct mammoths revealed a "genetic signature" of a range expansion after the last interglacial period. After the mammoths' migration, the population apparently leveled off, and one of two lineages died out

"In combination with the results on other species, a picture is emerging of extinction not as a sudden event at the end of the last ice age, but as a piecemeal process over tens of thousands of years involving progressive loss of genetic diversity," said Dr. Ian Barnes, of Royal Holloway, University of London. "For the mammoth, this seems much more likely to have been driven by environmental rather than human causes, even if humans might have been responsible for killing off the small, terminal populations that were left."

Barnes, along with Dr. Adrian Lister of the University College London and the Natural History Museum in London and others, had earlier found evidence that bison, bears, and lions underwent major population shifts twenty-five to fifty thousand years ago. Those results came as a surprise, the researchers said, because scientists tended to think that the major environmental changes happened about fifteen to twenty-five thousand years ago, when the glaciers reached their fullest extent. The findings also offered early human hunters a potential alibi; they didn't come on the scene in large numbers until even later.

In search of a general pattern in the new study, Barnes and Lister's team looked to the extinct woolly mammoth. What they found, however, was an "interesting pattern, not like those of the other species."

Their genetic data indicate that Siberian mammoths expanded from a small base some time before sixty thousand years ago. Moreover, they found two distinct genetic groups, implying that mammoths had diverged in isolation for some time before merging back into a single population. The DNA further suggests that no later than forty thousand years ago, one of the groups died out, leaving only the second alive at the time of the mammoth's last gasp.

"At a time when we should be very concerned about the potential extinction of many existing large mammals, studying those that occurred in the geologically recent past can provide many insights," Lister said. "Our work, together with that of others, shows that the conditions for extinction can be set up long before the actual extinction event."

The researchers include Ian Barnes of Royal Holloway, University of London in Surrey, UK; Beth Shapiro of University of Oxford in Oxford, UK; Mark G. Thomas of University College London in London, UK; Adrian Lister of the Natural History Museum and University College London in London, UK;Tatiana Kuznetsova of Moscow State University in Moscow, Russia; Andrei Sher of Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences in Moscow, Russia; Dale Guthrie University of Alaska in Fairbanks, Alaska.

http://www.sciencedaily.com/releases/2007/06/070607171134.htm

Woolly Mammoth Skull
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March 24, 2005—Fresh from the Siberian tundra, an 18,000-year- old frozen woolly mammoth went on display today at the opening of the 2005 World Exposition in Aichi, Japan. Still partially tufted with hair, the Ice Age plant-eater's head and other parts are stored in a giant refrigerator-turned-laboratory. Scientists at the expo say they hope to use the specimen to uncover why mammoths went extinct. 

Woolly mammoths roamed Siberia until about 10,000 years ago, when they may have fallen victim to warming weather, human hunters, disease, or a combination thereof. Standing about 11 feet (3.4 meters) tall at the shoulder and weighing some seven tons, they not surprisingly loomed large in the minds of their human contemporaries, who immortalized the beasts in carvings and cave paintings.
 
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#3
Baby mammoth discovery unveiled 
By Paul Rincon 
Science reporter, BBC News 

A baby mammoth unearthed in the permafrost of north-west Siberia could be the best preserved specimen of its type, scientists have said. 

The frozen carcass is to be sent to Japan for detailed study. 

The six-month-old female calf was discovered on the Yamal peninsula of Russia and is thought to have died 10,000 years ago. 

The animal's trunk and eyes are still intact and some of its fur remains on the body. 

Mammoths are an extinct member of the elephant family. Adults often possessed long, curved tusks and a coat of long hair. 

The 130cm (4ft 3ins) tall, 50kg Siberian specimen dates to the end of the last Ice Age, when the great beasts were vanishing from the planet. 

It was discovered by a reindeer herder in May this year. Yuri Khudi stumbled across the carcass near the Yuribei River, in Russia's Yamal-Nenets autonomous district. 

Missing tail 

Last week, an international delegation of experts convened in the town of Salekhard, near the discovery site, to carry out a preliminary examination of the animal. 

"The mammoth has no defects except that its tail was bit off," said Alexei Tikhonov, deputy director of the Zoological Institute of the Russian Academy of Sciences and a member of the delegation. 


"In terms of its state of preservation, this is the world's most valuable discovery," he said. 

Larry Agenbroad, director of the Mammoth Site of Hot Springs research centre in South Dakota, US, said: "To find a juvenile mammoth in any condition is extremely rare." Dr Agenbroad added that he knew of only three other examples. 

Some scientists hold out hope that well preserved sperm or other cells containing viable DNA could be used to resurrect the mammoth lineage. 

Despite the inherent difficulties, Dr Agenbroad remains optimistic about the potential for cloning. 

"When we got the Jarkov mammoth [found frozen in Taimyr, Siberia, in 1997], the geneticists told me: 'if you can get us good DNA, we'll have a baby mammoth for you in 22 months'," he told BBC News. 

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The baby mammoth, discovered in north-western Siberia, may have been less than a year old.

Lucrative trade 

That specimen failed to yield DNA of sufficient quality, but some researchers believe it may only be a matter of time until the right find emerges from Siberia. 

Bringing mammoths back from the dead could take the form of injecting sperm into the egg of a relative, such as the Asian elephant, to try to create a hybrid. 

Alternatively, scientists could attempt to clone a pure mammoth by fusing the nucleus of a mammoth cell with an elephant egg cell stripped of its DNA. 

But Dr Agenbroad warned that scientifically valuable Siberian mammoth specimens were being lost to a lucrative trade in ivory, skin, hair and other body parts. 

The city of Yakutsk in Russia's far east forms the hub for this trade. 

Local people are scouring the Siberian permafrost for remains to sell on, and, according to Dr Agenbroad, more carcasses could be falling into the hands of dealers than are finding their way to scientists. 

Japan transfer 

"These products are primarily for collectors and it is usually illicit," he explained. 

"Originally it was for ivory, now it is everything. You can now go on almost any fossil marketing website and find mammoth hair for $50 an inch. It has grown beyond anyone's imagination." 

Dr Agenbroad added: "Russia says that any mammoth remains are the property of the Russian government, but nobody really pays attention to that." 

The Yamal mammoth is expected to be transferred to Jikei University in Tokyo, Japan, later this year. 

A team led by Professor Naoki Suzuki will carry out an extensive study of the carcass, including CT scans of its internal organs. 

Mammoths first appeared in the Pliocene Epoch, 4.8 million years ago. 

What caused their widespread disappearance at the end of the last Ice Age remains unclear; but climate change, overkill by human hunters, or a combination of both could have been to blame. 

One population of mammoths lived on in isolation on Russia's remote Wrangel Island until about 5,000 years ago.

http://news.bbc.co.uk/2/hi/science/nature/6284214.stm
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#4
Paleontologists Study A Remarkably Well-preserved Baby Siberian Mammoth

Science Daily — University of Michigan paleontologist Daniel Fisher just returned from Siberia where he spent a week as part of a six-member international team that examined the frozen, nearly intact remains of a 4-month-old female woolly mammoth.

Samples will be sent to Fisher's Ann Arbor laboratories for analysis, he said. "It's the best and most complete mammoth carcass—baby or adult—ever found," said Fisher, curator of paleontology at the U-M Museum of Paleontology.

Fisher has studied elephant-like mammoths and mastodons since 1979 and has worked on more than 20 excavations of the prehistoric pachyderms. But examining the latest Siberian discovery stands out as a career highlight, he said.

"I've studied these animals for so many years and imagined for so long what they must have looked like," Fisher said. "But now, for the first time, I saw one face-to-face in its entirety, and that was a profound experience."

The baby mammoth was discovered by a reindeer herder, Yuri Khudy, in mid-May in western Siberia, after it eroded out of a riverbank. The frozen carcass was taken to a nearby museum, where Fisher, several colleagues, and U-M graduate student Adam Rountrey examined, measured and photographed it.

The baby stood 3 feet tall and measured 52 inches from the base of its trunk to its tail. In its current, partially freeze-dried state, it weighs 110 pounds, including traces of ice and dirt still clinging to the body.

The animal's trunk and eyes and the rest of its external soft tissues are virtually intact, though most of its hair is gone. Its tail and right ear lobe have been chewed off, probably by arctic foxes or other scavengers that fed on the carcass after it eroded from the riverbank, Fisher said.

No tusks are externally visible, but X-rays revealed the presence of nascent tusks—no larger than a human's little finger—as well as molars.

Fisher hopes to bring one of the tiny tusks and one of the molars to his laboratories for analysis, possibly by the end of this year.

Mammoth tusks grew in layers that can be used to age the animal, much like a tree's annual growth rings can be counted to determine its age. But in the case of mammoth tusks, the layers can pinpoint the age to within weeks.

Fisher and Rountrey will also conduct stable-isotope studies on tusk and molar samples to determine the animal's health, the changing fat content of its mother's milk, and variations in local air temperature during its lifetime.

"One of the things we're closing in on and will be able to evaluate further with this specimen is the season of birth of mammoth calves," Fisher said. "We'll also be able to say something more about how fast they grew and how their teeth developed.

"And this is all part of developing a better ability to age these animals and get a better sense of when they matured and when they reproduced," he said.

Contrary to several news reports, the researchers don't yet know how long ago the baby mammoth lived. A small tissue sample has been collected for radiocarbon dating, but right now all the researchers can say is that it lived some time before about 10,000 years ago, when most mainland mammoths went extinct, Fisher said.

A CT-scan will be conducted in Japan, then a dissection will be performed in St. Petersburg, he said.

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http://www.sciencedaily.com/releases/2007/07/070722113641.htm
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#5
DNA Extracted From Woolly Mammoth Hair

Science Daily — Stephan C. Schuster and Webb Miller of Penn State, working with Thomas Gilbert from Copenhagen and a large international consortium, discovered that hair shafts provide an ideal source of ancient DNA -- a better source than bones and muscle for studying the genome sequences of extinct animals. Their research achievement, described in a paper to be published in the journal Science on Sept. 28, includes the sequencing of entire mitochondrial genomes from 10 individual woolly mammoths.

Schuster and Miller, working at Penn State's Center for Comparative Genomics and Bioinformatics, and Gilbert, from the Center for Ancient Genetics at the University of Copenhagen, led a team of collaborators that includes a large group of researchers and museum curators from the United States, Russia, Belgium, Denmark, France, Italy, Sweden and the United Kingdom.

The research team obtained hair from 10 woolly mammoths collected from a wide swathe of northern Siberia and with dates of death spanning approximately 38,000 years -- from 50,000 years to 12,000 years ago. Before this study, only seven mitochondrial genomes from extinct animals had been published: four from ancient birds, two from mammoths and one from a mastodon. 

"DNA in bones and muscle usually degrades and becomes contaminated with genetic material from other sources such as bacteria, limiting its usefulness in scientific studies," Schuster explained. Because only a tiny proportion of ancient bones and muscle are preserved in such a way that uncontaminated DNA can be recovered, research with such materials has involved laborious efforts, sometimes spanning as long as six years for a single study. In contrast, Miller said, "Once I get the data from the genome sequencer, it takes only five minutes to assemble the entire mitochondrial genome." 


The discovery to be published in Science demonstrates that hair clippings can give researchers enormous power and efficiency for divining the genetic makeup of ancient species.

The methods the team members developed for efficiently generating and analyzing large amounts of ancient mitochondrial-genome sequences now position them to generate such data for other extinct species, as well as to sequence the huge nuclear genome of an extinct species. "The data already generated from this study set the stage for the sequencing of a complete mammoth genome," said Schuster.

"We realized that the keratin in hair could protect the DNA it contains from outside influences and hence from the sorts of degradation that affect DNA in other parts of the body, such as bone," Gilbert said. Hair also can more easily be cleaned of environmental contaminants, such as bacteria. The researchers discovered that, even if the hair is washed in a solution that kills and washes off external DNA, the genetic material within the hair is unaffected.

"When people thought of sequencing DNA from hair, the usual assumption was that the material must come from the hair root, which contains recognizable cells, because the hair shaft appears to be dead," Miller explained; "however, we now know that a hair shaft consists essentially of DNA encased in a kind of biological plastic." Protected in this way, the DNA resists damage and readily can be separated from any bacteria that may contaminate the sample. "We discovered, moreover, that the DNA in hair shafts is remarkably enriched for mitochondrial DNA, the special type of DNA frequently used to measure the genetic diversity of a population," Gilbert added.

Several of the hair samples investigated were up to 50,000 years old. One of the samples came from the first specimen ever recorded: the so-called Adams mammoth, found in 1799 and dug out of the permafrost between1804 and 1806 by the botanist Michael Adams and members of the Tungus tribe. This mammoth died around 36,000 years ago. "Hair samples from this find were stored in a Russian museum for 200 years at room temperature, but still allowed for a complete analysis of its mitochondrial genome using only 0.2 grams of hair," Schuster said. As a result, he uses the term "museumomics" for his dream of deriving molecular-genomic-analysis data from the specimens stored in the collections of Charles Darwin, Alexander von Humboldt and Carl von Linne.

The new route to the genetic material of extinct animals also will enable researchers to study the relatedness of individual animals from different populations at a much higher resolution than previously thought possible. "We plan to use hair and other keratin-containing body parts, such as nail and horn, to untangle the secrets of populations that lived long ago, so these populations can send a message from the past about what it might have taken for them to survive," Schuster said. "This discovery is good news for anyone interested in learning more about how species of large mammals can go extinct."

Note: This story has been adapted from a news release issued by Penn State University.

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http://www.sciencedaily.com/releases/2007/09/070927141921.htm
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#6
Climate Change, Then Humans, Drove Mammoths Extinct 

Kimberly Johnson
for National Geographic News

April 1, 2008

Ancient climate change cornered the woolly mammoth into a shrinking habitat, but humans delivered the final blow by hunting the species into extinction, a new study suggests. 

Climate change and hunting have long been blamed for forcing the mammoth into decline at the end of the Pleistocene era about 10,000 years ago. The last mammoth died out 4,000 years ago, experts estimate. 

But this study marks the first time that the massive, shaggy-haired animal's demise has been explained using combined population and climate change modeling, researchers say. 

Previously seaprating the individual impact of each factor on the mammoths had been difficult. 

For instance, warming temperatures that emerged during and immediately after the late Pleistocene opened up new territories for human migration—ushering them into the woolly mammoth's backyard. 

Robust Maps 

David Nogués-Bravo, of the National Museum of Natural Sciences in Madrid, Spain, led the new research, which was published recently in the journal PLoS Biology. 

"Only in the last [few] years we have [had] robust paleoclimatic simulations" that chart climates for historical periods, Nogués-Bravo said. 

"These paleoclimatic maps allow us to model the area covered by the climatic niche of the woolly mammoth." 

That area is then considered a variable when modeling human-hunting intensity, he explained. 

The researchers charted the climate and distribution timeline of the mammoth from 126,000 to 6,000 years ago by modeling ocean currents, rainfall, and other factors.

It's the same type of modeling used today in predicting global warming, Nogués-Bravo said. 

Last Blow 

Modern humans likely entered the mammoth's core habitat areas around 40,000 years ago, he said. 

Before then, however, the animals' cold, dry tundra habitat in Eurasia and North America collapsed when wetter and warmer weather set in about 42,000 years ago, he said. 

At the same time, forests were expanding north, eventually outcompeting the shrubby plants that mammoths depended on for survival. 

"As an herbivore feeding on coarse tundra vegetation, the woolly mammoth had huge specialized teeth and a lower jaw that swung back and forward to shred plants," he said. 

These changes slashed the mammoth's habitat by almost 90 percent, from about a three-million-square-mile area (about an eight-million-square-kilometer area) about 42,000 years ago to a range of about 308,000 square miles (800,000 square kilometers) about 6,000 years ago. 

Nogués-Bravo stopped short of saying that the mammoths would have survived had humans not happened along. But he did point out the species adapted to an earlier collapse of favorable environmental conditions before humans emerged. 

A Good Lesson 

Larry Agenbroad, site director for the Mammoth Site research facility in Hot Springs, South Dakota, was not involved in the new study. 

He applauded any new attempt to use modeling as a means to root out the causes of the mammoth's extinction. 

But Agenbroad cautioned that no study should be considered the only answer to the extinction riddle. 

"There are too many unknowns, which include the estimate of mammoth population densities through time, the even more elusive estimates of mammoth hunting, and human populations in the northern reaches of Siberia at the time intervals proposed," Agenbroad said. 

Data for the earliest range and population of mammoths are thin for the northern Eurasia region, as is the documented presence of hunters in that region, he added. 

The new study's findings are relevant to understanding the current trend of human-induced climate change, according to Nogués-Bravo. 

"Our study shows that species could become extinct because the combined effect or climate change and direct human impacts," he said. 

"It's a good [lesson] to know why we haven't [got] woolly mammoths in our backyards." 


[Image: 2008-04-01T142028Z_01_NOOTR_RTRIDSP_3_SC...OTH-DC.jpg]
A boy looks at the skeleton of a mammoth in the Ice Age Museum in Moscow September 4, 2007. Climate change drove woolly mammoths to the edge of extinction and then humans finished them off, according to a Spanish study on Tuesday that adds to the debate over the demise of the Ice Age behemoths. 
http://www.newsdaily.com/stories/l27785603-climate-mammoth/ 
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#7
Baby Mammoth CT Scan Reveals Internal Organs

James Owen
for National Geographic News

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April 11, 2008

The frozen body of a baby woolly mammoth discovered last year in Arctic Russia has provided the first detailed internal look at a prehistoric mammal, scientists report. 

The remarkably preserved mammoth calf is named Lyuba after the wife of the hunter who found the 37,000-year-old carcass in the remote Yamalo-Nenetsk region in May 2007. 

The oxygen-deprived environment of its final resting place, likely a watery marsh or bog, prevented decay and kept it intact save for only its tail and shaggy coat. 

Estimated to be just three to four months old when it died, the female has now been returned to Russia from Japan after undergoing computer tomography (CT) scans. 

The Jikei University School of Medicine in Tokyo produced 3-D images of Lyuba's innards, including her heart, liver, and other organs. 

"Now we can see all the internal organs in their natural position inside the body," said study team member Alexei Tikhonov, deputy director of the Russian Academy of Science's Zoological Institute in St. Petersburg. 

"We received very, very good results," he said, adding that Lyuba represents the best-preserved mammoth specimen so far found. 

"This is really the first case where we can see the internal structure of an extinct animal." 

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Watery Death 

The CT scans showed healthy fat tissues and no signs of damage to the skeleton, indicating the 110-pound (50-kilogram) calf was in good shape when it died, Tikhonov said. 

It's thought the Ice Age mammal met its end suddenly, when it drowned in a river or a lake, as its trunk, mouth, and digestive tract contained large amounts of mud. 

"The last movements of the trunk and its last breathing was bringing a lot of silt inside," Tikhonov said. 

The mammoth calf probably had milk for its last meal, because, like elephant offspring, it wouldn't have been able to digest any other food until it was at least a year old. 

The new findings represent only the preliminary results of the CT scans, Tikhonov pointed out. 

A team lead by Naoki Suzuki of the Jikei University School of Medicine is still working to complete 3-D images of Lyuba's entire body as well as individual body parts such the organs and muscles. 

The team hopes those images will be ready by the end of May. 

The next stage of the study will involve analysis of tissue and bone samples based at the Zoological Museum in St. Petersburg. 

These biopsies should provide researchers a wealth of information, Tikhonov said. 

As well as giving insights into the structure of mammoth organs, glands, and muscles, "prehistoric viruses may be preserved within these tissues," he said. 

"We now have probably the first chance to take fragments of DNA from ancient viruses from inside [an animal]," Tikhonov added. 

Scientists are also keen to study the contents of the mammoth's intestines, "because inside there will be the pollen and spores of plants, and so then we can reconstruct the landscapes of this time," Tikhonov said. 

Cloned to Life? 

In addition, labs in the United States, Canada, and Russia are set to work on DNA samples from the fossil in a bid to decode the complete genome of mammoths. 

Techniques developed during this genetic research could one day help in bringing extinct species back from the dead, Tikhonov suggests. 

He sees no point in attempting to revive the woolly mammoth, because the type of environment and climate it needs no longer exist. But other disappeared animals could be accommodated, he said. 

Possible candidates include the Stellers sea cow, a manatee-like sea mammal from the North Pacific that was hunted to extinction in the 1760s, and giant flightless birds such as New Zealand's moa, which also fell victim to humans, he said. 

Lyuba's long-term legacy, Tikhonov said, could help "mankind to pay his debt to the extinct animals of historical times." 
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#8
Woolly Mammoths Existed in Two Distinct Groups

By Andrea Thompson, Senior Writer
posted: 09 June 2008 5:00 pm ET

Two genetically distinct groups of woolly mammoths once roamed northern Siberia, a new study suggests, with one group dying out long before humans showed up.

The finding suggests humans were not the only reason for the beasts' demise, as some have suggested.

Scientists had long thought that woolly mammoths were one large homogeneous group, but an international group of scientists studied the mitochondrial DNA — the DNA in the genes of the mitochondria structures within cells — to paint a new picture of the ancient pachyderms.

They extracted the DNA from frozen hair samples obtained from individual woolly mammoth specimens, found throughout a wide swath of northern Siberia. They compared 18 complete genomes of mitochondrial DNA and found evidence of two genetically distinct clades, or groups of the elephant-like beasts.

"The population was split into two groups, then one of the groups died out 45,000 years ago, long before the first humans began to appear in the region," said study team leader Stephan C. Schuster of Penn State University.

Schuster and his team also found that each group had a low genetic diversity — in other words, individuals within each of the woolly-mammoth groups were very closely related to one another.

"This low genetic divergence is surprising because the woolly mammoth had an extraordinarily wide range: from Western Europe, to the Bering Strait in Siberia, to North America," said study team member Webb Miller, also of Penn State. He added that this low genetic diversity "may have degraded the biological fitness of these animals in a time of changing environments and other challenges."

The research, funded by Penn State, Roche Applied Science and a private sponsor, indicates that the diversity of the two woolly-mammoth groups was as low centuries ago as it is now in Asian elephants living in southern India, which has been suggested as contributing to the problem of maintaining thriving groups of Asian elephants, Schuster said.

In their paper, which appears in the June 9 issue of the journal Proceedings of the National Academy of Sciences, the researchers note that the smaller clade appears to have died out before the larger clade, possibly as a result of genetic drift, or the frequencies with which certain forms of a gene are passed to later generations, purely as a matter of chance. Because the population had such a small range, the lack of diversity could have left them vulnerable to a sudden change in their environment.

"This discovery is particularly interesting because it rules out human hunting as a contributing factor, leaving climate change and disease as the most probably causes of extinction," Schuster said.

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Drawing of a woolly mammoth. 

http://www.livescience.com/animals/080609-woolly-mammoth.html
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#9
Siberian Woolly Mammoths Had North American Blood

Rebecca Carroll
for National Geographic News
September 04, 2008

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Siberia's last woolly mammoths descended from North American, not Eurasian, stock, according to new research. 

Scientists studying DNA from the remains of 160 of the animals found the ancient beasts migrated back and forth between Eurasia and Alaska several times over hundreds of thousands of years. 

Cousins of present-day elephants, woolly mammoths are believed to have descended from African mammoths that traveled north through Eurasia and grew "woolly" long hair to survive the harsh climate of Siberia. 

They went extinct after the last ice age ended 10,000 years ago. 

"The woolly mammoth is not exclusively a Eurasian beast," said lead study author Regis Debruyne of McMaster University in Canada. 

"What happened to the mammoths in North America is part of the story and probably at the core of [woolly mammoth evolution]," he said. 

Hendrik Poinar, who helped oversee the research, said people tend to think of migration between Siberia and North America going in one direction. 

But the search for food drove the North American animals back to Eurasia, said Poinar, an evolutionary geneticist at McMaster University. 

"The grass is greener on either side at some point," he said. 

The study appears today in the current issue of Current Biology. However, some argue the research team is jumping to conclusions based on limited data. 

Land Bridge Crossings 

The scientists pulled DNA from the teeth and compact bones, such as jaws, of 135 mammoths and took a closer look at 108 of the best samples. 

The scientists also considered previously published information on DNA of 52 more woolly mammoths. 

The research included DNA from more than 60 North American woolly mammoths, only a handful of which had been carefully studied before. 

The Siberian and North American permafrost has preserved much genetic material from woolly mammoths, allowing scientists a clearer glimpse into the ancient DNA than is possible in other climates. 

After radiocarbon dating the woolly mammoth samples, the scientists concluded that the ancient creature's first migration from Siberia across the Bering Strait may have taken place as long as 700,000 years ago, lead author Debruyne said. 

The migration was possible via a land bridge north of the Bering Sea that linked Siberia and Alaska during icier times, when sea levels were lower. 

[Image: _44987913_siberia_226.gif]

For several hundred thousand years, the animals evolved separately in North America, developing unique genetic markers distinct from the Siberian populations, the scientists said. 

Then another migration took place back over the strait about 300,000 years ago, they said. 

"Until recently everybody has assumed the migration of the woolly mammoths into North America was a late event," Debruyne said. 

The original Siberian population disappeared after that—about 40,000 years ago—while the North American crew came to dominate the next 30,000 years, the scientists concluded. 

"What we don't know now is why those Siberians went extinct first, and if it was somehow the Americans' fault," Poinar said of the woolly mammoths. 

"Out on a Limb" 

Critics worry the McMaster team jumps to conclusions. 

Stephan Schuster, a Pennsylvania State University biochemist who researches woolly mammoths on the genes, said the authors "go out on a limb" in interpreting their information. 

The theory that woolly mammoths crossed back and forth over the Bering Strait and that the North American descendents outlived the original Siberians is plausible enough, he said. 

But the genetic evidence presented is insufficient, he said, noting that the conclusions are based on only a single marker from mitochondrial DNA—the genetic information passed down from mothers. 

"This would have been a much more significant study if this scientific team could have provided the complete mitochondrial DNA sequences and not just a short stretch," he said. 

Schuster said the final word on mammoth extinctions will require an analysis of the genetic markers found in conventional or "nuclear" DNA, which is more difficult to isolate from ancient bones. 

The authors of today's paper, however, stand by their science. 

"Of course more data is good, but I'm not sure he's asking for the right data," said Debruyne, adding more detailed genetic analyses have not so far challenged their conclusions. 

Debruyne said DNA studies of more individual woolly mammoths is critical to understanding about the whole population, while Schuster emphasized more detailed study of the existing samples. 

Molecular paleobiologist Ian Barnes of the Royal Holloway University of London said the new study both confirms and builds on conclusions he published last year based on the remains of far fewer woolly mammoths.

[Image: 080331-mammoth-02b.jpg]
Woolly mammoths were driven to extinction by climate change and human impacts.

http://news.nationalgeographic.com/news/2008/09/080904-woolly-mammoth.html
http://www.livescience.com/animals/080904-mammoth-origins.html
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#10
Woolly-mammoth Genome Sequenced

ScienceDaily (Nov. 20, 2008) — Scientists at Penn State are leaders of a team that is the first to report the genome-wide sequence of an extinct animal, according to Webb Miller, professor of biology and of computer science and engineering and one of the project's two leaders.

The scientists sequenced the genome of the woolly mammoth, an extinct species of elephant that was adapted to living in the cold environment of the northern hemisphere. They sequenced four billion DNA bases using next-generation DNA-sequencing instruments and a novel approach that reads ancient DNA highly efficiently.

"Previous studies on extinct organisms have generated only small amounts of data," said Stephan C. Schuster, Penn State professor of biochemistry and molecular biology and the project's other leader. "Our dataset is 100 times more extensive than any other published dataset for an extinct species, demonstrating that ancient DNA studies can be brought up to the same level as modern genome projects."

The researchers suspect that the full woolly-mammoth genome is over four-billion DNA bases, which they believe is the size of the modern-day African elephant's genome. Although their dataset consists of more than four-billion DNA bases, only 3.3 billion of them -- a little over the size of the human genome -- currently can be assigned to the mammoth genome. Some of the remaining DNA bases may belong to the mammoth, but others could belong to other organisms, like bacteria and fungi, from the surrounding environment that had contaminated the sample. The team used a draft version of the African elephant's genome, which currently is being generated by scientists at the Broad Institute of MIT and Harvard, to distinguish those sequences that truly belong to the mammoth from possible contaminants.

"Only after the genome of the African elephant has been completed will we be able to make a final assessment about how much of the full woolly-mammoth genome we have sequenced," said Miller. The team plans to finish sequencing the woolly mammoth's genome when the project receives additional funding.

The team sequenced the mammoth's nuclear genome using DNA extracted from the hairs of a mammoth mummy that had been buried in the Siberian permafrost for 20,000 years and a second mammoth mummy that is at least 60,000-years-old. By using hair, the scientists avoided problems that have bedeviled the sequencing of ancient DNA from bones because DNA from bacteria and fungi, which always are associated with ancient DNA, can more easily be removed from hair than from bones. Another advantage of using hair is that less damage occurs to ancient DNA in hair because the hair shaft encases the remnant DNA like a biological plastic, thus protecting it from degradation and exposure to the elements.

The researchers previously had sequenced the woolly mammoth's entire mitochondrial genome, which codes for only 13 of the mammoth's roughly 20,000 genes but is relatively easy to sequence because each of the mammoth's cells has many copies. In their most recent project, the team sequenced the mammoth's nuclear genome, which codes for all the genetic factors that are responsible for the appearance of an organism. The two methods combined have yielded information about the evolution of the three known elephant species: the modern-day African and Indian elephants and the woolly mammoth. The team found that woolly mammoths separated into two groups around two million years ago, and that these groups eventually became genetically distinct sub-populations. They also found that one of these sub-populations went extinct approximately 45,000 years ago, while another lived until after the last ice age, about 10,000 years ago. In addition, the team showed that woolly mammoths are more closely related to modern-day elephants than previously was believed.

"Our data suggest that mammoths and modern-day elephants separated around six-million years ago, about the same time that humans and chimpanzees separated," said Miller. "However, unlike humans and chimpanzees, which relatively rapidly evolved into two distinct species, mammoths and elephants evolved at a more gradual pace," added Schuster, who believes that the data will help to shed light on the rate at which mammalian genomes, in general, can evolve.

The team's new data also provide additional evidence that woolly mammoths had low genetic diversity. "We discovered that individual woolly mammoths were so genetically similar to one another that they may have been especially susceptible to being wiped out by a disease, by a change in the climate, or by humans," said Schuster. While members of the team previously ruled out humans as a cause of extinction for at least one of the Siberian sub-populations -- the group appears to have gone extinct at least 45,000 years ago at a time when there were no humans living in Siberia -- much debate still remains regarding the causes of extinction for the other group and for those populations that lived in other places, such as North America.

Currently, the team is searching the mammoth's genome for clues about its extinction. "For example," said Miller, "most animal genomes contain integrated viral sequences and, though these are not directly associated with disease, evidence of multiple recent integration events could indicate a perturbation of virus-host interaction that might be responsible for disease. Alternatively, it might turn out that long generation times and limited outbreeding result in accumulation of deleterious genetic mutations. We are considering a number of possible causes of extinction."

The new data are allowing the Penn State team to begin looking for genetic causes of some of the mammoth's unique characteristics, such as their adaptation to extremely cold environments. For instance, the team already has identified a number of cases in which all previously sequenced mammals, except mammoths, have the same protein segment. "One has to wonder whether a particular protein that has remained the same in animals for several billion years of combined evolution and then became different in mammoths could result in a mammoth-specific trait," said Miller.

Investigating the unique characteristics of woolly mammoths and why they went extinct are just some of the many tasks that the research team plans to pursue now that they have access to such a large quantity of sequence data. "This really is the first time that we have been able to study an extinct animal in the same detail as the ones living in our own time," said Schuster.

Another significant aspect of the study is that it was completed by a small group of scientists at a relatively low cost and over a short period of time, whereas previous reports of modern mammalian genome sequences -- including human sequences -- have taken millions of dollars and several years of analysis by large groups of scientists to complete. Miller hopes that after he completes a few additional genome projects he can produce computer software that will enable others to perform low-cost mammalian genome analysis, and Schuster already is preparing to decode extinct genomes at an even faster pace.

Schuster hopes that lessons learned from the mammoth genome about why some animals go extinct while others do not will be useful in protecting other species from extinction, such as the Tasmanian devil, whose survival is threatened by a deadly facial cancer. "In addition," added Schuster, "by deciphering this genome we could, in theory, generate data that one day may help other researchers to bring the woolly mammoth back to life by inserting the uniquely mammoth DNA sequences into the genome of the modern-day elephant. This would allow scientists to retrieve the genetic information that was believed to have been lost when the mammoth died out, as well as to bring back an extinct species that modern humans have missed meeting by only a few thousand years."

In addition to being members of the faculty of Penn State's Department of Biochemistry and Molecular Biology, Miller and Schuster are researchers associated with Penn State's Center for Comparative Genomics and Bioinformatics. The study also involved researchers from the Severtsov Institute of Ecology and Evolution and the Zoological Institute in Russia, the University of California, the Broad Institute, the Roche Diagnostics Corporation, and the Sperling Foundation in the United States. This research was funded by Penn State, Roche Applied Sciences, a private sponsor, the National Human Genome Research Institute, and the Pennsylvania Department of Health

http://www.sciencedaily.com/releases/2008/11/081119140712.htm 
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#11
Mammoths survived late in Britain

By Paul Rincon
Science reporter, BBC News

Posted Image
Mammoths were in Britain 6,000 years longer than had been suspected

Woolly mammoths lived in Britain as recently as 14,000 years ago, according to new radiocarbon dating evidence.

Dr Adrian Lister obtained new dates for mammoth bones unearthed in the English county of Shropshire in 1986.

His study in the Geological Journal shows the great beasts remained part of Britain's wildlife for much longer than had previously been supposed.

Mammoths may finally have died out when forests encroached on the grassland habitats they favoured for grazing.

The radiocarbon results from the adult male and four juvenile mammoths from Condover, Shropshire, reveal that the great beasts were in Britain more than 6,000 years longer than had previously been thought.

Researchers had supposed that mammoths disappeared from North-West Europe between 21,000 and 19,000 years ago, during a climatic freeze known as the last glacial maximum (LGM).

Britain's mammoth populations may indeed have vanished with this big chill.

But according to the new study, they were not gone forever. Instead, they returned when conditions eased and clung on in southern England until 14,000 years ago.

"What this usually means is that (mammoths) die out locally and then re-emigrate from refugia somewhere else," Dr Lister told BBC News.

Purification method

The specimens have been radiocarbon dated before. But the Natural History Museum researcher used a relatively new method of radiocarbon dating to get very accurate ages for the Condover fossils.

"The big issue with all radiocarbon dating is contamination from different sources. You have to be sure the sample you extracted from the fossil is absolutely pure," said Dr Lister.

"There have to be methods for purifying the sample that is extracted from the bone. In the last few years, a new method of purification has been developed at Oxford University called ultra-filtration."

"Various bone specimens that were dated before they developed this new purification method have been shown to be out by a significant amount. Not always, but often. What they do is re-run the sample using the new method and obtain a more accurate date. That's what we did here."

Other large mammals that disappeared as the last Ice Age relented include woolly rhino, bison and giant deer.

At the same time as these species were vanishing from the Earth, human populations were expanding.

Similar die-outs of so-called "megafauna" occurred around the world at similar times, prompting some scientists to ask whether climate or human hunting played the dominant role in their extinction.

Human question

No traces of human occupation were found at the Shropshire site. But it is entirely possible that humans could have been in Britain at the same time as these last mammoths.

Dr Lister said that humans might have finished off some of the last remaining pockets of mammoths in Siberia. But he did not think people were the main cause of megafaunal extinctions at the end of the last Ice Age.

During the Ice Age, grasslands were commonplace in Europe because conditions were too cold for trees.

But as the climate warmed up, forests began to spread north, squeezing out the grassland habitats favoured by the majestic beasts.

"It's driven by climate change, but it's not the climate - in the main - that affects these animals. The climate affects the vegetation and the vegetation affects them," said Dr Lister.

"These were grass-eating animals."

Mammoths first appeared in the Pliocene Epoch, about 4.8 million years ago.

One population lived on in isolation on Russia's remote Wrangel Island until about 5,000 years ago, making them the most recent surviving population known to science.

http://news.bbc.co.uk/2/hi/science/nature/8106090.stm
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#12
Mammoths had 'anti-freeze blood', gene study finds 

By Paul Rincon 
Science reporter, BBC News 
Page last updated at 18:58 GMT, Sunday, 2 May 2010 19:58 UK

[Image: _44989073_mammoth_bbc_226.jpg] 
The mutation may have helped mammoths survive in the Ice Age

Mammoths had a form of "anti-freeze" blood to keep their bodies supplied with oxygen at freezing temperatures.

Nature Genetics reports that scientists "resurrected" a woolly mammoth blood protein to come to their finding. 

This protein, known as haemoglobin, is found in red blood cells, where it binds to and carries oxygen. 

The team found that mammoths possessed a genetic adaptation allowing their haemoglobin to release oxygen into the body even at low temperatures. 

The ability of haemoglobin to release oxygen to the body's tissues is generally inhibited by the cold.

The researchers sequenced haemoglobin genes from the DNA of three Siberian mammoths, tens of thousands of years old, which were preserved in the permafrost. 

The mammoth DNA sequences were converted into RNA (a molecule similar to DNA which is central to the production of proteins) and inserted into E. coli bacteria. 

The bacteria faithfully manufactured the mammoth protein. 

"The resulting haemoglobin molecules are no different than 'going back in time' and taking a blood sample from a real mammoth," said co-author Kevin Campbell, from the University of Manitoba in Canada. 

Scientists then tested the "revived" mammoth proteins and found three distinctive changes in the haemoglobin sequence allowed mammoth blood to deliver oxygen to cells even at very low temperatures. 

This is something the haemoglobin in living elephants cannot do. 

"It has been remarkable to bring a complex protein from an extinct species back to life and discover important changes not found in any living species," said co-author Alan Cooper, director of the Australian Centre for Ancient DNA at the University of Adelaide. 

Without their genetic adaptation, mammoths would have lost more energy in winter, forcing them to replace that energy by eating more. 

The ancestors of woolly mammoths and modern-day elephants originated in equatorial Africa. 

But between 1.2 and 2.0 million years ago, members of the mammoth lineage migrated to higher latitudes. 

Writing in Nature Genetics, the scientists say that this genetic specialisation may have been crucial in allowing the ancestors of mammoths to exploit new, colder environments during Pleistocene times.

http://news.bbc.co.uk/2/hi/science/nature/8657464.stm
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#13
Extinction of Woolly Mammoth, Saber-Toothed Cat May Have Been Caused by Human Predators

ScienceDaily (July 1, 2010) — A new analysis of the extinction of woolly mammoths and other large mammals more than 10,000 years ago suggests that they may have fallen victim to the same type of "trophic cascade" of ecosystem disruption that scientists say is being caused today by the global decline of predators such as wolves, cougars, and sharks.

In each case the cascading events were originally begun by human disruption of ecosystems, a new study concludes, but around 15,000 years ago the problem was not the loss of a key predator, but the addition of one -- human hunters with spears.

In a study published in the journal BioScience, researchers propose that this mass extinction was caused by newly-arrived humans tipping the balance of power and competing with major predators such as saber-toothed cats. An equilibrium that had survived for thousands of years was disrupted, possibly explaining the loss of two-thirds of North America's large mammals during this period.

"For decades, scientists have been debating the causes of this mass extinction, and the two theories with the most support are hunting pressures from the arrival of humans, and climate change," said William Ripple, a professor of forest ecosystems and society at Oregon State University, and an expert on the ecosystem alterations that scientists are increasingly finding when predators are added or removed.

"We believe humans indeed may have been a factor, but not as most current theory suggests, simply by hunting animals to extinction," Ripple said. "Rather, we think humans provided competition for other predators that still did the bulk of the killing. But we were the triggering mechanism that disrupted the ecosystem."

In the late Pleistocene, researchers say, major predators dominated North America in an uneasy stability with a wide range of mammals: mammoths, mastodons, ground sloths, camels, horses, and several species of bison. The new study cites previous evidence from carnivore tooth wear and fracture, growth rates of prey, and other factors that suggest that there were no serious shortages of food caused by environmental change 10,000 to 15,000 years ago.

Quite contrary to that, the large herbivores seemed to be growing quickly and just as quickly had their numbers reduced by a range of significant carnivorous predators, not the least of which was lions, dire wolves, and two species of saber-toothed cats. Food was plentiful for herbivores, the system was balanced, but it was dominated by predators.

"When human hunters arrived on the scene, they provided new competition with these carnivores for the same prey," said Blaire Van Valkenburgh, an expert at UCLA on the paleobiology of carnivores, and a co-author with Ripple on this study.

"The humans were also omnivores, and could live on plant foods if necessary," Van Valkenburgh said. "We think this may have triggered a sequential collapse not only in the large herbivores but ultimately their predators as well. Importantly, humans had some other defenses against predation, such as fire, weapons and living in groups, so they were able to survive."

But the driving force in eliminating the large mammals, according to the new theory, was not humans -- they just got the process started. After that, predators increasingly desperate for food may have driven their prey to extinction over long periods of time -- and then eventually died out themselves.

In recent studies in Yellowstone National Park and elsewhere, scientists from OSU and other institutions have explored these "trophic cascades," often caused by the loss or introduction of a single major predator in an ecosystem. With the elimination of wolves from Yellowstone, for instance, the numbers of elk exploded. This caused widespread overgrazing; damage to stream ecosystems; the slow demise of aspen forests; and ultimate effects on everything from trees to beaver, fish, birds, and other life forms. When wolves were re-introduced to Yellowstone, studies are showing that those processes have begun to reverse themselves.

"We think the evidence shows that major ecosystem disruptions, resulting in these domino effects, can be caused either by subtracting or adding a major predator," Ripple said. "In the case of the woolly mammoths and saber-toothed tiger, the problems may have begun by adding a predator, in this case humans."

The new analysis draws on many other existing studies in making its case.

For instance, other research describes this process with a model in modern times in Alaska. There, the allowance of relatively limited human hunting on moose caused wolves to switch some of their predation to sheep, ultimately resulting in a precipitous decline in populations not only of moose but also wolves and sheep.

The loss of species in North America during the late Pleistocene was remarkable -- about 80 percent of 51 large herbivore species went extinct, along with more than 60 percent of important large carnivores. Previous research has documented the growth rates of North American mammoths by studying their tusks, revealing no evidence of reduced growth caused by inadequate food -- thus offering no support for climate-induced habitat decline.

It seems that diverse and abundant carnivores kept herbivore numbers below levels where food becomes limiting. By contrast, the large population of predators such as dire wolves and saber tooth cats caused them to compete intensely for food, as evidenced by heavy tooth wear.

"Heavily worn and fractured teeth are a result of bone consumption, something most carnivores avoid unless prey is difficult to acquire," says Van Valkenburgh.

Trophic cascades initiated by humans are broadly demonstrated, the researchers report. In North America, it may have started with the arrival of the first humans, but continues today with the extirpation of wolves, cougars and other predators around the world. The hunting of whales in the last century may have led to predatory killer whales turning their attention to other prey such as seals and sea otters -- and the declines in sea otter populations has led to an explosion of sea urchins and collapse of kelp forest ecosystems.

"In the terrestrial realm, it is important that we have a better understanding of how Pleistocene ecosystems were structured as we proceed in maintaining and restoring today's ecosystems," the researchers wrote in their conclusion. "In the aquatic realm, the Earth's oceans are the last frontier for megafaunal species declines and extinctions."

"The tragic cascade of species declines due to human harvesting of marine megafauna happening now may be a repeat of the cascade that occurred with the onset of human harvesting of terrestrial megafauna more than 10,000 years ago. This is a sobering thought, but it is not too late to alter our course this time around in the interest of sustaining Earth's ecosystems."

[Image: 100701072732-large.jpg]
Both woolly mammoths and saber toothed tigers may have fought each other and ultimately driven themselves to extinction thousands of years ago after humans arrived on the scene, upsetting a delicate balance that had previously existed.

Journal Reference:

William J. Ripple and Blaire Van Valkenburgh. Linking Top-down Forces to the Pleistocene Megafaunal Extinctions. Bioscience, July/August 2010 

http://www.sciencedaily.com/releases/2010/07/100701072732.htm
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#14
Woolly mammoth extinction 'not linked to humans'

By Pallab Ghosh
Science correspondent, BBC News 
17 August 2010 Last updated at 23:22 GMT

Woolly mammoths died out because of dwindling grasslands - rather than being hunted to extinction by humans, according to a Durham University study. 

After the coldest phase of the last ice age 21,000 years ago, the research revealed, there was a dramatic decline in pasture on which the mammoths fed. 

The woolly mammoth was once commonplace across many parts of Europe. 

It retreated to northern Siberia about 14,000 years ago, where it finally died out approximately 4,000 years ago. 

The reasons for its extinction are unclear and have been a matter of heated scientific debate. 

Some scientists have argued that it was principally the result of climate change while others say that it was driven by pressures of a growing human population, or even a cataclysmic meteor strike. 

Now, according to Professor Brian Huntley of Durham University, that debate has been settled.

"What our results have suggested is that the changing climate - through the effect it had on vegetation - was the key thing that caused the reduction in the population and ultimate extinction of mammoths and many other large herbivores," he said. 

Professor Huntley and his colleagues created a computer simulation of vegetation in Europe, Asia and North America over the last 42,000 years. 

They did this by combining estimates of what the climate was like during this period with models of how various plants grow under different conditions. 

They found that the cold and dry conditions during the ice age, with reduced concentrations of carbon dioxide, didn't favour the growth of trees. 

So instead of forests there were vast areas of pasture, which was ideal for large herbivores, such as woolly mammoths. But as a result of a warmer, wetter climate and rising concentrations of carbon dioxide at the end of the ice age, trees emerged at the expense of the grasslands.

"During the height of the ice age, mammoths and other large herbivores would have had more food to eat," said Professor Huntley.

"But as we shifted into the post-glacial stage, trees gradually displaced those herbaceous ecosystems and that much reduced their grazing area."

[Image: _48771334_mammoth-spl.jpg]
The woolly mammoth finally died out approximately 4,000 years ago 

http://www.bbc.co.uk/news/science-environment-11000635 
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#15
Being Good Moms Couldn't Save the Woolly Mammoth

ScienceDaily (Dec. 21, 2010) — New research from The University of Western Ontario leads investigators to believe that woolly mammoths living north of the Arctic Circle during the Pleistocene Epoch (approx. 150,000 to 40,000 years ago) began weaning infants up to three years later than modern day African elephants due to prolonged hours of darkness.

This adapted nursing pattern could have contributed to the prehistoric elephant's eventual extinction. The findings were published recently in the journal, Palaeogeography, Palaeoclimatology, Palaeoecology.

By studying the chemical composition of adult and infant mammoth teeth, Jessica Metcalfe, an Earth Sciences PhD student working with professor Fred Longstaffe, was able to determine woolly mammoths that once inhabited Old Crow, Yukon didn't begin eating plants and other solid foods before the age of two (and perhaps as late as three) and considers predatory mammals like saber-toothed cats and a lack of sufficient vegetation to be the secondary reasons for delayed weaning.

"In modern Africa, lions can hunt baby elephants but not adults. They can't kill adults. But they can kill babies and by and large, they tend to be successful when they hunt at night because they have adapted night vision," explains Metcalfe, who examined fossil specimens alongside Grant Zazula of the Yukon Paleontology Program. "In Old Crow, where you have long, long hours of darkness, the infants are going to be more vulnerable, so the mothers nursed longer to keep them close."

Metcalfe says delayed weaning by Old Crow mammoths may have further significance for understanding mammoth life histories and extinction.

"Today, a leading cause of infant elephant deaths in Myanmar is insufficient maternal milk production," offers Metcalfe. "Woolly mammoths may have been more vulnerable to the effects of climate change and human hunting than modern elephants not only because of their harsher environment, but also because of the metabolic demands of lactation and prolonged nursing, especially during the longer winter months."

Metcalfe concludes that knowing more about the past, can only help researchers understand more about the present and the future.

"Mammoths lived all over the world for thousands of years, even millions of years, and then became extinct about 10,000 years ago, which was around the time the climate started warming the last time," says Metcalfe. "Understanding their ecology, their adaptations and their behaviour not only gives us insight into why they became extinct but also, potentially, gives us a better understanding of modern day mammals and how they might respond to the current warming of the planet."

[Image: 101221114807-large.jpg]
By studying the chemical composition of adult and infant mammoth teeth, researchers were able to determine that woolly mammoths that once inhabited Old Crow, Yukon didn't begin eating plants and other solid foods before the age of two (and perhaps as late as three).

--------------------------------------------------------------------------------

Journal Reference:

Jessica Z. Metcalfe, Fred J. Longstaffe, Grant D. Zazula. Nursing, weaning, and tooth development in woolly mammoths from Old Crow, Yukon, Canada: Implications for Pleistocene extinctions. Palaeogeography, Palaeoclimatology, Palaeoecology, 2010; 298 (3-4): 257 DOI: 10.1016/j.palaeo.2010.09.032 

http://www.sciencedaily.com/releases/2010/12/101221114807.htm
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