วันพุธที่ 4 เมษายน พ.ศ. 2555

Woolly mammoth may have been killed by humans


The mammoth which was found in a frozen ice cliff in Siberia is "exquisitely preserved"

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The discovery of a well-preserved juvenile woolly mammoth suggests that ancient humans "stole" mammoths from hunting lions, scientists say.
Bernard Buigues of the Mammuthus organisation acquired the frozen mammoth from tusk hunters in Siberia.
Scientists completed an initial assessment of the animal, known as Yuka, in March this year.
Wounds indicate that both lions and humans may have been involved in the ancient animal's death.

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These are remarkably rare finds and have huge significance”
Kevin CampbellUniversity of Manitoba
"Already there is dramatic evidence of a life-and-death struggle between Yuka and some top predator, probably a lion," says leading mammoth expert, Daniel Fisher, professor of earth and environmental sciences at the University of Michigan.
"Even more interesting, there are hints that humans may have taken over the kill at an early stage."
If further investigation by Mr Buigues, Professor Fisher and fellow scientists at the Sakha Academy of Sciences in Yakutsk confirms this analysis, it will be the first carcass to show signs of interaction with ancient humans found in this part of the world.
The Yuka mammoth was filmed as part of the BBC/Discovery Co-Production programme Woolly Mammoth: Secrets from the Ice.

Find out more about mammoths

Woolly mammoth image
  • The woolly mammoth (Mammuthus primigenius)evolved from hairless elephants in Africa.
  • Thought to have become extinct around 3700 years ago.
  • Lived in the northern hemisphere, and were forced northwards to Siberia and northern Europe when the Pleistocene ice age began to draw to an end around 15,000 years ago.
  • Woolly mammoths had a 10 centimetre thick layer of fat under their skin to provide insulation.
  • Their small ears, short tails and thick coat of hair helped prevent heat loss.
  • Their tusks were around 5 metres long and were used for digging in deep snow and fighting.
By analysing the teeth and tusks, the team estimate Yuka was about two and a half years old when it died.
Teeth, tusks and bone are the most common ways extinct animals such as mammoths are studied, as these parts of the body take a relatively long time to decompose.
Soft tissues such as muscle, skin and internal organs decompose far quicker, and are very rarely found on old carcasses. This means that vital information is usually lost.
But much of Yuka's soft tissue as well as its woolly coat has remained intact, well-preserved in its icy tomb for possibly more than 10,000 years.
Kevin Campbell, associate professor of environmental and evolutionary physiology at the University of Manitoba said: "These are remarkably rare finds and have huge significance."
One of the most striking things about Yuka is its strawberry-blonde hair, he said.
The possibility of mammoths having lighter coat colours was proposed in 2006 after scientists studied the genes extracted solely from a mammoth bone.
Yuka provides direct evidence that mammoths did have lighter-coloured coats.
Associate Professor Campbell said the find "will be a boon to researchers as it will help them link observed phenotypes (morphological features that we can see) with genotype (DNA sequences)".
The Yuka mammothYuka was found with many bones missing and cuts that may have been made by ancient hunters
These links will allow scientists to determine how widespread physical traits such as eye and hair colour were "within and among mammoth populations" simply from studying genes from bone or hair samples in the future.
Professor Fisher agreed the find was extraordinary: "It's like a diary or journal someone has just handed you - you just haven't had a chance to read it."
Lion attacks
Healed scratches found on the skin indicate a lion attack that Yuka survived earlier in its relatively short life.
However, similar deep cuts that had not healed suggest a subsequent lion attack that either caused or happened very near the time of Yuka's death.
Also, when moving one of Yuka's legs, Professor Fisher recognised evidence of a freshly broken leg when it died and suggested this may have occurred as Yuka tried to flee from attackers.
The lions in question (Panthera leo spelea) are an extinct subspecies of the African lion, known commonly as Eurasian cave lions but were present at the same time as the mammoths.
Yuka mammoth footYuka's foot pads and hair remain intact after more than 10,000 years
"Did we know lions hunted mammoths? Well, we guessed they did. But could we ever have expected to see such graphic evidence? No - but here it is," explained Professor Fisher.
In modern-day Africa, young elephants are attacked by lions, providing a means of comparing their injuries with Yuka's.
Lions will usually enter the carcass through the belly, clamp their teeth over the mouth in order to suffocate their prey, and chew at an elephant's muscular trunk.
However, Yuka's trunk is not damaged and there is only slight damage to the hide around the face.
Instead of entering Yuka's body via the belly, there is what Professor Fisher describes as "a bizarre set of damage on the hide".
This includes a "long, straight cut that stretches from the head to the centre of the back" as well as "very unusual patterned openings" into the skin and "scalloped margins" on the upper right-hand flank.
The skull, spine, ribs and pelvis were all removed from Yuka's body, but the skull and pelvis were found nearby. However, most of the spine and three-quarters of the ribs are missing.
Human interference
Each scalloped mark on the skin is made up by 15-30 small, serrations that "could be the saw-like motion of a human tool" and there are "some quite striking cut marks" on the leg bones, according to Professor Fisher.
Prof Fisher said they had questioned whether the cuts could have been made more recently.
"We asked the people who found this mammoth multiple times if they had done this. They replied 'No! We did not get our knives out' which suggests we're looking at some sort of interaction of humans, mammoths and lions.
"Were humans using the lions to catch mammoths and then moving the lions off their kill... was that what happened? I don't know but I wouldn't have thought about it without seeing it [the evidence]."
Supporting this argument, the Dorobo tribe still practise the art ofstealing kills from lions in Kenya.
Lyuba the baby mammoth on display at the Shemanovskiy Museum and Exhibition Center, Salekhard, RussiaProf Alice Roberts with Lyuba, one of the best-preserved mammoths that had been previously found
"Each new specimen has something to teach us, but Yuka provides some of the most dramatic evidence yet available for events surrounding the death of a woolly mammoth on the arctic steppes of Siberia."
Professor Alice Roberts was part of the film crew that followed Yuka being recovered from the tusk hunters.
She said: "There are some odd things. What we need to do is find out if this was human interference near the time of death or was it something that happened much later?
"If it happened near the time of death then it means Yuka is a very important specimen as there are not many [mammoths] that show human interactions."
She said seeing Yuka in the flesh was almost "poignant".
"You feel it has only just died as it is so beautifully preserved."
Woolly Mammoth: Secrets from the Ice is on BBC Two at 21:00 BST on Wednesday 4 April and will be shown on the Discovery Channel in the US at a future date.

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