Documentary, Extinct Complete Series Episode Episode 5 -The Irish Elk
#ExtinctCompleteSeries #IrishElk #Documentary #Extinct
#ExtinctCompleteSeries #IrishElk #Documentary #Extinct
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AnimalsTranscript
00:00You
00:30You
00:34After a hundred thousand years the ice age is coming to an end
00:46This treeless grassland is the domain of a spectacular creature a
00:53Creature which ranged across Europe from the French Pyrenees to the Russian steppes
00:58But in Ireland it found a homeland which human hunters had not reached
01:08It has antlers so vast and elaborate they stretch 12 feet from tip to tip
01:16They are the crowning glory of the magnificent Irish Elk
01:20But this giant deer has presented science with an intractable mystery
01:30Why having flourished for millennia did it undergo catastrophic extinction?
01:36Were its massive antlers to blame?
01:40The Irish Elk has a sort of iconic status among Irish biologists
01:52And it seems to me that it's a great animal to study the great themes of evolution for example
01:58How did it get to be as it is and in this particular case? How did it die?
02:03A disused army barracks in the heart of Dublin is the final resting place for prehistoric remains
02:13Which have been excavated over the last 200 years?
02:18Paleontologist Tom Hayden has come to take a closer look
02:21Stored here are the peat blackened remains of hundreds of Irish Elk which died between 10 and 15,000 years ago
02:43The stag skulls are extraordinary boasting the largest antlers of any deer that has ever existed
02:51This is what all the fuss has been about
02:55A male Irish Elk
02:57This animal had antlers
02:59Which weighed about 40 kilos
03:01And measured in large specimens 12 feet from end to end
03:06I could stretch myself along the antlers from one tip to the other twice
03:16No modern animal comes close
03:18To find out how it coped with such a massive burden
03:22Tom needs to examine a fully assembled skeleton
03:27It's clear that the Irish Elk had specialised
03:29Evolving a physique capable of supporting its vast antlers
03:34There's a massive rib cage
03:36And this in life of course supported a very large heart
03:39And very large lungs
03:41And this is what we would expect
03:44For an animal that had a lifestyle like the giant deer
03:47An open plains runner
03:49Probably high stamina
03:51And this essentially is typical of an aerobic machine
04:01And now we come to the more spectacular end of the animal
04:04Where we find the antlers
04:05And quite apart from being extremely heavy
04:07They're also extremely awkward
04:08Because a lot of the weight is a long way away
04:11From the centre of the animal's body
04:13So it's like holding very large buckets
04:15At arm's length and trying to manoeuvre them
04:17It puts a lot of torsion and stresses on its neck
04:21And for that reason
04:22The vertebrae and its neck are very large
04:25Quite strong to try and cope with the stresses and strains
04:28Of moving this great weight about
04:30Behind the neck
04:31Behind the neck
04:32The spines and the vertebrae
04:33Are very, very tall
04:35And in life
04:36These would have acted as anchor points
04:38For a system of cables
04:40Ligaments
04:41Which ran from here to the neck
04:43And helped the animal to raise it
04:44And move it around
04:45Antlers place a further demand on a deer
04:49It must shed and regrow them each year
04:52So how did the Irish elk fuel the growth
04:55Of their unusually massive antlers?
04:58What did they eat?
05:00Tom Hayden is looking for clues
05:02Amongst the teeth of a mature stag skull
05:06These white enamel ridges
05:09Have very, very fine scratches
05:12And there is only one substance we know about
05:14Which will produce these scratches
05:16And that is grass
05:17Grass are silica particles in between the cells
05:20Which act like sandpaper
05:22As far as the teeth are concerned
05:23And if you look at the enamel on a giant deer
05:26And compare it to the enamel on a cow
05:28They are identical
05:30So this is strong evidence to suggest
05:32That they ate mainly grass
05:33Pollen samples reveal late Ice Age Ireland
05:40Was an open, treeless landscape
05:42Its abundant grasslands rich in nutrients
05:47Like calcium
05:48A perfect environment
05:50A perfect environment
05:51For the bulk grass feeding
05:52The Irish elk's antlers require
05:55Back in the 19th century
06:14Charles Darwin's detractors seized upon these antlers
06:17To attack his heretical theory of natural selection
06:20If the survival of the fittest really designed animals to survive
06:25What possible advantage could such an extravagant burden provide?
06:30They used the Irish elk to cast doubt on Darwin's theory
06:37To this day researchers continue to question how natural selection could have produced such large antlers
06:43Why invest so much in them?
06:48What was their purpose?
06:50Palaeontologist Adrian Lister believes that today's fallow deer can provide vital clues
07:00The bucks have got their antlers about half grown
07:04But you can already see
07:06The way the antlers grow horizontally out from the head
07:10Just like in the Irish elk
07:12There they go
07:15He's conducted anatomical studies that have thrown up a surprising result
07:20They reveal the tiny fallow deer is a distant cousin of the Irish elk
07:25The Irish elk has got particularly strongly developed neck vertebrae
07:31Which were to hold up the very heavy head with the weight of the antlers
07:35And the fallow deer, if we look at the neck vertebrae
07:38They've got the same structures
07:39Although of course they haven't got such heavy antlers now
07:42They've got the similar structure and that proves the relationship
07:46But can the fallow deer provide an insight into how Irish elk stags use their vast antlers?
07:53Sex may provide the answer
07:56Fallow deer have a mating system called lecking
08:00In which females move among the stags
08:03And choose their mate on the merits of his antlers
08:06In the fallow deer, the male will do a kind of display
08:10Moving his head from side to side
08:12And he's got these flattened palmations of the antlers
08:15Which will be shown off in that way
08:17To the female who's following on behind him
08:19With the Irish elk
08:21With the flattened parts going straight out horizontally like that
08:26And also being so large
08:27Maybe the animal didn't have to do that kind of behaviour
08:30Just standing there would have been impressive enough
08:33If the female was interested enough then mating would ensue
08:36The huge palms of the stag's antlers flash like mirrors across the open landscape
08:45Attracting a female willing to mate
08:49For females the choice is simple because for them
09:07Bigger antlers indicate a fitter male
09:10So the genes of large antlered males were continually passed on
09:16Sexual selection was driving the development of these enormous antlers
09:23For over a hundred years scientists denied the antlers could have any other role
09:32Now biomechanics expert Andrew Kitchener can prove they were also deadly weapons
09:39What my research has shown is that the antlers are not just designed for display
09:45There's too much material in here to just be used as an elaborate advertisement hoarding
09:50They're designed for fighting
09:52Both at the structural level as to how they actually fit together
09:55And also at the mechanical level
09:57They are actually strong enough to take the massive forces that would have been produced in fighting
10:02The highest density of bone occurs where the antlers impact and lock together
10:08From his observations of other deer
10:11Andrew has demonstrated how these points, known as tines, could be used for defence and attack
10:17In the mating season stags challenge each other for the right to mate
10:25At first the stags size each other up
10:35But what would happen if battle commenced?
10:38The next stage would be to twist the head right round
10:42Drop it down to the ground
10:44So that the nose points back between the front legs
10:48And now you can see the different parts of the antler coming into function for fighting
10:53Here we have the brow tines and also the secondary tines which act in a defensive way
11:00They protect the head and the eye from accidental injury if the antlers were to slip against each other
11:05And on the outside on the palms here we have these very long offensive tines
11:10Which point in towards the neck and the flank of the opponent
11:14And during fighting the aim is to try and wrestle your opponent off balance
11:19And hopefully knock him over so that you can use these tines to actually stab your opponent in the flank or the neck
11:26Andrew's research revealed stag fights would have been brutal and violent
11:33This stag has proved he is the alpha male and secured his access to the females
11:53In attracting a mate and fighting off rivals the antlers were the key to passing on an individual stag's genes
12:06But could this design have also brought the Irish elk's downfall?
12:12Carbon dating of the Dublin bones reveals that ten and a half thousand years ago it vanished from Ireland
12:20Why, just as the ice age was ending and conditions improved, did the Irish elk face extinction?
12:43Eleven thousand years ago the ice age was coming to an end
12:47Rising global temperatures pushed back the icy tundra that had stretched across northern Europe
12:56In Ireland, the Irish elk, a giant deer with vast antlers had evolved to graze the rich ice age grassland
13:08Irish elk were once plentiful
13:10Over a hundred individuals have been excavated from one peat bog alone
13:17But around ten thousand six hundred years ago
13:20The fossil record reveals the Irish elk disappeared suddenly and completely
13:25What caused this catastrophic decline?
13:31Geologist Pete Coxon is trying to find out
13:38He's investigating what happened to the local climate in Ireland at the end of the ice age
13:44Almost three meters below the surface
13:49He finds soil which dates back eleven thousand years to the late ice age
13:52When the Irish elk was still thriving
13:59These late ice age soils are rich in pollen
14:02They show it was cooler than today, but there was abandoned grassland
14:07You can see organic sediment being laid down with seeds and bits of leaf and so on
14:12And in this call we can even pick out fragments of plant, fossils of plant
14:18There's some cuticle there of a grass or a sage
14:23When Pete takes a sample from slightly higher up and 400 years later, the very end of the ice age
14:29There's a dramatic change
14:32The grass pollen has been replaced by eroded rock and sand
14:36For Pete it's evidence of an unexpected climate change that wiped out vegetation
14:43We see in this section this very sudden cold snap
14:46You see sand and inorganic material in here
14:49You get a lot of erosion, a lot of movement of soil down the slope
14:53And that's why we see these inorganic sediments
14:55And this cold snap lasted a thousand years
14:58Temperatures seven degrees colder than the present day
15:02Suddenly the biological productivity plummets
15:05Ironically, as the rest of the world warmed up at the end of the ice age
15:11Ireland was hit locally by severe cold
15:14It seems to defy logic
15:17But the sea provides an answer
15:20As rising temperatures melted the great polar ice caps
15:26Cold water flooded into the Atlantic Ocean
15:29Cooling it by an estimated 8 degrees Celsius
15:33Warm gulf stream currents flowing up from the tropics were blocked
15:39Ireland lost its central heating
15:45And was plunged into freezing conditions
15:48In a severe cold period stags with smaller antlers less of a burden
16:00Would have had a better chance of surviving
16:03Natural selection would predict they would now be the fittest
16:07But is there any evidence that the Irish elk evolved to become smaller?
16:13Tom Hayden has measured hundreds of antlers from this crucial period
16:18But he can't find any indication that they were shrinking
16:24Ironically, sexual instinct may have outweighed survival instinct
16:30The Irish elk was caught in a dilemma in a sense
16:35It was being forced in one direction to maintain large size and large antlers
16:39At a very expensive cost by sexual selection
16:42And on the other hand, natural selection would have been dictating a downsizing
16:46Smaller animal, smaller antlers, a less expensive lifestyle
16:51Unfortunately it couldn't make that transition
16:54In the grip of sudden climate change
17:00It appears the Irish elk could not evolve quickly enough
17:03In the grip of sudden climate change, it appears the Irish elk could not evolve quickly enough
17:07The Irish elk took no longer than extinction
17:26Ten and a half thousand years ago
17:28The Irish elk had succumbed to extinction
17:32For scientists that's long been the end of the story but bones stored here are
17:44adding a new twist to the case of the Irish elk. They're not from Ireland,
17:51they're from the Isle of Man which was then connected to Britain by a land
17:55bridge. In 2000 Adrian Lister started to carbon date Irish elk remains from
18:06Northern Britain. The result from the Manx skeleton was a bombshell. We've got the
18:16radiocarbon dates back from the lab and amazingly they show that this Irish elk
18:21skull is the latest one that we have from anywhere in the world. This specimen is
18:25only 9200 years old and so this specimen shows that the species did actually
18:31survive for nearly 1500 years longer than we'd previously imagined. The question is
18:39why? Ireland's cold spell had been severe but local. To the east of Ireland the Isle
18:48of Man and southern Scotland were more sheltered and Irish elk here must have
18:54been able to cling on for another 1500 years. Yet these late dates mean that the
19:01remaining Irish elk may have encountered a new threat. At Edinburgh University
19:09archaeologists are sifting through the debris from a human encampment. Clear
19:16evidence that late Stone Age hunters had reached southern Scotland at the same time
19:21as the remaining Irish elk were escaping the cold. Did they hunt them down?
19:28they're best spent on destruction. Don?
19:32they Tell the animals that Conrad Bikannai
19:33surprised us to not hunt them down.
19:37The
19:52Intrigued by this possibility, Adrian Lister goes to examine the Edinburgh evidence to
20:06search for signs that manhunted the remaining Irish elk.
20:10There's a deer tooth, that's a red deer upper molar, that's a deer humerus, forearm bone,
20:21that's red deer size, that's a little bit of the bottom end of a so-called cannon bone,
20:28which is the lower leg bone, again that's red deer.
20:31There's a clear impression here that red deer is the dominant prey animal.
20:36There are plenty of deer bones, but no sign of Irish elk at this site.
20:41No hard evidence to point the finger at man.
20:48What else could explain the animal's final extinction?
20:53Yet again, were its giant antlers implicated?
21:00Ten thousand years ago, the landscape across Britain and Ireland was transformed once more.
21:09It's so dramatic, it's like a light switch clicking on.
21:12And instantly, this landscape is warm, soils begin to form, and any plant that's close
21:18by will suddenly be able to colonise that landscape.
21:21So by this point, nine and a half thousand years ago, find a piece of pine wood, there
21:26you can see the nice bright red colour in the bark.
21:28And right at the very top of the core here is the shell of part of a hazelnut.
21:35Grasslands gave way to forests after the Ice Age, at first, birch, pine and hazel.
21:43But by 9,200 years ago, even oak was colonising Northern Britain.
21:50Ironically, Adrian Lister believes the changing countryside may have brought further problems
21:55for the Irish elk.
21:58The kind of habitat the Irish elk liked was lots of open grassy areas where it could graze.
22:03But it wouldn't have liked the dense forests that started to grow up as the climate warmed
22:07in the present interglacial.
22:10Dense forests didn't give it the variety of food, especially grass that it liked.
22:14Also of course, with those very huge antlers, they would have been an encumbrance in the
22:19forest and also would have put the Irish elk under pressure as its preferred habitat shrunk
22:24and shrunk.
22:26The warming climate would have sealed the animal's fate.
22:30As the ice caps melted, sea levels were rising some 30 feet every thousand years.
22:40The Irish Sea was created and new islands like the Isle of Man appeared.
22:45The remaining Irish elk were split into small vulnerable groups, literally marooned.
22:52This may have had disastrous consequences for the gene pool.
22:55If they're in a situation where they can't easily exchange genes between the populations, then
23:01the relic populations may become inbred and that's not healthy either, especially if they're
23:07in a situation where they would need to adapt quite quickly to changing conditions.
23:11They may not have the genetic resources to do that.
23:149,000 years ago the remaining pockets of Irish elk were on the brink of extinction.
23:25It had prospered for tens of thousands of years, but finally climate change isolated the Irish
23:41elk in small populations, struggling in an increasingly forested landscape.
23:479,000 years ago the Irish elk had crafted a highly specialised animal, dependent on open
23:56grassland to nourish its extraordinary antlers.
24:00Clearly the general design and lifestyle of the Irish elk was tremendously successful while
24:06the going was good.
24:07And they in a sense specialised for this high life.
24:11And then suddenly when the climate changes, they're almost locked into this expensive lifestyle
24:16and they can't pay the bills anymore.
24:18The case of the Irish elk reveals that faced with a changing world, too highly evolved a design
24:27can actually prove an animal's undoing.
24:30Specialised animals are usually the ones that go to the wall first.
24:35The generalists like the meek inherit the earth.
24:48To be continued...
25:01To be continued...
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