0:00:06 > 0:00:10Two and a half million years ago,
0:00:10 > 0:00:15life on Planet Earth faced the dawn of a new era.
0:00:22 > 0:00:24The Ice Age.
0:00:27 > 0:00:30Now we can go back in time.
0:00:32 > 0:00:34Because out of the permafrost...
0:00:36 > 0:00:38..from deep inside caves...
0:00:40 > 0:00:43..and from hostile deserts...
0:00:44 > 0:00:49..the astonishing remains of giant animals are emerging.
0:00:49 > 0:00:54How amazing to be one of the first people to see this ancient creature.
0:00:57 > 0:01:02The Ice Age was the last time such creatures would walk the Earth.
0:01:05 > 0:01:10A lost Eden with mammoths taller than any elephant,
0:01:10 > 0:01:14cats with seven-inch teeth,
0:01:14 > 0:01:19and some of the strangest beasts that have ever existed.
0:01:19 > 0:01:24I'm fascinated by what the remains of ancient animals can tell us
0:01:24 > 0:01:29about them, and the world that they lived in.
0:01:29 > 0:01:34Using new scientific advances, we can reveal how they lived,
0:01:34 > 0:01:36and why they died out.
0:01:44 > 0:01:48Come with me, back to the Ice Age.
0:01:51 > 0:01:53A world ruled by giants.
0:02:15 > 0:02:18For tens of thousands of years,
0:02:18 > 0:02:22ice had covered half of North America and much of Europe.
0:02:26 > 0:02:31Huge swathes of the Northern Hemisphere had been locked in deep freeze.
0:02:36 > 0:02:41Then around 18,000 years ago, a great thaw began.
0:02:44 > 0:02:48At last, the Ice Age was releasing its grip.
0:02:51 > 0:02:54From Siberia to Scotland, from Alaska to the Hudson Bay,
0:02:54 > 0:02:56the ice sheets went into retreat.
0:02:56 > 0:03:01Water, warmth and life returned to the landscape.
0:03:07 > 0:03:12Even after thousands of years of brutal cold, the world
0:03:12 > 0:03:16was still home to millions of spectacular giants.
0:03:18 > 0:03:24Mighty Columbian mammoths migrated across the coastal plains of California.
0:03:27 > 0:03:32Sabre-toothed cats were on the prowl from Los Angeles to Miami.
0:03:49 > 0:03:53Woolly mammoths and woolly rhinos roamed the steppes of Siberia.
0:04:04 > 0:04:08Giant armoured glyptodonts basked in the Arizona swamps.
0:04:16 > 0:04:20The future for the megafauna seemed bright.
0:04:24 > 0:04:29So why do none of these spectacular giants roam our world today?
0:04:44 > 0:04:48In the Northern Hemisphere, the continent which saw most
0:04:48 > 0:04:51extinctions was this one - North America.
0:04:51 > 0:04:56For hundreds of thousands of years, huge animals had roamed across this land.
0:04:56 > 0:04:58They've long since disappeared.
0:04:58 > 0:05:03The causes of those extinctions have sparked fierce debate.
0:05:03 > 0:05:08It's a difficult mystery to unravel, but the remains of the megafauna themselves
0:05:08 > 0:05:11hold clues to their demise.
0:05:15 > 0:05:22These ancient remains have a story to tell - if you know where to look.
0:05:28 > 0:05:33One of the most poignant cases is that of a mother.
0:05:36 > 0:05:42This is the University of Michigan Museum of Natural History, home to some remarkable animals.
0:05:42 > 0:05:48And the stories of their lives and deaths encapsulate this mystery.
0:05:48 > 0:05:53These are mastodons, extinct relatives of elephants
0:05:53 > 0:05:58and mammoths, and this one is a female. Her name is Owosso.
0:06:02 > 0:06:06Owosso was one of the last surviving mastodons.
0:06:09 > 0:06:15And she is SO special, because hidden deep inside her tusks,
0:06:15 > 0:06:20she kept a secret recording of her tumultuous life.
0:06:22 > 0:06:26Dan Fisher is the world's expert tusk decoder.
0:06:30 > 0:06:35So what can you tell about the life of one of these animals by looking at its tusks?
0:06:35 > 0:06:38One of the most basic things you can tell is its age.
0:06:38 > 0:06:40You can count the years in the tusk.
0:06:40 > 0:06:45This is the tip of the tusk of a male mastodon.
0:06:45 > 0:06:48I've cut it here, and even on the rough-cut surface you can see
0:06:48 > 0:06:50very clearly these years.
0:06:50 > 0:06:54Each dark/light couplet represents one year of life.
0:06:54 > 0:06:57- That's fantastic, just to be able to see that with the naked eye. - Isn't it?
0:06:57 > 0:07:01You can also tell things like the condition of the animal,
0:07:01 > 0:07:05how it was responding to its environment, to the food that was available to it,
0:07:05 > 0:07:12because good years, good times, when there's plenty of food, are represented by thicker rings.
0:07:12 > 0:07:14Hard times are represented by thinner layers.
0:07:17 > 0:07:23By analysing her tusks, Dan can tell when a mother was pregnant,
0:07:23 > 0:07:26and even when she was suckling her baby.
0:07:36 > 0:07:39Owosso is 13.
0:07:39 > 0:07:42She's just had her first calf.
0:07:45 > 0:07:48He will rely on her milk for at least two years.
0:07:54 > 0:07:57What can you tell about Owosso's life?
0:07:57 > 0:08:01Owosso's reproductive life began with a successful calving interval.
0:08:01 > 0:08:04She had that fist calf, no problem,
0:08:04 > 0:08:08but after that she lost calf after calf after calf,
0:08:08 > 0:08:14a sequence of three, that died apparently as soon as they were born.
0:08:19 > 0:08:23Owosso is feeding quietly.
0:08:23 > 0:08:27She's just lost her third calf.
0:08:27 > 0:08:32Is she a bad mother or a victim of her times?
0:08:41 > 0:08:46To find out, I need to discover what was happening as the ice disappeared...
0:08:50 > 0:08:53..and how it affected the Ice Age giants.
0:09:03 > 0:09:09Grisly discoveries made in Hope Avenue in Tennessee may hold a clue.
0:09:15 > 0:09:19Behind its finely clipped hedges and manicured lawns,
0:09:19 > 0:09:24this immaculate neighbourhood hides a terrible secret.
0:09:26 > 0:09:31Excavations for a new golf course beyond the gardens' edge
0:09:31 > 0:09:36uncovered the dismembered remains of three mastodons.
0:09:43 > 0:09:46And now a major archaeological dig is underway.
0:09:52 > 0:09:56Alongside the bones, John Broster and Mike Waters
0:09:56 > 0:10:00unearthed tell-tale signs of a new breed of predator.
0:10:03 > 0:10:07- Yeah.- ..down at the Tennessee River. That was quarried for...
0:10:09 > 0:10:14They had come to North America from Asia, around 15,000 years ago.
0:10:17 > 0:10:19The first Americans.
0:10:28 > 0:10:32There were around six or eight tools found with the mastodons.
0:10:32 > 0:10:37One of the main ones is called a blade, and it's a long cutting tool
0:10:37 > 0:10:41made out of flint and was probably used to cut and strip meat with.
0:10:41 > 0:10:46Another tool called gravers, and they have these very sharp tips.
0:10:46 > 0:10:50These points were created so that they could score bone with it
0:10:50 > 0:10:54so they could split bone and turn the bones actually into tools.
0:10:54 > 0:10:57It was a very important aspect of butchery,
0:10:57 > 0:10:59was to get the bones as well as the meat.
0:11:00 > 0:11:07So it seems that early Americans could skilfully cut up a mastodon carcass,
0:11:07 > 0:11:11but were they actually killing them?
0:11:11 > 0:11:13The team kept looking for clues.
0:11:15 > 0:11:18When we were removing the ribs of the mastodon,
0:11:18 > 0:11:23underneath the ribs was the tip of a bone projectile point, probably
0:11:23 > 0:11:27the spear point used to kill the mastodon, so then we knew for sure
0:11:27 > 0:11:32it had been killed versus actually scavenged, or something like this.
0:11:33 > 0:11:36Hope Avenue isn't alone.
0:11:36 > 0:11:40Another famous mastodon find from the same period, at the Manis
0:11:40 > 0:11:45site, preserved the murder weapon, still embedded in its victim.
0:11:51 > 0:11:53The mastodon rib was scanned.
0:11:56 > 0:11:59The image reveals a spearhead
0:11:59 > 0:12:03penetrating about two-and-a-half centimetres into the bone.
0:12:12 > 0:12:18A 3-D reconstruction reveals that the tip broke off during impact.
0:12:25 > 0:12:31It's irrefutable evidence that humans were hunting mastodons.
0:12:31 > 0:12:35The bone projectile point that was found at the Manis site would have looked something like this.
0:12:35 > 0:12:38Now, what we did is we took a sample
0:12:38 > 0:12:42of the tip end of the bone point, ran DNA analysis on it
0:12:42 > 0:12:46and the DNA analysis showed that it was made of mastodon bone.
0:12:46 > 0:12:49So this indicated that at least one other mastodon had been
0:12:49 > 0:12:54hunted by these people and that they'd taken the bone from the mastodon
0:12:54 > 0:12:57and fashioned a bone projectile point from it.
0:12:59 > 0:13:02Other sites in North America tell a similar story
0:13:02 > 0:13:07of early humans hunting and butchering mastodons
0:13:07 > 0:13:09and other Ice Age giants -
0:13:09 > 0:13:15evidence that seems to implicate humans in the extinction of the megafauna.
0:13:17 > 0:13:21It's tempting to think of those first Americans as rampaging
0:13:21 > 0:13:26across the continent going on a massive killing spree.
0:13:26 > 0:13:31But there were only small numbers of hunter-gatherers in this vast
0:13:31 > 0:13:34landscape and we now know that the megafauna
0:13:34 > 0:13:39survived for thousands of years after humans first arrived here.
0:13:39 > 0:13:41So that leaves us looking
0:13:41 > 0:13:45for another threat to the survival of the megafauna.
0:13:58 > 0:14:02Around the same time as the animals went extinct,
0:14:02 > 0:14:06there were cataclysmic changes to the environment.
0:14:09 > 0:14:15Some of the greatest ice sheets the world has known were melting.
0:14:20 > 0:14:22And as the world warmed up,
0:14:22 > 0:14:26the thaw posed a great danger to the survivors of the Ice Age.
0:14:38 > 0:14:41The evidence isn't hard to find.
0:14:41 > 0:14:45It's scoured into the landscapes of northwest America.
0:14:51 > 0:14:54And this has to be the best way to appreciate it.
0:14:59 > 0:15:03Climbing this rock, I can almost feel the colossal forces that
0:15:03 > 0:15:07surged through here 14,000 years ago.
0:15:14 > 0:15:17This is certainly tougher than it looked from the bottom,
0:15:17 > 0:15:20but I'm hoping that it's all going to be worth it
0:15:20 > 0:15:23when I get to the top and I can look out at this view.
0:15:27 > 0:15:32Before the break-up of the ice, there was no canyon here.
0:15:37 > 0:15:41Just endlessly rolling hills, full of life.
0:15:46 > 0:15:50But something demolished that idyllic landscape.
0:16:11 > 0:16:14Wow, that's incredible! Just look at that.
0:16:17 > 0:16:19This is Frenchman Coulee -
0:16:19 > 0:16:22part of the Channeled Scablands of Washington State
0:16:22 > 0:16:26and I've just climbed up one of the gigantic basalt columns which
0:16:26 > 0:16:31forms the side of this huge gouge in the landscape,
0:16:31 > 0:16:36which itself was created by phenomenally destructive natural forces.
0:16:39 > 0:16:44Frenchman Coulee puzzled geologists for decades,
0:16:44 > 0:16:49with its distinctive square profile, sheer cliffs and flat bottom.
0:16:53 > 0:16:58With no sign of there ever having been a river here,
0:16:58 > 0:17:02what could have carved out a canyon like this?
0:17:04 > 0:17:1250 miles north, there are vast bowls at the feet of huge cliffs.
0:17:12 > 0:17:16Signs of an enormous ancient waterfall,
0:17:16 > 0:17:19over three times the size of Niagara.
0:17:24 > 0:17:28This is evidence of an earth-shattering mega-flood.
0:17:32 > 0:17:34So where did all the water come from?
0:17:41 > 0:17:4515,000 years ago, to the east there stood
0:17:45 > 0:17:51an incredible natural structure, more than a mile tall - an ice dam.
0:17:55 > 0:18:00A glacier holding back a vast lake of meltwater
0:18:00 > 0:18:04with a volume of 500 cubic miles.
0:18:06 > 0:18:09This was Glacial Lake Missoula.
0:18:14 > 0:18:18During the depths of the Ice Age, the dam held fast.
0:18:20 > 0:18:25But as it got warmer, you can guess what happened.
0:18:37 > 0:18:42The resulting flood was more than ten times the combined flow
0:18:42 > 0:18:45of all the rivers in the world today.
0:18:48 > 0:18:51The raging waters were 100 metres deep.
0:18:51 > 0:18:55Racing along at 65 miles per hour,
0:18:55 > 0:19:01the flood carried boulders, trees and the carcasses of any animals caught in its path.
0:19:06 > 0:19:12On its way to the Pacific, it gouged out a gaping wound in the landscape,
0:19:12 > 0:19:16through Idaho, Oregon and Washington.
0:19:16 > 0:19:19And it wasn't just one flood.
0:19:25 > 0:19:30Over 2,000 years, as the Ice Age relinquished its grip,
0:19:30 > 0:19:35the ice repeatedly retreated and advanced.
0:19:35 > 0:19:38With every melt, there was another flood...
0:19:43 > 0:19:46..wreaking destruction and creating chaos.
0:19:56 > 0:20:00Geologists believe there were over 100 mega-floods.
0:20:11 > 0:20:15The devastation unleashed by the flood from Glacial Lake Missoula
0:20:15 > 0:20:19was immense - the landscape still looks ruined today.
0:20:19 > 0:20:23It was a catastrophic event on a massive scale
0:20:23 > 0:20:27that spelled the end for any animals in its path.
0:20:29 > 0:20:32Enormous meltwater floods like these occurred
0:20:32 > 0:20:35right round the Northern Hemisphere.
0:20:39 > 0:20:42But away from these scenes of destruction,
0:20:42 > 0:20:44animals would have been safe.
0:20:51 > 0:20:55As catastrophic as these events were, it seems
0:20:55 > 0:21:01unlikely that it was mega-floods that killed off the Ice Age giants.
0:21:01 > 0:21:03Whatever caused their extinction
0:21:03 > 0:21:06must have been something on an even larger scale.
0:21:10 > 0:21:13There is one possibility -
0:21:13 > 0:21:17the wider impact of that huge shift in climate.
0:21:21 > 0:21:25The Ice Age had created very different landscapes to what we see today.
0:21:37 > 0:21:42On the dry grass plains of Siberia, woolly mammoths
0:21:42 > 0:21:45and woolly rhinos are grazing.
0:21:45 > 0:21:52Both are supremely adapted to the unique cold yet sunny Ice Age environment.
0:21:54 > 0:21:58Their double-layered woolly coats keep them warm.
0:21:58 > 0:22:03Both depend on a diet mainly consisting of grass,
0:22:03 > 0:22:06and both require a vast amount of food every day...
0:22:09 > 0:22:15..something that the sunny open steppes are perfectly able to provide.
0:22:22 > 0:22:26Woolly mammoths and rhinoceroses didn't just live in a different age,
0:22:26 > 0:22:32they evolved to thrive in a habitat which just doesn't exist anywhere today.
0:22:32 > 0:22:37They were the kings of the mammoth steppe, a unique Ice Age environment,
0:22:37 > 0:22:42a vast dry grassland which once stretched almost around the world.
0:22:47 > 0:22:53From northern Europe, across Siberia, all the way to Alaska,
0:22:53 > 0:22:59the dry, cold conditions of the Ice Age created this unique habitat.
0:23:05 > 0:23:08A paradise for the megaherbivores.
0:23:29 > 0:23:31Even in the depths of winter,
0:23:31 > 0:23:34there was very little snow to cover the grass.
0:23:36 > 0:23:42But as the Ice Age drew to a close, the world didn't simply get warmer.
0:23:46 > 0:23:49The meltdown also brought with it wet weather.
0:23:49 > 0:23:52Gone were the clear blue skies that had fostered
0:23:52 > 0:23:55the spread of the great mammoth steppe,
0:23:55 > 0:23:58and the gathering rain clouds and snow clouds
0:23:58 > 0:24:02posed a great threat to the Ice Age megaherbivores.
0:24:06 > 0:24:09It seems like a paradox.
0:24:09 > 0:24:13But there's evidence that as the ice retreated,
0:24:13 > 0:24:17it snowed more heavily than it had done for thousands of years.
0:24:22 > 0:24:26The changing conditions allowed trees to return to the north.
0:24:30 > 0:24:36The vast grasslands of the Ice Age gave way to forest and boggy tundra.
0:24:43 > 0:24:49And in winter, everything disappeared under a lethal white blanket.
0:25:00 > 0:25:07Without snow shoes, trudging through this deep snow is really difficult.
0:25:07 > 0:25:10For a large animal it would be a struggle moving around
0:25:10 > 0:25:13in this landscape, a struggle finding food,
0:25:13 > 0:25:17and you'd never know where the next attack was going to come from.
0:25:17 > 0:25:22You can just imagine how exhausting and nerve-racking that could be.
0:25:33 > 0:25:38The deep snow is a particular problem for the woolly rhinoceros.
0:25:41 > 0:25:45This young female is desperately searching for food.
0:25:46 > 0:25:49She's exhausted.
0:25:49 > 0:25:52Her short legs can't carry her any further.
0:26:00 > 0:26:03The last evidence we have of woolly rhinoceros
0:26:03 > 0:26:06dates to about 14,000 years ago in Siberia.
0:26:06 > 0:26:10It seems they just couldn't cope with that dramatic climate change.
0:26:10 > 0:26:13Their habitat shrank and finally disappeared
0:26:13 > 0:26:17and when the steppe went, so did they.
0:26:19 > 0:26:24Climate change now hit habitats right across the Northern Hemisphere,
0:26:24 > 0:26:26but in quite different ways.
0:26:30 > 0:26:32On my journey through Ice Age America,
0:26:32 > 0:26:36I encountered the strangest mammal I had ever seen.
0:26:40 > 0:26:45Today, its remains are found scattered in the Arizona desert.
0:26:46 > 0:26:48How amazing,
0:26:48 > 0:26:53to be one of the first people to see this ancient creature.
0:26:55 > 0:26:58But the glyptodont wasn't a desert-loving animal.
0:26:58 > 0:27:01It was a creature of the swamp.
0:27:02 > 0:27:04During the Ice Age,
0:27:04 > 0:27:08the vast American ice sheet diverted the rain south...
0:27:10 > 0:27:14..turning desert into wetland,
0:27:14 > 0:27:17and creating the ideal home for these mammals.
0:27:20 > 0:27:25But during the thaw, the rains moved north,
0:27:25 > 0:27:28turning the southern swamps into the deserts we see today...
0:27:36 > 0:27:39..spelling the end for these mighty beasts.
0:27:54 > 0:27:59Could climate change also explain the disappearance
0:27:59 > 0:28:03of other great mammals of the Ice Age, such as mastodons?
0:28:11 > 0:28:15Evidence is now emerging across the eastern United States.
0:28:21 > 0:28:25In the Appalachian mountains of Virginia, palaeontologists
0:28:25 > 0:28:28are unearthing bones -
0:28:28 > 0:28:35the remains of mastodons that died during this period of most intense climate change.
0:28:35 > 0:28:39- Just get the trowel and see if you can pop it out.- OK.
0:28:45 > 0:28:47What we have here is fossils from
0:28:47 > 0:28:50the end of the Ice Age, here in Saltville.
0:28:50 > 0:28:52We have mammoths, we have mastodons.
0:28:52 > 0:28:57Right here behind me is a mastodon tusk that they are excavating.
0:28:57 > 0:29:00We have a gravel layer that represents an old river bed,
0:29:00 > 0:29:05and right above that are these clay deposits from an old lake bed as well.
0:29:05 > 0:29:10So we get these two different time frames represented from the very end of the Ice Age.
0:29:10 > 0:29:16The most valuable clues are these -
0:29:16 > 0:29:19giant pieces of jaw, complete with teeth.
0:29:23 > 0:29:29Mastodon's teeth were a key part of what made them such successful animals.
0:29:31 > 0:29:35Inside their mouths are mountainous molars.
0:29:38 > 0:29:44Superb munching tools, designed to mangle trees and grind up shrubs.
0:29:48 > 0:29:52Mastodons were particularly fond of the spruce woodlands
0:29:52 > 0:29:54that once dominated this part of America.
0:30:08 > 0:30:14Mastodon teeth like these hold clues as to how they responded
0:30:14 > 0:30:16when their food supply dwindled.
0:30:18 > 0:30:24Trace elements within the teeth reveal where an animal foraged
0:30:24 > 0:30:26during its lifetime.
0:30:30 > 0:30:33As climate change kicked in, some mastodons
0:30:33 > 0:30:38were migrating large distances to find their favourite food.
0:31:01 > 0:31:05We're getting a glimpse of how mastodons' lives were disrupted
0:31:05 > 0:31:07as their world changed.
0:31:11 > 0:31:15But is there any evidence that they were under threat of extinction?
0:31:22 > 0:31:26One thing that might help is these.
0:31:30 > 0:31:35Surprising new research on bison in Kansas is revealing
0:31:35 > 0:31:38the scale of the North American extinctions.
0:31:44 > 0:31:48Remarkably, these bison have helped scientists to find
0:31:48 > 0:31:53clues in the landscape, which reveal just how many giant mammals
0:31:53 > 0:31:59once roamed these lands and precisely when they disappeared.
0:32:09 > 0:32:15Bison are America's largest surviving species of Ice Age mammal
0:32:15 > 0:32:19and here, they're protected in their favourite environment.
0:32:23 > 0:32:29Kendra McLauchlan studies a microscopic fungus called Sporomiella,
0:32:29 > 0:32:35which leaves its spores in the dung of large herbivores like bison.
0:32:38 > 0:32:44Even though the dung rots away, the spores are extremely tough
0:32:44 > 0:32:45and persist in the soil.
0:32:47 > 0:32:49We can trap some of those spores
0:32:49 > 0:32:54passively in our traps, and the idea is that we can measure
0:32:54 > 0:32:56how many spores are in the traps
0:32:56 > 0:33:00and get an idea of how many grazers are on the landscape.
0:33:02 > 0:33:06The number of spores is a good indicator of the size
0:33:06 > 0:33:07of animal populations.
0:33:11 > 0:33:17The same fungus grew in the dung of Ice Age giants
0:33:17 > 0:33:22and its spores are still found in soil dating from that time.
0:33:25 > 0:33:29The spores reveal what happened to whole populations
0:33:29 > 0:33:33of giant mammals at the end of the Ice Age.
0:33:37 > 0:33:42Ice Age soil samples, from California to New York, were analysed.
0:33:45 > 0:33:52They revealed that 18,000 years ago the soil was full of spores -
0:33:52 > 0:33:54the giants were thriving.
0:33:59 > 0:34:05But around 14,000 years ago the spores almost disappeared -
0:34:05 > 0:34:09the sign of a massive population crash.
0:34:14 > 0:34:22The big question is, was this crash caused by changes in climate and environment?
0:34:24 > 0:34:27As well as containing spores,
0:34:27 > 0:34:31the soil samples preserved a record of the vegetation.
0:34:38 > 0:34:41But the results were a shock.
0:34:43 > 0:34:46The vegetation did indeed change,
0:34:46 > 0:34:50but after the crash of giant mammals.
0:34:52 > 0:34:55So if climate change wasn't responsible for the crash...
0:34:57 > 0:34:59..what was?
0:35:05 > 0:35:09There's one more piece to this puzzle.
0:35:09 > 0:35:13The last mastodons hold a dark secret.
0:35:16 > 0:35:20Amongst their remains, Dan Fisher has identified
0:35:20 > 0:35:25a number of bones which tell a harrowing story.
0:35:25 > 0:35:28And this is another female mastodon.
0:35:28 > 0:35:32So this is a female. It's one we call Eldridge,
0:35:32 > 0:35:39and she has this very pronounced area of trauma to the front of her skull.
0:35:39 > 0:35:41The skull has been broken
0:35:41 > 0:35:45but the bony regrowth shows that she recovered from this assault.
0:35:50 > 0:35:55And there's more evidence of violence.
0:35:55 > 0:36:00These are parts of the skeleton that was recovered from a female known as Powers.
0:36:00 > 0:36:02So this is all the same individual?
0:36:02 > 0:36:05All the same individual. There's much more of her
0:36:05 > 0:36:10but these are a few of her skeletal parts that display unusual sorts of injuries.
0:36:12 > 0:36:16Her injuries are horrific.
0:36:16 > 0:36:19Her neck vertebrae have been shattered.
0:36:23 > 0:36:28But on this animal, the perpetrator has left its calling card.
0:36:30 > 0:36:35In her shoulder blade, there's a deep puncture.
0:36:35 > 0:36:41The shape of the hole tells Dan exactly what the weapon was -
0:36:41 > 0:36:43a tusk!
0:36:43 > 0:36:48I think this is evidence for a mastodon attacking another mastodon.
0:36:48 > 0:36:52As unusual as that sounds, that's what the nature of the damage suggests.
0:37:06 > 0:37:10What could possibly lead mastodons into attacking each other?
0:37:14 > 0:37:19Mastodons' surviving cousins, modern elephants, may provide an answer.
0:37:22 > 0:37:26This herd is made up of adult females and their young.
0:37:29 > 0:37:37As the cows come into season, a mature dominant bull joins them for mating.
0:37:37 > 0:37:42His presence suppresses the sexual behaviour of younger males.
0:37:47 > 0:37:51Today, though, magnificent bull elephants are frequently targeted
0:37:51 > 0:37:55by hunters and poachers for their huge tusks.
0:37:57 > 0:38:03And this has a devastating impact - if dominant males are absent,
0:38:03 > 0:38:09the younger, testosterone-pumped males go on the rampage,
0:38:09 > 0:38:13often with tragic consequences for the breeding females.
0:38:22 > 0:38:24The butchered skull of a mastodon male.
0:38:26 > 0:38:32Dan believes that - as with elephants today - the large bulls were targeted.
0:38:33 > 0:38:37So we've got some very disparate specimens here, Dan,
0:38:37 > 0:38:40some showing evidence of injury mastodon-on-mastodon,
0:38:40 > 0:38:45one here showing evidence of human interaction in the form of butchery.
0:38:45 > 0:38:48Is there something which you think links all of this together?
0:38:48 > 0:38:54I think there is. When we look early in the almost 3,000 years
0:38:54 > 0:38:57of human/mastodon interaction that we have recorded in this region,
0:38:57 > 0:38:59we see for instance,
0:38:59 > 0:39:05a predominance of focusing of this hunting activity on mature adult males,
0:39:05 > 0:39:12perhaps because they were solitary individuals and easier to surprise, easier to ambush.
0:39:12 > 0:39:17That focusing of hunting activity on mature adult males
0:39:17 > 0:39:20would have gradually depleted those from populations.
0:39:20 > 0:39:25Dan's theory is that simply killing off the mature bulls
0:39:25 > 0:39:31destabilized mastodon herds, helping to drive them to extinction.
0:39:41 > 0:39:45Owosso has a new calf, a little female.
0:39:53 > 0:39:55Two young bulls approach.
0:39:58 > 0:40:00They are full of testosterone.
0:40:14 > 0:40:18Owosso shields her baby, but lays herself open to attack.
0:40:25 > 0:40:29A few weeks later, she's still limping,
0:40:29 > 0:40:32and her calf is nowhere to be seen.
0:40:38 > 0:40:41Owosso died when she was 29 years old,
0:40:41 > 0:40:44middle-aged for a mastodon.
0:40:48 > 0:40:52From her tusks, we know that three of her four calves
0:40:52 > 0:40:56must have died close to birth.
0:40:56 > 0:40:58Only one survived past weaning.
0:41:00 > 0:41:03It's a story of tragic loss,
0:41:03 > 0:41:07and Owosso was one of the last of her species.
0:41:09 > 0:41:13So from your research, do you think we finally have an answer
0:41:13 > 0:41:16as to why these animals went extinct?
0:41:16 > 0:41:22What I see is a very slow-motion process,
0:41:22 > 0:41:25a very long-term pattern of change.
0:41:25 > 0:41:28I don't think humans doing this would have necessarily
0:41:28 > 0:41:34even been aware of the long-term consequences of their actions.
0:41:34 > 0:41:39Because for so long, the world was more or less as it had been -
0:41:39 > 0:41:42for so long, there were the same animals,
0:41:42 > 0:41:47and I'm sure they felt they depended on these animals, they could continue this hunting activity
0:41:47 > 0:41:50that had been so successful for so long.
0:41:50 > 0:41:56But what we can see from OUR perspective, is what happened finally.
0:41:56 > 0:41:59And it was these very long-term consequences
0:41:59 > 0:42:03of the hunting behaviour that in the end spelled extinction.
0:42:08 > 0:42:10Owosso was just one animal
0:42:10 > 0:42:15but her story illustrates the plight of her whole species.
0:42:15 > 0:42:18It seems that the early Americans didn't have to slaughter
0:42:18 > 0:42:21entire herds of mastodon to have an impact.
0:42:21 > 0:42:26Instead, over thousands of years, there may have been just enough
0:42:26 > 0:42:31hunting and scavenging by humans to be unsustainable,
0:42:31 > 0:42:34to seal the fate of those giant mammals.
0:42:42 > 0:42:46Megafauna were especially vulnerable to such hunting,
0:42:46 > 0:42:48for a very particular reason.
0:42:50 > 0:42:54Populations of huge, slow-breeding animals
0:42:54 > 0:43:00just can't cope with even limited hunting over such a long period of time.
0:43:00 > 0:43:05The effect of human predation was to spread like a ripple
0:43:05 > 0:43:08through the populations of giant mammals.
0:43:12 > 0:43:19Around the same time other giants, such as Columbian mammoths, also went extinct.
0:43:32 > 0:43:36The disappearance of giant predators like the sabre-toothed cat though,
0:43:36 > 0:43:40seems more puzzling - humans didn't hunt them.
0:43:40 > 0:43:44But once the large herbivores were in trouble,
0:43:44 > 0:43:48the future for anything that preyed on them was precarious.
0:43:52 > 0:43:59This predator of the Ice Age is built to bring down large animals.
0:43:59 > 0:44:06But she lacks the agility and endurance to hunt smaller, swifter prey.
0:44:06 > 0:44:10With her main source of food gone, she'll struggle to feed her cubs.
0:44:24 > 0:44:28It's a complicated story and undoubtedly some species
0:44:28 > 0:44:31were affected by the changing climate more than others.
0:44:31 > 0:44:34But now perhaps more than ever,
0:44:34 > 0:44:39it seems that humans really were to blame for the extinction
0:44:39 > 0:44:43of so many North American animals at the end of the last Ice Age.
0:44:48 > 0:44:51BELLOWS
0:44:55 > 0:45:00Though the true giants didn't make it, many other large animals did.
0:45:02 > 0:45:04And their biology may explain why.
0:45:11 > 0:45:16Unlike mammoths and mastodons, elk are prolific breeders.
0:45:23 > 0:45:28Bison give birth to new calves each year, and can also migrate.
0:45:34 > 0:45:38Adaptability combined with rapid reproduction
0:45:38 > 0:45:41probably helped both species survive.
0:45:45 > 0:45:50Another good survival strategy is to run away.
0:45:54 > 0:45:58Pronghorn antelope are some of the fastest creatures on Earth.
0:46:03 > 0:46:07Back in the Ice Age they had to run from giant predators.
0:46:09 > 0:46:14Now they are on the lookout for an attack that will never come.
0:46:17 > 0:46:21Perhaps their speed and agility kept enough of them safe
0:46:21 > 0:46:24from the spears of early human hunters as well.
0:46:30 > 0:46:33For the animals who preferred the cold,
0:46:33 > 0:46:35there was one other means of escape.
0:46:39 > 0:46:43As ice retreated north, they moved with it.
0:46:47 > 0:46:53The Arctic became a refuge for species like musk oxen and reindeer.
0:47:08 > 0:47:14And another animal that until recently survived in the north
0:47:14 > 0:47:16was the most iconic giant of them all.
0:47:28 > 0:47:31The woolly mammoth almost made it to the present day
0:47:31 > 0:47:34and scientists have recently been investigating what could have been
0:47:34 > 0:47:36their last stronghold.
0:47:36 > 0:47:41Mammoth expert Dan Fisher joined an expedition to a remote island
0:47:41 > 0:47:47off the north coast of Siberia in the Arctic Ocean - Wrangel Island.
0:48:01 > 0:48:0580 miles north of the Siberian mainland,
0:48:05 > 0:48:08this mystical island is rarely visited.
0:48:15 > 0:48:19The Russian authorities give it maximum protection -
0:48:19 > 0:48:24scientists are now amongst the very few humans allowed to land here.
0:48:28 > 0:48:32Wrangel Island is an important place to come for the study of mammoths
0:48:32 > 0:48:36because it's the place where the last populations survived.
0:48:36 > 0:48:40The last mammoths before they finally went extinct lived here,
0:48:40 > 0:48:44and we'd like to study them, to learn about the sorts of ecological stresses
0:48:44 > 0:48:49that they were experiencing in their last millennia,
0:48:49 > 0:48:52centuries - decades, even - if that's possible.
0:48:53 > 0:48:54Wrangel is unique.
0:48:56 > 0:49:00On the southern side of the island are some sheltered valleys
0:49:00 > 0:49:04with their own special microclimate.
0:49:04 > 0:49:08Here, a lost Ice Age habitat still survives.
0:49:10 > 0:49:15The closest thing to the mammoth steppe,
0:49:15 > 0:49:18where Ice Age animals still roam.
0:49:27 > 0:49:30Woolly mammoths lived here so recently,
0:49:30 > 0:49:33you can drive around and find their bones lying on the ground.
0:49:36 > 0:49:38Well, but not so bad.
0:49:40 > 0:49:45It's not long before Dan and the team start to uncover mammoth remains.
0:49:54 > 0:49:58A magnificent tusk, untouched for thousands of years.
0:50:04 > 0:50:06And another.
0:50:06 > 0:50:10Dan can't help but start to read its record.
0:50:10 > 0:50:15Winter-time, winter-time, winter-time.
0:50:15 > 0:50:18This is how much it grew in one year.
0:50:20 > 0:50:24Within a few days, the team finds the remains of 65 animals.
0:50:27 > 0:50:30But it soon becomes apparent that something is different
0:50:30 > 0:50:31about these mammoths.
0:50:33 > 0:50:35Their bones are all small.
0:50:39 > 0:50:43The last mammoths on the planet weren't giants.
0:50:46 > 0:50:51In this, their final island refuge, they were becoming dwarves.
0:51:02 > 0:51:06It's 2,000 BC.
0:51:06 > 0:51:08The pyramids are being built in Egypt
0:51:08 > 0:51:11and here on Wrangel Island,
0:51:11 > 0:51:15a herd of woolly mammoths is migrating into the mountains.
0:51:16 > 0:51:20They are retreating from a new predator,
0:51:20 > 0:51:23one which poses a great danger to them.
0:51:25 > 0:51:30Humans have recently arrived on the south coast of the island.
0:51:42 > 0:51:48Though they died out thousands of years ago, some believe that these
0:51:48 > 0:51:52may not be the last mammoths to live on Planet Earth.
0:51:58 > 0:52:02Permafrost has preserved some incredible new specimens...
0:52:06 > 0:52:10..complete with flesh, fur and even bone marrow.
0:52:22 > 0:52:26And right now, scientists are hoping to extract their DNA.
0:52:33 > 0:52:38Genetic technology may mean that it's possible to clone a woolly mammoth.
0:52:47 > 0:52:54We could be on the brink of being able to resurrect Ice Age species.
0:53:01 > 0:53:04Personally, I'd rather imagine them
0:53:04 > 0:53:08as they were back in the Ice Age, roaming free on the steppes.
0:53:12 > 0:53:16But in a way, and by accident,
0:53:16 > 0:53:20humans have already saved many Ice Age species from extinction.
0:53:34 > 0:53:40This is the Camargue in France, where herds of white horses roam free,
0:53:40 > 0:53:44living as their ancestors did back in the Ice Age.
0:53:49 > 0:53:53Horses evolved in North America, millions of years ago.
0:54:04 > 0:54:10They were a global success story, spreading out right across the world.
0:54:16 > 0:54:20Some even made it to Africa, where they became Zebras.
0:54:23 > 0:54:27But as the Ice Age ended, horses suffered badly.
0:54:29 > 0:54:34They died out completely in their ancestral home -
0:54:34 > 0:54:37horses went extinct in America.
0:54:42 > 0:54:46But in Europe and Asia they survived.
0:54:56 > 0:55:01In a very few places, it's still possible to see why.
0:55:09 > 0:55:11Animals like these are some of the most amazing
0:55:11 > 0:55:14survivors of the Ice Age, not just because they survived
0:55:14 > 0:55:18all those horrendous shifts in climate and the depredations,
0:55:18 > 0:55:24but because they finally took an incredible step which would ensure their survival.
0:55:29 > 0:55:33Every autumn, a very special event takes place here.
0:55:39 > 0:55:43The brown foals, which until now have roamed free,
0:55:43 > 0:55:48are about to take a massive step that will change their destiny.
0:55:53 > 0:55:58They're rounded up to be separated from their white mothers,
0:55:58 > 0:56:02ready to be tamed and trained as working horses.
0:56:05 > 0:56:09These foals are about to be domesticated.
0:56:12 > 0:56:15As our ancestors transformed themselves from hunter-gatherers
0:56:15 > 0:56:18to farmers at the end of the last Ice Age,
0:56:18 > 0:56:21horses made that leap with us.
0:56:21 > 0:56:23It's almost as though they made a pact with us.
0:56:23 > 0:56:27Suddenly their value is transformed from not being just prey.
0:56:27 > 0:56:29They entered into a partnership
0:56:29 > 0:56:33where they gave us their labour in exchange for food and care.
0:56:35 > 0:56:39Horses are amongst a few species of large animals
0:56:39 > 0:56:43which survived beyond the Ice Age, by teaming up with people.
0:57:05 > 0:57:12Domesticated Ice Age animals helped us humans create the modern civilisations of today.
0:57:19 > 0:57:23We're getting a glimpse into the wild past of this magnificent
0:57:23 > 0:57:27animal that played such a huge part in the story of that
0:57:27 > 0:57:30other great Ice Age survivor - us.
0:57:33 > 0:57:38But as these magnificent horses thunder past, we can imagine,
0:57:38 > 0:57:45for a moment, what their lost Ice Age world was like in all its majesty.
0:58:05 > 0:58:10A time when the mighty Ice Age giants ruled the world.
0:58:47 > 0:58:50Subtitles by Red Bee Media Ltd