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Documentary, Evolutions - Ep 3 Before They Were Bears-2008
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AnimalsTranscript
00:00On planet Earth, one creature embodies all that is amazing about survival.
00:09It has adapted to wildly varying habitats.
00:15And evolved weapons unique to the animal kingdom.
00:22Its greatest asset, a bone crushing bite.
00:28This mystical creature has overcome extreme climate change, ferocious rivals and the deadliest threat of all.
00:42To emerge as one of evolution's ultimate survivors.
00:5845,000 years ago, North America.
01:16Vast grasslands dominate the landscape.
01:26This is one of the most feared carnivores on planet Earth.
01:35The giant, short-faced bear weighed as much as a small car.
01:49For decades, scientists believed this was the ultimate predator.
01:57The earliest paleontologists thought this would be an incredible runner.
02:00This was an animal well adapted for high speeds.
02:03With long strides that could go really fast and chase down bison or mammoths and be an incredible super predator.
02:11But the biggest bear ever died out.
02:16And yet smaller bears, its relatives, not only thrived, but colonized the planet.
02:26Few animals can match modern bears for versatility.
02:32They can survive on meat, on vegetation.
02:37They can even survive on insects.
02:41They live in wildly different habitats.
02:44From the steaming subtropical forests of India,
02:49to the icy wastes of the Arctic.
02:53The paleontologists discovered that during man's quest to master nature,
03:00bears proved a formidable opponent.
03:03Yet the most formidable of all died out.
03:10What skills have other bears evolved to survive?
03:14The secrets of bear evolution
03:20lie buried in the Earth itself.
03:28Paleontologists are time travelers.
03:31They visit our ancient past by digging down into the Earth's surface.
03:41Each layer of rock is like a time capsule,
03:45recording major events in the planet's history.
03:49asteroid strikes.
03:52Asteroid strikes.
03:55Natural disasters.
04:01And climate change.
04:04It's all recorded in sediment.
04:06Planet Earth's DNA.
04:09The mystery of bear evolution starts 20 million years ago in Central Europe.
04:30Planet Earth is hotter than today and clothed in forests.
04:34Man's rise is still many millions of years away.
04:46This is the first true bear.
04:49The dawn bear is the size of a fox terrier dog.
04:53It comes from a long line of dedicated carnivores.
04:59However, on the ground, it's dangerous.
05:02He struggles to compete with dogs, hyenas, and cats.
05:08Forcing him to take refuge in the treetops.
05:15How can a creature survive on meat up there?
05:20What genetic X factor transformed a small dog-like creature into the bears we know today?
05:33Dr. Anjali Goswami, of the University of Cambridge, is an expert in mammal evolution.
05:50By comparing the skull of a modern bear to another typical carnivore like a big cat, she can reveal the secret gift the father of all bears passed on to its descendants.
06:06Well, if you look at really a more standard carnivore, something like a tiger, you'll find that they have these really blade-like upper premolar.
06:19And that occludes with this really blade-like lower molar.
06:24And that creates a shearing action that's really well evolved for slicing meat.
06:33Now bears, although they've descended from these carnivorous ancestors, have actually done something quite different.
06:39So when you look at a bear skull, you can see that they've taken this premolar, and instead of having it blade-like, it's instead more triangular.
06:47So they have a dentition that's very well evolved for grinding.
06:50Well, having the ability to slice meat with these carnassial teeth and having these really broad molars gives them a lot of evolutionary flexibility.
07:07Because bears have slicing and grinding teeth, they can eat meat and vegetation.
07:14Critically, for the dawn bear, these teeth allow it to feed high up in the trees, safe from ground predators.
07:28Dental flexibility is the crucial gift the dawn bear passes on to all of its descendants.
07:35Over the next six million years, planet Earth basks in warm temperatures.
07:49But then the climate changes dramatically.
07:52And so do the fortunes of the early bear.
07:55Temperatures dip sharply, 14 million years ago.
08:05Colder weather strips away the subtropical forests.
08:10The tree-dwelling dawn bear must somehow adapt to this grassier world.
08:28Fossil records reveal that 14 million years ago, two descendants of the dawn bear had spread all over the world.
08:42The ancestor of the giant panda.
08:45And the bear that would eventually become the giant short-faced bear.
08:58The lesser short-faced bear looks like a bulldog.
09:10With its forest habitat vanishing, it takes to the ground in search of food.
09:28But the fossil record throws up a puzzle.
09:31It shows that 14 million years ago, the lesser short-faced bear lives in North America.
09:51Today, a 56-mile waterway known as the Bering Sea separates Eurasia from North America.
09:59How did the ancestors of the short-faced bear make this incredible journey to the New World?
10:14The answer to the mystery lies further north.
10:18In the Arctic.
10:22The cold snap 14 million years ago causes water in the polar regions to freeze.
10:29Ice has a profound effect on planet Earth.
10:40Water that normally flows down into the oceans remains frozen at both poles.
10:46This triggers a dramatic fall in global sea levels.
10:47This triggers a dramatic fall in global sea levels.
11:00Suddenly, land emerges out of the seas.
11:07Terrain appears between what is today Alaska and Eastern Siberia.
11:14Known as Beringia, or the Bering Land Bridge, it stretches 1,000 miles from North to South.
11:28And connects Asia to North America.
11:30Beringia, or the Beringia, or the Bering Land Bridge, served as a corridor for the exchange of plants and mammals and eventually people between the old and the new world.
11:42The ancestors of the bears probably came from Asia, crossed the Bering land bridge, moved into North America, and then bear evolution took place here.
11:5514 million years before man would make the same epic journey.
12:01Early bears take this bridge to the new world.
12:04Over thousands of years, temperatures rise again.
12:15The polar ice melts.
12:21The seas reclaim Beringia.
12:23The polar ice melts, the seas reclaim Beringia.
12:30The short-faced bear is trapped in the new world.
12:37Where the cold has also destroyed large areas of woodland.
12:53The shrinking wooded habitats of the lesser short-faced bear, they see that there's all this ripe, fresh meat out on the open plains.
13:04Either does it evolve and go after that fresh meat, or does it hang out in the shrinking forest and perish?
13:13The short-faced bear must adapt to hunt on the plains.
13:18Or face wipeout.
13:28About 2.5 million years ago, one of the most cataclysmic climatic events ever strikes planet Earth.
13:39And dramatically alters the course of bear evolution.
13:49A cold current has isolated Antarctica from the influence of warm currents.
13:58Antarctica forms a permanent ice cap, which it retains to this day.
14:02Then, South America connects to North America.
14:16This isolates the Atlantic Ocean from the Pacific Ocean.
14:22Now the Arctic develops permanent ice.
14:26The planet's temperature drops sharply.
14:35Two million years ago, Earth is in the grip of the Ice Age.
14:38The Ice Age spells doom for hundreds of species.
14:47It wipes out the saber-toothed tiger.
14:53Woolly mammoths.
14:56And the ground sloth.
14:57Only the toughest, most adaptable, will survive.
15:04Bears evolved some of the natural world's most ingenious tools.
15:12But not all the bear species will make it through.
15:15The ancestral dawn bear, from 20 million years ago, has now given rise to at least three separate species.
15:30The short-faced bear is trapped in North America.
15:33The ancestor of black and brown bears emerges in Eurasia, where the ancient panda makes an extraordinary transformation to survive the cold.
15:50First, the panda turns black and white.
16:05Scientists believe to act as camouflage against snow and rock.
16:09When its meat supply vanishes, the panda evolves a simple but ingenious solution to hunger.
16:24Two million years ago, in China, he finds a potential food source.
16:30Bamboo.
16:31There's lots of it, but the pandas are carnivore.
16:43There is another drawback.
16:46It literally can't handle this tough, chewy crop.
16:51This carnivore's paws are designed for hunting animals, not for snapping off vegetation.
17:01But hunger is often a major driving force in evolution.
17:09The panda has five claws, but they can't grip a thin bamboo shoot.
17:17To counter this, evolution exploits a bone below the claws.
17:21It grows into a bump that acts as an opposable force to the five claws.
17:26It's known as the panda's thumb.
17:29This thumb allows it to grip and snap bamboo.
17:36Now the bears' crushing jaw and grinding teeth play their part.
17:41Pandas have to really break up the bamboo as much as possible before they digest it in order to withdraw as many nutrients.
17:44as possible.
17:45So having this very, very strong bite force and this really strong grinding dentition allows them to do that and subsist on this otherwise very nutrient poor diet.
18:06The panda solves its food crisis.
18:16Now, elsewhere in Asia, a group of ancient bears must do the same.
18:21Huge glaciers colonize the Himalaya mountain range, driving a group of ancient bears into the temperate forests of India.
18:40Here, the carnivore struggles to eke out a living.
18:47Wolves and hyenas beat it to the available meat.
18:54These bears now produce a bizarre and amazing set of tools to survive.
19:06Two million years ago, in the temperate forests of India, a group of starving bears stumbles across one unusual but crucially untapped source of food.
19:30To exploit it, the species relies on its ancient gift, an adaptable mouth and teeth.
19:43It develops a long tongue, a larger mobile snout, and he loses his first pair of incisor teeth, thereby sacrificing the bear's trademark bite.
19:58It now becomes a new species, the sloth bear.
20:02The sloth bear has evolved this bizarre oral tool set to target a particular source of food.
20:18The sloth bear has found a different source of food that actually does maintain a steady supply throughout all the different seasons, and that's ants and termites.
20:28It has a very strong claws that it uses to actually break the top of a termite mound, and by using its very mobile nose, it can actually create a suction across the top of the termite mound, close its nostrils, and almost vacuum out the termites from the mound.
20:48The sloth bear, like the panda, adopts an extraordinary strategy to survive the ice age.
20:58At the same time in the new world, another bear has adapted to the cold by becoming massive.
21:16We know this because of a spectacular fossil find.
21:26In a river in the Yukon region of Canada, a gold prospector found an enormous skull.
21:50It looks like the skull of some sort of ancient monster.
21:58But what is it?
22:02What is it?
22:14Paleontologist Grant Cezula has a cast of the giant skull at his lap in the Yukon town of Whitehorse.
22:26Its huge size tells me that this animal is built for power and intimidation.
22:32We can see this large muscle attachment that runs down the back of a head.
22:38The muscles attached to this jaw were powerful. Powerful if they could bite through almost anything.
22:43And these carnaceal teeth, these cheek teeth here, would have been amazing bone-cracking hammers.
22:53So if they came across a carcass, a bison, a nice-aged mammoth, or a horse,
22:58they could crack that bone, get at the marrow, and eat the fat in the marrow.
23:02It was an amazing adaptation to take apart carcasses. An amazing carnivore.
23:18This amazing carnivore lived 200,000 years ago in the Yukon.
23:23It's still the ice age.
23:32Grasslands have colonized the land mass, triggering a population explosion of hoofed animals.
23:41The short-faced bear has become the giant short-faced bear.
23:53The largest ever to stalk the earth.
24:00It's huge, weighing 900 kilos.
24:063.4 meters tall on two legs.
24:08It could reach higher than a basketball hoop.
24:17He has evolved a set of lethal weapons.
24:23Slender legs mean he can run at 50 kilometers per hour, faster than most horses.
24:29Inside his forehead, the organ that controls smell is enlarged, allowing him to sniff out a carcass ten kilometers away.
24:40Combined with his bone-crushing jaw,
24:45the giant short-faced bear looks every inch evolution's ultimate hunter.
24:53The evolution makes him massive for good reason.
24:56Competition for meat on the plains is intense.
25:02The evolution makes him massive for good reason.
25:08Competition for meat on the plains is intense.
25:11This guy evolved huge because it needed to defend itself from other scary predators like lions, wolves.
25:32When lions and wolves were running around the landscape, they lived in packs.
25:44But short-faced bears were actually solitary creatures.
25:49So they needed to be huge and intimidating to defend themselves and their food.
25:58The giant short-faced bear will need its extra size for another reason.
26:03Life on the open prairie is about to get tougher.
26:07Soon, it will face a battle for territory with a powerful rival.
26:22History repeats itself.
26:25Once again, 50,000 years ago.
26:27Frozen water at the poles resurrects the long-disappeared land bridge between Asia and Alaska.
26:42Beringia is back.
26:45But by now, Beringia acts as more than a land bridge from Asia to the New World.
27:00While glaciation descends all about it, Beringia remains largely ice-free.
27:08This is due to warm winds and currents from the Pacific Ocean.
27:12Beringia becomes a lush haven for migrating species from Asia.
27:22Lions.
27:24Elephants.
27:26Early man.
27:29But most importantly, the ancestor of black and brown bears.
27:37The black bear simply can't compete on the plains of Beringia.
27:43With big cats.
27:45And larger bears.
27:59However, the ancient grizzly is feisty and powerful.
28:03He challenges his distant cousin.
28:05But the giant short-faced bear has no plans to share this fertile new land with a smaller rival.
28:15The most dramatic phase of bear evolution starts 50,000 years ago.
28:21Back then, Beringia is a land mass that links what is today Alaska to Siberia and acts as a gateway to the New World.
28:42The ancestor to the grizzly wants to migrate from Asia to this fertile new land.
28:55The native giant short-faced bear is bigger, stronger, and has no plans to share.
29:03No plans to share.
29:07Surely the brown bear doesn't stand a chance.
29:33The fossil record confirms that the brown or grizzly bear vanished from Beringia 35,000 years ago.
29:44The giant short-faced bear...
29:49...sends it packing back to Asia.
29:51The dramatic change in the fossil record of bears in Beringia is incredible.
30:05Their short-faced bear population seemed to explode while we have no record of grizzly bears at all.
30:09It seems like the competition for food resources amongst the carnivores was just too high for the grizzly bears.
30:18They had to leave Beringia.
30:20The giant short-faced bear dominates North America for over one million years.
30:26Yet we know that ultimately, the grizzly bear returns to populate and conquer North America.
30:42Somehow, it must have found a way to overpower its larger ancient enemy.
30:47Something unique would tilt the balance of survival in favour of the grizzly.
31:05Meanwhile, in Eurasia, a new giant bear species emerges.
31:10In the vaults of Cambridge University, Anjali Goswami tracks down the skull of one of these ancient monsters.
31:21And this is the skull of a cave bear.
31:25And this is a bear that diverged from the brown bears about 1.2 million years ago.
31:31You would think that the cave bear had a lot of the traits that have seen bears through many other things.
31:40and other extinction events.
31:41It has this more generalised dentition.
31:43Even though it had specialised a bit more towards a vegetarian diet,
31:46it certainly was capable of taking a wide range of prey in addition to vegetation.
31:52So it certainly seemed to have all of the characteristics that bears would like to have to come out of the last glycation and do well.
31:59The cave bear is larger and more powerful than the Eurasian black and brown bear.
32:13It has a broad, domed skull and a deep forehead.
32:23And teeth that can devour both meat and vegetation.
32:30To combat the cold, it hibernates in caves.
32:34The cave bear looks an evolutionary masterpiece.
32:48But 21,000 years ago, the story of bear evolution in Eurasia and North America takes a dramatic turn.
32:56The brown bear, the ancestor of the grizzly, has been muscled out of Beringia for thousands of years.
33:09Defending the corridor to the new world, the seemingly invincible giant short-faced bear.
33:16But 21,000 years ago, there's a rematch, and this time, a remarkably different outcome.
33:37Once again, the Beringia fossil record reveals what happens.
33:41It shows that suddenly, 21,000 years ago, brown bears lived all over Beringia.
33:55While the previously dominant giant short-faced bear has vanished.
34:04Why did it surrender this fertile territory?
34:07Grant Zuzula finds clues to the mystery in the spectacular local topography.
34:2621,000 years ago, bear evolution is altered completely by the dramatic events in these mountains.
34:43Well, in these mountains surrounding Beringia here, these were the accumulation centers for all the glacial ice that surrounded the continent of Beringia.
34:51This is where the ice age began for Beringia.
34:52Massive sheets of ice accumulated here, advanced over the landscape, creating an incredibly harsh, cold ice age environment.
35:03Well, 21,000 years ago is considered the last glacial maximum.
35:09This was the deep freeze that covered the earth.
35:12This was the coldest time ever during the ice age.
35:15Probably the coldest temperatures that large mammals ever encountered.
35:18The brown bear's teeth allow it to eat meat and vegetation.
35:27Now, it thrives in Beringia.
35:30May have been a result of competition, may have been a result of just environmental change, changing the resource base that these two different bears rely on.
35:40And it seems like the grizzly bears won here.
35:41They were able to survive and continue on until present day in Beringia.
35:51The extreme cold drives hoofed animals out of Beringia.
35:54The giant short-faced bear's food source has gone.
35:59The carnivore heads south of the glaciers to the warmer climes of what is today the United States.
36:06Leaving the gateway to North America, wide open for brown bears.
36:17Over the next 11,000 years, brown bears radiate all over North America, where they still battle for supremacy of the plains.
36:28But by now, bears of the new world face a new enemy.
36:40It's possible that conflicts could have arose between short-faced bears and humans.
36:44The brown bear, the giant short-faced bear, and now also man, are rivals for food and shelter.
37:00The biggest of the three, the giant short-faced bear, will be wiped out.
37:18Yukon paleontologist Grant Zazula has a theory as to why this happened.
37:23It comes down to one critical design flaw.
37:34This weakness turns its enormous size into a deadly burden.
37:40The most striking feature of the short-faced bear skeleton is that it has this large, bulky mass on its trunk, its chest area.
37:47But when you look at its long limbs, they're incredibly long, but incredibly thin.
37:54These are spindly little legs.
37:57It's not something that can accelerate fast from a standing position,
38:01or something that can be running at full tilt and turn on a dime.
38:05So, predators today, and predators during the ice ages,
38:09needed to be able to have that explosive turning power and explosive speed
38:12to chase down the herds of bison and horses.
38:17In other words, unlike the brown bear, the giant short-faced bear cannot chase and catch prey.
38:28How does a giant carnivore that can't hunt source enough meat to survive?
38:34A short-faced bear would travel around the landscape using its highly evolved sense of smell to smell out the carrion,
38:44these carcasses of mammoths and bison.
38:47But those carcasses are also highly sought after by other predators as well.
38:54The lions, the wolves would have went after those carcasses for a free meal too.
38:58So the short-faced bear had to be highly evolved to be really big,
39:03so it could intimidate those other carnivores on the landscape, scare it away,
39:08and it had to look intimidating.
39:10So this was an intimidating creature.
39:11It was not built to fight, it was built to look scary.
39:14And that's exactly what it did when it got to its carcass and had to defend itself and defend its food.
39:18The giant short-faced bear wasn't a super predator.
39:25It was a super scavenger.
39:31Stealing the kills from other creatures.
39:36Early man sets a trap for his flesh-greedy rival.
39:49The question is, which will triumph?
39:56Rain?
40:00Or brawn?
40:06Rain?
40:33Rain?
40:34Climate is changing rapidly, the environment is changing rapidly, and then people show
40:54up and it seems like a combination of several of these different types of factors may have
40:59been involved in the extinction of these guys.
41:0610,000 years ago, the giant short-faced bear vanishes off the face of the earth.
41:19In Eurasia, the cave bear has dominated the animal kingdom for tens of thousands of years.
41:28Now it faces a new nemesis, early man.
41:34In this cold climate, man wants caves all to himself, but to get them, he must evict the
41:43cave bear.
41:45Seeing as that they lived in caves, there is a great potential for interactions with humans,
41:52and humans have had negative interactions with many of the other large animals that were around
41:56at the end of the late glacial period.
41:59So it's quite possible that the cave bear also fell prey to human hunters.
42:0910,000 years ago, in what is now Germany, early man has developed a new weapon in the war with
42:16cave bears.
42:18Around this time, cave bears vanish.
42:31Resourceful early man plays a role, but there are other factors in the cave bear's extinction.
42:38There have been some studies that show that they did start to incorporate more carnivorous
42:48material into their diet, so potentially that could have brought them into competition with
42:52other carnivores, and they could have simply been out-competed.
42:56They could also have increased their interactions with humans, as humans were also using the caves
43:01for shelter.
43:04Either way, we know that 10,000 years ago, man lived in caves, and the cave bear had been
43:14wiped out.
43:16Yet the smaller black and brown bears survive and flourish on both sides of the Atlantic.
43:26Today, the brown bear is the most widely distributed bear on planet Earth, and for good reason.
43:39It can eat anything.
43:41To kill prey, it develops a large hump of muscle behind its shoulders.
43:47It's been known to break the neck or spine of a bison with a single blow.
43:54But its reflexes are so well honed, it's quick enough to stomp on mice with its feet.
44:05Its powerful legs and balance mean it can run faster than most horses.
44:11But the brown bear's most dramatic transformation is arguably evolution's greatest story of all.
44:27The Arctic, 200,000 years ago.
44:40Brown bears regularly invade these icy wastes to hunt.
44:59The appeal is large, clumsy prey.
45:06Seals, walruses, and even the occasional trapped whale.
45:12Then, a sudden change of climate traps these brown bears in the Arctic.
45:25They try but fail to make it back to their natural grassland habitat.
45:33A population of grizzly bears becomes isolated from the rest of the pack, somewhere in northern Eurasia, in the Arctic regions.
45:44And they face a situation, they either evolve or they perish.
45:48Their problems are manifold.
45:52They are visible against the snow.
45:55Prey can see them coming.
45:57The fur is not designed for such extreme cold.
46:01There is little vegetation.
46:06Gradually, they start to die out.
46:10They have to figure out how to make a new way of life really fast.
46:16So this is rapid evolution at its best.
46:21To survive, it turns into a super predator.
46:30He evolves his nose to smell a seal, 32 kilometers away.
46:37A huge stomach.
46:38He can eat 20% of his own body weight in one sitting.
46:46And he becomes invisible to prey.
46:53The brown bear trapped in the Arctic evolves into the polar bear.
47:03Despite its appearance, the polar bear's skin is actually brown.
47:08The brown bear's skin is white.
47:10Each hair of its fur is transparent, designed to store heat.
47:16But the reflection of snow and sunshine makes it look white.
47:21It is strong enough to swim for 60 miles without taking a break.
47:28The journey it has made to get here is incredible.
47:37About 20 million years ago, the tree-dwelling dawn bear adapts to eat vegetation.
47:45vegetation. The panda evolves to eat bamboo. The sloth bear, ants and termites. The short-faced
47:57bear masters the plains. And this bear, the caves. The brown bear adapts to all these
48:06habitats and to ice. Having endured so much, six bear species are listed as
48:17vulnerable, threatened or endangered, as a result of human activity.
48:24The panda is running out of bamboo.
48:30The sloth bear is running out of space.
48:36And because of global warming, the polar bear is running out of ice.
48:46In recent years, faced with a lack of partners and shrinking ice, polar bears have begun to
48:53reverse evolution. Polar bears are mating with grizzlies to form a new bear, known as a growler.
49:03This growler was shot by a hunter in Canada in 2006.
49:09A growler is a hybrid between a grizzly bear and a polar bear. And it's maybe a new species,
49:17something of a new type of bear that we've never seen on Earth before.
49:22It's evolution in action. We're seeing it take place before our eyes. And it's not too often we get a
49:28chance to see evolution take place right in front of us. You know, the bears, they have a rich fossil
49:34history. Now we're seeing that evolution right in front of us taking place in the land in the north
49:39today.
49:51.
49:53.
49:57.
49:59.
50:01.
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