Documentary, Monsters Resurrected - Ep 5 Bear Dog -2009
#AncientEarth #Documentary #Dinosaurs #Prehistoric #Evolutionary
#AncientEarth #Documentary #Dinosaurs #Prehistoric #Evolutionary
Category
🐳
AnimalsTranscript
00:00We are reconstructing a monster.
00:07A combination of a lion, a wolf, and a bear.
00:13Visualize it as a dog on steroids.
00:18All rolled up into one invincible megabeast.
00:22You're just one ferocious animal.
00:28Amphysion in James.
00:33Bear Dog combines everything that's scary about most big predators today.
00:41Monsters resurrected.
00:46Bear Dog.
00:57The urban jungle.
00:59But this jungle exists in a parallel universe where evolution turned out slightly differently.
01:09There you go.
01:10There you go.
01:11What?
01:13What?
01:14You're a baby.
01:16You're a baby.
01:18Go.
01:19You're a baby.
01:21You're a baby.
01:22Fortunately for the Tigers, this animal has been extinct for a very long time, but 19
01:49million years ago, this ferocious carnivore was the terror of North America.
02:04It wasn't a bear or a dog, but rather a Frankenstein's monster made up of the deadliest killing parts
02:13of a dog, a bear, and a lion. For this reason, it was its own unique species, and for five
02:21million years, it was the apex predator of the continent.
02:31They have big sharp canines that can stab and kill like those of a lion, and they have
02:35big bodies that could probably move very quickly in short bursts.
02:40If we look at the size of the animal, the size of the skull, you have to visualize this animal
02:47as a super predator. This is a huge animal. The entire skull and skeleton are larger than
02:53any predator alive today, including the huge Kodiak bears, the largest living predator.
02:58As you see, the skeleton is almost ten feet long from the tip of the snout to the tip
03:04of the tail.
03:06To manufacture this monster, start with the head and muscular jaw of a large wolf. Something
03:13with long, sharp canine teeth. Then double its size. Put that huge, menacing head on the body
03:22of a grizzly bear and give it the bear's strong, robust legs with razor sharp claws. Then add
03:30a long tail and the manual dexterity of a lion. When we put it all together, we end up with
03:37one of the most lethal killing machines in natural history. A giant alpha predator, the
03:44like of which we have never seen before or since.
03:47The bear dog was like the NFL lineman of its time. Huge, fast, powerful. Except it also ate you.
04:01Bear dogs were carnivores belonging to the suborder Caniformia or dog-like animals.
04:08However, bear dogs were not part of the dog family, but a separate branch of the evolutionary tree
04:14called Amphysionids.
04:18So you have to picture the sort of bear-like skeleton and then you put a dog-ish head on
04:23this animal. So it's a relatively large head, but it has a set of teeth that like dogs is capable of
04:31both doing some slicing of meat and some crushing of bones. So they're kind of a jack of all trades
04:36kind of animal. And it is these adaptations that make the giant bear dog a super predator.
04:46But the bear dog wasn't the only predator around. He had some deadly competition and there could only be
04:54one winner.
05:05North America 19 million years ago. A new breed of carnivore has appeared on the continent.
05:13It's a vicious immigrant from Eurasia. Amphysion Injens, the giant bear dog.
05:24What strange evolutionary path could have created this mega beast?
05:41To find out, we must resurrect the bear dog. But we have a problem.
05:46Giant bear dog fossils are so rare that there's only one complete skeleton in existence.
05:54This is such a rare animal. If you found any part of it all, it would be a major find.
06:00It's something you would add to that very, very small collection of these things that are known so far.
06:05Because they're known from such a limited number of places right now.
06:09With so few fossils to work from, putting the flesh on the bear dog's bones presents a challenge.
06:16It would have looked more or less like a bear, but with a little bit funnier head with a longer snout.
06:24However, with bear dogs, it's not a case of one size fits all. In fact, some species were as small as a fox.
06:32But the largest known individual species of the North American bear dog is Amphysion Injens.
06:38And it was huge.
06:44All right, let's get up. Come on, get up, get up.
06:47Good, good. So to give you some idea of scale, I'm 6'3". This grizzly bear is about eight feet tall.
06:54And a bear dog is another foot above that.
07:00Jesus. Okay, got it.
07:04He's 6'50 pounds. A bear dog's 900 pounds. You don't want him leaning up against you.
07:11Amphysion, the giant bear dog, wasn't native to North America.
07:16It was an invader sweeping in from Eurasia during the Miocene Epoch, about 19 million years ago.
07:25Scientists believed that it traveled to where the food was, literally eating its way across two continents.
07:34There were plenty of prey to choose from, for this was an amazing period in history.
07:38The Golden Age of Mammals, a time when a wide variety of creatures roamed throughout the world.
07:46At the time, the American Northwest was a vast prairie similar to the African Serengeti today.
07:54We're developing grasslands, open country for the first time.
07:58Groves of trees here and there, and in between, sort of an African savanna-like environment.
08:04The grasslands were a meeting ground for a wide range of prey animals.
08:13A walking food store for an opportunistic super predator.
08:19We're very near the peak of mammalian diversity, when we had the maximum number of species on the
08:24landscape and some of the largest things that ever existed.
08:27And the giant bear dog had a wide range of weapons to attack and kill.
08:39Such as powerful but short forelinds, capable of lightning quick bursts of speed.
08:47Maneuverable paws with long menacing claws.
08:51An enormously strong jaw.
08:53And of course, razor sharp teeth.
08:57All designed for one purpose.
09:00To kill.
09:06Look at the front end of this animal has really, really large upper and lower canine teeth,
09:11which are the slashing teeth, the biting teeth it uses to grab prey, stab it and pull it down.
09:16Almost all the rest of the tooth row here is these back teeth, which are huge compared to
09:24most other mammals you would find in this time, especially this big tooth right here called the
09:28carnassial. And these are the teeth they used as like scissors to slice up flesh and cut up the
09:34meat after they've torn it apart. The striking thing you see about the skull is this huge ridge
09:41over the top of the brain case called the sagittal crest. This supports gigantic jaw muscles that ran
09:47down from this crest and down in the gap here and attached to the lower jaw and pull the lower jaw up.
09:54So this would have given it a very strong bite force for the size of this skull.
09:58It allows them to kill things the way we see grizzly bears kill things today, which is often
10:12with a massive swat that knocks the animal over and then they can place their killing bites wherever
10:17they want. But how does that work in reality? When you're talking about the tools of a bear dog,
10:24have a look at this grizzly bear's paw, just like a bear dog's. Now, this can be used just like a big
10:30sludge hammer. If it gets too close to its prey, boom, it's going to come down, use all of this power
10:35here and just knock it down, knock it out and start eating.
10:39Five claws. These claws, ripping, tearing and oftentimes just slugging. Look at the back of this, all power.
10:58One big swipe, it's down and out and it's dinner.
11:02And like the modern day bear, the bear dog had a super sensitive sense of smell.
11:09It has a reasonably long snout. And when we look at the snout, we can tell that it probably had
11:15a pretty good smelling apparatus. And so it probably hunted after prey based on smelling it from a long
11:22distance away. From everything we know about the bear dog, their senses are very similar to a grizzly bear.
11:29They have six million times the smell power that we have. And then that's just honing on,
11:34where can I get my next meal, using their ears, see if they can hear something going through the bush.
11:38When they go up, they want to see what's around them. They'll get up on their haunches,
11:42they'll start sniffing around, start using their eyes, looking around and their ears. And all of that
11:48is just focusing on, where can I get something to eat? And then once they find it, this is just like a
11:54a 600 pound missile.
12:00And when it first entered North America, the giant bear dog was definitely the new beast in town.
12:07It cut a killing swathe through every prey item in its path.
12:23However, bear dog wasn't the only killer roaming the continent.
12:38Meet Dino Hyas, also known as the Terminator pig.
12:43This is Dino Hyas, the biggest pig of all. Its skull is over a meter long.
12:52This ferocious beast was like a wild boar on steroids.
12:56Think of a razorback hog that's the size of a bison. And now you give it all the attitude to that
13:01razorback. It is an extremely impressive animal. And that's where that term got coined, the Terminator pig.
13:09It was a true monster, bigger and meaner than the bear dog. It ate what it wanted, when it wanted.
13:18Dino Hyas walked into the area and it was in charge. It was probably the king of all it surveyed.
13:27And those teeth, absolutely enormous.
13:30These incisors that are very large and then these enormous, enormous canines. And this is for biting
13:39and pulling off parts of a carcass or any other food. These premolars, extremely large, very thick
13:46enamel, crunching, breaking, mostly just breaking things. Imagine a bone in there just being broken
13:52in half. Nothing has had teeth that big before.
14:07If it was hungry, it would kill meat and it would eat it. But if there's already a carcass laying on
14:12the ground, it didn't matter who was on that carcass. Dino Hyas came up and said, it's mine now.
14:17I visualize it more as sort of the garbage collector of this grassland savanna,
14:22as the first animal that could go in and could claim any carcass that it wanted. Sort of the bully
14:29on the block. There wasn't anything quite like Dino Hyas. Even a big bear-sized amphicryon
14:37by itself would probably have been intimidated by Dino Hyas.
14:40Dino Hyas belonged to a family of mammals known as entelodonts, huge pig-like carnivores that were
14:50over two meters tall to the shoulder, as tall as an American buffalo.
14:56This is an entelodont specimen that was discovered about 100 years ago. It is a fantastic skull. There's
15:03been a few bones and teeth found of this animal, but this is the only skull like this. It's a one of a kind.
15:08The startling thing is, this huge skull came from a medium-sized terminator pig,
15:15and it is still larger than the skull of a fully-grown crocodile.
15:20Entelodonts could open their jaw amazingly wide, amazingly wide. Now remember,
15:26they have these big fangs here, these huge, huge teeth. And with these huge teeth,
15:31they have to be able to open their mouth up large enough to get a part of a rhinoceros carcass in there.
15:35That's a lot of food to get into that mouth. We see similar things happening today with some
15:40reptiles. Crocodiles have to open their mouth very wide. The terminator pig was in no danger
15:47of biting off more than it could chew. Its jaw was as big as its appetite and evolved for maximum
15:54effectiveness. Well, when an animal has its jaw that wide, it gets popped in the jaw. It's going to
16:01dislocate the jaw. It's very, very dangerous for the animal to open its mouth that wide,
16:05unless you have a bunch of muscles stabilizing it from the side. Now, the only way to stabilize
16:11muscles from the side is to have something out like this cantilevered out to bring the muscles in.
16:17And what this allowed for was stabilizing the jaw while it was open. And the reason is so it could put
16:25big food in its mouth. A comparison of the skulls shows how much of an advantage in size the terminator
16:35pig had over the bear dog. This is a bear dog skull about 45 centimeters, nearly three times the size of
16:44a human skull. And this is a giant terminator pig skull. At nearly a meter long, it's twice the size of
16:52the bear dog skull. But even though its skull was huge, the terminator pig did not have a large brain.
17:00They weren't too bright, were they? They had a pretty small cranial capacity. We overplay how small
17:06their brain was. Now, it has a small brain compared to its skull. But when you look at the overall body
17:10size of the animal, we find that the brain is comparable to other animals. Like a hippo, like you said.
17:16Such as hippo, such as other animals. It still wasn't a real bright animal.
17:23A giant bear dog would have to rely on its own wits and weapons if it encountered a terminator pig.
17:31It could menace the pig, nipping at it, circling, swatting, jabbing. But it would be hard pressed to
17:40outfight the pig head to head, jaw to jaw. For now, the bear dog would have to bow to the terminator pig.
17:50But evolution would eventually give the bear dog the upper hand. However, success would ultimately lead
17:58to catastrophic failure.
18:10Let's go.
18:20Let's go.
18:32Let's go.
18:36Let's go.
18:40Let's go.
18:44Let's go.
18:46Let's go.
18:49In today's world, the giant bear dog would be a dangerous predator and scavenger,
18:55much as it was in its own time around 18 million years ago.
19:02Its only competitor on the continent is Dino Hyas, the terminator pig.
19:16The terminator pig's size and ferocity make it nearly invincible.
19:25But evolution gives the bear dog an advantage.
19:29Over thousands of years, it has been getting bigger, stronger, and more aggressive.
19:34As time passes, Amphysion grows into a true mega beast.
19:39This dramatic growth can be seen in the fossilized teeth from the giant bear dog and its older relatives.
19:51Let's compare the size of some of the earliest Amphysion-like animals.
19:56This is from a specimen about 28 million years old.
19:59That's an awfully small animal.
20:00Yeah, you know, and this is about the size maybe of a small fox, jackal size kind of thing,
20:05compared to our big Amphysion friend. Let's compare the same teeth again,
20:11and we see a huge size increase in Amphysionids as we go through time.
20:16It's a general trend. It's a small bear dog and a big bear dog.
20:19And this is still a bear dog, but it's just a little bitty guy.
20:22It's pretty obvious, you don't have to figure this out too hard, that there's a big size increase
20:27through time.
20:28We see this over and over again in the history of carnivores. They tend to get larger over time.
20:39The bear dogs get enormous. One huge, huge animal, but incredibly ferocious,
20:45way more ferocious than a bear even. There's no question this is a big, massive animal. But one of
20:51the things we forget when we look at skeletons is that you're just looking at bones, and bones are
20:55great. But on top of the bones, you also had muscle, some fat, some skin, some fur.
21:02So when you look at this skeleton, you see something that's this tall. But when you add
21:05all the soft tissue, you're talking about an animal who was like this big at the shoulder.
21:11So this was a really massive animal.
21:16The Terminator pig's tremendous size is no longer an advantage,
21:21especially when it comes to competing for food.
21:29Over time, you can imagine those bear dogs getting crafty, getting smart,
21:32and maybe coming in and stealing that food.
21:36The balance of power has shifted. After a million years of competition,
21:41the fearsome Terminator pig becomes extinct.
21:48After dominating North America for millions of years, Dino Hias has finally been overwhelmed.
21:55I don't think that there's any evidence that would suggest that Amphysion caused the extinction of Dino Hias.
22:11But it's very possible that once Dino Hias disappears, it does open up a great ecological niche,
22:17as far as sort of being the garbage collector on the grassland savannas,
22:21that a large Amphysion could have filled very easily.
22:27The giant bear dog is now the apex predator on the continent.
22:32Certainly, if you look at the variety of different types of carnivores
22:37that are on the landscape at the time, immediately after the extinction of Dino Hias,
22:42bear dog is going to be one of the largest.
22:45But size isn't everything.
22:47What made this Frankenstein's monster of carnivores such a deadly hunter?
22:52A unique set of fossilized tracks allows us to answer this question.
22:58This 15 million year old bear dog trail, found near Barstow, California in 1960,
23:05is a forensic path to tell us how the giant bear dog hunted and killed.
23:10Trackways are exciting things.
23:11Okay, paleontologists like to study skeletons because that's what we get.
23:14But every once in a while you get lucky and you find what we like to refer to as the smoking gun
23:19of an animal's behavior. And that's what trackways are. Okay, so for instance, the trackways here
23:24are separated by a distance that tells us how quickly it was moving. And in this case,
23:30what we find is that the distance between the prints is about the same as the distance
23:33between the limbs. So it's meant this animal is actually moving in a pretty good clip.
23:36If you take a look at the feet of Amphysion, you can see that it's up on its toes.
23:43It's up on its toes like that. That's sort of like a cat or a dog. When you're up on your toes,
23:47we call that digitigrade. If you're flat footed like a bear or like us for that matter,
23:52it's called plantigrade. Well, this animal is a little bit in between. So this is an animal that did
23:57run up on its toes. It wasn't flat footed like us or like a bear. It was sort of like a fast moving
24:04big football player. Altogether, this animal is an animal that is a combination of some of
24:11the best features of both fleet footed dogs and powerful bears. But the bear dog was not built for
24:19a pursuit. Take a look at the length of the upper arm bone, the humerus, and compare that to the length
24:26of the forearm bones. What you see in very fast moving animals is that the humerus tends to be
24:31significantly shorter than the forearm or the hand. We don't see that in a bear dog, okay?
24:37In Amphysion, what happens is that the humerus and the forearm, okay, the upper arm and the forearm
24:43are about the same length. And because of that, we know it could move moderately quickly, but not as
24:48quickly as, say, a cheetah or a wolf or something like that. This is an animal that could move quickly,
24:57probably in short bursts, but it wasn't a super high speed sprinter.
25:02One of the things that's important about locomotion and movement is that it's not just
25:08limbs, it's the entire body. And when we look at the way, especially the way carnivores move,
25:13is that we look at the backbone. If you look at the backbone, you can see some of the spines in
25:17the front angle back and some of the spines in the back angle forward. And so there's got to be a
25:21point where those spines angling back and those spines angling forward come together. And that's
25:25the spot right there. And that vertebra has a particular name, we call it the anticlinal vertebra.
25:30The anticlinal vertebra is an indicator that this was an animal with a moderately flexible backbone,
25:35and that's an indicator of an animal that can move fairly quickly. Animals that bend their back
25:39can run fairly quickly. If you were to look at something like a cat or a dog, they'd have a really
25:44tiny anticlinal vertebra, right? This animal has one, but it's not that tiny. So it was an animal
25:51that could run, but not quite as fast as, say, a cat or a dog. It's not built for very fast running,
25:58especially compared to something as fleet as a gazelle like camel or three-toed horse. This animal
26:04more likely would have stayed in the bushes and ambushed a prey item by rushing out from a game trail
26:09and knocking it down and grabbing it and killing it. It was not going to be able to outrun it for
26:14very long distances any more than a lion can outrun zebras or wildebeest for very long distances.
26:23In this respect, the bear dog was similar to a modern lion.
26:29In order to understand how this hybrid functioned, we need to bridge the gap between species.
26:35Animal trainer and zoologist Dave Salmoni has worked up close and personal with some of the most
26:41dangerous predators on the planet.
26:45All right, hey! Cut it out! Cut it out!
26:49Dave has experienced firsthand how large predators such as lions hunt and kill.
26:55Hey! Hey! That's enough out of you! Get out of here!
26:59There's a big difference between working with a lion and a bear. The biggest difference is that
27:03a lion is a true predator. They're just an opportunistic animal that's always looking
27:08for their opportunity to get a meal. Everything we know about the bear dog suggests that the bear
27:14dog was an ambush predator. Now, a lion, when he's by himself, that's exactly how he hunts. You're
27:19talking about an animal that was just lion weight. So an animal like this is just out there constantly
27:24keying on something saying, can I eat it? And how can I kill it? And that's what the bear dog was like.
27:30A bear dog is a big, big animal and super fast, but only over a short period of time. It takes a
27:37lot of energy to move that much weight over a distance. He sits there and he waits and no one's
27:43going to see it. Once he figures, okay, I've got that animal within 20 feet, he launches his attack.
27:51And that launch comes out like a shotgun coming at prey that won't even know it's there until it's already
27:57on the ground. And once those teeth sink into that flesh, it's all over. The animal's not getting
28:05away and it's dinner time. With the terminator pig gone, the bear dog was free to terrorize the
28:14North American continent. Nothing could stop it.
28:23But there were other contenders for the throne. Bear dogs fought each other both for territory and mates.
28:31All carnivores engage in territorial behavior. So amphiccyon for sure would have had a territory.
28:40And we do know that in amphiccyon, it's in general, they often show what we call sexual dimorphism,
28:47which one sex is different in some way from the other. And in this case, the males are larger.
28:51That suggests that the males were competing for females.
29:02And neighboring males might battle for those females occasionally. And sometimes probably the
29:08younger or smaller one, the weaker one in any case, would lose and often die. These are usually to the
29:14death. An animal this large encounters another bear dog this size. They probably have been in a pretty
29:20amazing fight. These animals probably can inflict serious damage on one another if they chose to go
29:25all out. Other than its own kind, the bear dog had hardly any rivals. With its territory secure,
29:35the bear dog had free reign over the Miocene landscape. It could catch and feast upon the bountiful prey.
29:44But the bear dog had one weakness. It was a solitary beast. It hunted alone.
29:59However, there was safety and species survival for animals that hunted in packs.
30:07This creature, a native of North America, was an evolutionary grandfather to modern dogs and wolves.
30:14Its scientific name is epicyon. But it is commonly known as the true dog.
30:21These are large wolf-like canids. And the largest species was definitely as large and probably larger
30:27than the largest wolves we have today. Epicyon was a more specialized carnivore than the bear dog.
30:34It had a huge head and powerful jaw with razor-sharp incisors and canines and bone-crushing molars.
30:43It was a pure meat-eater and a natural killer.
30:46And it had one more killing advantage. The other thing about epicyon that was really different from
30:55amphicyon is almost certainly epicyon was social, ran in packs.
30:59It would have given the true dogs a tactical advantage in any confrontation they might have had with a bear dog.
31:08When you're in an ecological environment for a couple of million years together,
31:14there's bound to be some time when you're going to run across one another.
31:19I think both animals more or less avoided each other, but certainly they ate the same kinds of prey.
31:27They would have likely encountered over a dead carcass.
31:30Now and then, when one or the other scavenged something that one or the other killed, they likely
31:37were interacting. And I guess you could say that they were annoying one another at times.
31:42Just like today, in Yellowstone National Park, we have bears and wolves. It was that kind of a
31:49relationship in many ways between amphicyon and dogs that were around.
32:08Wolves today work as a team to kill animals much larger than themselves.
32:14If the bear dog was the big bully, the true dogs were the gang.
32:19One against one, the bear dog was better equipped to catch and kill large prey animals.
32:30A pack of true dogs, however, wouldn't hesitate to steal a carcass from a bear dog.
32:38The bear dog was about twice the size of the true dog and could easily kill one with a single swipe.
32:44But several true dogs attacking at once presented a big problem.
32:49The bear dog would be simply outnumbered.
32:53I think true dogs could have stolen from bear dog pretty easily most of the time if their
32:58group size was large enough. So here you have this social, highly carnivorous, aggressive animal
33:04animal, moving around in groups and a single amphicyonid is going to have to deal with these.
33:10So these were two species that were on a collision course. And only one would win the ultimate battle.
33:24For four million years, Amphicyon, the giant bear dog, and Epicyon, the massive true dog,
33:40lived side by side in northwestern America.
33:42But it probably wasn't a peaceful coexistence.
33:51As the competition for food grew more intense, the true dogs may have resorted to a brutal
33:57means to eliminate their rival.
34:04Paleontologists have found evidence that small species of bear dogs, like their modern
34:09counterparts, use dens for their litters. If so, Amphicyon may have used dens in a similar fashion,
34:17which may have been a fatal flaw.
34:19The thing that's interesting about dens and denning behavior to a paleontologist,
34:25this is another example of one of those smoking guns. If you find a den, that means you know a
34:30little bit about how it protected itself or how it cared for its young.
34:33The females probably had litters that contained maybe two to four individuals,
34:39and they probably excavated a den or used a den of another animal to hide their young in while they
34:45went hunting so that the young would be safe from other predators that might come around and
34:51decide they looked pretty tasty. True dogs may have gone after the most defenseless
34:56members of the bear dog species, the pups.
35:07There is a modern day precedent for this shocking behavior. The gray wolf faces a variety of competitors
35:14for food, among them coyotes. But the wolf is not fast enough to catch a coyote. So rather than hunt
35:22adults, it goes after the pups.
35:30The wolves actually excavate the dens and kill the pups within while the parents are off to the side
35:36yelping and trying to do whatever they can, but it's pretty hopeless when there's five or six wolves
35:40going after your pups. They don't eat them generally, they're just killing them to eliminate a competitor.
35:47These kinds of competitions between carnivores are very much a part of their life in an evolutionary
35:53sense and in an ecological sense. And I think it's very important in driving the evolution of
35:58carnivores is the interactions between them, both over carcasses and the fact that they actually
36:04seek out and kill the young of each other or the adults.
36:19And I think it doesn't make itzy I'll to judge you better tell anyone.
36:29Oh, crazy!
36:30No!
36:35Oh, man.
36:41Oh, crap!
36:41Bye!
36:45Love you!
36:47Confronted with the superior hunting and killing tactics of the true dogs, the bear dog's survival
37:02is at stake.
37:08As with the terminator pig, the bear dog's larger size is no longer an advantage.
37:14There's obvious reasons why you'd want to get big, you can beat up more individuals,
37:20you are able to take a wider range of prey, you can dominate carcasses more easily.
37:26But there are disadvantages to getting big.
37:29And that disadvantage is that as you get big, your population size of a species gets smaller.
37:37If you have fewer individuals, you're more vulnerable to random events causing extinction.
37:42It could be disease, it could be climate change, it could be the disappearance of your favorite
37:46food item for whatever reason or the introduction of a new competitor.
37:51The second big disadvantage of getting large is you have a greater need, absolute need for
37:57food resources per day.
38:00If you're quite large, you may have trouble getting enough food to sustain yourself.
38:06Size matters, and size can dictate a vicious cycle that ends in species extinction.
38:13The bigger you are, the more food you need.
38:15And of course, they're mammals with a very high metabolic rate.
38:19It's almost like a runaway train morphologically.
38:22You get bigger and you need more food, you get more food, you can get bigger.
38:25There's an advantage to being bigger, you win all your fights.
38:28And you have very few enemies.
38:30On the other hand, you have to serve that body.
38:36Once you get to a large body size, you have a higher probability of going extinct.
38:42And Amphysion with its large body size, that may have been one of the contributing factors
38:47for it going extinct about 15 million years ago.
38:55But finding food is getting harder.
39:00The largest bear dogs need as much as 50 pounds of food a day, which isn't easy to come by
39:05because the North American ecology is changing.
39:11The grasslands are turning into treeless prairies, depriving the bear dog of the cover it needs
39:16for ambush.
39:19But it isn't about survival of the fittest, it is all about survival of the most agile.
39:26The prey items like the camels, the horses, the pronghorns are all much faster and longer
39:30legged.
39:31They may have been harder to catch.
39:32It's likely this thing was no longer as efficient or predator as the one when it first arrived.
39:38Relying on its age old ambush tactic, the bear dog awaits its chance.
39:43This time, the prey is a step quicker and gets away.
39:49One more missed meal.
39:51One more step towards extinction.
39:54As the prey changes, the predators need to change with it.
39:58And sometimes they change successfully as the Amphysionids did early on, and sometimes
40:03they don't change successfully.
40:12The bear dog is being squeezed by the more modern creatures it resembles, the true dogs
40:19and the bears.
40:23They go extinct just about the time that we see the first real bears appearing in North America.
40:29So here are some animals that are more specialized for plant-eating and omnivory on one side
40:34of Amphysionid.
40:35And on the other side of Amphysionid, they've got these large wolf-like animals that are more
40:39specialized for hunting than an Amphysionid, who was the jack of all trades in the middle.
40:46As the bear dog is pressed from both sides, its population dwindles.
40:54In this numbers game, it's only a matter of time before the bear dog is history.
41:02A lot of people think that this animal probably was out-competed at the time that it died out,
41:08because after five million years, more advanced predators had come into the scene, and the
41:12prey items, of course, were harder to catch.
41:16It's likely this thing was no longer as efficient as predators when it first arrived.
41:21Why didn't Amphysionid evolve into something else?
41:26Why did the last ones disappear?
41:28That's a good question.
41:30There are so many possible reasons why they went extinct.
41:34It certainly wasn't a failure to be adapted to their environment in and of itself.
41:38We might argue that they over-consumed their available herbivores that they were preying
41:45on, but we know that's not the case.
41:47We know there is an ample supply of things like corn runes, camels, all these kinds of
41:52things.
41:53We know that's there.
41:54Why did Amphysion go extinct?
41:56We really don't know.
41:58And that's always the million dollar question of paleontology.
42:03Why did something go extinct?
42:05We can look at the ecology, we can look at the climate, or we can just simply think about
42:10it going extinct because of it being an old species that had been around for many millions
42:16of years.
42:17It could have been any of a number of different factors that contributed to the demise of the
42:22bear dog.
42:23What's important to remember is that they were around for a long time.
42:27Human beings, our lineage has only been around for about four million years, and the lineage
42:31that led to bear dogs was around for a lot longer than that.
42:33So we shouldn't think of them as a failed experiment.
42:36We should think of them as a very successful group for a very long time.
42:45For five million years, the enormous, ferocious, giant bear dog ruled North America.
42:51It came as a hostile intruder and exploited the food resources of its new home, growing beyond
43:02its capacity for survival.
43:05Every apex predator occupies a vulnerable position at the pinnacle, whether it's a bear dog or a
43:12human.
43:13The bear dog's time at the top has been and gone.
43:18It is now a collection of fossils and bones.
43:22And we are currently the apex beast, ruling this planet.
43:29But for just how long?
43:31We are now on start.
43:40By getting pooped.
43:43Let's go now.
Comments