Horizon (1964) s40e14 Episode Script

They say this is the most savage killer ever to have walked the earth.
With teeth that could have sliced through steel.
Jaws that could have crushed a car.
They say it was a six tonne, twelve metre long killing machine.
Or could they have got it all wrong? Now one scientist has uncovered evidence that tells a very different story.
He claims the king of the dinosaurs wasn't a hunter killer at all, but a stinking lumbering scavenger.
He says T.
rex was not a warrior but a wimp.
Could he possibly be right? Horizon investigates the science that's challenging the legend.
Tyrannosaurus fever has infected people all over the worid for generations.
Children in particular seem to know more about - Rex than any other beast, alive or dead.
Because they're fascinated by its viciousness.
Extinct for over 65 million years yet T-Rex lives on, a ferocious killing machine.
A tyrant monster we all love to hate.
The king of killers.
From the moment it was discovered in 1902, palaeontologists were agreed T-Rex must have been a ferocious killer.
Yet the truth was it was all based on very little evidence.
All scientists could tell from the twelve meagre specimens they had was that T-Rex had a formidable physique and enormous jaws.
And exactly how deadly it was remained a mystery.
To fully understand the beast, palaeontologists needed to get their hands on the perfect specimen.
Only that way could they really know just how fast or strong or vicious T-Rex was.
The search was on.
Enter palaeontology's bad boy.
This is Pete Larson, dinosaur expert and fossil hunter.
Palaeontologists don't like him, for one big reason, he digs up fossils for money.
But in thirty years dinosaur hunting he never dared dream he might be the one to find the T-Rex the worid was waiting for.
To Larson and his then girlfriend Susan, he 12th August 1990 was a day like any other.
We were out actually digging on a Triceratops skull that my ten year old son Matthew had found.
And we were just having a grand old time, it was a very, very nice small Triceratops skull.
And all of a sudden Susan walks, walked up with a couple of bone fragments.
And I said is there more, and she said there's lots more.
Nothing could have prepared them for what they'd found.
I looked up the face of the cliff and I saw an expanse of about eight feet wide and perhaps two feet deep with bones jutting out everywhere.
And as I crawled up to the top of the, this exposure, I saw three articulated vertebrae.
I knew that they had to come from a T-Rex because of the size of the curve of those bones, they were obviously parts of vertebrae from a meat eating dinosaur.
And when I saw those three articulated vertebrae I knew this was going to be the most important specimen I had ever dug up, I just knew it.
Pete Larson marvelled at the size of the partially exposed killer dinosaur.
And nicknamed it Sue, after his girlfriend.
It was like clawing our way to the top of Mount Everest.
And as we were uncovering it we could see the top.
And as we got her out of the ground we were there, we had climbed the Mount Everest of palaeontology.
We got the biggest, baddest of all the T-Rexs that ever was.
And it got even better.
Sue was extremely well preserved and nearly complete, exactly what Pete Larson had dreamed of finding.
At long last here was a chance to study the worid's ultimate killing machine in extraordinary detail, and all from just this one specimen.
Then for Larson at least the dream turned to a nightmare.
Two weeks later I got up in the morning and was taking a shower and one of our employees knocked on my bathroom door and said get out here, this place is surrounded with FBI agents.
And I walk out and literally there are 35 FBI agents with guns.
Yellow police tape all over the place.
And they had a search warrant demanding the surrender of the T-Rex known as Sue.
The US government threw the book at Larson for taking the T-Rex away without the right type of permissión.
Larson countersued sparking the first ever legal battle for custody of a dinosaur.
While the lawyers wrangled the worid's most important dinosaur was impounded, beyond the reach of science, incarcerated in a basement store room.
Four years later Pete Larson was found guilty of minor offences, unrelated to Sue.
From that conviction I was sentenced to two years in prison and two years probation.
With Larsen behind bars Sue went under the hammer.
It's in the room, on the phone at seven million six.
Seven million six hundred thousand.
The big money behind the purchase, donated what was now the worid's most expensive dinosaur, to the prestigious Field Museum in Chicago.
At long last everyone could admire this most perfectly preserved T-Rex.
Now too palaeontologists could study its every bone.
Science had waited almost a century to find out for real what the worid's most feared predator was capable of.
The wait was over.
And Sue didn't disappoint.
What was T-Rex like as a living animal? It stood approximately twelve feet at the hips.
The top of a T-Rex hip would be about there.
It was approximately forty feet long in an adult.
That's longer than a double-decker bus.
- Rex may have weighed as much as six tonnes, like these two ladies here combined.
That kind of muscle could have defeated anybody.
Look like a, you know a gigantic scaled up, you know, roadrunner from hell.
A roadrunner that was twice the speed of the fastest man.
I think if we'd met T-Rex we would have been blooming frightened of him.
All this added up to one thing, - Rex was every bit as deadly as they'd always thought.
And because Sue was almost the perfect specimen, scientists couldn't wait to dig deeper and find out precisely how this monstrous killer went about its deadly business.
The man charged with getting in to the killer's mindset was Chris Brochu.
One of the first things he wanted to discover was how good was its sight.
Because eyesight is often critical to how a predator works.
A predator's power lies in its eyesight's ability to spot prey long distance.
He can then guide it with pinpoint precisión to the kill.
Keen eyesight is a hallmark of a master predator.
Too heavy to be mounted on its skeleton, Sue's real skull had been encased behind glass.
This is it, this is Sue's skull.
Skulls really are a thing of beauty when you look at them.
There is a lot of delicate structure here that you might not appreciate if you just think of it as a big powerful Tyrannosaur.
In terms of the senses, the eye would have been pretty much where that hole is there.
It would have faced a little bit forward, and not just out to the side.
They did have an improved amount of depth perception and ability to judge distance compared to their earlier relatives.
At first glance the large forward facing eye opening in the skull suggested T-Rex probably had keen eyesight.
But to be sure Brochu had to do more than examine the skull from the outside.
He had to get inside the head.
And to do that he needed the latest technology.
Basically when it comes down to it I was told to describe the thing inside and out.
I took that literally, I knew they wouldn't let me break the skull apart, so CT scanning is the answer.
CT scanning is an advance X-ray imaging technique.
It allowed Chris Brochu to build up computer images of slices through the head, which he moulded together to produce a three dimensional likeness, of a T-Rex skull.
Then painstakingly, millimetre by millimetre, he followed the contours on the inside of this skull to reveal the structure of a T-Rex brain.
The first time I saw the individual slices themselves they didn't seem all that exciting, it wasn't 'til I built the first animation, the first flip through a bunch of slices all going through the skull, that was when it really struck me that there were a lot of things here to see.
It turns out we got really good data, we got great data.
The CT scans revealed something scientists had never before been able to see in such detail.
Protruding from the delicate network of brain tissue was the optic nerve.
This nerve was responsible for relaying information from the eyes to the visual centres in the brain.
And it was big enough to carry a lot of information.
The scan seemed to confirm T-Rex did indeed have a key attribute to a skilled predator.
It would have been able to seek out its prey at a distance, and destroy it with the accuracy of an assassin.
Having established how this hunter tracked down its prey, scientists turned their attention to how it would have killed it.
Just how powerful was the strength of that bite? The first place they began to look for clues were the jaws.
But not T-Rex jaws.
Greg Erickson is an expert on crocodilians, the animal group that includes crocodiles and their cousins the alligators.
Erickson has studied the animals at the St Augustine Alligator reserve in Florida for 10 years.
And likes to get up close and personal.
Latcha, Latcha, Latcha.
Erickson studies crocodilians so he can find out more about T-Rex and the dinosaur family to which it belongs, the theropods.
Gators and crocodiles make a great model for studying the feeding biomechanics of extinct theropod dinosaurs, they have very similar musculature, and just the basic leverage of their jaws and things like that are actually just a good analogy for Tyrannosaur feeding.
The similarity between crocodile jaws and T-Rex jaws makes these animals ideal for Erickson's research.
But it also makes them very dangerous.
Ok grab that pole.
Watch, watch your feet, watch your feet.
Remember she can run forward.
One, two, three, Go, go, go.
Watch your feet.
This is a female American crocodile, Stevie.
A youngster at thirty one years old, she's only half the size she could become.
She may be small but her strength is obvious.
Back up, back up, back up, back up, back up.
It's Erickson's job to try to persuade her to take part in his research.
Because her jaws are thought to work in a similar way to T-Rex jaws, Erickson plans to measure her bite to see what it may reveal about the power behind a T-Rex bite.
Yet as she's small, and he's not tested her before, he has no idea what kind of results he'll get.
Pull the leg out of that.
First Stevie is gently restrained.
Her keeper covers her eyes, because it not only keeps her calm, but will prevent her biting too soon.
Erickson needs to get the crocodile to crunch on to a specially designed pressure sensor, which will record the force of the bite.
The tricky bit is getting the timing right.
The bite needs to be a spontaneous one.
Here we go, hang on.
Eight hundred and nineteen pounds, good bite.
Stevie's bite results are impressive.
We registered a very aggressive defensive bite from this American crocodile.
I think the highest force we had was 820 pounds, which is you know is an incredible amount of force.
It's a remarkable bite, especially considering she's not even fully grown.
An eight hundred pound bite is comparable to what a lion can do, or a spotted hyena which is the bone crushing champion among mammals, so a very small crocodilian is capable of doing bite forces equal to what, you know some of these large carnivorian mammals do.
If you matched up an equal sized crocodile say to a large lion, the crocodile will bite probably three times more forcefully.
Watch your legs.
If jaws like these give crocodiles a bite force well above what their weight implies, then Erickson believes the same must have been true of T-Rex jaws.
Nice canine on this one.
His work suggested the power of a T-Rex bite may have been on a scale beyond anything we have ever seen.
It's not a natural thing to stick your hand inside the mouth of a crocodile but.
Perhaps you shouldn't try this at home kids.
To get an idea of how much more powerful Erickson worked on doing more than just scale up the bite.
Snout width is fourteen point two.
He measured every physical detail of his crocodiles to try to map the differences in skull shape and body weight compared to an animal the size and shape of a T-Rex.
Fifty point two.
Erickson's preliminary maximum estimate of a T-Rex bite could be as much as forty thousand pounds of force.
That's about fifty times more powerful than our crocodile.
- Rex would have had easily the most powerful bite of any animal that has ever lived.
So all those movies seemed to have got it about right.
Scientists' first assumptions about T-Rex appeared to have been proved correct.
The facts were every bit as shocking as the popular fiction.
With a predator like this around it would seem this Triceratops didn't stand a chance.
- Rex, the most feared creature ever to have walked the earth.
But there's someone out there who thinks they've got it all wrong.
Someone with a completely different view of T-Rex.
This is Jack Horner, one of the worid's most respected palaeontologists.
He's a man used to standing out on his own.
In a worid of T-Rex fanatics, Horner is unique, he doesn't even like the beast.
Palaeontology is one of those kinds of sciences where you actually end up studying what you can find.
I went out looking for duckbilled dinosaurs about five years ago and started finding nothing but T-Rex, and so I just kind of got, I guess I got kind of lured in to the, lured in to the mm, T-Rexs, I don't like them much.
Jack Horner was lured in to the murky worid of Tyrannosaurus Rex when an amateur fossil hunter named Cathy Wankel presented him with a single T-Rex bone.
The rest of the beast was buried deep in the Montana Badlands.
After years of excavation, without the fuss or fanfare associated with Tyrannosaurus Sue, the Wankel T-Rex emerged.
Now and rather reluctantly, Jack Horner had a T-Rex in his backyard.
If for the sake of science he had to study it, then he was going to do it thoroughly and impartially.
Jack Horner would look at the T-Rex skeleton as if he'd heard nothing of the beast's fearsome reputation.
And it was then that he noticed something.
It was the arms, something about the arms was not quite right.
The upper arm bone is a little bit longer than my upper arm bone, and the ulna, the lower arm bone, is half the length of mine, I mean it is tiny.
Then it struck him, something nobody else had dared consider.
This tiny arm didn't seem to be the arm of a creature that survived by killing.
You start thinking about, you know, what T-Rex did for a living.
What is this animal like as a living creature? Predatory animals have to grab things, they, I mean, they have to actually get a hold of them.
But if you look at, at Tyrannosaurus Rex and you look at animals that, that we know to have been predatory animals, like Velociraptor.
If you look at just the size of their arms compared to their bodies.
It's just this incredible difference.
An adult Tyrannosaurus Rex is 12 meters long from nose to tail.
Its arm is tiny.
The lower arm bone is just 22 centimetres, that's less than two percent of its body length.
By comparison the predator Velociraptor has a lower arm bone that's proportionally 3 times longer, a more useful six percent of its body length.
- Rex had arms far shorter for its size than any other predatory dinosaur.
If we look at, you know the actual arms, we can see that T-Rex couldn't put its arms together, has very little motion on them, probably couldn't do any more than scratch its belly after it ate.
Horner was now puzzled, this just didn't add up.
He began to wonder if for over a century the common perception of T-Rex had been wrong.
For years people had just assumed that T-Rex was a killer, and no one had questioned it, I mean it just, it was sort of ingrained in to everyone's minds from, from the time they were kids to grownups.
But you know once we had the Wankel T-Rex and we could actually see a whole specimen it was really quite clear that it was very, very different than predatory dinosaurs.
So Jack Horner continued his rigorous scientific investigation to find out if anything else about T-Rex didn't add up.
The next place Horner looked was the teeth.
He looked not only at T-Rex teeth but at the teeth of other dinosaurs known to be predators.
And again he noticed a significant difference.
A T-Rex tooth is long, strong and slightly curved, a bit like a banana.
In cross section it's almost round.
A very robust design, strong enough to pulverise bone.
But the teeth of predators like Velociraptor, or Deinonychus are different.
This Velociraptor tooth is blade like and serrated.
Its cross section is laterally compressed, just like a steak knife.
Which makes it ideal for slicing through flesh.
It begs the question, if Velociraptor and Deinonychus are predatory dinosaurs and they have laterally compressed flattened teeth and T-Rex doesn't, then T-Rex must be doing something different.
To find out what meant turning not to the bones of T-Rex but to the remains of an animal eaten by one, a Triceratops.
These animals were hefty herbivores, ten tonnes of muscle with a characteristic armoured head.
And when scientists began to uncover bones baring huge tooth marks, they knew Triceratops had been T-Rex food.
So Horner turned to a plaster cast of part of a Triceratops, the sacrum, fused vertebrae littered with nearly 60frenzied T-Rex tooth marks.
Baring such terrible scars this enormous bone had been held up as conclusive proof of - Rex as a predator.
Horner wanted to reanalyse the specimen, to see if there was anything previous researchers had missed, and they had.
It was not the size or the shape of the bite marks they'd overlooked, it was where they were.
The sacrum is a well protected part of a Triceratops skeleton.
It's the reinforced bone at the base of the spine, enclosed by the heavy muscle of the legs and the belly.
The bite marks were on the underside of this concealed bone.
The one part of a Triceratops body, impossible for a T-Rex to get to if its meal was still alive and kicking.
That animal had to be literally torn to pieces before, before you could, before a T-Rex could leave those puncture marks.
To Jack Horner the pattern of the bite marks pointed to just one conclusión, a T-Rex hadn't killed the Triceratops, something else had, and a T-Rex had simply chewed up the leftovers.
Jack Horner was now certain T-Rex couldn't have been the killer they said he was.
The predator theory had been make believe, pure fantasy.
Now there was evidence of arms that couldn't grab on prey, teeth that couldn't slice flesh, yet crush bone, and chew marks on an already dead Triceratops.
The facts led Horner to believe there was only one thing a T-Rex could be.
A scavenger.
To see the king of the dinosaurs as nothing more regal than a giant vulture or hyena was heresy.
Scavengers are nobody's heroes, they feed on the abandoned carcasses of animals killed by real predators, they survive on leftovers.
Jack Horner presented the case in favour of the scavenger theory.
He was instantly dismissed as a crackpot.
But then came some independent support, and from a most unlikely source.
On the other side of the worid, two scientists from the University of Glasgow couldn't resist joining in the controversy.
But David Houston and Graeme Ruxton knew nothing about T-Rex.
What they did know about was scavenging.
And they wanted to put Horner's theory to the test by asking a question no palaeontologist had thought of.
Was it even possible for an animal the size of T-Rex to survive just by scavenging scraps? Any animal can really only survive if the amount of energy that it uses in foraging each day is less than the amount of energy it's able to get back from its food.
So what we were doing was trying to calculate what the energy requirements would have been for a T-Rex, for locomotion and for general maintenance.
And also to consider how much food would be available within that foraging range, and whether it would have been able to find enough carcasses to balance its energy budget.
The first thing Ruxton and Houston wanted to do was to analyse each link in a cretaceous food chain.
But they couldn't, that ecosystem had disappeared 65 million years ago.
So they searched for the next best thing, a largely unspoiled flourishing environment teeming with life.
They found it in the Serengeti National Park in Africa.
Here was an abundance of predators, prey and scavengers, all in the one ecosystem.
We chose the Serengeti because there's been much more work done there than almost any other area.
The wildlife system is still relatively undisturbed.
What Ruxton and Houston needed to determine from the Serengeti ecosystem was just how much dead meat might be available to a scavenger.
The answer was more than you'd think.
I think a lot of people think that the majority of animals when they die, die because they get killed by a predator, but in fact in systems like the Serengeti that really isn't true.
The majority of Animals which die will die from some other cause, mainly because of old age or food shortage, starvation, parasite burden, perhaps they just have an accident.
In other words because animals just drop down dead more meat is available to a scavenger than most people assume.
Yet this amount was still very low.
The research suggested as little as 4 kilos of meat a day in every square kilometre.
It seemed life might be tough for a scavenging T-Rex.
But then Ruxton and Houston set up a computer model to calculate just how much food a T-Rex would have needed to survive.
Based upon its weight and build they were expecting a figure to be high, but that's not what they found.
When they calculated its likely metabolic rate, similar to that of a reptile, they found T-Rex didn't use much energy at all.
Their estimate revealed T-Rex probably only needed to eat something the size of a human every five or six days.
Despite the facts that it's many, many times the size of us, the amount of energy it uses when it's really not doing much, is only 5 or 6 times the amount of energy you and I spend.
This thing doesn't need to find an awful lot of food.
And up here we have the density of carrion or food available to it in the environment.
Ruxton and Houston's calculation suggested there would have been enough food lying around for a T-Rex to survive by scavenging, but on one condition.
That it could find the food in the first place.
Everything about being a scavenger depends on being able to find carcasses which are going to be very widely dispersed, they're going to be difficult to locate, so you clearly need to be able to detect carcasses from a considerable distance.
And we get results from this graph here.
The critical distance their calculations produced was 50 metres.
All T-Rex needed to do was to see across a stretch of land half the length of a football pitch.
And scientists already knew T-Rex was likely to have had excellent eyesight.
I think given that it was likely to be preying on fairly large things, spotting things at a distance of 50 metres wouldn't be too challenging.
For the very first time Jack Horner's theory had significant independent backup.
Not only did the scavenger theory seem to fit the fossil evidence, it fitted the ecological evidence.
- Rex could have survived by scavenging alone.
So if Jack Horner was right all those movies and most scientists had got it wrong.
- Rex wasn't a terrifying predator, the truth was something altogether less glamorous.
- Rex may have been a king, but a king of scavengers.
Jack Horner appeared to have won the argument, but then along came something and someone that would once again tear the debate wide open.
Ken Carpenter is curator of the Denver Museum of Nature and Science, in charge of over three thousand dinosaur bones.
Among his vast collection were Hadrosaurs.
These gentle duckbilled vegetarians were likely to have formed a large proportion of a T-Rex diet.
Herds of these placid beasts roamed the planes in vast numbers.
They were the cows of the cretaceous.
Ken Carpenter had never believed in Horner's idea of T-Rex the scavenger, and it prompted him to take a closer look at one of his Hadrosaurs.
It was then that he noticed something quite remarkable.
It wasn't until Jack Horner asked the question, was T-Rex a scavenger or a predator, that I thought mm, there is something about this specimen that's very different and unique.
It was something so obvious that everyone else had missed it.
When I looked at the tail it's rather unusual because one of the vertebrae is incomplete near the top.
What's missing is the top roughly third of that long bladelike bone that's on the top.
We can feel those same bones along our backs, those are the tops of the vertebrae.
So part of this vertebrae is missing.
I also noticed there were some little puncture rooms on some of the adjacent spines.
They're rather unusual in that they form a broad U shape which looks like, an awful lot like it was a bite mark.
If the broad U shape was indeed a bite mark, then this Hadrosaur had been attacked by something with large and powerful bone crushing jaws, there could be only one suspect, and Ken Carpenter had the weapon to prove it.
We can see that almost a third on one of these spines is missing.
Also we can see that there's some damage here, there's actually some more damage on the back of this one, and damage here.
But it's this trough that's been cut through this bone that's most intriguing.
Because we can actually take the tooth of a Tyrannosaurus Rex and put it right in there.
It just fits so perfectly.
The scavenger theory would dictate that the Hadrosaur must have been dead when this happened, but Ken Carpenter suspected otherwise.
What was rather interesting, not only did we have this U shape groove but there was re-healed bone around it.
The bone could only have re-healed if the animal was alive, and if the animal was alive that made the T-Rex a predator.
It seemed T-Rex was capable of hunting after all.
All this time the answer to the question of whether - Rex was a scavenger or predator was just in my backyard practically.
There was now a straight contradiction, Ken Carpenter's evidence suggested T-Rex had been a predator.
Jack Horner's evidence suggested - Rex had been a scavenger.
Science was faced with a problem.
But the fierce debate that once drove a rift through palaeontology has started to bring the two sides together.
Because scientists have now begun to accept that the boundary between scavenger and predator can be blurred.
Scavengers do kill.
And predators aren't above scavenging.
I think it's sometimes not very sensible to think of animals as being either scavengers or predators.
If we think of modern carnivores, particularly mammalian carnivores, there really is no modern mammalian carnivore which is either a total scavenger or a total predator.
So the suggestion now is that T-Rex was some kind of hybrid, an animal capable of both killing and scavenging.
I think that we, we have evidence of, of both in this animal, so I think it probably was a predator sometimes and a scavenger at other times.
I think the meaningful distinction we had to make here is, what was it doing most of the time, how did it get most of its meals.
Just what the balance was between hunting and scavenging remains, for the moment at least, a mystery.
But one thing is clear, - Rex had a truly bizarre anatomy for a killer, so if it did on occasión hunt for a living then it seems it must have done so in a way different from any other predator.
In the end Jack Horner may have been both right and wrong about T-Rex.
But in raising the question he had done far more than help solve one small riddle within dinosaur biology.
He had reminded palaeontologists what their science should be all about.
We have to gather together evidence, and we have to test that evidence, we have to test the individual hypotheses that come out in order to come together with all this cumulative data.
I think in one sense palaeontology had got in to a rut, and just automatically assumed that certain ideas that we had were automatically true.
We can't do that, we have to go in there and, and address these questions, and, and come up with the evidence.
Whether my colleagues believe that or not I think that in the end kids are going to learn more about how science works from this argument or this discussión.
I think this engages them.
And because of Horner's work a new generation will grow up with a completely different view of T-Rex.