WEBVTT 00:00:00.000 --> 00:00:02.560 Welcome back to the Deep Dive. Today we are clearing 00:00:02.560 --> 00:00:06.599 the table. We are pushing aside the niche topics 00:00:06.599 --> 00:00:09.460 and the obscure mysteries for a moment to tackle 00:00:09.460 --> 00:00:11.539 the big one. And you really don't mean big. I 00:00:11.539 --> 00:00:13.740 do mean the big one. The ultimate dinosaur. The 00:00:13.740 --> 00:00:16.920 one that every single person listening from, 00:00:16.980 --> 00:00:20.500 you know, toddlers to grandparents knows by name. 00:00:20.679 --> 00:00:22.260 Or at least they know the abbreviation. Yeah. 00:00:22.280 --> 00:00:24.059 It's the only dinosaur that has that kind of 00:00:24.059 --> 00:00:25.719 celebrity status where you don't even need the 00:00:25.719 --> 00:00:29.089 full name. T -Rex. Exactly. We are talking about 00:00:29.089 --> 00:00:32.590 Tyrannosaurus Rex, the king. And honestly, I 00:00:32.590 --> 00:00:34.929 think most of us carry around a very specific 00:00:34.929 --> 00:00:38.049 mental model of this animal. Oh, for sure. It's 00:00:38.049 --> 00:00:40.189 the movie monster. It's the thing rippling the 00:00:40.189 --> 00:00:42.590 water in the plastic cup. It's the jeep chaser. 00:00:42.770 --> 00:00:46.270 But looking through this massive stack of research 00:00:46.270 --> 00:00:49.630 you've brought today. The reality is so much 00:00:49.630 --> 00:00:52.369 stranger than the blockbuster version. It really 00:00:52.369 --> 00:00:54.689 is. The popular image of T -Rex has been, well, 00:00:54.770 --> 00:00:56.770 it's been frozen in time since the early 90s, 00:00:56.770 --> 00:00:58.929 essentially. But the science, the science has 00:00:58.929 --> 00:01:01.250 been moving at light speed. We aren't just looking 00:01:01.250 --> 00:01:03.890 at a movie monster anymore. We are looking at 00:01:03.890 --> 00:01:06.099 a biological marvel. We're going to be talking 00:01:06.099 --> 00:01:09.540 about an animal that pushes the absolute limits 00:01:09.540 --> 00:01:13.260 of what is physically possible for a bipedal 00:01:13.260 --> 00:01:15.060 predator. And that's what I want to do today. 00:01:15.120 --> 00:01:17.900 I want to peel back all those layers of pop culture. 00:01:18.000 --> 00:01:20.930 We're going to reconstruct the real king. We're 00:01:20.930 --> 00:01:22.909 going to talk about whether it had lips, the 00:01:22.909 --> 00:01:25.390 raging debate over whether it had feathers, the 00:01:25.390 --> 00:01:27.430 controversy over whether it's actually three 00:01:27.430 --> 00:01:30.370 different species, and the absolute nightmare 00:01:30.370 --> 00:01:32.409 mechanics of its bite. And we're going to do 00:01:32.409 --> 00:01:34.689 this by looking at how paleontology actually 00:01:34.689 --> 00:01:37.230 works, because we aren't just guessing anymore. 00:01:37.390 --> 00:01:40.150 We're moving from looking at broken bones to 00:01:40.150 --> 00:01:43.590 understanding life history, growth rates, cellular 00:01:43.590 --> 00:01:47.060 biology. and even complex social behavior. It's 00:01:47.060 --> 00:01:49.140 like a detective story. It is. It's a detective 00:01:49.140 --> 00:01:50.900 story that's been running for over 100 years. 00:01:51.060 --> 00:01:53.560 So let's set the stage. We all know the name, 00:01:53.659 --> 00:01:57.599 Tyrannosaurus Rex. Tyrant Lizard King. It has 00:01:57.599 --> 00:01:59.379 to be the coolest scientific name ever coined. 00:01:59.579 --> 00:02:02.540 It is hard to beat, I have to admit. It was named 00:02:02.540 --> 00:02:06.140 by Henry Fairfield Osborne way back in 1905. 00:02:06.760 --> 00:02:09.909 And right from the start, there was this recognition 00:02:09.909 --> 00:02:13.069 that this animal was the ruler of its domain. 00:02:13.349 --> 00:02:15.810 Where was that domain exactly? It lived in western 00:02:15.810 --> 00:02:18.610 North America on what was then a separate island 00:02:18.610 --> 00:02:21.030 continent called Laramidia. This was right at 00:02:21.030 --> 00:02:23.610 the very end of the age of dinosaurs, the Maastrichtian 00:02:23.610 --> 00:02:26.729 age, so about 69 to 66 million years ago. So 00:02:26.729 --> 00:02:29.389 it was there for the curtain call. Exactly. It 00:02:29.389 --> 00:02:31.889 was one of the last non -avian dinosaurs to walk 00:02:31.889 --> 00:02:34.560 the Earth before the asteroid hit. It saw the 00:02:34.560 --> 00:02:36.979 end of the world. Wow. But before that, it was 00:02:36.979 --> 00:02:39.419 the apex. And when I say apex, I don't just mean 00:02:39.419 --> 00:02:41.180 it was at the top of the food chain. I mean, 00:02:41.199 --> 00:02:44.020 it dominated the ecosystem in a way very few 00:02:44.020 --> 00:02:46.599 predators ever have. Okay, let's unpack the sheer 00:02:46.599 --> 00:02:48.919 scale of this beast, because I think sometimes 00:02:48.919 --> 00:02:51.539 the numbers get lost. We hear big, but how big 00:02:51.539 --> 00:02:53.099 are we talking? Well, let's look at the most 00:02:53.099 --> 00:02:55.960 famous specimen, Sue, which is housed at the 00:02:55.960 --> 00:02:58.840 Field Museum in Chicago. Sue has been the gold 00:02:58.840 --> 00:03:00.719 standard for a long time. Right, everyone knows 00:03:00.719 --> 00:03:04.090 Sue. And for good reason. We are talking about 00:03:04.090 --> 00:03:08.449 a skeleton that is roughly 12 .3 to 12 .4 meters 00:03:08.449 --> 00:03:12.169 long. Which is what? In feet? About 40? About 00:03:12.169 --> 00:03:15.250 40 to 41 feet, yeah. That's a school bus. A living, 00:03:15.389 --> 00:03:18.550 breathing school bus with teeth. A very heavy 00:03:18.550 --> 00:03:22.009 school bus. Sue stands nearly 4 meters tall at 00:03:22.009 --> 00:03:24.830 the hips. That's 13 feet. So its back is higher 00:03:24.830 --> 00:03:27.659 than a basketball hoop. Unbelievable. But the 00:03:27.659 --> 00:03:29.659 weight is where the modern science has really 00:03:29.659 --> 00:03:31.740 changed our understanding. How so? Did we used 00:03:31.740 --> 00:03:34.240 to think they were lighter? Oh, much. For a long 00:03:34.240 --> 00:03:36.860 time, we thought of dinosaurs as these sluggish, 00:03:36.860 --> 00:03:39.599 tail -dragging lizards. The models were, let's 00:03:39.599 --> 00:03:42.150 say... A bit shrink -wrapped. Right. But modern 00:03:42.150 --> 00:03:44.830 estimates, using 3D mathematical slicing and 00:03:44.830 --> 00:03:47.270 volumetric displacement models, have bulked them 00:03:47.270 --> 00:03:49.770 up significantly. We now put the mass of a mature 00:03:49.770 --> 00:03:53.870 adult like Sue around 8 .8 to 9 .2 tons. Nine 00:03:53.870 --> 00:03:56.909 tons. That is significant. That's two large African 00:03:56.909 --> 00:03:59.370 elephants taped together. And balancing on two 00:03:59.370 --> 00:04:01.169 legs. That's the key. And Sue isn't even the 00:04:01.169 --> 00:04:03.050 biggest one we've found, right? Possibly not. 00:04:03.330 --> 00:04:06.539 There is a specimen called Scotty. in Saskatchewan 00:04:06.539 --> 00:04:09.439 that might be even heavier. Some estimates put 00:04:09.439 --> 00:04:12.219 Scotty at nearly nine tons as well, maybe even 00:04:12.219 --> 00:04:14.159 pushing the upper limit of 10. So this isn't 00:04:14.159 --> 00:04:16.959 just big. This is pushing the biological limits 00:04:16.959 --> 00:04:19.060 of walking on two legs, isn't it? It absolutely 00:04:19.060 --> 00:04:21.899 is. When you get that heavy, gravity becomes 00:04:21.899 --> 00:04:24.800 your biggest enemy. Every single step places 00:04:24.800 --> 00:04:28.019 immense stress on the bones. And all that bulk 00:04:28.019 --> 00:04:30.699 is centered around a massive torso and a tail 00:04:30.699 --> 00:04:34.339 that has to balance, well, the business end. 00:04:34.720 --> 00:04:36.860 The head. The skull. Let's talk about that skull. 00:04:36.959 --> 00:04:38.860 Because it's iconic, but it's also a piece of 00:04:38.860 --> 00:04:41.079 engineering. It is massive. The largest skulls 00:04:41.079 --> 00:04:43.100 are over 1 .5 meters. That's five feet long. 00:04:43.480 --> 00:04:45.839 But it's the shape that's fascinating. If you 00:04:45.839 --> 00:04:48.199 look at other large meat -eating dinosaurs, like 00:04:48.199 --> 00:04:50.600 the Giganotosaurus from South America, or the 00:04:50.600 --> 00:04:52.019 Spinosaurus. Right, they're kind of long and 00:04:52.019 --> 00:04:54.160 narrow. Exactly. Their skulls are often narrow. 00:04:54.180 --> 00:04:55.860 They look like knife blades from the front or 00:04:55.860 --> 00:04:59.420 top. Thin and slicey. Exactly. But T -Rex, you 00:04:59.420 --> 00:05:02.259 look at a T -Rex skull from the back, it is incredibly 00:05:02.259 --> 00:05:05.290 wide. It's flared out. but the snout is narrow. 00:05:05.490 --> 00:05:07.990 Okay, so wide at the back, narrow at the front. 00:05:08.410 --> 00:05:11.069 Why does that shape matter? It's all about vision. 00:05:11.529 --> 00:05:14.230 That shape allows the eyes to face forward, not 00:05:14.230 --> 00:05:17.050 just to the sides. It grants T -Rex binocular 00:05:17.050 --> 00:05:20.889 vision. Depth perception. Precisely. Most dinosaurs 00:05:20.889 --> 00:05:23.629 had eyes on the sides of their heads. Great for 00:05:23.629 --> 00:05:25.689 peripheral vision. You know, seeing a predator 00:05:25.689 --> 00:05:27.870 coming from behind. But terrible for judging 00:05:27.870 --> 00:05:29.970 distance. But the T -Rex is looking right at 00:05:29.970 --> 00:05:32.769 you. Right at you. With overlapping visual fields. 00:05:32.910 --> 00:05:35.740 And not just okay depth perception. There was 00:05:35.740 --> 00:05:37.819 a landmark study by Ken Stevens at the University 00:05:37.819 --> 00:05:40.300 of Oregon. He modeled the visual field of T. 00:05:40.360 --> 00:05:43.920 rex using lasers and facial reconstruction. Lasers. 00:05:43.920 --> 00:05:45.740 That sounds cool. Yeah, it was very cool. And 00:05:45.740 --> 00:05:47.279 what did he find? He found it had a binocular 00:05:47.279 --> 00:05:50.519 range of 55 degrees. 55 degrees. How does that 00:05:50.519 --> 00:05:54.500 compare to, say, us or a bird of prey? It's better 00:05:54.500 --> 00:05:56.810 than a modern hawk. Right. Better than a hawk? 00:05:56.829 --> 00:05:59.649 In terms of the binocular overlap, yes. And it 00:05:59.649 --> 00:06:02.649 gets crazier. Stevens estimated the T -Rex had 00:06:02.649 --> 00:06:06.050 13 times the visual acuity of a human. 13 times? 00:06:06.449 --> 00:06:09.769 Yes. And significantly better than an eagle. 00:06:09.850 --> 00:06:12.550 He calculated that a T -Rex could distinguish 00:06:12.550 --> 00:06:16.610 objects as separate from the horizon up to 6 00:06:16.610 --> 00:06:19.170 kilometers away. 6 kilometers? That's almost 00:06:19.170 --> 00:06:22.199 4 miles. Yep. It could see you long, long before 00:06:22.199 --> 00:06:24.399 you could see it. Okay, so that scene in Jurassic 00:06:24.399 --> 00:06:26.959 Park. Oh, you mean the don't move, its vision 00:06:26.959 --> 00:06:30.240 is based on movement scene? Yeah. That's busted. 00:06:30.639 --> 00:06:32.680 Completely and utterly busted. It is one of the 00:06:32.680 --> 00:06:35.959 biggest myths in pop culture. If you stood still 00:06:35.959 --> 00:06:37.740 in front of a T -Rex, it would see you comfortably 00:06:37.740 --> 00:06:40.079 in high definition, and it would probably be 00:06:40.079 --> 00:06:41.899 wondering why the snack is presenting itself 00:06:41.899 --> 00:06:44.720 so politely. That is terrifying. It completely 00:06:44.720 --> 00:06:47.079 changes the dynamic. It's not a clumsy monster 00:06:47.079 --> 00:06:49.759 flailing around. It's a sniper. A sniper is a 00:06:49.759 --> 00:06:51.579 good analogy. Yeah. And it's not just vision. 00:06:51.600 --> 00:06:53.639 We have to talk about smell. I remember reading 00:06:53.639 --> 00:06:57.000 about the brain casts. Right. We can use CT scans 00:06:57.000 --> 00:06:59.000 on the inside of the skull to see the shape of 00:06:59.000 --> 00:07:01.139 the brain or at least the cavity it sat in. The 00:07:01.139 --> 00:07:03.759 endocast, right? The endocast, exactly. And the 00:07:03.759 --> 00:07:05.720 olfactory bulbs, the part of the brain dedicated 00:07:05.720 --> 00:07:09.189 to smell in T. rex. are huge. Relative to its 00:07:09.189 --> 00:07:12.129 brain size, they are massive. In fact, research 00:07:12.129 --> 00:07:14.329 showed that of 21 different dinosaur species 00:07:14.329 --> 00:07:16.970 sampled, T. rex had the most highly developed 00:07:16.970 --> 00:07:19.310 sense of smell. It's basically a bloodhound the 00:07:19.310 --> 00:07:21.790 size of a bus. A bloodhound with eagle eyes. 00:07:22.029 --> 00:07:24.750 It could likely smell a carcass or prey from 00:07:24.750 --> 00:07:28.129 kilometers away. This combination of senses is 00:07:28.129 --> 00:07:30.829 actually quite rare. Usually animals specialize. 00:07:30.889 --> 00:07:33.810 They prioritize one or the other. T -Rex double 00:07:33.810 --> 00:07:36.089 down on both. Okay, so it finds you. It sees 00:07:36.089 --> 00:07:40.170 you from miles away. It smells you. Now we have 00:07:40.170 --> 00:07:43.430 to talk about the lethal bananas. Ah, yes. The 00:07:43.430 --> 00:07:45.689 teeth. I love that description. Lethal bananas 00:07:45.689 --> 00:07:47.290 because they aren't flat, right? They're not 00:07:47.290 --> 00:07:49.569 like knives. No. And this is a key distinction 00:07:49.569 --> 00:07:52.259 from other predators. Many carnivorous dinosaurs 00:07:52.259 --> 00:07:54.579 had teeth that were like steak knives, flat, 00:07:54.860 --> 00:07:57.920 serrated, designed to slice through flesh. We 00:07:57.920 --> 00:08:00.300 call those ziphodont teeth. T -Rex teeth are 00:08:00.300 --> 00:08:02.939 different. They are encrasate. Encrasate. That's 00:08:02.939 --> 00:08:05.300 a new one for me. It just means thickened. They 00:08:05.300 --> 00:08:07.319 are D -shaped in cross -section. They are thick, 00:08:07.360 --> 00:08:09.199 round, and reinforced with ridges on the back. 00:08:09.319 --> 00:08:11.319 They look like railroad spikes. So they aren't 00:08:11.319 --> 00:08:14.540 just for slicing. They are for crushing. That 00:08:14.540 --> 00:08:17.149 shape. Prevents the tooth from snapping when 00:08:17.149 --> 00:08:19.490 the animal bites down with tremendous force and 00:08:19.490 --> 00:08:23.310 pulls. If you bite into bone with a flat, knife 00:08:23.310 --> 00:08:26.250 -like tooth and the prey twists, your tooth snaps. 00:08:26.649 --> 00:08:28.990 But if you use a railroad spike... The bone snaps. 00:08:29.269 --> 00:08:31.610 That is a gruesome image. What's the biggest 00:08:31.610 --> 00:08:33.789 tooth we've ever found? The largest one is over 00:08:33.789 --> 00:08:36.470 30 centimeters. Yeah. That's 12 inches long. 00:08:36.730 --> 00:08:39.549 But that includes the root. Oh. And the root 00:08:39.549 --> 00:08:41.490 is actually two -thirds of the tooth. It's anchored 00:08:41.490 --> 00:08:44.649 into the jaw like a pylon in concrete. This animal 00:08:44.649 --> 00:08:47.149 wasn't just nipping at you. It was engaging in 00:08:47.149 --> 00:08:49.889 osteophagy. Osteophagy? Bone eating. We find 00:08:49.889 --> 00:08:52.450 coprolites, fossilized poop attributed to tyrannosaurs 00:08:52.450 --> 00:08:55.149 that are just full of pulverized bone fragments. 00:08:55.429 --> 00:08:57.250 They were eating the marrow, the rich nutrients 00:08:57.250 --> 00:08:59.190 inside the bone that other predators couldn't 00:08:59.190 --> 00:09:01.549 access. It's a whole other level of predation. 00:09:01.710 --> 00:09:03.929 It's total consumption. Okay, speaking of the 00:09:03.929 --> 00:09:06.909 mouth, we have to address a recent controversy. 00:09:07.559 --> 00:09:09.559 The lips. Oh, the great lip debate. This has 00:09:09.559 --> 00:09:11.679 really heated up in the last few years. It's 00:09:11.679 --> 00:09:13.720 one of those things that seems small, but it 00:09:13.720 --> 00:09:16.139 totally changes how you picture the animal. Because 00:09:16.139 --> 00:09:18.240 in movies, the teeth are always hanging out, 00:09:18.279 --> 00:09:20.860 right? Like a crocodile. They look snaddle -toothed 00:09:20.860 --> 00:09:22.620 and scary. It's part of the monster aesthetic. 00:09:23.220 --> 00:09:25.519 But there's been a pushback on that. There has. 00:09:25.740 --> 00:09:28.100 For a long time, the assumption was that, like 00:09:28.100 --> 00:09:31.879 crocodiles, T -Rex didn't have lips. But there's 00:09:31.879 --> 00:09:34.220 a problem with that model. What's that? Crocodiles 00:09:34.220 --> 00:09:36.019 are aquatic. They spend most of their time in 00:09:36.019 --> 00:09:37.720 the water, so they don't need to worry about 00:09:37.720 --> 00:09:41.240 their enamel drying out. But T. rex was terrestrial. 00:09:41.460 --> 00:09:43.000 And if your teeth dry out, they get brittle. 00:09:43.320 --> 00:09:46.500 Exactly. Enamel needs hydration to stay strong 00:09:46.500 --> 00:09:50.279 and not crack. A study came out in 2023 by Thomas 00:09:50.279 --> 00:09:52.720 Cullen and his colleagues that looked at this 00:09:52.720 --> 00:09:55.580 specifically. They compared the wear patterns 00:09:55.580 --> 00:09:58.480 on tyrannosaur teeth to crocodiles and monitor 00:09:58.480 --> 00:10:00.899 lizards. What did the forensic evidence show? 00:10:01.389 --> 00:10:03.990 They found that the enamel on T -Rex teeth didn't 00:10:03.990 --> 00:10:05.909 show the kind of wear you see in crocodiles. 00:10:06.230 --> 00:10:08.450 Croc teeth get eroded on the outside because 00:10:08.450 --> 00:10:10.149 they are constantly exposed to the elements. 00:10:10.870 --> 00:10:13.330 Tyrannosaur teeth look pristine, much more like 00:10:13.330 --> 00:10:16.070 a monitor lizard, which has lips covering its 00:10:16.070 --> 00:10:18.169 teeth when the mouth is closed. So T -Rex likely 00:10:18.169 --> 00:10:21.269 had lips. It's the leading theory right now based 00:10:21.269 --> 00:10:23.710 on that study. Now, it wouldn't have looked like 00:10:23.710 --> 00:10:26.309 a human mouth with big fleshy kissing lips. Right, 00:10:26.470 --> 00:10:29.620 right. Think more like a Komodo dragon. A thin, 00:10:29.679 --> 00:10:33.539 scaly covering. The teeth would be hidden when 00:10:33.539 --> 00:10:35.279 the mouth was closed. That actually makes it 00:10:35.279 --> 00:10:39.360 scarier to me. It looks more calculating. Less 00:10:39.360 --> 00:10:41.720 like a mindless monster with teeth sticking out 00:10:41.720 --> 00:10:44.379 everywhere and more like a giant focused reptile. 00:10:44.480 --> 00:10:47.080 It cleans up the lines of the face. It changes 00:10:47.080 --> 00:10:49.580 the profile completely. It makes it look less 00:10:49.580 --> 00:10:52.600 like a fantasy dragon and more like a real plausible 00:10:52.600 --> 00:10:55.019 animal. So we have this massive, keen -eyed, 00:10:55.080 --> 00:10:59.009 lip -having, bone -crushing beast. The big question 00:10:59.009 --> 00:11:02.110 is, can I outrun it? The age -old question. The 00:11:02.110 --> 00:11:04.210 one everyone asks. The movie scene. The jeep 00:11:04.210 --> 00:11:06.590 chase. Must go faster. Could a T -Rex actually 00:11:06.590 --> 00:11:09.090 chase down a jeep doing 30 or 40 miles per hour? 00:11:09.210 --> 00:11:11.909 In a word, no. Really? You're crushing dreams 00:11:11.909 --> 00:11:15.330 here. I'm saving lives. Or, well, ruining the 00:11:15.330 --> 00:11:18.230 movie at least. The jeep chase is pure Hollywood. 00:11:18.779 --> 00:11:21.340 When we look at the biomechanics of an animal 00:11:21.340 --> 00:11:23.860 that weighs eight or nine tons, running in the 00:11:23.860 --> 00:11:26.299 strictly biomechanical sense of having both feet 00:11:26.299 --> 00:11:28.879 off the ground at the same time becomes nearly 00:11:28.879 --> 00:11:32.039 impossible. Why? Is it just too heavy? It's the 00:11:32.039 --> 00:11:35.840 skeletal load. A 2017 study modeled this using 00:11:35.840 --> 00:11:39.379 stress analysis on the bones. If a T -Rex tried 00:11:39.379 --> 00:11:42.200 to run at, say, 70 kilometers per hour, which 00:11:42.200 --> 00:11:44.759 is about 45 miles per hour. Yeah. The forces 00:11:44.759 --> 00:11:47.360 generated when its foot hit the ground would 00:11:47.360 --> 00:11:50.279 likely shatter its leg bones. Oh, so it would 00:11:50.279 --> 00:11:52.399 literally break its own legs if it tried to sprint. 00:11:52.899 --> 00:11:55.820 Likely, yes. The impact force would exceed the 00:11:55.820 --> 00:11:57.659 sheer strength of the bone. It's a physics problem. 00:11:58.039 --> 00:11:59.899 And that's not even getting into the muscles. 00:12:00.039 --> 00:12:01.500 What about the muscles? The muscle mass required 00:12:01.500 --> 00:12:04.519 to move that fast would be impossible. Some studies 00:12:04.519 --> 00:12:05.879 calculated it would need to be something like 00:12:05.879 --> 00:12:08.360 86 % of its body weight just in its legs. Which 00:12:08.360 --> 00:12:10.519 is not feasible. Not even close. There'd be no 00:12:10.519 --> 00:12:12.460 room for organs. So what is the speed limit? 00:12:12.539 --> 00:12:14.720 What's the real number? Most modern studies put 00:12:14.720 --> 00:12:17.120 the top speed around 27 kilometers per hour. 00:12:17.220 --> 00:12:19.700 That's about 17 miles per hour. 17 miles per 00:12:19.700 --> 00:12:21.610 hour. That's attainable. A good human sprinter 00:12:21.610 --> 00:12:24.009 can do that. Usain Bolt can do 27 -kilometer 00:12:24.009 --> 00:12:26.929 error. A reasonably fit human might hit 15 or 00:12:26.929 --> 00:12:29.570 16 -mile error in a panic sprint. So it's going 00:12:29.570 --> 00:12:32.610 to be close. But here's the thing. T -Rex wasn't 00:12:32.610 --> 00:12:34.710 built for sprinting. It was built for efficiency. 00:12:35.169 --> 00:12:36.809 What do you mean by that? There was a study in 00:12:36.809 --> 00:12:40.289 2020 that looked at the leg proportions. T -Rex 00:12:40.289 --> 00:12:42.750 has relatively long legs, but not for speed. 00:12:42.889 --> 00:12:45.539 It's for energy -efficient walking. They are 00:12:45.539 --> 00:12:48.179 power walkers. Power walkers? I'm picturing a 00:12:48.179 --> 00:12:50.460 T -Rex in a mall walking club with light weights. 00:12:50.700 --> 00:12:53.240 It's funny, but it's biomechanically accurate. 00:12:53.519 --> 00:12:56.320 They could cover huge distances with very little 00:12:56.320 --> 00:12:58.799 energy expenditure. They were the marathon walkers 00:12:58.799 --> 00:13:00.919 of the Cretaceous. So they were stalkers. Exactly. 00:13:01.000 --> 00:13:03.059 They could stalk prey for days, just keeping 00:13:03.059 --> 00:13:05.220 pace, waiting for an opening. While you were 00:13:05.220 --> 00:13:07.759 sprinting and getting tired, it is just walking 00:13:07.759 --> 00:13:10.340 tirelessly. And there was something about the 00:13:10.340 --> 00:13:13.179 tail, right? Helping them walk. That seems counterintuitive. 00:13:13.629 --> 00:13:17.409 It does. But a 2021 study by Pasha van Beelert 00:13:17.409 --> 00:13:20.309 in the Netherlands changed how we see it. They 00:13:20.309 --> 00:13:22.649 modeled the tail not just as a dead weight for 00:13:22.649 --> 00:13:25.570 balance, but as a resonating ligament. Like a 00:13:25.570 --> 00:13:28.649 spring. Almost exactly. Imagine a giant rubber 00:13:28.649 --> 00:13:31.570 band running down the tail. As the animal walks, 00:13:31.769 --> 00:13:35.049 the tail sways up and down naturally. The ligaments 00:13:35.049 --> 00:13:37.789 store energy on the upswing and release it on 00:13:37.789 --> 00:13:40.210 the downswing, helping to propel the animal forward. 00:13:40.450 --> 00:13:43.309 It acts like a suspension system. That is incredible 00:13:43.309 --> 00:13:46.340 engineering, so it made walking... cheaper energetically. 00:13:46.440 --> 00:13:48.919 It is. And their model found a preferred walking 00:13:48.919 --> 00:13:52.759 speed, a resonant frequency. It's roughly 4 .6 00:13:52.759 --> 00:13:55.240 kilometers per hour, which is almost exactly 00:13:55.240 --> 00:13:57.440 the preferred walking speed of a human. That 00:13:57.440 --> 00:13:59.539 is creepy. So if you were walking through the 00:13:59.539 --> 00:14:01.919 Cretaceous forest, a T -Rex could just silently 00:14:01.919 --> 00:14:04.299 pace you step for step without getting tired. 00:14:04.580 --> 00:14:06.659 Precisely. It's the persistence hunter model. 00:14:06.820 --> 00:14:08.799 And while they weren't fast in a straight line, 00:14:09.000 --> 00:14:11.269 they might have been surprisingly agile. Agile. 00:14:11.309 --> 00:14:14.169 A nine -ton animal. How? Relative to other giants, 00:14:14.250 --> 00:14:15.889 of course, they have a specific foot structure 00:14:15.889 --> 00:14:18.210 called the arctometatarsus. Break that down for 00:14:18.210 --> 00:14:20.669 me. The middle foot bone, the metatarsal, is 00:14:20.669 --> 00:14:22.649 pinched at the top between the other two bones. 00:14:23.549 --> 00:14:26.750 This locks the foot bones together into a single 00:14:26.750 --> 00:14:29.309 stable unit, making them very good at transmitting 00:14:29.309 --> 00:14:32.120 force without twisting. A more efficient foot. 00:14:32.159 --> 00:14:34.460 A much more efficient foot. Combined with massive 00:14:34.460 --> 00:14:37.100 leg muscles and low rotational inertia because 00:14:37.100 --> 00:14:39.500 the weight is centered near the hips, some studies 00:14:39.500 --> 00:14:42.039 suggest they could pirouette. Pirouette? Like 00:14:42.039 --> 00:14:45.240 a ballerina? A horrifying nine -ton ballerina. 00:14:45.460 --> 00:14:47.840 They could pivot on one foot very quickly to 00:14:47.840 --> 00:14:50.220 turn and face a threat or prey. So you might 00:14:50.220 --> 00:14:52.700 outrun it in a long straight line if you're fast, 00:14:52.940 --> 00:14:55.259 but don't try to outmaneuver it in close quarters. 00:14:55.440 --> 00:14:58.460 It can spin faster than you think. Okay, noted. 00:14:58.559 --> 00:15:00.879 Don't play tag with a T -Rex. Now we have to 00:15:00.879 --> 00:15:03.600 talk about the arms. We can't avoid them. The 00:15:03.600 --> 00:15:06.500 elephant in the room. Or the tiny arm theropod 00:15:06.500 --> 00:15:08.720 in the room. It is the joke of the paleontology 00:15:08.720 --> 00:15:10.820 world. The tiny arms, they're only about a meter 00:15:10.820 --> 00:15:12.919 long. About the size of a human arm, really. 00:15:13.340 --> 00:15:16.360 Which sounds big, but not on that body. But attached 00:15:16.360 --> 00:15:19.259 to a building -sized animal, are they vestigial? 00:15:19.379 --> 00:15:22.080 Like, were they just on their way out evolutionarily? 00:15:22.340 --> 00:15:24.940 That's been the assumption for a long time. But 00:15:24.940 --> 00:15:27.779 vestigial implies useless. And when you look 00:15:27.779 --> 00:15:30.370 at the bones, they aren't useless at all. What 00:15:30.370 --> 00:15:32.269 do you see? The areas where the muscles attach, 00:15:32.590 --> 00:15:35.450 the insertion points, are huge. The cortical 00:15:35.450 --> 00:15:39.049 bone, the outer layer, is extremely thick. These 00:15:39.049 --> 00:15:41.690 were not flimsy, weak little arms. So they were 00:15:41.690 --> 00:15:44.909 strong. Very strong. Estimates suggest the bicep 00:15:44.909 --> 00:15:48.250 alone could lift nearly 199 kilograms. That's 00:15:48.250 --> 00:15:52.470 over 400 pounds. Wait, each arm? Yes. So this 00:15:52.470 --> 00:15:55.139 animal could curl a motorcycle. That doesn't 00:15:55.139 --> 00:15:57.759 sound vestigial. If they were useless, evolution 00:15:57.759 --> 00:15:59.659 would have withered the muscles away. But they're 00:15:59.659 --> 00:16:01.740 so short, they can't even reach the mouth. What 00:16:01.740 --> 00:16:03.679 were they doing with them? That is the million 00:16:03.679 --> 00:16:06.279 -dollar question. There have been so many theories 00:16:06.279 --> 00:16:09.720 over the decades. Back in 1906, Osborne suggested 00:16:09.720 --> 00:16:12.700 they were for grasping mates. The romantic hug 00:16:12.700 --> 00:16:15.700 theory. A very strong, potentially painful hug. 00:16:16.100 --> 00:16:18.039 Then there was the push -up theory from Newman. 00:16:18.429 --> 00:16:20.909 The push -up theory. The idea that if a T -Rex 00:16:20.909 --> 00:16:23.250 was sleeping on its belly, it needed those strong 00:16:23.250 --> 00:16:25.750 little arms to push its front end up enough to 00:16:25.750 --> 00:16:27.889 get the legs under it to stand up. That makes 00:16:27.889 --> 00:16:29.610 some sense. It's a lot of weight to lift off 00:16:29.610 --> 00:16:31.350 the ground. It does. Then there's the weapon 00:16:31.350 --> 00:16:33.570 theory. Steve and Stanley suggested they were 00:16:33.570 --> 00:16:36.850 used for slashing. The claws were sharp. If it 00:16:36.850 --> 00:16:39.250 got close to prey, it could inflict deep gashes. 00:16:39.490 --> 00:16:42.269 But the reach is so short, you'd have to be basically 00:16:42.269 --> 00:16:45.529 chest -bumping the prey to use them. True. The 00:16:45.529 --> 00:16:47.570 range of motion is really limited, which brings 00:16:47.570 --> 00:16:49.870 us to a really interesting recent theory by Kevin 00:16:49.870 --> 00:16:53.470 Padian in 2022. He flipped the script completely. 00:16:53.710 --> 00:16:56.309 Oh, okay. He suggested the arms didn't get small 00:16:56.309 --> 00:16:59.429 for a function. They got small for safety. Safety? 00:16:59.450 --> 00:17:03.009 How is having smaller arms safer? Imagine a group 00:17:03.009 --> 00:17:06.170 of T -Rex feeding on a carcass. It's a frenzy. 00:17:06.250 --> 00:17:09.269 Giant jaws snapping, teeth crushing bone, heads 00:17:09.269 --> 00:17:12.170 thrashing around. If you have long, waving arms 00:17:12.170 --> 00:17:14.430 in that mix. Chop. Exactly. You get them bitten 00:17:14.430 --> 00:17:17.000 off. accidental amputation by a feeding partner. 00:17:17.579 --> 00:17:19.880 Padian argued that shrinking the arms got them 00:17:19.880 --> 00:17:22.680 out of the way of the jaws of other T. rex. It's 00:17:22.680 --> 00:17:25.099 adaptation by reduction. That is fascinating. 00:17:25.359 --> 00:17:27.660 So it's not, what are these for? It's, let's 00:17:27.660 --> 00:17:29.460 tuck these away so I don't lose them. It's a 00:17:29.460 --> 00:17:32.240 compelling hypothesis. It reminds us that evolution 00:17:32.240 --> 00:17:34.799 isn't always about building bigger weapons. Sometimes 00:17:34.799 --> 00:17:37.460 it's about damage control. Speaking of damage 00:17:37.460 --> 00:17:40.970 control, let's talk about growing up. Because 00:17:40.970 --> 00:17:43.990 a T -Rex doesn't start out nine tons. They hatch 00:17:43.990 --> 00:17:47.009 from an egg. No, and the growth curve is terrifying. 00:17:47.390 --> 00:17:49.289 We can determine their age by looking at the 00:17:49.289 --> 00:17:52.329 rings in their bones, like tree rings. It's called 00:17:52.329 --> 00:17:54.849 skeletochronology. And what does the life of 00:17:54.849 --> 00:17:57.470 a T -Rex look like based on those rings? It's 00:17:57.470 --> 00:18:00.369 an S -shaped curve. For the first decade or so, 00:18:00.430 --> 00:18:03.269 they grow relatively slowly. A teenage T -Rex, 00:18:03.309 --> 00:18:05.599 say... 13 or 14 years old. It's still a large 00:18:05.599 --> 00:18:08.579 animal, but it's lanky. It's built for speed. 00:18:08.779 --> 00:18:11.220 It doesn't have the massive bulk yet. It's the 00:18:11.220 --> 00:18:13.259 gazelle phase. Maybe the cheetah phase. They 00:18:13.259 --> 00:18:15.539 were likely chasing smaller, faster prey. But 00:18:15.539 --> 00:18:18.579 then around age 14, something happens. They hit 00:18:18.579 --> 00:18:20.880 a physiological growth spurt that is hard to 00:18:20.880 --> 00:18:22.960 comprehend. How fast are we talking? They start 00:18:22.960 --> 00:18:25.759 putting on about 600 kilograms a year. That's 00:18:25.759 --> 00:18:28.980 1 ,600 pounds every single year for four years 00:18:28.980 --> 00:18:31.539 straight. That is, they are gaining a cow and 00:18:31.539 --> 00:18:34.799 a half every year. Basically, they bulk up massively. 00:18:35.000 --> 00:18:37.599 The skull deepens, the bite force increases exponentially, 00:18:37.720 --> 00:18:40.099 they slow down, and they become the bruisers 00:18:40.099 --> 00:18:42.180 we know. It's one of the most extreme growth 00:18:42.180 --> 00:18:44.160 rates in the animal kingdom. This brings us to 00:18:44.160 --> 00:18:47.259 a huge controversy in the field. The dwarf tyrant. 00:18:48.309 --> 00:18:50.869 Nanotyrannus. Oh boy. This is one of the biggest 00:18:50.869 --> 00:18:53.750 fights in dinosaur paleontology. It gets heated 00:18:53.750 --> 00:18:55.769 at conferences. People have very strong feelings 00:18:55.769 --> 00:18:58.650 about this. So explain this to me. For years, 00:18:58.789 --> 00:19:01.890 we've found these smaller, sleeker tyrannosaur 00:19:01.890 --> 00:19:04.410 skulls. And some people say, that's a different 00:19:04.410 --> 00:19:07.349 species, Nanotyrannus. And others say, no, that's 00:19:07.349 --> 00:19:10.009 just a teenage T -Rex. That's the debate in a 00:19:10.009 --> 00:19:12.569 nutshell. The most famous specimens are Jane 00:19:12.569 --> 00:19:15.390 and the Bloody Mary specimen found in the Dueling 00:19:15.390 --> 00:19:18.009 Dinosaurs fossil. They have more teeth than adult 00:19:18.009 --> 00:19:20.369 T -Rex. Their skulls are flatter. They just, 00:19:20.430 --> 00:19:23.369 they look different. So who is winning this fight? 00:19:23.509 --> 00:19:26.269 Where does the science stand now? It swings back 00:19:26.269 --> 00:19:28.930 and forth like a pendulum. For a while, the teenage 00:19:28.930 --> 00:19:31.970 T -Rex theory was winning. A study by Holly Woodward 00:19:31.970 --> 00:19:34.869 in 2020 analyzed the bone rings of Jane and another 00:19:34.869 --> 00:19:37.250 specimen. They found that these animals were 00:19:37.250 --> 00:19:40.410 young, 13 to 15 years old, and were actively 00:19:40.410 --> 00:19:43.710 growing. So the bone ring said, I'm a kid. Right. 00:19:44.079 --> 00:19:46.640 Woodward argued that Nanotyrannus is just what 00:19:46.640 --> 00:19:49.160 a T -Rex looks like before that massive growth 00:19:49.160 --> 00:19:52.000 spurt. It filled that mid -sized predator niche 00:19:52.000 --> 00:19:54.180 while it was a juvenile. Case closed. You'd think 00:19:54.180 --> 00:19:57.579 so. But recently, in 2024, the separate species 00:19:57.579 --> 00:20:00.660 camp came back swinging. Researchers like Nick 00:20:00.660 --> 00:20:03.460 Longridge and Evan Sayeta put out a new paper 00:20:03.460 --> 00:20:06.019 arguing the growth curves just don't match up. 00:20:06.119 --> 00:20:09.000 How so? They argue the bone rings in the nanotyrannus 00:20:09.000 --> 00:20:11.420 specimens are getting close together, suggesting 00:20:11.420 --> 00:20:13.420 it was nearing its full size, a much smaller 00:20:13.420 --> 00:20:15.799 size than T. rex. And they identified distinct 00:20:15.799 --> 00:20:18.000 anatomical features that shouldn't change just 00:20:18.000 --> 00:20:19.660 because you grow up. So there might have been 00:20:19.660 --> 00:20:22.079 a mid -sized tyrannosaur running around alongside 00:20:22.079 --> 00:20:25.509 the giant T. rex. That's their argument. that 00:20:25.509 --> 00:20:27.990 there was another more grassy tyrannosaur in 00:20:27.990 --> 00:20:30.690 the ecosystem. It's an ongoing debate, science 00:20:30.690 --> 00:20:33.710 in action. We are watching the consensus form 00:20:33.710 --> 00:20:35.769 and break in real time. It's incredible that 00:20:35.769 --> 00:20:37.769 we're still arguing about the identity of these 00:20:37.769 --> 00:20:39.789 bones. It is, and it connects to life expectancy. 00:20:40.349 --> 00:20:43.250 Sue, the oldest T. rex we know of was only about 00:20:43.250 --> 00:20:46.710 28, maybe 33 years old. when she died that seems 00:20:46.710 --> 00:20:49.089 young for such a huge animal elephants live way 00:20:49.089 --> 00:20:51.490 longer it's the live fast die young strategy 00:20:51.490 --> 00:20:54.849 they grew explosively reach sexual maturity and 00:20:54.849 --> 00:20:58.069 then they died the fossil record suggests high 00:20:58.069 --> 00:21:00.230 mortality right around the time they become adults 00:21:00.230 --> 00:21:02.609 right what was killing them each other mostly 00:21:03.160 --> 00:21:06.220 Fighting for mates, reproductive stress, defending 00:21:06.220 --> 00:21:08.880 territory. The life of a T -Rex was violent. 00:21:09.099 --> 00:21:11.640 Almost every adult specimen we find has healed 00:21:11.640 --> 00:21:13.940 fractures, bite marks, or infections. They beat 00:21:13.940 --> 00:21:16.420 each other up constantly. Scotty had a broken 00:21:16.420 --> 00:21:19.359 rib, an infected jaw, and a bite mark on his 00:21:19.359 --> 00:21:21.220 tail from another Tyrannosaur. Which actually 00:21:21.220 --> 00:21:23.400 leads us to a specific discovery that changed 00:21:23.400 --> 00:21:25.539 everything. Not about bones, but what's inside 00:21:25.539 --> 00:21:28.019 the bones, the soft tissue. This is the Jurassic 00:21:28.019 --> 00:21:31.619 Park moment, for real. In 2005, Mary Schweitzer. 00:21:32.079 --> 00:21:34.700 Her work turned paleontology on its head. Tell 00:21:34.700 --> 00:21:36.440 us that story. I've heard it, but it's always 00:21:36.440 --> 00:21:39.380 amazing. She was studying a T. rex femur specimen, 00:21:39.640 --> 00:21:43.920 MOR1125. They had to break the bone to ship it 00:21:43.920 --> 00:21:46.440 via helicopter, which is usually a no -no, but 00:21:46.440 --> 00:21:47.980 it was a happy accident. It allowed her to look 00:21:47.980 --> 00:21:49.960 deep inside the marrow cavity. And she didn't 00:21:49.960 --> 00:21:52.900 just find rock? No. She dissolved the mineral 00:21:52.900 --> 00:21:56.140 part of the bone away using a weak acid, a process 00:21:56.140 --> 00:21:58.900 called demineralization, and she was left with 00:21:58.900 --> 00:22:02.269 flexible, stretchy tissue. She found transparent 00:22:02.269 --> 00:22:04.609 structures that looked like blood vessels. She 00:22:04.609 --> 00:22:06.789 found small red round things that looked like 00:22:06.789 --> 00:22:09.690 red blood cells. In a 68 million year old bone, 00:22:09.849 --> 00:22:11.769 that shouldn't be possible. Everyone thought 00:22:11.769 --> 00:22:14.109 it was impossible. Fossilization is supposed 00:22:14.109 --> 00:22:16.410 to replace everything with mineral. But she found 00:22:16.410 --> 00:22:19.349 collagen protein. It caused a massive storm in 00:22:19.349 --> 00:22:21.230 the scientific community. People said it was 00:22:21.230 --> 00:22:24.210 biofilm bacteria contamination. But it held up. 00:22:24.269 --> 00:22:26.859 It held up. Study after study has supported the 00:22:26.859 --> 00:22:30.039 idea that some original organic material can 00:22:30.039 --> 00:22:32.460 survive under the right conditions. That is mind 00:22:32.460 --> 00:22:34.420 -blowing. And it helped confirm the connection 00:22:34.420 --> 00:22:37.420 to birds, right? It did. The proteins they sequenced 00:22:37.420 --> 00:22:39.980 matched most closely with chickens and ostriches. 00:22:40.200 --> 00:22:42.880 But there was another clue in that femur. She 00:22:42.880 --> 00:22:46.660 found medullary bone. What is that? It's a special 00:22:46.660 --> 00:22:49.839 type of bone tissue that only female birds produce 00:22:49.839 --> 00:22:52.059 when they are pregnant, or rather, when they 00:22:52.059 --> 00:22:55.700 are ovulating, to create eggshells. It acts as 00:22:55.700 --> 00:22:59.579 a calcium reservoir. Finding it in a T -Rex proved 00:22:59.579 --> 00:23:01.440 this specimen was a female and she was pregnant 00:23:01.440 --> 00:23:03.480 when she died. That is incredible. We can actually 00:23:03.480 --> 00:23:06.380 sex the dinosaur from its bone tissue. Now, speaking 00:23:06.380 --> 00:23:09.000 of birds, feathers. The other big controversy. 00:23:09.680 --> 00:23:11.559 The one everyone wants to know about. Did T. 00:23:11.680 --> 00:23:13.859 rex look like a giant chicken? Because I've seen 00:23:13.859 --> 00:23:15.880 the art. Sometimes it's fluffy. Sometimes it's 00:23:15.880 --> 00:23:18.140 scaly. What's the verdict? It's complicated. 00:23:18.240 --> 00:23:20.880 We know for a fact that early Tyrannosauroids, 00:23:20.900 --> 00:23:24.099 the ancestors, had feathers. A fossil from China 00:23:24.099 --> 00:23:26.900 called Dilong had them. And Eudoranus. And the 00:23:26.900 --> 00:23:29.339 large Eudoranus, which also lived in China, was 00:23:29.339 --> 00:23:31.880 covered in shaggy filamentous feathers. And it 00:23:31.880 --> 00:23:34.940 was big, about nine meters long. So big Tyrannosaurs 00:23:34.940 --> 00:23:38.579 can have feathers. It's possible. Yes. It's definitely 00:23:38.579 --> 00:23:41.859 possible. However, for T. rex specifically, we 00:23:41.859 --> 00:23:44.200 have skin impressions. We have patches of skin 00:23:44.200 --> 00:23:47.380 from the neck, the tail, the hip, from a specimen 00:23:47.380 --> 00:23:50.839 nicknamed Y. rex. And what do they show? Scales. 00:23:51.859 --> 00:23:55.259 Tiny, bumpy, mosaic scales. No sign of feathers 00:23:55.259 --> 00:23:58.480 in those preserved patches. So, no feathers. 00:23:58.579 --> 00:24:00.619 Likely not a full coat. Think about it like an 00:24:00.619 --> 00:24:03.000 elephant. Elephants are mammals. Their ancestors 00:24:03.000 --> 00:24:05.619 were hairy. But elephants are huge and live in 00:24:05.619 --> 00:24:07.779 warm climates. If they were covered in thick 00:24:07.779 --> 00:24:10.380 fur, they'd overheat. Gigantothermy. They're 00:24:10.380 --> 00:24:12.640 so big, they generate their own heat. Exactly. 00:24:13.099 --> 00:24:16.400 Large animals retain heat well. A fully feathered 00:24:16.400 --> 00:24:18.440 adult T. rex might have cooked itself from the 00:24:18.440 --> 00:24:20.519 inside out. So the current thinking is that if 00:24:20.519 --> 00:24:22.440 they had feathers, they were sparse, maybe just 00:24:22.440 --> 00:24:24.720 along the back like elephant hair, or maybe they 00:24:24.720 --> 00:24:26.880 were born with downy feathers and lost them as 00:24:26.880 --> 00:24:29.119 they grew up. So less giant chicken and more 00:24:29.119 --> 00:24:32.279 scaly monster with maybe a feathery mullet. That's 00:24:32.279 --> 00:24:34.880 a fair visual. A very intimidating mullet. Okay, 00:24:34.940 --> 00:24:37.640 let's get into the behavior. The diet. Predator 00:24:37.640 --> 00:24:40.440 or scavenger? This was a huge debate in the 90s, 00:24:40.440 --> 00:24:44.000 thanks largely to Jack Horner. Right. Jack Horner. 00:24:44.319 --> 00:24:46.819 The famous paleontologist who advised on the 00:24:46.819 --> 00:24:49.759 Jurassic Park films, ironically, really pushed 00:24:49.759 --> 00:24:52.680 the pure scavenger hypothesis. And his argument 00:24:52.680 --> 00:24:55.680 was what? He looked at the tiny arms, useless 00:24:55.680 --> 00:24:58.279 for grappling, the relatively slow speed we just 00:24:58.279 --> 00:25:00.680 talked about, and that incredible sense of smell, 00:25:00.819 --> 00:25:03.480 and said, this thing is a glorified vulture. 00:25:03.539 --> 00:25:06.059 It walks around sniffing out dead things. It 00:25:06.059 --> 00:25:08.940 makes sense on paper. Why risk fighting a triceratops 00:25:08.940 --> 00:25:10.700 if you can just eat a dead one? It does make 00:25:10.700 --> 00:25:13.619 sense energetically. And to be clear, T -Rex 00:25:13.619 --> 00:25:15.640 absolutely scavenged. If it found a free meal, 00:25:15.740 --> 00:25:17.960 it would take it. Almost all large predators 00:25:17.960 --> 00:25:21.019 do. Lions scavenge. Wolves scavenge. But was 00:25:21.019 --> 00:25:22.960 it only a scavenger? That's where the theory 00:25:22.960 --> 00:25:25.119 falls apart. We have the smoking guns. Healed 00:25:25.119 --> 00:25:27.359 wounds. Yes. We have fossil evidence of failed 00:25:27.359 --> 00:25:30.619 predation. There is an Edmontosaurus, a duck 00:25:30.619 --> 00:25:32.839 -billed dinosaur with a tail vertebrae that has 00:25:32.839 --> 00:25:35.259 a chunk missing. And nestled in that wound... 00:25:35.390 --> 00:25:37.730 is a T -Rex tooth. And the key part. The bone 00:25:37.730 --> 00:25:39.750 has grown back over the wound and around the 00:25:39.750 --> 00:25:42.130 tooth. Which means? It means a T -Rex bit it 00:25:42.130 --> 00:25:45.190 and the Edmontosaurus got away and lived long 00:25:45.190 --> 00:25:47.890 enough for its bone to heal. You can't bite a 00:25:47.890 --> 00:25:50.589 dead animal and have it heal. Evidence of active 00:25:50.589 --> 00:25:53.650 hunting. The ultimate proof. There's also a Triceratops 00:25:53.650 --> 00:25:55.369 horn that was bitten off and the stump healed 00:25:55.369 --> 00:25:58.009 over. Oh. So T -Rex was actively hunting live, 00:25:58.130 --> 00:26:01.769 dangerous prey. And when it bit? The hardest. 00:26:02.190 --> 00:26:05.289 The bite force estimates are, frankly, astronomical. 00:26:05.650 --> 00:26:09.049 They're between 35 ,000 and 57 ,000 newtons. 00:26:09.170 --> 00:26:11.289 Put that in perspective for me. What's a human 00:26:11.289 --> 00:26:14.390 bite? A human is maybe 800 newtons on a good 00:26:14.390 --> 00:26:18.250 day. A lion is maybe 4 ,000 newtons. A saltwater 00:26:18.250 --> 00:26:20.289 crocodile, the living champion, is around 16 00:26:20.289 --> 00:26:22.650 ,000. T -Rex is more than double that, maybe 00:26:22.650 --> 00:26:24.950 triple. It's just off the charts. It's hydraulic 00:26:24.950 --> 00:26:27.329 press levels of force. You can simply crush the 00:26:27.329 --> 00:26:29.410 neck or back of its prey instantly. It didn't 00:26:29.410 --> 00:26:31.190 need to be surgical. It was overwhelming force. 00:26:31.470 --> 00:26:34.869 So a terrifying predator. But did it hunt alone? 00:26:35.359 --> 00:26:37.519 Or are we talking about the dino gang's hypothesis? 00:26:38.059 --> 00:26:39.799 This is fascinating. The idea of pack hunting 00:26:39.799 --> 00:26:41.799 tyrannosaurs was really pushed by Philip Curry. 00:26:42.220 --> 00:26:45.000 He based this on bone beds places where multiple 00:26:45.000 --> 00:26:47.000 tyrannosaurs of different ages died together. 00:26:47.279 --> 00:26:50.380 Like the dry island bone bed in Alberta. Exactly. 00:26:50.500 --> 00:26:53.720 For the related tyrannosaur Albertosaurus, you 00:26:53.720 --> 00:26:57.180 have two dozen individuals, from young juveniles 00:26:57.180 --> 00:27:00.200 to old adults, all dead in the same place. And 00:27:00.200 --> 00:27:02.799 Curry's idea was that this was a pack. His idea 00:27:02.799 --> 00:27:05.779 is that they had a division of labor. The fast, 00:27:05.940 --> 00:27:09.180 lanky teenagers, the nanotyrannostypes, would 00:27:09.180 --> 00:27:12.000 act as the drivers, flushing out the prey. And 00:27:12.000 --> 00:27:14.299 the massive, bone -crushing adults would be the 00:27:14.299 --> 00:27:17.460 anvil that the prey ran into. That is a terrifying 00:27:17.460 --> 00:27:20.500 coordinated strategy. Is it accepted? It's debated. 00:27:20.839 --> 00:27:23.559 Some argue that the bone beds could just be predator 00:27:23.559 --> 00:27:25.740 traps. Maybe they all got stuck in mud over time 00:27:25.740 --> 00:27:28.680 or gathered at a drying waterhole. But then there 00:27:28.680 --> 00:27:31.009 are the trackways. In Canada, we found tracks 00:27:31.009 --> 00:27:32.970 of three tyrannosaurs moving together in the 00:27:32.970 --> 00:27:35.150 same direction at the same speed. That sounds 00:27:35.150 --> 00:27:37.470 like a group to me. It definitely suggests some 00:27:37.470 --> 00:27:39.730 level of social behavior. They weren't just solitary 00:27:39.730 --> 00:27:42.410 loners. They tolerated each other, at least sometimes. 00:27:43.289 --> 00:27:45.589 Tolerated being the key word, because there is 00:27:45.589 --> 00:27:48.029 a darker side to their social life. Cannibalism. 00:27:48.109 --> 00:27:51.150 We have proof of this. We do. We have T -Rex 00:27:51.150 --> 00:27:54.279 bones with T -Rex tooth marks on them. And given 00:27:54.279 --> 00:27:57.140 the spacing and shape of the gouges, it can only 00:27:57.140 --> 00:27:59.819 be another T -Rex. So if it's a buddy died. Lunch 00:27:59.819 --> 00:28:01.880 is served. Or maybe they thought to the death 00:28:01.880 --> 00:28:04.319 and the winner ate the loser. It's a dog -eat 00:28:04.319 --> 00:28:08.200 -dog world. Rex eat Rex world. Brutal. Now, before 00:28:08.200 --> 00:28:10.059 we wrap up, we have to touch on the taxonomy 00:28:10.059 --> 00:28:12.680 wars. We mentioned Nanotyrannus, but there was 00:28:12.680 --> 00:28:15.940 that study in 2022 that tried to split T -Rex 00:28:15.940 --> 00:28:18.019 into three species. Oh, the king, queen, and 00:28:18.019 --> 00:28:20.460 emperor study. Like Gregory Paul and his colleagues. 00:28:20.640 --> 00:28:23.119 Right. They argued that the variation we see 00:28:23.119 --> 00:28:25.579 in skeletons, some are robust with two pairs 00:28:25.579 --> 00:28:27.980 of incisors, some are slender with one worn in 00:28:27.980 --> 00:28:31.500 three names. Tyrannosaurus Rex, the king. Tyrannosaurus 00:28:31.500 --> 00:28:34.670 Imperator. the emperor, and Tyrannosaurus Regina, 00:28:34.970 --> 00:28:38.309 the queen. Did that stick? Not really. The paleontological 00:28:38.309 --> 00:28:40.869 community largely rejected it. The consensus 00:28:40.869 --> 00:28:42.849 is that the differences are just natural variation 00:28:42.849 --> 00:28:45.630 within a single species. Just like humans vary 00:28:45.630 --> 00:28:47.990 in height and build, T. rex did too. Or maybe 00:28:47.990 --> 00:28:50.150 males and females were different sizes. Exactly. 00:28:50.250 --> 00:28:53.869 Sexual dimorphism could account for it. The boundaries 00:28:53.869 --> 00:28:57.009 between the proposed species were just too fuzzy 00:28:57.009 --> 00:28:59.369 to be taxonomically valid for most people. So 00:28:59.369 --> 00:29:01.609 for now, T. rex stands alone as the one king. 00:29:02.029 --> 00:29:05.089 Mostly. But there is a new twist from just this 00:29:05.089 --> 00:29:09.809 year, 2024. Tyrannosaurus micreansus. The New 00:29:09.809 --> 00:29:13.589 Mexico find? Yes. A partial skull found in the 00:29:13.589 --> 00:29:16.829 Hall Lake Formation. It looks incredibly similar 00:29:16.829 --> 00:29:19.750 to T. rex, but the dating suggests it might be 00:29:19.750 --> 00:29:23.390 6 to 7 million years older. Whoa. So the grandfather 00:29:23.390 --> 00:29:26.930 of T. rex. Or a very close cousin. A direct ancestor, 00:29:27.150 --> 00:29:29.750 perhaps? It suggests that the Tyrannosaurus lineage 00:29:29.750 --> 00:29:32.230 might have originated in southern Laramidia, 00:29:32.250 --> 00:29:34.369 what is now the southern U .S., rather than being 00:29:34.369 --> 00:29:36.230 an immigrant from Asia, which was a leading theory. 00:29:36.569 --> 00:29:38.710 So the king might be a native son after all. 00:29:38.789 --> 00:29:40.869 It rewrites the map of where the tyrant king 00:29:40.869 --> 00:29:42.849 came from. So let's bring it all together. The 00:29:42.849 --> 00:29:44.990 real T -Rex. It's not the movie monster. No, 00:29:45.049 --> 00:29:47.549 it's a smart, social, potentially lipped, power 00:29:47.549 --> 00:29:50.250 walking, bone crushing, attentive parent that 00:29:50.250 --> 00:29:53.250 grew from a lanky teen into a massive bulk. It's 00:29:53.250 --> 00:29:55.630 an animal that lived a violent life, grew faster 00:29:55.630 --> 00:29:58.089 than almost anything else, and died young. It's 00:29:58.089 --> 00:30:00.670 scarier than the movies because it's a real biological 00:30:00.670 --> 00:30:03.609 animal that was Perfectly adapted to its world. 00:30:03.789 --> 00:30:07.390 Exactly. The why it matters is that Tyrannosaurus 00:30:07.390 --> 00:30:11.230 is the standard bearer for paleontology. Every 00:30:11.230 --> 00:30:14.910 new technology, CT scans, molecular analysis, 00:30:15.190 --> 00:30:18.390 biomechanical modeling is tested on T. rex first. 00:30:18.990 --> 00:30:20.910 Understanding it helps us understand the limits 00:30:20.910 --> 00:30:23.509 of life itself. And that leads me to my final 00:30:23.509 --> 00:30:28.480 thought. The soft tissue. The collagen. If we 00:30:28.480 --> 00:30:31.299 can find proteins in a 68 million year old bone, 00:30:31.579 --> 00:30:33.460 what does that mean for the future of genetic 00:30:33.460 --> 00:30:35.839 research? We're not talking about cloning, but 00:30:35.839 --> 00:30:38.660 could we one day know the color of its eyes from 00:30:38.660 --> 00:30:41.460 melanosomes or the actual sound of its call from 00:30:41.460 --> 00:30:43.599 the structure of its inner ear and syrinx? We're 00:30:43.599 --> 00:30:45.799 opening doors we didn't even know existed. We 00:30:45.799 --> 00:30:47.660 may never resurrect them, but we might know them 00:30:47.660 --> 00:30:49.480 more intimately than we ever thought possible. 00:30:49.640 --> 00:30:51.180 Next time you see a pigeon on the street, just 00:30:51.180 --> 00:30:53.619 remember that's the distant fluttering cousin 00:30:53.619 --> 00:30:55.799 of the tyrant king. Thanks for diving deep with 00:30:55.799 --> 00:30:56.579 us. Always a pleasure.