1 00:00:01,233 --> 00:00:04,100 ♪ ♪ 2 00:00:05,833 --> 00:00:10,800 ♪ ♪ 3 00:00:12,066 --> 00:00:14,542 DAVID ATTENBOROUGH: Dinosaurs. 4 00:00:14,566 --> 00:00:16,809 {\an1}Perhaps some of the most dramatic animals 5 00:00:16,833 --> 00:00:19,576 {\an1}ever to have walked the Earth. 6 00:00:19,600 --> 00:00:21,476 (dinosaurs lowing) 7 00:00:21,500 --> 00:00:26,909 {\an1}They dominated the world for over 150 million years, 8 00:00:26,933 --> 00:00:31,266 {\an1}until a huge asteroid struck the planet. 9 00:00:36,233 --> 00:00:39,366 {\an1}But how exactly did they die? 10 00:00:40,500 --> 00:00:42,876 Paleontologists have been searching 11 00:00:42,900 --> 00:00:45,176 {\an1}for the answer for decades. 12 00:00:45,200 --> 00:00:46,476 ♪ ♪ 13 00:00:46,500 --> 00:00:50,809 {\an1}And now new evidence is coming to light. 14 00:00:50,833 --> 00:00:52,733 STEVE BRUSATTE: We're out looking for clues. 15 00:00:55,233 --> 00:00:57,476 {\an1}And each fossil is a clue, 16 00:00:57,500 --> 00:00:59,276 {\an1}and that tells us something 17 00:00:59,300 --> 00:01:02,009 {\an1}about what the world was like at that time. 18 00:01:02,033 --> 00:01:04,576 ATTENBOROUGH: Since 2012, 19 00:01:04,600 --> 00:01:07,242 {\an1}a team of paleontologists has been investigating 20 00:01:07,266 --> 00:01:12,533 {\an1}a remarkable site deep in the Badlands of North Dakota. 21 00:01:15,800 --> 00:01:19,176 The team's leader, Robert DePalma, 22 00:01:19,200 --> 00:01:21,809 {\an1}hopes it holds evidence of what happened 23 00:01:21,833 --> 00:01:24,709 on the very last day of the dinosaurs. 24 00:01:24,733 --> 00:01:27,776 (thunder rumbling) 25 00:01:27,800 --> 00:01:29,909 {\an1}Could it even contain the remains of an animal 26 00:01:29,933 --> 00:01:33,476 that bore witness to that terrible event? 27 00:01:33,500 --> 00:01:35,542 {\an1}We've got all these bones in the ground right now, 28 00:01:35,566 --> 00:01:39,376 {\an1}but the one thing that we would just dream of finding 29 00:01:39,400 --> 00:01:42,909 {\an1}is that one dinosaur that died on the day of the impact. 30 00:01:42,933 --> 00:01:45,176 ♪ ♪ 31 00:01:45,200 --> 00:01:47,409 BRUSATTE: The idea that there is a dinosaur fossil potentially 32 00:01:47,433 --> 00:01:49,576 {\an1}that's a direct victim of that, that's very exciting. 33 00:01:49,600 --> 00:01:51,776 {\an5}MAN: Whoa! DEPALMA: That's skin right there. 34 00:01:51,800 --> 00:01:53,442 {\an1}That's actually scaly skin. My God! 35 00:01:53,466 --> 00:01:55,776 ATTENBOROUGH: Can they find a dinosaur 36 00:01:55,800 --> 00:01:58,909 that died on the day the asteroid hit? 37 00:01:58,933 --> 00:02:02,009 ♪ ♪ 38 00:02:02,033 --> 00:02:06,176 {\an1}"Dinosaur Apocalypse: The Last Day," 39 00:02:06,200 --> 00:02:08,409 {\an1}right now, on "NOVA." 40 00:02:08,433 --> 00:02:13,266 ♪ ♪ 41 00:02:30,866 --> 00:02:34,842 ♪ ♪ 42 00:02:34,866 --> 00:02:36,442 ATTENBOROUGH: For ten years, 43 00:02:36,466 --> 00:02:39,376 {\an1}paleontologist Robert DePalma and his team 44 00:02:39,400 --> 00:02:41,809 {\an8}have been digging in a small corner 45 00:02:41,833 --> 00:02:43,542 {\an1}of the Hell Creek Formation, 46 00:02:43,566 --> 00:02:46,842 {\an1}an area famous for more than a century 47 00:02:46,866 --> 00:02:49,476 {\an1}of major dinosaur discoveries. 48 00:02:49,500 --> 00:02:52,909 {\an1}They've already found a wealth of fossilized creatures 49 00:02:52,933 --> 00:02:54,842 {\an1}in a patch of land they call Tanis. 50 00:02:54,866 --> 00:02:57,642 {\an8}(chuckling): Oh, wow. 51 00:02:57,666 --> 00:03:00,309 ATTENBOROUGH: What appears to be a piece of fossilized skin 52 00:03:00,333 --> 00:03:02,909 from a triceratops; 53 00:03:02,933 --> 00:03:05,242 the unhatched egg 54 00:03:05,266 --> 00:03:08,076 and what looks like a pterosaur embryo; 55 00:03:08,100 --> 00:03:10,209 jawbones of a mammal 56 00:03:10,233 --> 00:03:12,509 {\an8}called a pediomyid; 57 00:03:12,533 --> 00:03:14,109 and teeth 58 00:03:14,133 --> 00:03:16,709 {\an8}and footprints of carnivorous dinosaurs 59 00:03:16,733 --> 00:03:19,376 like T. rex. 60 00:03:19,400 --> 00:03:21,242 DEPALMA: There is no other dinosaur 61 00:03:21,266 --> 00:03:23,242 {\an1}that has teeth like this. 62 00:03:23,266 --> 00:03:24,542 ATTENBOROUGH: Many of these fossils 63 00:03:24,566 --> 00:03:28,576 {\an1}were found in a thick layer of crumbly rock. 64 00:03:28,600 --> 00:03:30,642 {\an1}The rock here is really not quite rocky, 65 00:03:30,666 --> 00:03:33,976 {\an1}and it just falls apart in your hands. 66 00:03:34,000 --> 00:03:38,376 ATTENBOROUGH: Right above the crumbly rock is the K-Pg boundary, 67 00:03:38,400 --> 00:03:42,642 {\an1}a layer of iridium-rich debris from the asteroid impact 68 00:03:42,666 --> 00:03:45,776 that hit the Earth 66 million years ago. 69 00:03:45,800 --> 00:03:49,776 {\an1}It marks the end of the age of dinosaurs. 70 00:03:49,800 --> 00:03:52,042 CATHY PLESKO: If you look below this layer, 71 00:03:52,066 --> 00:03:54,309 {\an7}you see fossils of dinosaurs. 72 00:03:54,333 --> 00:03:56,576 {\an7}If you look above this layer, no dinosaurs. 73 00:03:56,600 --> 00:04:00,476 ATTENBOROUGH: The four-foot-thick layer of rock at Tanis 74 00:04:00,500 --> 00:04:03,242 {\an1}is full of ejecta spherules. 75 00:04:03,266 --> 00:04:05,476 DEPALMA: And beautiful... look at that. 76 00:04:05,500 --> 00:04:08,809 ♪ ♪ 77 00:04:08,833 --> 00:04:13,009 ATTENBOROUGH: Tiny glass droplets created in a major asteroid impact. 78 00:04:13,033 --> 00:04:16,242 ♪ ♪ 79 00:04:16,266 --> 00:04:18,842 {\an1}Robert thinks that this is compelling evidence 80 00:04:18,866 --> 00:04:22,509 {\an1}that everything in the layer was buried while the spherules fell. 81 00:04:22,533 --> 00:04:27,042 ♪ ♪ 82 00:04:27,066 --> 00:04:30,209 If he's right, and the spherules he's found 83 00:04:30,233 --> 00:04:32,742 can be matched to the asteroid impact, 84 00:04:32,766 --> 00:04:35,309 {\an1}this dig site could provide a snapshot 85 00:04:35,333 --> 00:04:39,509 {\an1}of what happened on the very last day of the dinosaurs. 86 00:04:39,533 --> 00:04:40,642 BRUSATTE: Stories like this 87 00:04:40,666 --> 00:04:42,509 {\an7}are eminently plausible. 88 00:04:42,533 --> 00:04:44,542 {\an8}Proving them is more challenging. 89 00:04:44,566 --> 00:04:48,842 EMILY BAMFORTH: It opens up that whole debate about, how do we link 90 00:04:48,866 --> 00:04:53,409 {\an7}catastrophic events to fossil and geologic deposits? 91 00:04:53,433 --> 00:04:54,776 SONIA TIKOO: If we can 92 00:04:54,800 --> 00:04:58,409 both match spherules to the impact site, 93 00:04:58,433 --> 00:05:01,609 {\an7}geochemically and in terms of radiometric ages, 94 00:05:01,633 --> 00:05:04,333 {\an7}that's pretty accurate... That's a smoking gun. 95 00:05:05,900 --> 00:05:07,809 {\an7}After ten years of digging, 96 00:05:07,833 --> 00:05:10,909 {\an7}there is now enough evidence to piece together 97 00:05:10,933 --> 00:05:13,009 {\an7}much of the story of Tanis 98 00:05:13,033 --> 00:05:15,409 and the creatures which lived here. 99 00:05:15,433 --> 00:05:18,876 {\an1}But how, exactly, did they die? 100 00:05:18,900 --> 00:05:23,333 ♪ ♪ 101 00:05:30,466 --> 00:05:34,342 {\an1}The asteroid that struck the Earth 66 million years ago 102 00:05:34,366 --> 00:05:37,609 {\an1}created what is today known as the Chicxulub crater. 103 00:05:37,633 --> 00:05:39,942 ♪ ♪ 104 00:05:39,966 --> 00:05:42,942 {\an1}To find out if the ejecta spherules they've found 105 00:05:42,966 --> 00:05:44,776 {\an1}in North Dakota can be linked 106 00:05:44,800 --> 00:05:46,909 to Chicxulub, Robert has come 107 00:05:46,933 --> 00:05:48,642 to the Diamond Light Source Synchrotron 108 00:05:48,666 --> 00:05:51,576 in the U.K. 109 00:05:51,600 --> 00:05:55,942 {\an1}Joining him is Phil Manning of the University of Manchester. 110 00:05:55,966 --> 00:05:57,609 They've already run 111 00:05:57,633 --> 00:06:01,342 {\an1}initial tests in America on over a dozen spherules 112 00:06:01,366 --> 00:06:04,633 {\an1}found in different areas of the crumbly layer. 113 00:06:07,633 --> 00:06:09,176 {\an1}What have you found out so far? 114 00:06:09,200 --> 00:06:11,242 {\an1}These little glass spherules, these globs 115 00:06:11,266 --> 00:06:13,409 of molten material from the impact site, 116 00:06:13,433 --> 00:06:15,476 have a chemical signal that ties it 117 00:06:15,500 --> 00:06:16,709 {\an1}with where they came from. 118 00:06:16,733 --> 00:06:18,176 {\an1}'Cause when an asteroid hits, 119 00:06:18,200 --> 00:06:20,642 it melts the ground that it hits, 120 00:06:20,666 --> 00:06:24,009 {\an1}but also, that glass has a little bit of contamination 121 00:06:24,033 --> 00:06:25,276 {\an1}from the asteroid itself. 122 00:06:25,300 --> 00:06:28,576 {\an1}And that gives you a unique geochemical fingerprint. 123 00:06:28,600 --> 00:06:31,542 MANNING: We can see once we've scanned it, and looking at other sites 124 00:06:31,566 --> 00:06:33,209 from around the world... 125 00:06:33,233 --> 00:06:36,076 Haiti, Mexico, and North Dakota... 126 00:06:36,100 --> 00:06:39,342 We can get a baseline for what the ejecta 127 00:06:39,366 --> 00:06:42,109 should look like when it's related 128 00:06:42,133 --> 00:06:43,742 to the Chicxulub crater. 129 00:06:43,766 --> 00:06:45,676 You can see each element here 130 00:06:45,700 --> 00:06:47,342 and the ratios of those elements. 131 00:06:47,366 --> 00:06:48,976 {\an1}And when we look at Tanis, 132 00:06:49,000 --> 00:06:51,909 it's a match... I mean, 133 00:06:51,933 --> 00:06:53,309 {\an1}it perfectly overlays. 134 00:06:53,333 --> 00:06:56,276 So I think this is powerful evidence 135 00:06:56,300 --> 00:06:58,376 {\an1}supporting that Tanis and Chicxulub 136 00:06:58,400 --> 00:07:00,976 are linked. Wow. 137 00:07:01,000 --> 00:07:03,809 {\an1}And what do these findings mean 138 00:07:03,833 --> 00:07:05,776 {\an1}for the rest of the fossils that you're finding in Tanis? 139 00:07:05,800 --> 00:07:08,942 {\an8}This data is key for the entire site, 140 00:07:08,966 --> 00:07:11,042 {\an7}because once you have that link 141 00:07:11,066 --> 00:07:13,809 and you know what impact affected Tanis, 142 00:07:13,833 --> 00:07:16,009 {\an1}then you essentially know that 143 00:07:16,033 --> 00:07:18,409 {\an1}every object in that site, all the animals 144 00:07:18,433 --> 00:07:21,609 {\an1}and the plants and everything buried in those sediments, 145 00:07:21,633 --> 00:07:24,466 {\an1}are linked to the last day of the Cretaceous. 146 00:07:26,300 --> 00:07:27,909 {\an1}ANUSUYA CHINSAMY-TURAN: This is very important 147 00:07:27,933 --> 00:07:30,576 {\an7}because it immediately gives a time stamp 148 00:07:30,600 --> 00:07:33,476 {\an7}for the locality itself. 149 00:07:33,500 --> 00:07:34,742 {\an8}BAMFORTH: The Tanis site is 150 00:07:34,766 --> 00:07:38,242 {\an1}like a window into a snapshot of time. 151 00:07:38,266 --> 00:07:43,742 {\an8}ATTENBOROUGH: With ejecta spherules found everywhere throughout 152 00:07:43,766 --> 00:07:45,376 {\an7}the four-foot-thick deposit, 153 00:07:45,400 --> 00:07:47,409 {\an7}Robert and his team seem to be able 154 00:07:47,433 --> 00:07:49,876 {\an8}to link their site to a single day. 155 00:07:49,900 --> 00:07:52,142 ♪ ♪ 156 00:07:52,166 --> 00:07:53,676 {\an1}And the synchrotron here in the U.K. 157 00:07:53,700 --> 00:07:57,342 {\an1}reveals something even more remarkable. 158 00:07:57,366 --> 00:08:02,076 DEPALMA: So this is showing a beautiful synchrotron scan 159 00:08:02,100 --> 00:08:04,442 {\an1}of the half of one spherule. 160 00:08:04,466 --> 00:08:05,909 The glass 161 00:08:05,933 --> 00:08:08,376 is a good geochemical fingerprint, but, 162 00:08:08,400 --> 00:08:10,076 when we look at the entire thing, 163 00:08:10,100 --> 00:08:12,009 we see something quite unexpected. 164 00:08:12,033 --> 00:08:15,276 {\an8}That's your entire spherule. 165 00:08:15,300 --> 00:08:16,709 {\an8}What's this? 166 00:08:16,733 --> 00:08:19,709 {\an8}In this, we've got a little bit of a nugget. 167 00:08:19,733 --> 00:08:21,909 {\an7}There was a little particle right there. 168 00:08:21,933 --> 00:08:25,576 {\an7}So we scan it, and that's a lot of iron in there. 169 00:08:25,600 --> 00:08:28,442 {\an1}Over here, we've got chromium, a big peak in chromium. 170 00:08:28,466 --> 00:08:31,576 Over here, we've got a big peak in nickel. 171 00:08:31,600 --> 00:08:33,576 {\an1}And the abundances of iron, 172 00:08:33,600 --> 00:08:35,742 nickel, and chromium, all together, 173 00:08:35,766 --> 00:08:38,942 {\an1}that matches what you expect to see in a meteoric body. 174 00:08:38,966 --> 00:08:40,642 {\an1}That does not match what you would normally have 175 00:08:40,666 --> 00:08:42,376 down here. 176 00:08:42,400 --> 00:08:45,709 So this is extraterrestrial material. 177 00:08:45,733 --> 00:08:47,909 {\an1}If you were to sort of grind up 178 00:08:47,933 --> 00:08:51,309 and stuff into a, a spherule 179 00:08:51,333 --> 00:08:53,276 {\an1}a piece of meteorite, 180 00:08:53,300 --> 00:08:55,542 that's what it's gonna look like. 181 00:08:55,566 --> 00:08:56,576 DEPALMA: This could be 182 00:08:56,600 --> 00:08:58,576 piece of the Chicxulub asteroid. 183 00:08:58,600 --> 00:09:00,842 {\an7}The piece of the bullet that killed the dinosaurs. 184 00:09:00,866 --> 00:09:02,642 No. 185 00:09:02,666 --> 00:09:07,309 ♪ ♪ 186 00:09:07,333 --> 00:09:10,076 {\an1}Robert's team may have found a fragment 187 00:09:10,100 --> 00:09:13,676 {\an1}of the asteroid itself in North Dakota, 188 00:09:13,700 --> 00:09:19,476 {\an1}physical evidence linking this site to the Chicxulub impact. 189 00:09:19,500 --> 00:09:22,876 But Tanis is almost 2,000 miles away 190 00:09:22,900 --> 00:09:24,442 {\an1}from where the asteroid hit. 191 00:09:24,466 --> 00:09:28,409 {\an1}So exactly how did the asteroid 192 00:09:28,433 --> 00:09:32,176 cause the death of the animals here? 193 00:09:32,200 --> 00:09:34,309 {\an1}To answer that question, 194 00:09:34,333 --> 00:09:36,876 Robert is searching in something he calls 195 00:09:36,900 --> 00:09:39,566 {\an1}the mass death assemblage. 196 00:09:40,966 --> 00:09:44,342 {\an8}DEPALMA: Right here we've got this intertangled mass of fish. 197 00:09:44,366 --> 00:09:46,976 {\an7}There's one fish here, another sturgeon goes this way, 198 00:09:47,000 --> 00:09:48,842 {\an7}underneath the body of a paddlefish. 199 00:09:48,866 --> 00:09:51,342 {\an7}There's another sturgeon that goes this way, 200 00:09:51,366 --> 00:09:54,309 {\an7}underneath this log, and continues out the other side. 201 00:09:54,333 --> 00:09:56,542 {\an7}And his head hit that log, 202 00:09:56,566 --> 00:09:58,700 {\an7}and has deflected downward at a 90-degree angle. 203 00:10:01,633 --> 00:10:06,809 ATTENBOROUGH: Robert uncovered a tangled mass of fossilized creatures and logs 204 00:10:06,833 --> 00:10:10,509 {\an1}surrounded by spherules and crushed together 205 00:10:10,533 --> 00:10:13,442 {\an1}in what's known as a logjam. 206 00:10:13,466 --> 00:10:16,476 He has a theory that the creatures were swept 207 00:10:16,500 --> 00:10:20,009 {\an1}to their death in some kind of turbulent surge of water, 208 00:10:20,033 --> 00:10:22,176 {\an1}and quickly entombed in sediment, 209 00:10:22,200 --> 00:10:24,842 {\an1}which is why they are so well-preserved. 210 00:10:24,866 --> 00:10:27,709 {\an1}But what could have caused the wave? 211 00:10:27,733 --> 00:10:30,009 ♪ ♪ 212 00:10:30,033 --> 00:10:33,309 {\an1}One hypothesis is a tsunami: 213 00:10:33,333 --> 00:10:37,109 {\an1}the asteroid hit at sea. 214 00:10:37,133 --> 00:10:39,576 {\an7}We talk about a tsunami of completely different scale, 215 00:10:39,600 --> 00:10:42,809 {\an7}much higher, much larger than we've ever seen before 216 00:10:42,833 --> 00:10:45,209 in modern tsunamis. 217 00:10:45,233 --> 00:10:48,876 SEAN GULICK: So if you had 6,000 feet of water, 218 00:10:48,900 --> 00:10:51,942 {\an7}at least half of that would have left as the rim wave. 219 00:10:51,966 --> 00:10:55,209 {\an1}So at least 3,000 feet high at a minimum. 220 00:10:55,233 --> 00:10:59,576 ATTENBOROUGH: The tsunami raced towards land. 221 00:10:59,600 --> 00:11:01,876 TITOV: When they reached the coastlines, 222 00:11:01,900 --> 00:11:06,742 {\an1}they were still very high waves of up to 300 feet high. 223 00:11:06,766 --> 00:11:11,542 {\an1}At least... probably as high as 1,000-feet-high wave. 224 00:11:11,566 --> 00:11:13,333 {\an1}That's, that's very impressive wave. 225 00:11:14,833 --> 00:11:17,042 Imagine the wave that's the size of a building 226 00:11:17,066 --> 00:11:20,076 {\an1}approaching the coastline. 227 00:11:20,100 --> 00:11:21,642 ATTENBOROUGH: In the Late Cretaceous, 228 00:11:21,666 --> 00:11:24,676 {\an1}North America was divided by a narrow sea 229 00:11:24,700 --> 00:11:28,409 that has been called the Western Interior Seaway. 230 00:11:28,433 --> 00:11:31,342 {\an1}The tsunami could have theoretically 231 00:11:31,366 --> 00:11:35,642 {\an1}traveled up this towards Hell Creek. 232 00:11:35,666 --> 00:11:37,609 {\an1}Tsunamis generally travel 233 00:11:37,633 --> 00:11:39,233 {\an1}at about the speed of a jet plane. 234 00:11:40,700 --> 00:11:43,709 {\an1}It's not something you could, say, run away from. 235 00:11:43,733 --> 00:11:46,909 {\an1}It had plenty of energy to get over the, the coastline. 236 00:11:46,933 --> 00:11:50,276 {\an1}It could easily still have been tens of meters high 237 00:11:50,300 --> 00:11:54,176 {\an1}by the time it reached well into the seaway. 238 00:11:54,200 --> 00:11:58,209 (wind blowing) 239 00:11:58,233 --> 00:12:00,976 ATTENBOROUGH: Could the rapid deposition at Tanis 240 00:12:01,000 --> 00:12:02,609 {\an1}have been caused by a tsunami? 241 00:12:02,633 --> 00:12:07,033 {\an1}To test the idea, the team needs to look at the timing. 242 00:12:08,266 --> 00:12:09,776 DEPALMA: Oh, which fish is that? 243 00:12:09,800 --> 00:12:11,766 {\an1}It's a new, it's a new contact. New one, yeah. 244 00:12:13,300 --> 00:12:14,742 ATTENBOROUGH: If a tsunami buried the fish, 245 00:12:14,766 --> 00:12:17,742 {\an1}it would have to have hit 246 00:12:17,766 --> 00:12:20,209 {\an1}while the ejecta spherules were falling, 247 00:12:20,233 --> 00:12:22,576 {\an1}because spherules were found everywhere, 248 00:12:22,600 --> 00:12:25,042 {\an1}including in the fishes' gills. 249 00:12:25,066 --> 00:12:27,042 (typing) 250 00:12:27,066 --> 00:12:28,942 {\an1}So much depends on determining 251 00:12:28,966 --> 00:12:33,409 when the spherules were falling at the site. 252 00:12:33,433 --> 00:12:38,009 RILEY BLACK: Modeling the ejecta always has error bars on it, 253 00:12:38,033 --> 00:12:41,676 {\an1}in that we're not there to measure it 254 00:12:41,700 --> 00:12:45,042 {\an7}and we've had no equivalent impact like this on Earth 255 00:12:45,066 --> 00:12:48,409 since then. 256 00:12:48,433 --> 00:12:51,242 PLESKO: But we can look at the computational models 257 00:12:51,266 --> 00:12:53,676 {\an7}that we do and say, all right, 258 00:12:53,700 --> 00:12:56,142 {\an7}this material is coming from 259 00:12:56,166 --> 00:13:00,409 this point, it's now moving away this fast, 260 00:13:00,433 --> 00:13:02,409 {\an1}with about this much mass. 261 00:13:02,433 --> 00:13:04,642 {\an1}And then we can tell, with the sorts of equations 262 00:13:04,666 --> 00:13:08,342 {\an1}that we might use to calculate the trajectory of a cannonball, 263 00:13:08,366 --> 00:13:09,609 where it would go. 264 00:13:09,633 --> 00:13:12,509 {\an1}And we can observe from these simulations 265 00:13:12,533 --> 00:13:14,309 {\an1}how long it takes these ejecta 266 00:13:14,333 --> 00:13:16,542 to reach their final destinations 267 00:13:16,566 --> 00:13:20,176 down to the order of a few minutes. 268 00:13:20,200 --> 00:13:24,742 ATTENBOROUGH: What the calculation shows is surprising. 269 00:13:24,766 --> 00:13:29,309 {\an1}Robert and his team have found that these ejecta spherules 270 00:13:29,333 --> 00:13:32,476 {\an1}landed at Tanis between 13 minutes 271 00:13:32,500 --> 00:13:35,700 {\an1}and two hours after the impact. 272 00:13:37,866 --> 00:13:40,109 {\an1}So, if a wave buried the fish, 273 00:13:40,133 --> 00:13:44,409 {\an1}it must also have reached the site within two hours. 274 00:13:44,433 --> 00:13:47,809 {\an1}Data from recent tsunamis show 275 00:13:47,833 --> 00:13:50,909 {\an1}even a powerful wave would take much longer than this 276 00:13:50,933 --> 00:13:53,142 {\an1}to travel almost 2,000 miles 277 00:13:53,166 --> 00:13:57,742 from the impact site to North Dakota. 278 00:13:57,766 --> 00:13:59,809 ♪ ♪ 279 00:13:59,833 --> 00:14:02,909 {\an1}So, if it wasn't a tsunami, 280 00:14:02,933 --> 00:14:06,876 {\an1}what could have caused a surge of water at Tanis? 281 00:14:06,900 --> 00:14:12,800 ♪ ♪ 282 00:14:19,333 --> 00:14:23,442 {\an1}Stein Bondevik is an expert in tsunamis. 283 00:14:23,466 --> 00:14:26,300 (water sloshing) 284 00:14:28,366 --> 00:14:31,166 BONDEVIK: The fjords in Norway are very special. 285 00:14:32,866 --> 00:14:36,409 {\an1}We have tall mountains surrounding bodies of water. 286 00:14:36,433 --> 00:14:39,409 {\an8}So the water is usually very calm. 287 00:14:39,433 --> 00:14:42,642 {\an8}ATTENBOROUGH: In 2011, 288 00:14:42,666 --> 00:14:45,009 {\an7}something very strange happened. 289 00:14:45,033 --> 00:14:48,742 {\an1}The water in the fjord began to move violently. 290 00:14:48,766 --> 00:14:50,176 BONDEVIK: The height of the water 291 00:14:50,200 --> 00:14:53,376 increased by one-and-a-half meter, 292 00:14:53,400 --> 00:14:55,476 like a maelstrom 293 00:14:55,500 --> 00:14:57,942 {\an7}with the turbulent water. 294 00:14:57,966 --> 00:14:58,976 {\an8}Someone said that 295 00:14:59,000 --> 00:15:00,142 {\an7}the fjord was boiling. 296 00:15:00,166 --> 00:15:02,609 ♪ ♪ 297 00:15:02,633 --> 00:15:05,809 ATTENBOROUGH: News started to roll in, there'd been an earthquake 298 00:15:05,833 --> 00:15:07,942 {\an1}5,000 miles away in Japan. 299 00:15:07,966 --> 00:15:10,509 ♪ ♪ 300 00:15:10,533 --> 00:15:13,542 BONDEVIK: A journalist from the local newspaper called me 301 00:15:13,566 --> 00:15:15,942 {\an1}and he said that people were observing waves 302 00:15:15,966 --> 00:15:18,033 here in the fjords. 303 00:15:19,900 --> 00:15:22,976 {\an1}I got a video clip of the waves. 304 00:15:23,000 --> 00:15:26,909 {\an1}And I saw immediately that they looked like a tsunami wave. 305 00:15:26,933 --> 00:15:29,709 {\an1}Here you can see that that the fjord is perfectly calm. 306 00:15:29,733 --> 00:15:31,376 (water rushing) 307 00:15:31,400 --> 00:15:32,842 {\an1}But at the beach here, 308 00:15:32,866 --> 00:15:36,076 {\an1}you could see that the water is sloshing back and forth. 309 00:15:36,100 --> 00:15:39,909 {\an1}And no one had ever seen anything like it. 310 00:15:39,933 --> 00:15:43,176 {\an1}Some people got very upset and afraid. 311 00:15:43,200 --> 00:15:47,742 ♪ ♪ 312 00:15:47,766 --> 00:15:50,142 ATTENBOROUGH: A magnitude 9.0 earthquake 313 00:15:50,166 --> 00:15:53,642 {\an1}had devastated the northeast of Japan. 314 00:15:53,666 --> 00:15:59,100 {\an7}But how did that affect a fjord so far away? 315 00:16:01,166 --> 00:16:03,876 {\an8}BONDEVIK: So no one in Norway could feel the earthquake. 316 00:16:03,900 --> 00:16:07,742 {\an8}but I could see that the times matched 317 00:16:07,766 --> 00:16:10,700 {\an7}the arrival of the waves here in the fjord. 318 00:16:13,966 --> 00:16:15,476 {\an8}♪ ♪ 319 00:16:15,500 --> 00:16:18,776 {\an8}ATTENBOROUGH: Eventually, Stein and his team realized 320 00:16:18,800 --> 00:16:22,742 {\an7}that this might have something to do with seismic waves, 321 00:16:22,766 --> 00:16:25,542 {\an7}shock waves that pass quickly 322 00:16:25,566 --> 00:16:27,942 through the earth during an earthquake. 323 00:16:27,966 --> 00:16:30,476 BONDEVIK: So it took only 12 minutes before 324 00:16:30,500 --> 00:16:32,542 {\an1}the first signal of the earthquake in Japan 325 00:16:32,566 --> 00:16:35,509 {\an1}reached all the way here to, to western Norway. 326 00:16:35,533 --> 00:16:38,942 ♪ ♪ (birds twittering) 327 00:16:38,966 --> 00:16:42,642 ATTENBOROUGH: So it was the seismic waves that caused the normally calm water 328 00:16:42,666 --> 00:16:47,342 {\an1}in the fjord to slosh turbulently back and forth. 329 00:16:47,366 --> 00:16:50,676 BONDEVIK: Just thinking of that, scientifically, 330 00:16:50,700 --> 00:16:52,409 {\an1}it's, it's fantastic. 331 00:16:52,433 --> 00:16:58,409 ♪ ♪ 332 00:16:58,433 --> 00:17:01,633 ATTENBOROUGH: Could something similar have happened in Tanis? 333 00:17:03,066 --> 00:17:05,076 MARK RICHARDS: Been large weather fronts coming through... 334 00:17:05,100 --> 00:17:07,300 (indistinct chatter) 335 00:17:08,766 --> 00:17:11,309 ATTENBOROUGH: Geophysicist Mark Richards 336 00:17:11,333 --> 00:17:14,376 {\an1}has been studying the site for several years. 337 00:17:14,400 --> 00:17:16,409 The events in Norway 338 00:17:16,433 --> 00:17:19,209 support a hypothesis that he's been working on 339 00:17:19,233 --> 00:17:21,876 with Robert's team about what could have caused 340 00:17:21,900 --> 00:17:24,476 {\an1}the surge of water here. 341 00:17:24,500 --> 00:17:29,076 ♪ ♪ 342 00:17:29,100 --> 00:17:34,442 RICHARDS: A tsunami can't get here in less than minimum 12 hours. 343 00:17:34,466 --> 00:17:36,342 {\an7}But seismic waves traveling 344 00:17:36,366 --> 00:17:38,642 {\an7}from the Yucatan impact site 345 00:17:38,666 --> 00:17:40,109 {\an7}to North Dakota can arrive here 346 00:17:40,133 --> 00:17:41,110 {\an8}fairly quickly. 347 00:17:41,134 --> 00:17:44,142 ♪ ♪ 348 00:17:44,166 --> 00:17:46,009 ATTENBOROUGH: In the Late Cretaceous, 349 00:17:46,033 --> 00:17:49,376 {\an1}the Western Interior Seaway that bisected North America 350 00:17:49,400 --> 00:17:52,142 {\an1}could have been connected to Tanis 351 00:17:52,166 --> 00:17:56,142 {\an1}through the extensive river system that once flowed here. 352 00:17:56,166 --> 00:17:58,409 ♪ ♪ 353 00:17:58,433 --> 00:18:00,909 RICHARDS: If you have a very large body of water, 354 00:18:00,933 --> 00:18:03,942 like the Western Interior Seaway, 355 00:18:03,966 --> 00:18:06,876 and you can shake it back and forth, 356 00:18:06,900 --> 00:18:09,809 you can generate a large water wave 357 00:18:09,833 --> 00:18:13,509 {\an1}coming up this river at Tanis. 358 00:18:13,533 --> 00:18:17,176 GULICK: So this is bigger than any tectonic generated earthquake. 359 00:18:17,200 --> 00:18:20,900 {\an1}You would have shaking literally everywhere on the planet. 360 00:18:22,500 --> 00:18:27,009 ATTENBOROUGH: So, their hypothesis suggests seismic waves from the impact 361 00:18:27,033 --> 00:18:29,142 {\an1}could have caused surges of water 362 00:18:29,166 --> 00:18:31,376 {\an1}in the Hell Creek river system. 363 00:18:31,400 --> 00:18:34,376 RICHARDS: Seismic waves get here quickly enough 364 00:18:34,400 --> 00:18:39,976 {\an1}to cause this wall of water, coming up the Tanis river, 365 00:18:40,000 --> 00:18:41,842 {\an1}inundating this area, 366 00:18:41,866 --> 00:18:43,342 {\an1}arriving at the same time these spherules 367 00:18:43,366 --> 00:18:44,542 are still falling out of the air. 368 00:18:44,566 --> 00:18:47,076 ♪ ♪ 369 00:18:47,100 --> 00:18:51,242 {\an8}ATTENBOROUGH: If they're right, seismic waves traveling through the earth, 370 00:18:51,266 --> 00:18:54,976 {\an7}could have caused a powerful surge of water at Tanis... 371 00:18:55,000 --> 00:18:57,576 (wave crashing) 372 00:18:57,600 --> 00:19:01,042 at the same time as spherules fell. 373 00:19:01,066 --> 00:19:04,476 ♪ ♪ 374 00:19:04,500 --> 00:19:07,909 {\an1}And ultimately dumping it on the Tanis sandbank, 375 00:19:07,933 --> 00:19:11,133 burying everything in the churned-up mud. 376 00:19:13,400 --> 00:19:18,009 {\an1}Debris and fine iridium dust from the asteroid 377 00:19:18,033 --> 00:19:19,776 would have gradually covered the deposit, 378 00:19:19,800 --> 00:19:24,442 {\an1}forming the K-Pg boundary. 379 00:19:24,466 --> 00:19:28,076 {\an1}Over millions of years, the surge of mud would become 380 00:19:28,100 --> 00:19:32,176 {\an1}the four-foot-deep layer of crumbly rock. 381 00:19:32,200 --> 00:19:35,676 RICHARDS: And that's the beauty of Tanis. 382 00:19:35,700 --> 00:19:38,076 {\an1}What you're seeing is a deposit 383 00:19:38,100 --> 00:19:41,542 {\an1}that is literally recording the last, say, 384 00:19:41,566 --> 00:19:43,676 {\an1}45 minutes to an hour-and-a-half 385 00:19:43,700 --> 00:19:46,109 of the Cretaceous. 386 00:19:46,133 --> 00:19:50,733 ♪ ♪ 387 00:19:53,700 --> 00:19:57,076 ATTENBOROUGH: If the extinction of the dinosaurs was a crime, 388 00:19:57,100 --> 00:20:01,542 {\an7}the detective solving it would have plenty of evidence. 389 00:20:01,566 --> 00:20:03,376 {\an7}They would see that the asteroid 390 00:20:03,400 --> 00:20:05,709 {\an7}was in the right place at the right time. 391 00:20:05,733 --> 00:20:10,542 {\an1}They would see that no dinosaurs survived after the hit. 392 00:20:10,566 --> 00:20:13,442 {\an1}They would have a piece of the murder weapon, 393 00:20:13,466 --> 00:20:15,176 {\an1}a fragment of the asteroid. 394 00:20:15,200 --> 00:20:19,942 {\an1}But they would be missing one very important thing: 395 00:20:19,966 --> 00:20:20,910 a body. 396 00:20:20,934 --> 00:20:23,209 ♪ ♪ 397 00:20:23,233 --> 00:20:24,976 BLACK: A lot of the bones that exist 398 00:20:25,000 --> 00:20:27,700 {\an1}from those last Cretaceous days were basically destroyed. 399 00:20:29,166 --> 00:20:32,342 BRUSATTE: As far as we know, we've never actually found a fossil 400 00:20:32,366 --> 00:20:36,609 {\an7}of a dinosaur individual, a single skeleton, let's say, 401 00:20:36,633 --> 00:20:38,109 {\an7}that we can unequivocally say 402 00:20:38,133 --> 00:20:40,909 {\an8}was there on the day the asteroid hit. 403 00:20:40,933 --> 00:20:44,376 ♪ ♪ 404 00:20:44,400 --> 00:20:47,109 {\an8}ATTENBOROUGH: But before the site was timestamped 405 00:20:47,133 --> 00:20:50,542 {\an7}to the Chicxulub impact, Robert's team did find 406 00:20:50,566 --> 00:20:55,042 {\an1}part of a triceratops in the crumbly layer at Tanis. 407 00:20:55,066 --> 00:20:56,642 {\an1}So could that be the body? 408 00:20:56,666 --> 00:21:01,209 A dinosaur that died on that day? 409 00:21:01,233 --> 00:21:02,876 {\an1}Something that would help them 410 00:21:02,900 --> 00:21:05,576 {\an1}would be establishing the cause of death, 411 00:21:05,600 --> 00:21:06,976 {\an1}which can be difficult 412 00:21:07,000 --> 00:21:10,400 {\an1}when you only have a piece of skin and horn to go on. 413 00:21:12,533 --> 00:21:16,942 This is the horn after they've cleaned it up. 414 00:21:16,966 --> 00:21:18,342 {\an7}The team is particularly 415 00:21:18,366 --> 00:21:21,309 {\an7}interested in these lines here. 416 00:21:21,333 --> 00:21:23,642 And they found that the fractures 417 00:21:23,666 --> 00:21:26,642 {\an1}go right through the horn. 418 00:21:26,666 --> 00:21:29,976 {\an7}So rather than dying as a result of the impact, 419 00:21:30,000 --> 00:21:33,176 {\an1}they wondered whether it had been killed in a fight. 420 00:21:33,200 --> 00:21:37,433 (dinosaurs growling, horns clashing) 421 00:21:38,900 --> 00:21:41,409 {\an1}But when they looked at the fractures in more detail, 422 00:21:41,433 --> 00:21:44,109 {\an1}they found signs of new bone growth here. 423 00:21:44,133 --> 00:21:48,542 {\an1}An indication that the bone had started to heal. 424 00:21:48,566 --> 00:21:51,876 {\an1}So it looked as though the triceratops survived the event 425 00:21:51,900 --> 00:21:53,642 that broke its horn. 426 00:21:53,666 --> 00:21:56,333 {\an8}(dinosaur grunting) 427 00:21:58,266 --> 00:22:01,242 {\an8}Could this triceratops have survived 428 00:22:01,266 --> 00:22:03,376 {\an8}until the day of the impact? 429 00:22:03,400 --> 00:22:05,509 {\an7}This drooping in the skin 430 00:22:05,533 --> 00:22:07,942 {\an7}and the disarticulation of some of the bones 431 00:22:07,966 --> 00:22:12,076 {\an7}suggested to the team that there was decay underneath. 432 00:22:12,100 --> 00:22:14,776 {\an8}That means its body had started to rot 433 00:22:14,800 --> 00:22:16,876 {\an8}before it was entombed 434 00:22:16,900 --> 00:22:18,309 {\an8}and preserved by the surge. 435 00:22:18,333 --> 00:22:21,276 So, it seems that this dinosaur 436 00:22:21,300 --> 00:22:25,276 {\an1}didn't die as a result of the asteroid impact. 437 00:22:25,300 --> 00:22:28,009 ♪ ♪ (dinosaur grunting) 438 00:22:28,033 --> 00:22:32,942 Given the signs of partial decay... 439 00:22:32,966 --> 00:22:36,376 {\an1}it's likely this Triceratops wouldn't have lived 440 00:22:36,400 --> 00:22:38,666 to see the last day of the dinosaurs. 441 00:22:40,433 --> 00:22:44,009 (thunder rumbling) 442 00:22:44,033 --> 00:22:47,609 {\an1}However, the triceratops fossil does show 443 00:22:47,633 --> 00:22:51,276 {\an1}that dinosaurs were alive shortly before the asteroid hit, 444 00:22:51,300 --> 00:22:56,309 {\an1}perhaps even within weeks of the impact. 445 00:22:56,333 --> 00:22:58,709 {\an1}This is an extraordinary discovery, 446 00:22:58,733 --> 00:23:02,000 {\an1}and one that has never been found before. 447 00:23:04,000 --> 00:23:06,509 But if it's true that dinosaurs were here 448 00:23:06,533 --> 00:23:09,909 {\an1}until the final weeks before the impact, 449 00:23:09,933 --> 00:23:15,376 {\an1}there could be even more still to find in this deposit. 450 00:23:15,400 --> 00:23:18,809 DEPALMA: This is, like, looking down onto the side of a dinosaur 451 00:23:18,833 --> 00:23:21,309 {\an1}that died weeks to months before the impact. 452 00:23:21,333 --> 00:23:22,976 {\an1}That is such a cool thing. 453 00:23:23,000 --> 00:23:25,042 {\an1}We've got all these bones in the ground right now, 454 00:23:25,066 --> 00:23:29,776 {\an1}but the one thing that we would just dream of finding 455 00:23:29,800 --> 00:23:32,566 {\an1}is that one dinosaur that died on the day of the impact. 456 00:23:37,633 --> 00:23:40,842 ATTENBOROUGH: And the weather isn't helping his search. 457 00:23:40,866 --> 00:23:42,366 Got... 458 00:23:47,733 --> 00:23:49,066 (groans) 459 00:23:56,200 --> 00:23:58,142 {\an7}That therapod print is toasted. 460 00:23:58,166 --> 00:24:00,542 {\an8}BURNHAM: Yeah, it was in a low corner. 461 00:24:00,566 --> 00:24:03,442 {\an7}Look, it's all... it's full of mud and water. 462 00:24:03,466 --> 00:24:05,576 {\an7}The problem is it's wet, look. 463 00:24:05,600 --> 00:24:09,476 {\an7}See, if we're not careful, we're gonna lose the print. 464 00:24:09,500 --> 00:24:11,833 {\an7}And that's the biggest theropod print we've got. 465 00:24:13,133 --> 00:24:15,766 {\an7}I see some areas that could use glue right now, too. 466 00:24:17,900 --> 00:24:20,342 {\an8}♪ ♪ 467 00:24:20,366 --> 00:24:23,642 {\an8}ATTENBOROUGH: The team is racing to excavate dozens of fossils 468 00:24:23,666 --> 00:24:25,976 {\an7}before the rains wash them away. 469 00:24:26,000 --> 00:24:29,609 ♪ ♪ 470 00:24:29,633 --> 00:24:31,109 DEPALMA: We are up against the clock here. 471 00:24:31,133 --> 00:24:33,376 {\an1}This stuff that could be exposed right now 472 00:24:33,400 --> 00:24:35,966 {\an1}is gonna get ruined by the rain. 473 00:24:37,166 --> 00:24:39,542 ATTENBOROUGH: But then, the team comes across something 474 00:24:39,566 --> 00:24:41,809 {\an1}that looks very unusual. 475 00:24:41,833 --> 00:24:43,666 {\an1}(speaking indistinctly) 476 00:24:44,766 --> 00:24:48,042 BURNHAM: What is going on right there? 477 00:24:48,066 --> 00:24:49,442 {\an8}Are we sure this isn't crocodilian? 478 00:24:49,466 --> 00:24:51,076 {\an7}That's not crocodilian. No. 479 00:24:51,100 --> 00:24:53,742 {\an8}GURCHE: Let me try this piece right here. 480 00:24:53,766 --> 00:24:56,309 {\an8}I'll go in from the top and then twist up, 481 00:24:56,333 --> 00:24:58,009 and it separates right on that line. 482 00:24:58,033 --> 00:25:00,542 {\an1}DEPALMA: Oh... that's skin right there. 483 00:25:00,566 --> 00:25:03,009 {\an1}That's actually scaly skin. Oh my God. 484 00:25:03,033 --> 00:25:04,909 {\an1}No, no, no, no, no, look, look, look. 485 00:25:04,933 --> 00:25:06,942 {\an1}Look at that pattern right there. 486 00:25:06,966 --> 00:25:09,542 {\an1}Have you ever seen elongated scales like that before, Dave? 487 00:25:09,566 --> 00:25:11,876 BURNHAM: Scutellates in birds. 488 00:25:11,900 --> 00:25:13,576 {\an1}Just careful. 489 00:25:13,600 --> 00:25:15,909 {\an4}Oh, my God. BURNHAM: It's changing again. 490 00:25:15,933 --> 00:25:18,376 {\an1}It's changing again. My God. 491 00:25:18,400 --> 00:25:22,242 {\an1}We're seeing it for the first time in 66 million years. 492 00:25:22,266 --> 00:25:26,000 {\an1}I think we got ourselves a dinosaur. 493 00:25:27,766 --> 00:25:29,209 ATTENBOROUGH: A dinosaur fossil. 494 00:25:29,233 --> 00:25:33,209 {\an8}In the same mass death assemblage as the fish 495 00:25:33,233 --> 00:25:35,866 {\an8}with the spherules in their gills. 496 00:25:38,100 --> 00:25:40,776 ♪ ♪ 497 00:25:40,800 --> 00:25:42,242 DEPALMA: This is the most incredible thing 498 00:25:42,266 --> 00:25:43,542 {\an1}that we could possibly imagine here, 499 00:25:43,566 --> 00:25:45,642 {\an7}the best-case scenario. 500 00:25:45,666 --> 00:25:48,309 {\an7}We're excavating this mass death layer of fish 501 00:25:48,333 --> 00:25:50,076 {\an7}from the surge sent up by the impact, 502 00:25:50,100 --> 00:25:53,176 {\an1}and we've got dinosaur remains. 503 00:25:53,200 --> 00:25:54,842 {\an1}The one thing that we 504 00:25:54,866 --> 00:25:56,476 {\an1}would always want to find at this site, 505 00:25:56,500 --> 00:25:59,342 {\an7}and here we've got it. 506 00:25:59,366 --> 00:26:00,609 {\an7}This is unreal. 507 00:26:00,633 --> 00:26:02,542 {\an7}I, I, I cannot process this in my brain. 508 00:26:02,566 --> 00:26:06,342 {\an7}No, I am absolutely blown away by this. 509 00:26:06,366 --> 00:26:07,909 {\an1}Just my heart is literally pumping out of my chest 510 00:26:07,933 --> 00:26:09,342 {\an1}wondering what is behind there, 511 00:26:09,366 --> 00:26:11,109 {\an1}just a couple of centimeters back in the outcrop. 512 00:26:11,133 --> 00:26:13,400 {\an1}What is waiting for us back there? 513 00:26:17,100 --> 00:26:19,342 {\an8}This is amazing. 514 00:26:19,366 --> 00:26:21,976 {\an8}ATTENBOROUGH: The team keeps digging. 515 00:26:22,000 --> 00:26:23,142 {\an7}BURNHAM: So this could be a ribcage, 516 00:26:23,166 --> 00:26:24,442 {\an7}it could be laying against ribs that are curved. 517 00:26:24,466 --> 00:26:26,942 DEPALMA: There's something here. 518 00:26:26,966 --> 00:26:28,042 That's hard. 519 00:26:28,066 --> 00:26:29,976 {\an1}That's bone right next to the skin. 520 00:26:30,000 --> 00:26:31,942 {\an8}Look, that, that's an articular surface right there. 521 00:26:31,966 --> 00:26:35,776 {\an8}So this is either a hip or a shoulder element. 522 00:26:35,800 --> 00:26:38,309 ♪ ♪ 523 00:26:38,333 --> 00:26:42,042 {\an8}ATTENBOROUGH: After hours of painstaking work... 524 00:26:42,066 --> 00:26:44,809 {\an8}♪ ♪ 525 00:26:44,833 --> 00:26:47,442 DEPALMA: And we can go from the thigh of the animal. 526 00:26:47,466 --> 00:26:48,609 There's the knee. 527 00:26:48,633 --> 00:26:49,976 And then you've got the 528 00:26:50,000 --> 00:26:52,576 little calf muscles of the, uh, dinosaur 529 00:26:52,600 --> 00:26:53,609 over there bulging out, 530 00:26:53,633 --> 00:26:55,809 {\an8}and you go down to the anklebones, 531 00:26:55,833 --> 00:26:59,142 {\an8}and these are the toes of the feet. 532 00:26:59,166 --> 00:27:01,242 We've got nails at the tips of the toes. 533 00:27:01,266 --> 00:27:03,109 It's a beautifully preserved leg, 534 00:27:03,133 --> 00:27:06,142 all articulated, covered with skin. 535 00:27:06,166 --> 00:27:10,309 {\an8}ATTENBOROUGH: The complete leg of a dinosaur. 536 00:27:10,333 --> 00:27:12,309 {\an8}DEPALMA: In my wildest dreams, 537 00:27:12,333 --> 00:27:14,242 {\an7}I never expected to find a dinosaur leg in this deposit. 538 00:27:14,266 --> 00:27:15,309 Yeah. 539 00:27:15,333 --> 00:27:17,642 {\an1}I mean, and then it's got skin and tissue. 540 00:27:17,666 --> 00:27:20,742 {\an7}It does look just like a drumstick. 541 00:27:20,766 --> 00:27:21,809 {\an8}It looks like a Thanksgiving turkey 542 00:27:21,833 --> 00:27:23,542 {\an7}just laid out in the ground. 543 00:27:23,566 --> 00:27:28,676 ATTENBOROUGH: Robert and his team think they've found the body 544 00:27:28,700 --> 00:27:30,176 {\an1}missing from the crime scene... 545 00:27:30,200 --> 00:27:32,976 {\an1}a dinosaur that might itself have witnessed 546 00:27:33,000 --> 00:27:37,109 {\an1}the cataclysmic impact. 547 00:27:37,133 --> 00:27:38,376 DEPALMA: Dinosaur fossils 548 00:27:38,400 --> 00:27:42,076 {\an1}are not known from the last years of the Cretaceous. 549 00:27:42,100 --> 00:27:44,709 {\an1}And it was unclear whether they were already extinct, 550 00:27:44,733 --> 00:27:47,009 or in decline, or what was going on. 551 00:27:47,033 --> 00:27:48,642 So they were just sort of absent. 552 00:27:48,666 --> 00:27:52,176 ♪ ♪ 553 00:27:52,200 --> 00:27:55,042 {\an1}And this answers that question: were dinosaurs still there then? 554 00:27:55,066 --> 00:27:59,276 {\an1}Well, yes, they were there weeks to months before the impact. 555 00:27:59,300 --> 00:28:02,109 This one likely died in that surge. 556 00:28:02,133 --> 00:28:05,042 ♪ ♪ 557 00:28:05,066 --> 00:28:08,633 ATTENBOROUGH: But such big claims need verification. 558 00:28:09,533 --> 00:28:12,809 ♪ ♪ 559 00:28:12,833 --> 00:28:13,876 RILEY BLACK: Paleontologists, 560 00:28:13,900 --> 00:28:15,509 {\an1}we kind of fight like tyrannosaurs. 561 00:28:15,533 --> 00:28:17,242 {\an7}There are lots of different opinions. 562 00:28:17,266 --> 00:28:19,176 {\an7}There are lots of different hypotheses. 563 00:28:19,200 --> 00:28:21,209 {\an7}And this is all because 564 00:28:21,233 --> 00:28:22,576 {\an7}science is a process. 565 00:28:22,600 --> 00:28:25,009 {\an7}Science isn't a matter of just going out into the rock, 566 00:28:25,033 --> 00:28:26,276 {\an1}and we found a new dinosaur. 567 00:28:26,300 --> 00:28:27,876 STEVE BRUSATTE: So I think we always 568 00:28:27,900 --> 00:28:29,009 {\an1}want to be skeptical, 569 00:28:29,033 --> 00:28:31,309 {\an7}but I think we want to be extra skeptical 570 00:28:31,333 --> 00:28:32,976 {\an7}when there are big claims. 571 00:28:33,000 --> 00:28:35,742 {\an7}And it all goes back to that expression that we hear 572 00:28:35,766 --> 00:28:38,142 {\an1}all the time, and that's that extraordinary claims 573 00:28:38,166 --> 00:28:40,909 {\an1}require extraordinary evidence. 574 00:28:40,933 --> 00:28:43,742 ATTENBOROUGH: Robert is in the process of sharing the team's finds 575 00:28:43,766 --> 00:28:46,242 {\an1}with the wider scientific community. 576 00:28:46,266 --> 00:28:49,909 {\an7}As part of this process, he has brought the dinosaur leg 577 00:28:49,933 --> 00:28:50,942 {\an8}to London, England, 578 00:28:50,966 --> 00:28:53,476 {\an7}to get a second opinion 579 00:28:53,500 --> 00:28:57,342 from paleontologist Paul Barrett... 580 00:28:57,366 --> 00:28:59,076 {\an8}an expert in ornithischian dinosaurs 581 00:28:59,100 --> 00:29:01,976 {\an7}from the Natural History Museum. 582 00:29:02,000 --> 00:29:04,342 So what do you think this might be? 583 00:29:04,366 --> 00:29:05,509 {\an1}When we look at the leg, 584 00:29:05,533 --> 00:29:07,809 {\an1}it has claws like the claws 585 00:29:07,833 --> 00:29:10,442 {\an1}we see in small, agile, 586 00:29:10,466 --> 00:29:12,942 {\an7}bipedal running dinosaurs that are plant eaters. 587 00:29:12,966 --> 00:29:15,209 {\an1}We can also rule out things like Triceratops 588 00:29:15,233 --> 00:29:17,209 partly just because 589 00:29:17,233 --> 00:29:18,576 {\an1}it's not big and stocky. 590 00:29:18,600 --> 00:29:20,276 {\an1}And the proportions of those legs 591 00:29:20,300 --> 00:29:24,042 {\an1}are also different from some of the other plant eaters we see 592 00:29:24,066 --> 00:29:25,942 {\an1}in that they have this rather long ankle 593 00:29:25,966 --> 00:29:28,876 {\an1}and shin compared with its thigh bone. 594 00:29:28,900 --> 00:29:31,376 {\an1}So as we narrow those possibilities down 595 00:29:31,400 --> 00:29:32,709 {\an1}what we're left with probably 596 00:29:32,733 --> 00:29:34,642 {\an1}is an animal called a thescelosaur. 597 00:29:34,666 --> 00:29:37,009 (dinosaur grunts) 598 00:29:37,033 --> 00:29:38,876 (growls) 599 00:29:38,900 --> 00:29:42,442 {\an8}ATTENBOROUGH: Thescelosaurus are thought to have lived next to rivers. 600 00:29:42,466 --> 00:29:43,576 {\an8}(dinosaur grunts) 601 00:29:43,600 --> 00:29:47,876 {\an8}♪ ♪ 602 00:29:47,900 --> 00:29:49,609 {\an7}They had leaf-shaped teeth 603 00:29:49,633 --> 00:29:51,909 {\an1}common amongst herbivores, 604 00:29:51,933 --> 00:29:54,942 {\an1}and claws on their short front limbs, 605 00:29:54,966 --> 00:29:58,209 {\an1}which they may have used for digging. 606 00:29:58,233 --> 00:30:00,276 ♪ ♪ 607 00:30:00,300 --> 00:30:03,042 {\an1}At the front of their mouth they had specialized, 608 00:30:03,066 --> 00:30:05,409 {\an1}pointed teeth that could help them to pull roots 609 00:30:05,433 --> 00:30:09,409 out of the ground. 610 00:30:09,433 --> 00:30:12,342 So it's possible they dug for food. 611 00:30:12,366 --> 00:30:14,142 ♪ ♪ 612 00:30:14,166 --> 00:30:16,709 (biting flesh) 613 00:30:16,733 --> 00:30:18,942 {\an1}But how did the thescelosaur 614 00:30:18,966 --> 00:30:22,542 {\an1}that Robert's team found die? 615 00:30:22,566 --> 00:30:26,042 Could it have killed by another dinosaur? 616 00:30:26,066 --> 00:30:27,209 {\an1}BARRETT: It's a possibility. 617 00:30:27,233 --> 00:30:29,309 {\an1}This is a relatively agile animal. 618 00:30:29,333 --> 00:30:33,142 {\an1}And that turn of speed would've been its primary defense 619 00:30:33,166 --> 00:30:35,409 {\an1}against the large predators living alongside it. 620 00:30:35,433 --> 00:30:37,800 (insects chirping, dinosaur grunting) 621 00:30:39,100 --> 00:30:41,976 DAVID MARTILL: Whenever we're excavating a dinosaur, 622 00:30:42,000 --> 00:30:43,542 {\an8}one of the things that we're always keen to know 623 00:30:43,566 --> 00:30:44,642 {\an7}is how did the animal die? 624 00:30:44,666 --> 00:30:46,876 {\an1}It's not always easy to do that. 625 00:30:46,900 --> 00:30:48,409 BRUSATTE: So maybe we can find 626 00:30:48,433 --> 00:30:51,442 {\an1}evidence for things like broken bones that didn't heal back up. 627 00:30:51,466 --> 00:30:56,042 {\an1}Sometimes we can even see things like bone tumors and gout. 628 00:30:56,066 --> 00:30:57,842 CHINSAMY-TURAN: There are some wonderful fossils 629 00:30:57,866 --> 00:31:00,376 {\an7}where you can find bite marks on them. 630 00:31:00,400 --> 00:31:04,776 {\an8}You can even find a, a predator tooth buried 631 00:31:04,800 --> 00:31:06,309 {\an8}within the bones. 632 00:31:06,333 --> 00:31:07,809 EMILY BAMFORTH: In science, we don't prove things. 633 00:31:07,833 --> 00:31:10,009 {\an1}We just disprove some things. 634 00:31:10,033 --> 00:31:11,609 {\an7}Generally speaking, unless 635 00:31:11,633 --> 00:31:14,476 {\an1}a cause of death leaves a signature on the skeleton, 636 00:31:14,500 --> 00:31:16,342 it's hard to tell. 637 00:31:16,366 --> 00:31:19,809 ATTENBOROUGH: CT scans Robert and the team have taken of the dinosaur leg 638 00:31:19,833 --> 00:31:23,709 {\an1}allow a closer look at what the animal might have gone through 639 00:31:23,733 --> 00:31:26,009 before it died. 640 00:31:26,033 --> 00:31:27,642 {\an1}It doesn't seem to me like there is any evidence 641 00:31:27,666 --> 00:31:29,476 {\an1}that this animal was predated. 642 00:31:29,500 --> 00:31:32,942 {\an1}None of the obvious tooth marks or left over bits 643 00:31:32,966 --> 00:31:34,409 of carnivore teeth 644 00:31:34,433 --> 00:31:35,509 {\an1}to suggest it's been eaten. 645 00:31:35,533 --> 00:31:37,676 {\an1}So we can see that the bones look okay. 646 00:31:37,700 --> 00:31:39,609 {\an7}So this was an animal that was probably living 647 00:31:39,633 --> 00:31:43,076 {\an7}and healthy at the time that this happened to it. 648 00:31:43,100 --> 00:31:47,209 {\an7}ATTENBOROUGH (voiceover): Could this be a dinosaur that was swept up in the surge? 649 00:31:47,233 --> 00:31:49,242 {\an8}BRUSATTE: The idea that there is a dinosaur fossil, 650 00:31:49,266 --> 00:31:51,276 {\an7}potentially, that's a direct victim of that, 651 00:31:51,300 --> 00:31:52,576 {\an1}that's very exciting. 652 00:31:52,600 --> 00:31:55,742 {\an1}I think ultimately it comes down to a couple of things. 653 00:31:55,766 --> 00:31:58,976 {\an1}You know, are there injuries on that fossil that show 654 00:31:59,000 --> 00:32:02,742 that this dinosaur was bobbing about, 655 00:32:02,766 --> 00:32:04,676 {\an1}heaving about in the water? 656 00:32:04,700 --> 00:32:06,576 {\an1}So are there things like breaks on the bone or other things 657 00:32:06,600 --> 00:32:08,609 {\an1}that have not healed? 658 00:32:08,633 --> 00:32:10,876 This is actually a shoulder bone. 659 00:32:10,900 --> 00:32:12,909 {\an1}And this bone in the living animal would actually be 660 00:32:12,933 --> 00:32:14,476 way over here. 661 00:32:14,500 --> 00:32:16,309 And similarly this little bone here 662 00:32:16,333 --> 00:32:17,609 {\an1}would have been from about 663 00:32:17,633 --> 00:32:21,042 {\an1}a third of the way along the tail, maybe halfway down. 664 00:32:21,066 --> 00:32:24,009 {\an1}So somehow these two bones 665 00:32:24,033 --> 00:32:25,476 {\an1}have been telescoped together. Yeah. 666 00:32:25,500 --> 00:32:27,976 {\an1}So maybe this animal has been tumbled around. 667 00:32:28,000 --> 00:32:34,276 Could this be a victim of the meteor strike? 668 00:32:34,300 --> 00:32:36,542 {\an1}I think it's entirely possible. 669 00:32:36,566 --> 00:32:38,376 {\an1}We've ruled out a lot of other possible 670 00:32:38,400 --> 00:32:39,976 {\an1}causes of death for this animal. 671 00:32:40,000 --> 00:32:42,942 {\an1}So it could well be that this was an animal that was there 672 00:32:42,966 --> 00:32:45,842 {\an1}being tumbled around in its death throes in that river 673 00:32:45,866 --> 00:32:50,709 as a result of the asteroid impact. 674 00:32:50,733 --> 00:32:53,142 {\an7}Paleontologists do depend a lot on tragedy. 675 00:32:53,166 --> 00:32:54,742 {\an7}Every little disaster 676 00:32:54,766 --> 00:32:58,942 {\an1}is the material we need to actually develop our subject. 677 00:32:58,966 --> 00:33:01,409 Tragic for the individual concerned, 678 00:33:01,433 --> 00:33:04,576 {\an1}but we're just really happy that it happened. 679 00:33:04,600 --> 00:33:09,766 ♪ ♪ 680 00:33:12,933 --> 00:33:15,842 ATTENBOROUGH: After years of work at this site, 681 00:33:15,866 --> 00:33:18,076 Robert and his team have uncovered 682 00:33:18,100 --> 00:33:23,942 {\an1}unprecedented detail about the animals living there. 683 00:33:23,966 --> 00:33:27,042 {\an7}And he thinks that many of them were alive on that fateful day 684 00:33:27,066 --> 00:33:30,566 {\an7}when the asteroid devastated our planet. 685 00:33:31,566 --> 00:33:33,842 {\an1}But how exactly did they die? 686 00:33:33,866 --> 00:33:38,709 {\an1}The team's finds give us new clues to answer that question. 687 00:33:38,733 --> 00:33:41,609 ♪ ♪ 688 00:33:41,633 --> 00:33:44,642 {\an1}One of the most important days in Earth's history 689 00:33:44,666 --> 00:33:48,609 {\an1}probably started much like any other late spring morning. 690 00:33:48,633 --> 00:33:50,442 ♪ ♪ 691 00:33:50,466 --> 00:33:54,109 {\an1}We think it was late spring because paleobotanists 692 00:33:54,133 --> 00:33:56,876 {\an1}have found key evidence about the season 693 00:33:56,900 --> 00:34:00,142 {\an1}from fossilized flowers. 694 00:34:00,166 --> 00:34:02,509 The Tanis finds are consistent with this, 695 00:34:02,533 --> 00:34:06,442 {\an1}including the fossils of young fish that died at the size 696 00:34:06,466 --> 00:34:08,909 {\an1}they reach at that time of year. 697 00:34:08,933 --> 00:34:15,176 ♪ ♪ 698 00:34:15,200 --> 00:34:18,976 {\an1}Perhaps this day, that would end with so much death, 699 00:34:19,000 --> 00:34:20,976 {\an1}began with something different. 700 00:34:21,000 --> 00:34:23,809 ♪ ♪ 701 00:34:23,833 --> 00:34:26,709 A new life. 702 00:34:26,733 --> 00:34:29,842 Robert only found one pterosaur egg, 703 00:34:29,866 --> 00:34:32,309 {\an1}so it's possible that it had a brother or sister 704 00:34:32,333 --> 00:34:34,609 {\an1}that hatched before the impact. 705 00:34:34,633 --> 00:34:36,342 (pterosaur squawks) 706 00:34:36,366 --> 00:34:39,142 To see the world for one final day. 707 00:34:39,166 --> 00:34:40,942 (pterosaur squawks) 708 00:34:40,966 --> 00:34:43,676 ♪ ♪ 709 00:34:43,700 --> 00:34:48,142 (insects chirping, creature bellowing in distance) 710 00:34:48,166 --> 00:34:51,142 {\an1}No one can be certain of the exact timings of the day 711 00:34:51,166 --> 00:34:53,942 {\an1}when the asteroid collided with our planet. 712 00:34:53,966 --> 00:34:58,209 {\an1}But it's estimated that within just 40 minutes of the impact, 713 00:34:58,233 --> 00:35:00,876 the consequences for the creatures of Tanis 714 00:35:00,900 --> 00:35:02,809 {\an1}would have been profound. 715 00:35:02,833 --> 00:35:06,976 ♪ ♪ 716 00:35:07,000 --> 00:35:08,842 {\an1}Based on the team's finds, 717 00:35:08,866 --> 00:35:11,576 {\an1}and the latest evidence from other scientists, 718 00:35:11,600 --> 00:35:15,742 {\an1}this is how the catastrophe might have unfolded. 719 00:35:15,766 --> 00:35:20,176 {\an1}The asteroid is around seven miles across... 720 00:35:20,200 --> 00:35:24,042 {\an1}bigger than Mount Everest... 721 00:35:24,066 --> 00:35:28,776 {\an7}and traveling at close to 45,000 miles an hour. 722 00:35:28,800 --> 00:35:33,842 {\an8}♪ ♪ 723 00:35:33,866 --> 00:35:39,509 {\an1}The impact causes an explosion with over a billion times 724 00:35:39,533 --> 00:35:43,142 {\an1}the power of the first atomic bomb. 725 00:35:43,166 --> 00:35:45,509 GULICK:: It comes in so fast 726 00:35:45,533 --> 00:35:47,976 {\an7}that it wouldn't even have been visible passing through 727 00:35:48,000 --> 00:35:49,242 {\an8}the atmosphere. 728 00:35:49,266 --> 00:35:51,809 {\an7}Right, it would have just come in and hit in a moment. 729 00:35:51,833 --> 00:35:55,242 ATTENBOROUGH: At Tanis, almost 2,000 miles away, 730 00:35:55,266 --> 00:35:58,009 {\an1}there might have been an initial flash of light, 731 00:35:58,033 --> 00:36:00,866 {\an1}yet it is completely silent. 732 00:36:03,833 --> 00:36:05,109 {\an1}But at the impact site... 733 00:36:05,133 --> 00:36:07,509 ♪ ♪ 734 00:36:07,533 --> 00:36:11,142 {\an1}...the asteroid vaporizes. 735 00:36:11,166 --> 00:36:15,709 {\an1}More than three trillion tons of rock are ejected into space 736 00:36:15,733 --> 00:36:19,209 {\an1}in a blast of superheated violence. 737 00:36:19,233 --> 00:36:23,009 ♪ ♪ (rocks crashing, wind whipping) 738 00:36:23,033 --> 00:36:26,009 Winds higher than 600 miles a hour. 739 00:36:26,033 --> 00:36:28,542 ♪ ♪ 740 00:36:28,566 --> 00:36:31,276 {\an1}A colossal earthquake. 741 00:36:31,300 --> 00:36:33,909 Followed by a ring of massive tsunamis. 742 00:36:33,933 --> 00:36:40,433 ♪ ♪ 743 00:36:43,066 --> 00:36:44,609 {\an1}All the while the creatures at Tanis 744 00:36:44,633 --> 00:36:46,809 {\an1}go about their business... 745 00:36:46,833 --> 00:36:50,776 {\an1}(pterosaurs grunting) 746 00:36:50,800 --> 00:36:52,942 {\an1}...just like any other day. 747 00:36:52,966 --> 00:36:55,976 ♪ ♪ 748 00:36:56,000 --> 00:36:59,276 (animals chittering) 749 00:36:59,300 --> 00:37:02,266 {\an1}(dinosaur makes guttural sound) 750 00:37:04,533 --> 00:37:06,942 (snorts) 751 00:37:06,966 --> 00:37:09,976 (thunder rumbling) 752 00:37:10,000 --> 00:37:11,376 (pterosaur squawks) 753 00:37:11,400 --> 00:37:14,909 {\an1}The evidence suggests that baby pterosaurs may have emerged 754 00:37:14,933 --> 00:37:19,942 {\an1}from eggs ready to fend for themselves. 755 00:37:19,966 --> 00:37:22,076 And that includes... 756 00:37:22,100 --> 00:37:24,742 ♪ ♪ 757 00:37:24,766 --> 00:37:26,176 Flying? 758 00:37:26,200 --> 00:37:30,542 Well, almost. 759 00:37:30,566 --> 00:37:31,909 {\an1}(pterosaur chittering) 760 00:37:31,933 --> 00:37:35,942 ♪ ♪ 761 00:37:35,966 --> 00:37:37,942 {\an1}Elsewhere, as the reverberations of the impact 762 00:37:37,966 --> 00:37:41,476 {\an1}race out across North America... 763 00:37:41,500 --> 00:37:43,309 {\an1}(low-pitched rumbling) 764 00:37:43,333 --> 00:37:46,776 {\an1}...dinosaurs and creatures of all shapes and sizes 765 00:37:46,800 --> 00:37:49,566 {\an1}are obliterated by the blast... 766 00:37:52,933 --> 00:37:58,409 {\an1}Incinerated in a firestorm unlike anything seen since. 767 00:37:58,433 --> 00:37:59,709 TIKOO: If I were a dinosaur 768 00:37:59,733 --> 00:38:01,642 {\an7}standing on the coast of North America, 769 00:38:01,666 --> 00:38:04,509 {\an1}I would just see a flash and a fireball coming at me 770 00:38:04,533 --> 00:38:06,276 {\an1}and then I would be fried. 771 00:38:06,300 --> 00:38:08,576 All you feel is an awfully sharp, 772 00:38:08,600 --> 00:38:10,476 {\an1}stabbing pain in your ears, 773 00:38:10,500 --> 00:38:13,809 then you explode. 774 00:38:13,833 --> 00:38:18,009 ♪ ♪ 775 00:38:18,033 --> 00:38:21,142 ATTENBOROUGH: At Tanis, for a few more precious minutes, 776 00:38:21,166 --> 00:38:24,876 life continues. 777 00:38:24,900 --> 00:38:26,742 {\an1}But the clock is ticking. 778 00:38:26,766 --> 00:38:28,909 ♪ ♪ 779 00:38:28,933 --> 00:38:30,676 {\an1}(creature chittering) 780 00:38:30,700 --> 00:38:33,233 (dinosaurs growling, horns clashing) 781 00:38:34,766 --> 00:38:38,800 ♪ ♪ 782 00:38:39,900 --> 00:38:44,209 {\an7}The blast from the impact never reaches Tanis, 783 00:38:44,233 --> 00:38:48,409 {\an7}but seismic shockwaves do. 784 00:38:48,433 --> 00:38:50,876 {\an1}(creatures chittering) 785 00:38:50,900 --> 00:38:52,742 (rumbling) 786 00:38:52,766 --> 00:38:56,309 ♪ ♪ 787 00:38:56,333 --> 00:39:00,909 {\an1}They are far more powerful than any earthquake ever recorded. 788 00:39:00,933 --> 00:39:03,742 PLESKO: If you were standing on the Gulf Coast of Texas, 789 00:39:03,766 --> 00:39:07,509 {\an7}that magnitude 12 earthquake would have been strong enough 790 00:39:07,533 --> 00:39:12,176 {\an7}to actually jam your femurs up into your body cavity 791 00:39:12,200 --> 00:39:15,042 ATTENBOROUGH: While the earthquake that reached Tanis 792 00:39:15,066 --> 00:39:17,409 {\an1}was likely less destructive, 793 00:39:17,433 --> 00:39:21,276 {\an1}the effects would have been felt by all that lived there. 794 00:39:21,300 --> 00:39:23,209 (loud rumbling) 795 00:39:23,233 --> 00:39:25,476 {\an1}Seismic waves are now slowly shaking 796 00:39:25,500 --> 00:39:28,209 {\an1}the whole region, causing water 797 00:39:28,233 --> 00:39:30,176 to slosh and churn. 798 00:39:30,200 --> 00:39:36,442 ♪ ♪ 799 00:39:36,466 --> 00:39:39,742 {\an7}At Tanis, these strange currents in the river may be some of 800 00:39:39,766 --> 00:39:41,776 {\an8}the first signs of what is coming. 801 00:39:41,800 --> 00:39:46,776 {\an8}♪ ♪ 802 00:39:46,800 --> 00:39:50,642 (thunder rolls) 803 00:39:50,666 --> 00:39:52,042 {\an1}Next, it begins to rain. 804 00:39:52,066 --> 00:39:55,209 (pattering) 805 00:39:55,233 --> 00:39:59,176 {\an1}Ejecta spherules are falling back to earth. 806 00:39:59,200 --> 00:40:05,976 ♪ ♪ 807 00:40:06,000 --> 00:40:09,942 {\an1}As the spherules plummet, 808 00:40:09,966 --> 00:40:12,776 friction heats them until they're red hot. 809 00:40:12,800 --> 00:40:14,000 ♪ ♪ 810 00:40:18,966 --> 00:40:21,966 {\an7}They soon transfer their heat to the atmosphere... 811 00:40:24,866 --> 00:40:27,542 which grows hotter by the second. 812 00:40:27,566 --> 00:40:30,709 ♪ ♪ 813 00:40:30,733 --> 00:40:35,109 {\an8}(sizzling) 814 00:40:35,133 --> 00:40:37,576 {\an1}As the searing heat builds, 815 00:40:37,600 --> 00:40:39,842 {\an1}the creatures of Tanis are fighting for their lives. 816 00:40:39,866 --> 00:40:42,609 ♪ ♪ 817 00:40:42,633 --> 00:40:43,876 (dinosaur bellowing) 818 00:40:43,900 --> 00:40:47,642 ♪ ♪ 819 00:40:47,666 --> 00:40:50,676 {\an7}And then, as seismic waves rock the whole region... 820 00:40:50,700 --> 00:40:53,766 ♪ ♪ 821 00:40:59,200 --> 00:41:02,109 {\an7}...a violent surge wave 30 feet high 822 00:41:02,133 --> 00:41:04,233 {\an7}rushes up the Tanis River. 823 00:41:07,633 --> 00:41:12,766 {\an8}♪ ♪ 824 00:41:22,600 --> 00:41:23,909 {\an8}♪ ♪ 825 00:41:23,933 --> 00:41:26,809 {\an7}Surviving the turbulence of the surge is a challenge 826 00:41:26,833 --> 00:41:29,276 {\an7}even for the best swimmers. 827 00:41:29,300 --> 00:41:33,933 {\an8}♪ ♪ 828 00:41:35,566 --> 00:41:39,142 {\an7}Then, the slow but powerful rocking of the river system 829 00:41:39,166 --> 00:41:43,076 {\an1}draws the water back. 830 00:41:43,100 --> 00:41:47,900 ♪ ♪ 831 00:41:52,466 --> 00:41:57,633 ♪ ♪ 832 00:42:01,066 --> 00:42:04,576 {\an1}A large, robust animal like a T. rex 833 00:42:04,600 --> 00:42:07,776 {\an1}might have survived the surge. 834 00:42:07,800 --> 00:42:10,966 ♪ ♪ (pattering) 835 00:42:12,766 --> 00:42:16,209 {\an1}As might a hard-shelled reptile. 836 00:42:16,233 --> 00:42:19,509 {\an1}But there is much more to come. 837 00:42:19,533 --> 00:42:20,909 As billions of tons 838 00:42:20,933 --> 00:42:24,076 {\an1}of superheated spherules continue to fall, 839 00:42:24,100 --> 00:42:26,266 the atmosphere gets even hotter... 840 00:42:29,600 --> 00:42:31,209 {\an1}...igniting dead leaves 841 00:42:31,233 --> 00:42:33,642 {\an1}and sparking wildfires. 842 00:42:33,666 --> 00:42:38,433 ♪ ♪ 843 00:42:39,900 --> 00:42:41,876 Earthquakes... 844 00:42:41,900 --> 00:42:43,033 Fire... 845 00:42:45,000 --> 00:42:47,876 Devastation. 846 00:42:47,900 --> 00:42:49,076 (dinosaur grunts) 847 00:42:49,100 --> 00:42:51,009 {\an1}Little would survive for long, 848 00:42:51,033 --> 00:42:52,742 on land... 849 00:42:52,766 --> 00:42:57,542 (bellowing) 850 00:42:57,566 --> 00:42:59,576 Or in the air... 851 00:42:59,600 --> 00:43:02,742 ♪ ♪ 852 00:43:02,766 --> 00:43:04,833 (pterosaur groans) 853 00:43:09,033 --> 00:43:12,942 {\an8}BLACK: The air around the planet was effectively set to broil. 854 00:43:12,966 --> 00:43:15,309 {\an7}This was something that you couldn't escape 855 00:43:15,333 --> 00:43:16,342 {\an7}if you were out on the surface. 856 00:43:16,366 --> 00:43:21,533 ♪ ♪ 857 00:43:26,833 --> 00:43:30,609 ATTENBOROUGH: Those that live underground may have had a better chance. 858 00:43:30,633 --> 00:43:32,376 {\an1}(creature chittering) 859 00:43:32,400 --> 00:43:37,942 ♪ ♪ 860 00:43:37,966 --> 00:43:40,976 {\an1}As the slow rocking of the river system continues to move 861 00:43:41,000 --> 00:43:44,509 {\an1}the water to and fro, another powerful surge 862 00:43:44,533 --> 00:43:47,676 hits the riverbank. 863 00:43:47,700 --> 00:43:52,866 ♪ ♪ 864 00:44:03,300 --> 00:44:05,100 (loud crashing) 865 00:44:07,100 --> 00:44:10,966 {\an1}For most, there is no escaping the destruction. 866 00:44:13,533 --> 00:44:15,009 ♪ ♪ 867 00:44:15,033 --> 00:44:16,409 {\an1}For many of the creatures here, 868 00:44:16,433 --> 00:44:19,042 {\an1}their stories end underwater. 869 00:44:19,066 --> 00:44:21,666 ♪ ♪ 870 00:44:25,633 --> 00:44:28,042 No one knows if the giant tsunami caused by 871 00:44:28,066 --> 00:44:32,442 {\an1}the impact ever reaches this far north, 872 00:44:32,466 --> 00:44:35,600 {\an1}but life here has already changed forever. 873 00:44:38,866 --> 00:44:42,976 {\an1}The mud the two waves leave behind will gradually turn into 874 00:44:43,000 --> 00:44:45,409 {\an1}the thick layer of crumbly rock 875 00:44:45,433 --> 00:44:48,942 {\an7}entombing the creatures which died here. 876 00:44:48,966 --> 00:44:51,709 {\an8}(wind whipping) 877 00:44:51,733 --> 00:44:54,476 {\an7}Until 66 million years later, 878 00:44:54,500 --> 00:44:57,400 {\an7}when they are finally unearthed. 879 00:44:59,966 --> 00:45:01,409 CLAYTOR: We have a general idea 880 00:45:01,433 --> 00:45:03,776 {\an7}of what horrors were unleashed on the landscape 881 00:45:03,800 --> 00:45:05,609 {\an7}by the asteroid impact. 882 00:45:05,633 --> 00:45:07,742 {\an7}But I think these sites may give us the ability to actually 883 00:45:07,766 --> 00:45:10,176 put them in sequence and understand exactly 884 00:45:10,200 --> 00:45:12,342 what these organisms went through. 885 00:45:12,366 --> 00:45:14,176 {\an1}Even though there is a lot of debate, 886 00:45:14,200 --> 00:45:15,909 {\an1}and there is a lot of controversy, 887 00:45:15,933 --> 00:45:17,609 {\an1}every new thing that we find, 888 00:45:17,633 --> 00:45:19,676 every new hypothesis that's put forward, 889 00:45:19,700 --> 00:45:21,342 {\an1}whether it's accepted or rejected, 890 00:45:21,366 --> 00:45:25,376 {\an1}gets us a little bit closer to doing that mental time travel 891 00:45:25,400 --> 00:45:28,242 {\an1}and imagining ourselves back in that Cretaceous world. 892 00:45:28,266 --> 00:45:31,209 ♪ ♪ 893 00:45:31,233 --> 00:45:33,342 (fire crackling) 894 00:45:33,366 --> 00:45:36,342 ATTENBOROUGH: Robert's finds have helped us understand, 895 00:45:36,366 --> 00:45:39,442 {\an1}in remarkable detail, what might have happened 896 00:45:39,466 --> 00:45:43,476 {\an7}at Tanis in the minutes after the asteroid impact. 897 00:45:43,500 --> 00:45:45,709 But what about the rest of the world? 898 00:45:45,733 --> 00:45:49,309 ♪ ♪ 899 00:45:49,333 --> 00:45:54,776 {\an1}Fires rage, destroying many of the world's forests. 900 00:45:54,800 --> 00:45:56,376 ♪ ♪ 901 00:45:56,400 --> 00:45:59,042 As the horrific day draws to a close, 902 00:45:59,066 --> 00:46:01,576 {\an1}many of the world's dinosaurs 903 00:46:01,600 --> 00:46:03,633 {\an1}are likely already dead. 904 00:46:07,400 --> 00:46:11,576 {\an1}Research shows that the angle at which the asteroid hit, 905 00:46:11,600 --> 00:46:14,709 {\an1}and the sulfur-rich rocks at the impact site, 906 00:46:14,733 --> 00:46:17,009 {\an1}amplified the devastation. 907 00:46:17,033 --> 00:46:19,276 {\an8}♪ ♪ 908 00:46:19,300 --> 00:46:25,042 {\an7}Without sunlight, most plants died, and food became scarce. 909 00:46:25,066 --> 00:46:26,809 (thunder rumbling) 910 00:46:26,833 --> 00:46:28,609 {\an1}As the weeks and months passed, 911 00:46:28,633 --> 00:46:32,609 {\an1}any dinosaur left alive would have died of hunger. 912 00:46:32,633 --> 00:46:35,242 ♪ ♪ 913 00:46:35,266 --> 00:46:38,809 {\an1}In the oceans, it was the same. 914 00:46:38,833 --> 00:46:41,976 {\an1}Nearly all of the world's plankton died, 915 00:46:42,000 --> 00:46:46,542 {\an1}leading to the starvation of most marine creatures. 916 00:46:46,566 --> 00:46:48,276 It's thought that 917 00:46:48,300 --> 00:46:51,909 {\an7}the impact winter that followed caused a global temperature drop 918 00:46:51,933 --> 00:46:55,066 {\an7}of at least 48 degrees Fahrenheit. 919 00:46:56,266 --> 00:46:58,809 {\an7}After this huge change in climate, 920 00:46:58,833 --> 00:47:02,976 {\an1}the fossil record tells us that three-quarters of all species, 921 00:47:03,000 --> 00:47:06,542 {\an1}including the dinosaurs, were wiped out. 922 00:47:06,566 --> 00:47:08,109 (crackling) 923 00:47:08,133 --> 00:47:09,909 PLESKO: The location of the Chicxulub impact 924 00:47:09,933 --> 00:47:12,042 {\an1}really was a worst-case scenario. 925 00:47:12,066 --> 00:47:13,709 {\an7}If the asteroid actually had come in, you know, 926 00:47:13,733 --> 00:47:15,276 {\an8}30 seconds earlier, 927 00:47:15,300 --> 00:47:16,509 {\an8}30 seconds later, 928 00:47:16,533 --> 00:47:18,609 {\an1}it would have actually hit the Atlantic Ocean 929 00:47:18,633 --> 00:47:20,409 or the Pacific Ocean 930 00:47:20,433 --> 00:47:22,542 {\an1}and not the sediment-rich, sulfur-rich 931 00:47:22,566 --> 00:47:24,876 {\an1}target of the Yucatan Peninsula. 932 00:47:24,900 --> 00:47:26,409 {\an8}Forests collapsed. 933 00:47:26,433 --> 00:47:29,309 {\an7}The plant eaters didn't have any food to eat; they died. 934 00:47:29,333 --> 00:47:31,442 {\an7}The meat eaters didn't have any plant eaters to eat; they died. 935 00:47:31,466 --> 00:47:34,076 Ecosystems collapsed like houses of cards. 936 00:47:34,100 --> 00:47:36,342 BLACK: This unintentional accident 937 00:47:36,366 --> 00:47:41,909 {\an1}that just was set in motion long before dinosaurs even existed. 938 00:47:41,933 --> 00:47:46,276 {\an1}And it just happened to be the one case of bad luck, 939 00:47:46,300 --> 00:47:49,733 the one worst day in the history of the planet. 940 00:47:51,733 --> 00:47:55,509 ATTENBOROUGH: Studies suggest that the planet was in semi-darkness 941 00:47:55,533 --> 00:48:00,900 {\an1}for around a decade as dust and soot slowly fell to Earth. 942 00:48:01,800 --> 00:48:04,076 {\an1}But then came something wonderful... 943 00:48:04,100 --> 00:48:05,909 ♪ ♪ 944 00:48:05,933 --> 00:48:08,442 A new beginning. 945 00:48:08,466 --> 00:48:11,042 {\an1}Once the dust cleared from the atmosphere, 946 00:48:11,066 --> 00:48:12,676 {\an1}and the sunlight returned, 947 00:48:12,700 --> 00:48:16,342 {\an1}plant life was gradually restored, 948 00:48:16,366 --> 00:48:19,609 led by ferns, the spores of which 949 00:48:19,633 --> 00:48:22,009 had lain dormant deep underground. 950 00:48:22,033 --> 00:48:23,909 ♪ ♪ 951 00:48:23,933 --> 00:48:28,342 {\an1}And the world began to turn green once more. 952 00:48:28,366 --> 00:48:30,409 {\an1}But what about the animals? 953 00:48:30,433 --> 00:48:33,242 ♪ ♪ 954 00:48:33,266 --> 00:48:35,809 One of the reasons some mammals survived 955 00:48:35,833 --> 00:48:39,476 the Great Extinction were burrows. 956 00:48:39,500 --> 00:48:41,276 {\an1}During the impact winter, 957 00:48:41,300 --> 00:48:43,842 {\an1}a burrow would have provided warmth, 958 00:48:43,866 --> 00:48:46,742 {\an1}protection, and a place to store food. 959 00:48:46,766 --> 00:48:52,676 ♪ ♪ 960 00:48:52,700 --> 00:48:54,009 (sniffing) 961 00:48:54,033 --> 00:48:57,109 {\an1}Mammals which were able to thrive in the aftermath 962 00:48:57,133 --> 00:48:59,376 {\an1}were resourceful omnivores. 963 00:48:59,400 --> 00:49:01,709 {\an1}And the insects which survived 964 00:49:01,733 --> 00:49:04,466 {\an1}could have been one source of food. 965 00:49:07,500 --> 00:49:10,776 {\an1}Their size would have been another advantage. 966 00:49:10,800 --> 00:49:13,466 (chittering) 967 00:49:14,700 --> 00:49:19,009 {\an1}When catastrophe strikes and food is scarce, 968 00:49:19,033 --> 00:49:21,509 {\an1}the largest tend to die out, 969 00:49:21,533 --> 00:49:24,109 whilst the smallest often survive. 970 00:49:24,133 --> 00:49:25,809 {\an1}(creature chittering) 971 00:49:25,833 --> 00:49:28,842 {\an1}And they weren't alone. 972 00:49:28,866 --> 00:49:31,209 ♪ ♪ 973 00:49:31,233 --> 00:49:34,876 {\an1}The turtle found at the dig site may have been unlucky, 974 00:49:34,900 --> 00:49:37,409 {\an1}but many others survived. 975 00:49:37,433 --> 00:49:41,909 {\an7}As did crocodiles, snakes, 976 00:49:41,933 --> 00:49:45,842 {\an1}and many fish species. 977 00:49:45,866 --> 00:49:47,476 BRUSATTE: Life has found a way, 978 00:49:47,500 --> 00:49:49,076 {\an1}and life is now thriving again, 979 00:49:49,100 --> 00:49:52,509 {\an1}and it is those ecosystems formed in the recovery 980 00:49:52,533 --> 00:49:55,342 from the asteroid that are the foundations 981 00:49:55,366 --> 00:49:57,709 {\an1}of our ecosystems today. 982 00:49:57,733 --> 00:50:00,076 {\an1}It's kind of amazing that we're able to put our finger 983 00:50:00,100 --> 00:50:01,342 {\an1}on this one line in the rock. 984 00:50:01,366 --> 00:50:04,276 {\an1}And as much as we miss the dinosaurs, 985 00:50:04,300 --> 00:50:05,842 {\an1}say if this hadn't happened, 986 00:50:05,866 --> 00:50:08,776 we wouldn't be here. 987 00:50:08,800 --> 00:50:11,342 ATTENBOROUGH: And as for the dinosaurs... 988 00:50:11,366 --> 00:50:14,842 did the impact really kill them all? 989 00:50:14,866 --> 00:50:19,209 {\an1}Well, this beautiful fossilized feather isn't from a bird, 990 00:50:19,233 --> 00:50:21,942 {\an1}but from a predatory dinosaur. 991 00:50:21,966 --> 00:50:24,876 {\an1}So, we have to be careful when we say that dinosaurs 992 00:50:24,900 --> 00:50:26,042 are extinct. 993 00:50:26,066 --> 00:50:30,709 {\an1}Because what we call birds originally evolved 994 00:50:30,733 --> 00:50:33,742 {\an1}from the smallest feathered dinosaurs. 995 00:50:33,766 --> 00:50:35,809 So, to be correct, 996 00:50:35,833 --> 00:50:39,942 {\an1}we should say all non-avian dinosaurs are extinct. 997 00:50:39,966 --> 00:50:42,176 ♪ ♪ 998 00:50:42,200 --> 00:50:45,409 {\an1}The finds from Robert and his team have given us 999 00:50:45,433 --> 00:50:47,176 {\an1}a more detailed picture... 1000 00:50:47,200 --> 00:50:49,876 (insects chirping) 1001 00:50:49,900 --> 00:50:51,509 {\an1}...about what might have happened 1002 00:50:51,533 --> 00:50:53,442 {\an1}on the day that destroyed 1003 00:50:53,466 --> 00:50:58,776 {\an1}the largest beasts ever to walk the Earth. 1004 00:50:58,800 --> 00:51:01,776 ♪ ♪ 1005 00:51:01,800 --> 00:51:05,009 {\an1}Dinosaurs were perhaps some of nature's 1006 00:51:05,033 --> 00:51:07,442 {\an1}most extraordinary creatures, 1007 00:51:07,466 --> 00:51:11,409 {\an1}dominating the planet for over 150 million years 1008 00:51:11,433 --> 00:51:14,009 {\an7}before they became extinct. 1009 00:51:14,033 --> 00:51:16,142 {\an8}(dinosaurs grunting) 1010 00:51:16,166 --> 00:51:18,576 {\an8}But extinction comes in different forms, 1011 00:51:18,600 --> 00:51:22,342 {\an1}and many of the amazing creatures and plants alive today 1012 00:51:22,366 --> 00:51:24,542 are also threatened. 1013 00:51:24,566 --> 00:51:28,842 {\an1}It's possible that humanity is having as big an impact 1014 00:51:28,866 --> 00:51:31,642 {\an1}on the world as the asteroid 1015 00:51:31,666 --> 00:51:34,676 that ended the age of the dinosaurs. 1016 00:51:34,700 --> 00:51:38,076 As human beings, we are unique in our ability 1017 00:51:38,100 --> 00:51:40,609 {\an1}to learn from the distant past. 1018 00:51:40,633 --> 00:51:43,276 The question is: 1019 00:51:43,300 --> 00:51:46,176 {\an1}will we use that ability wisely and do our very best 1020 00:51:46,200 --> 00:51:49,409 {\an1}to protect the millions of species 1021 00:51:49,433 --> 00:51:53,776 {\an1}for whom, alongside us, this planet is home? 1022 00:51:53,800 --> 00:51:57,609 ♪ ♪ 1023 00:51:57,633 --> 00:51:59,933 {\an8}(water spraying) 1024 00:52:08,800 --> 00:52:11,333 (waves crashing) 1025 00:52:33,733 --> 00:52:37,933 {\an8}♪ ♪ 1026 00:53:02,866 --> 00:53:06,566 {\an8}♪ ♪ 1027 00:53:29,433 --> 00:53:32,600 ♪ ♪