1 00:00:04,800 --> 00:00:09,233 NARRATOR: It's the worst day in the history of life on Earth. 2 00:00:09,266 --> 00:00:14,000 {\an1}A cataclysm that ends the age of the dinosaurs. 3 00:00:14,033 --> 00:00:15,533 ♪ 4 00:00:15,566 --> 00:00:17,600 LINDSAY ZANNO: If they hadn't met their destruction, 5 00:00:17,633 --> 00:00:19,066 our story never would have begun. 6 00:00:19,100 --> 00:00:22,033 NARRATOR: From the ashes, 7 00:00:22,066 --> 00:00:26,733 {\an1}a band of survivors rises to become bigger... 8 00:00:26,766 --> 00:00:28,266 nimbler... 9 00:00:28,300 --> 00:00:32,733 and smarter than any that came before. 10 00:00:34,000 --> 00:00:38,666 {\an1}Our tribe-- the mammals. 11 00:00:38,700 --> 00:00:40,366 {\an1}It was only after we lose the dinosaurs 12 00:00:40,400 --> 00:00:42,133 {\an1}that mammals really explode 13 00:00:42,166 --> 00:00:44,200 {\an1}into the diversity of forms that we see today. 14 00:00:44,233 --> 00:00:47,633 ♪ 15 00:00:47,666 --> 00:00:49,500 {\an8}NARRATOR: What happened after the impact? 16 00:00:49,533 --> 00:00:51,533 ♪ 17 00:00:51,566 --> 00:00:55,400 {\an1}How did life surge back? 18 00:00:55,433 --> 00:00:57,666 {\an1}The clues have been elusive. 19 00:00:57,700 --> 00:00:59,866 IAN MILLER: You could go your entire career 20 00:00:59,900 --> 00:01:01,533 {\an1}and not find a skull from this time period. 21 00:01:01,566 --> 00:01:04,433 {\an1}That's how rare they are. 22 00:01:04,466 --> 00:01:09,133 NARRATOR: But now comes a remarkable discovery. 23 00:01:09,166 --> 00:01:11,466 SHARON MILITO: There's just nothing like picking up something 24 00:01:11,500 --> 00:01:13,766 and finding out it's something amazing. 25 00:01:13,800 --> 00:01:14,900 NEIL SHUBIN: It's like winning the lottery. 26 00:01:14,933 --> 00:01:17,500 TYLER LYSON: Bam! We hit it big. 27 00:01:17,533 --> 00:01:20,966 NARRATOR: An unprecedented trove of fossils 28 00:01:21,000 --> 00:01:26,600 {\an1}reveals a turning point in the history of life. 29 00:01:26,633 --> 00:01:30,100 KIRK JOHNSON: That moment of rapid mammal evolution 30 00:01:30,133 --> 00:01:32,633 {\an1}is effectively the trigger 31 00:01:32,666 --> 00:01:34,600 {\an1}to our existence here on planet Earth. 32 00:01:34,633 --> 00:01:36,066 ♪ 33 00:01:36,100 --> 00:01:40,900 NARRATOR: "Rise of the Mammals"-- right now, on "NOVA." 34 00:01:42,700 --> 00:01:47,266 ♪ 35 00:01:47,300 --> 00:02:02,800 {\an1}Major funding for "NOVA" is provided by the following: 36 00:02:04,933 --> 00:02:08,800 ♪ 37 00:02:08,833 --> 00:02:12,533 NARRATOR: We live in the age of mammals. 38 00:02:16,733 --> 00:02:20,366 {\an1}All across the globe, 39 00:02:20,400 --> 00:02:23,300 {\an1}they thrive in an astonishing array of forms... 40 00:02:23,333 --> 00:02:26,800 ♪ 41 00:02:26,833 --> 00:02:30,266 {\an1}From the great beasts of the forests 42 00:02:30,300 --> 00:02:33,900 {\an1}to giants that sound the ocean depths... 43 00:02:33,933 --> 00:02:35,366 ♪ 44 00:02:35,400 --> 00:02:37,133 to us, 45 00:02:37,166 --> 00:02:40,066 {\an1}mammals dominate the planet. 46 00:02:40,100 --> 00:02:43,066 (grunting) 47 00:02:43,100 --> 00:02:47,266 {\an1}But it wasn't always this way. 48 00:02:47,300 --> 00:02:48,933 {\an1}(dinosaur screeches) 49 00:02:48,966 --> 00:02:51,200 {\an1}For 150 million years, 50 00:02:51,233 --> 00:02:56,600 {\an1}mammals lived in the shadows of the dinosaurs. 51 00:02:56,633 --> 00:02:59,666 {\an1}Then, a catastrophe gave them an opening. 52 00:02:59,700 --> 00:03:02,566 {\an1}(explosion thunders) 53 00:03:04,700 --> 00:03:06,800 {\an7}For years, we've known just bits and pieces WEBVTT X-TIMESTAMP-MAP=MPEGTS:198018, LOCAL:00:00:00.000 54 00:03:04,700 --> 00:03:06,800 {\an7}For years, we've known just bits and pieces 55 00:03:06,833 --> 00:03:09,533 {\an7}about how mammals seized the moment 56 00:03:09,566 --> 00:03:12,400 {\an7}and made our story possible. 57 00:03:12,433 --> 00:03:15,233 {\an7}But now that's changing. 58 00:03:15,266 --> 00:03:18,900 {\an8}♪ 59 00:03:18,933 --> 00:03:23,266 {\an7}An extraordinary discovery in Colorado 60 00:03:23,300 --> 00:03:26,566 {\an7}is revealing an unparalleled collection of fossils 61 00:03:26,600 --> 00:03:30,233 {\an7}from the time when mammals began their reign. 62 00:03:30,266 --> 00:03:33,466 {\an8}♪ 63 00:03:33,500 --> 00:03:37,533 {\an7}This hoard lay hidden in plain sight 64 00:03:37,566 --> 00:03:42,533 {\an7}until a young fossil hunter made a once-in-a-lifetime discovery. 65 00:03:42,566 --> 00:03:46,666 {\an8}♪ 66 00:03:51,800 --> 00:03:55,000 LYSON: I grew up in a town of about 80 people, 67 00:03:55,033 --> 00:03:58,866 {\an1}basically the middle of nowhere in southwestern North Dakota. 68 00:03:58,900 --> 00:04:02,200 ♪ 69 00:04:02,233 --> 00:04:05,066 NARRATOR: Tyler Lyson's home might look like other outposts 70 00:04:05,100 --> 00:04:08,200 scattered across the American West, 71 00:04:08,233 --> 00:04:11,066 {\an1}but this place is unique. 72 00:04:11,100 --> 00:04:13,666 LYSON: Right by my hometown, about a mile away, 73 00:04:13,700 --> 00:04:17,366 {\an1}are badlands that preserve the very last moment of time 74 00:04:17,400 --> 00:04:20,133 {\an1}when dinosaurs were alive. 75 00:04:20,166 --> 00:04:22,933 {\an1}As a child, I would run around the badlands 76 00:04:22,966 --> 00:04:27,000 {\an7}and find dinosaur bone after dinosaur bone, 77 00:04:27,033 --> 00:04:30,033 {\an7}just tons of dinosaur bones just tumbling out of the hills. 78 00:04:30,066 --> 00:04:33,366 ♪ 79 00:04:33,400 --> 00:04:36,333 NARRATOR: Known as the Hell Creek formation, 80 00:04:36,366 --> 00:04:39,100 {\an1}this was the first place T. rex fossils were discovered 81 00:04:39,133 --> 00:04:41,466 a century ago. 82 00:04:41,500 --> 00:04:42,900 ♪ 83 00:04:42,933 --> 00:04:46,700 {\an1}Ever since, bone diggers have been searching 84 00:04:46,733 --> 00:04:49,066 for more traces of that lost world. 85 00:04:49,100 --> 00:04:52,466 ♪ 86 00:04:52,500 --> 00:04:55,000 {\an1}(helicopter rotors whirring) 87 00:04:56,366 --> 00:04:59,666 Even as a boy, Tyler was in the thick of it. 88 00:05:01,233 --> 00:05:05,166 JOHNSON: Years ago, I met a kid named Tyler Lyson. 89 00:05:05,200 --> 00:05:07,766 {\an1}And he was this gangly 12-year-old kid. 90 00:05:07,800 --> 00:05:09,933 {\an7}By the time he was 13, he was going out by himself 91 00:05:09,966 --> 00:05:11,666 {\an7}and finding amazing fossils. 92 00:05:11,700 --> 00:05:14,533 {\an7}He found an entire dinosaur when he was, like, 14 years old. 93 00:05:14,566 --> 00:05:18,366 NARRATOR: Tyler even discovered a new species 94 00:05:18,400 --> 00:05:20,366 {\an1}of feathered dinosaur. 95 00:05:20,400 --> 00:05:23,433 JOHNSON: He became sort of this dinosaur wunderkind. 96 00:05:23,466 --> 00:05:27,666 NARRATOR: It was a made-for-TV story. 97 00:05:27,700 --> 00:05:30,800 MAN: High school sophomore Tyler Lyson has walked 98 00:05:30,833 --> 00:05:33,400 {\an1}just about every inch of this land, 99 00:05:33,433 --> 00:05:37,733 {\an1}and has already headed 20 dinosaur excavations. 100 00:05:37,766 --> 00:05:41,866 NARRATOR: His most spectacular find? 101 00:05:41,900 --> 00:05:46,066 {\an1}A dinosaur fossil with preserved skin and muscle. 102 00:05:46,100 --> 00:05:48,866 {\an1}He kept finding more fossils, 103 00:05:48,900 --> 00:05:52,800 {\an1}and soon became an expert in ancient turtles. 104 00:05:54,466 --> 00:05:57,433 {\an1}He became fascinated by a well-known pattern 105 00:05:57,466 --> 00:06:01,200 {\an1}in where dinosaurs were and where they weren't. 106 00:06:01,233 --> 00:06:05,200 LYSON: I remember as a child crossing over this band WEBVTT X-TIMESTAMP-MAP=MPEGTS:198018, LOCAL:00:00:00.000 107 00:06:01,233 --> 00:06:05,200 LYSON: I remember as a child crossing over this band 108 00:06:05,233 --> 00:06:11,766 {\an1}and getting above that area and not finding any dinosaurs. 109 00:06:11,800 --> 00:06:16,866 NARRATOR: The distinct layer seemed to mark their disappearance. 110 00:06:16,900 --> 00:06:19,700 LYSON: So, this always fascinated me. 111 00:06:19,733 --> 00:06:23,933 {\an1}Why, above that boundary, were there no more dinosaurs? 112 00:06:23,966 --> 00:06:25,666 ♪ 113 00:06:25,700 --> 00:06:28,533 {\an1}What happened here? 114 00:06:30,933 --> 00:06:33,100 NARRATOR: The boundary layer, Tyler learned, 115 00:06:33,133 --> 00:06:38,333 {\an1}was the signature of an event that changed the world forever. 116 00:06:38,366 --> 00:06:41,533 (roars) 117 00:06:41,566 --> 00:06:46,366 ♪ 118 00:06:46,400 --> 00:06:48,400 {\an1}During the age of reptiles, 119 00:06:48,433 --> 00:06:53,000 {\an1}dinosaurs tower over mammals. 120 00:06:53,033 --> 00:06:57,466 Other reptiles rule the skies and seas. 121 00:06:57,500 --> 00:07:03,300 {\an1}They take on a wide range of shapes and lifestyles. 122 00:07:03,333 --> 00:07:06,033 {\an1}Many are gigantic. 123 00:07:06,066 --> 00:07:09,833 {\an1}Mammals had been around for millions of years. 124 00:07:09,866 --> 00:07:14,100 {\an7}But in all of that time, most grew no bigger than a rat. 125 00:07:18,700 --> 00:07:23,633 {\an1}Then, 66 million years ago, the cataclysm. 126 00:07:23,666 --> 00:07:26,466 ♪ 127 00:07:26,500 --> 00:07:29,566 A chunk of rock over six miles wide 128 00:07:29,600 --> 00:07:32,900 {\an1}tears through the atmosphere and slams into the planet. 129 00:07:32,933 --> 00:07:35,866 {\an1}(collision thunders) 130 00:07:35,900 --> 00:07:39,600 {\an1}The asteroid blasts a crater 20 miles deep 131 00:07:39,633 --> 00:07:41,633 {\an1}and over 100 miles wide 132 00:07:41,666 --> 00:07:43,533 {\an1}in the Yucatan Peninsula. 133 00:07:43,566 --> 00:07:48,200 {\an1}(dinosaurs screeching and rumbling) 134 00:07:48,233 --> 00:07:50,833 {\an1}It showers the planet with molten rock 135 00:07:50,866 --> 00:07:55,133 {\an1}and white-hot beads of glass. 136 00:07:55,166 --> 00:07:57,100 {\an1}(dinosaurs screeching and rumbling) 137 00:07:57,133 --> 00:08:01,200 LYSON: And this broils the surface of the Earth. 138 00:08:05,566 --> 00:08:08,333 NARRATOR: Creatures on the surface roast. 139 00:08:08,366 --> 00:08:11,766 {\an1}(creatures roaring) 140 00:08:11,800 --> 00:08:17,033 {\an1}Skies across the globe darken. 141 00:08:17,066 --> 00:08:20,933 {\an1}Fire gives way to frost. 142 00:08:23,500 --> 00:08:26,966 ANJALI GOSWAMI: You have intense global cooling. 143 00:08:27,000 --> 00:08:30,866 {\an1}You're talking about immediate global winter. 144 00:08:32,466 --> 00:08:38,266 NARRATOR: Deprived of sunlight, plants wither. 145 00:08:38,300 --> 00:08:41,433 {\an1}Lush forests collapse. 146 00:08:41,466 --> 00:08:44,333 {\an7}So the animals that rely on those plants for food, 147 00:08:44,366 --> 00:08:46,033 {\an7}the animals that rely on those animals 148 00:08:46,066 --> 00:08:48,366 {\an7}that rely on plants for food, they would all suffer. 149 00:08:48,400 --> 00:08:50,500 ♪ 150 00:08:50,533 --> 00:08:54,600 {\an1}You really are having the entire food chain fall apart. 151 00:08:56,000 --> 00:08:59,900 NARRATOR: All of the dinosaurs, except the birds, perish. 152 00:08:59,933 --> 00:09:01,300 SHUBIN: Three out of four species 153 00:09:01,333 --> 00:09:03,933 {\an7}that were alive on the planet before the impact 154 00:09:03,966 --> 00:09:05,066 {\an8}died. WEBVTT X-TIMESTAMP-MAP=MPEGTS:198018, LOCAL:00:00:00.000 155 00:09:03,966 --> 00:09:05,066 {\an8}died. 156 00:09:06,133 --> 00:09:09,166 {\an1}And that's just the species. 157 00:09:09,200 --> 00:09:10,533 {\an1}About 90% of the creatures 158 00:09:10,566 --> 00:09:12,033 that were alive before the impact 159 00:09:12,066 --> 00:09:13,966 {\an1}are dead afterwards. 160 00:09:14,000 --> 00:09:16,566 ZANNO: We think about the loss of dinosaurs, 161 00:09:16,600 --> 00:09:20,433 {\an1}but dinosaurs weren't the only animals to suffer from this. 162 00:09:20,466 --> 00:09:23,000 {\an7}Many, many groups of organisms took a very serious hit, 163 00:09:23,033 --> 00:09:24,200 {\an7}including mammals. 164 00:09:24,233 --> 00:09:28,166 ♪ 165 00:09:31,033 --> 00:09:36,033 LYSON: It's a really bad time for life on Earth. 166 00:09:36,066 --> 00:09:38,466 {\an1}Yet some things survive, right? 167 00:09:38,500 --> 00:09:40,766 {\an1}Including some of our earliest, earliest ancestors. 168 00:09:40,800 --> 00:09:44,166 ♪ 169 00:09:44,200 --> 00:09:47,266 NARRATOR: We don't know much about these creatures. 170 00:09:47,300 --> 00:09:48,766 ♪ 171 00:09:48,800 --> 00:09:50,933 {\an1}None was bigger than a squirrel. 172 00:09:53,533 --> 00:09:56,600 {\an1}And their size and scarcity have made their fossils 173 00:09:56,633 --> 00:09:59,233 hard to come by. 174 00:10:00,733 --> 00:10:05,766 {\an1}Yet somehow, this band of survivors and their descendants 175 00:10:05,800 --> 00:10:07,400 {\an1}will claim the Earth. 176 00:10:07,433 --> 00:10:10,133 {\an1}(birds twittering) 177 00:10:10,166 --> 00:10:13,166 ♪ 178 00:10:13,200 --> 00:10:17,333 {\an1}(animals grunting and chittering) 179 00:10:20,400 --> 00:10:24,333 LYSON: Today, there are over 6,000 species of mammals. 180 00:10:24,366 --> 00:10:26,866 ♪ 181 00:10:26,900 --> 00:10:29,933 {\an1}And they range in size from the tiny pygmy jerboa, 182 00:10:29,966 --> 00:10:33,033 {\an1}which weighs about as much as a coin, 183 00:10:33,066 --> 00:10:37,333 {\an7}to the largest animal to have ever lived, the blue whale, 184 00:10:37,366 --> 00:10:43,500 {\an7}which is about 180 tons, the size of 15 school buses. 185 00:10:46,833 --> 00:10:49,000 GOSWAMI: Over the last 66 million years, 186 00:10:49,033 --> 00:10:52,433 {\an1}they've evolved an incredible diversity of forms. 187 00:10:52,466 --> 00:10:55,366 ♪ 188 00:10:55,400 --> 00:10:58,133 SHUBIN: Mammals today live in almost every environment on the planet, 189 00:10:58,166 --> 00:11:00,233 from the tops of the highest mountains 190 00:11:00,266 --> 00:11:03,833 {\an1}to living in the trees, to living in the water. 191 00:11:03,866 --> 00:11:08,233 ♪ 192 00:11:08,266 --> 00:11:12,233 NARRATOR: They thrive in scorching deserts 193 00:11:12,266 --> 00:11:15,200 {\an1}and across the frozen tundra. 194 00:11:17,066 --> 00:11:21,300 {\an1}Mammals even patrol the depths of every ocean 195 00:11:21,333 --> 00:11:24,866 {\an1}and the moonlit reaches of the sky. 196 00:11:24,900 --> 00:11:27,933 ♪ 197 00:11:27,966 --> 00:11:31,833 LYSON: All this diversity can be traced back 198 00:11:31,866 --> 00:11:35,033 {\an1}to those survivors of the extinction. 199 00:11:35,066 --> 00:11:37,733 ♪ 200 00:11:37,766 --> 00:11:41,900 NARRATOR: What happened in the wake of that catastrophic impact? 201 00:11:41,933 --> 00:11:44,566 LYSON: That's what I'm interested in. 202 00:11:44,600 --> 00:11:48,766 ♪ 203 00:11:48,800 --> 00:11:51,200 {\an7}How long did it take for ecosystems to recover? 204 00:11:51,233 --> 00:11:55,800 {\an1}For habitats to reform? 205 00:11:55,833 --> 00:11:57,933 {\an1}For life to get big again? 206 00:11:57,966 --> 00:12:01,233 ♪ WEBVTT X-TIMESTAMP-MAP=MPEGTS:198018, LOCAL:00:00:00.000 207 00:12:05,333 --> 00:12:09,800 NARRATOR: The answers require fossils. 208 00:12:09,833 --> 00:12:12,433 {\an1}But such relics are rare. 209 00:12:14,466 --> 00:12:19,233 JOHNSON: I've spent much of the last 35 years looking at rocks 210 00:12:19,266 --> 00:12:20,666 {\an1}from the first million years 211 00:12:20,700 --> 00:12:24,100 {\an1}after the extinction of the dinosaurs. 212 00:12:24,133 --> 00:12:27,066 {\an7}I've studied the fossil plants from that time period. 213 00:12:27,100 --> 00:12:30,066 {\an7}And through that entire 35 years, 214 00:12:30,100 --> 00:12:32,500 {\an1}I think I've found 215 00:12:32,533 --> 00:12:37,366 one or two fossil mammal pieces. 216 00:12:37,400 --> 00:12:38,800 And I'm looking. 217 00:12:38,833 --> 00:12:42,266 {\an1}I'm out there looking, and I know how rare those things are. 218 00:12:45,500 --> 00:12:47,833 NARRATOR: For years, Tyler and others 219 00:12:47,866 --> 00:12:50,133 {\an1}search for these scarce specimens 220 00:12:50,166 --> 00:12:52,800 in North Dakota. 221 00:12:52,833 --> 00:12:55,566 {\an1}He targets the rock above the boundary layer-- 222 00:12:55,600 --> 00:12:59,333 {\an1}sediments laid down just after the impact. 223 00:12:59,366 --> 00:13:04,700 ♪ 224 00:13:04,733 --> 00:13:10,233 {\an1}Fossil hunters had occasionally found mammal traces here, 225 00:13:10,266 --> 00:13:12,666 {\an1}but Tyler has no such luck. 226 00:13:12,700 --> 00:13:16,900 JOHNSON: Small animals get broken up into fragments. 227 00:13:16,933 --> 00:13:18,900 {\an1}So, when you're looking for an early mammal, 228 00:13:18,933 --> 00:13:21,066 you're looking for effectively the tooth 229 00:13:21,100 --> 00:13:22,866 {\an1}of a mouse-sized animal. 230 00:13:22,900 --> 00:13:24,633 {\an1}You're looking for something that's about the size 231 00:13:24,666 --> 00:13:25,733 {\an1}of the head of a pin. 232 00:13:25,766 --> 00:13:28,466 {\an1}And they're excruciatingly hard to find. 233 00:13:28,500 --> 00:13:30,233 ♪ 234 00:13:30,266 --> 00:13:31,566 LYSON: Every year, I go back to my hometown, 235 00:13:31,600 --> 00:13:33,566 {\an1}and every year, I spend time above the boundary 236 00:13:33,600 --> 00:13:36,200 {\an1}looking for fossils. 237 00:13:36,233 --> 00:13:41,666 {\an1}And I've found so few fossils, it's, it's pathetic. 238 00:13:41,700 --> 00:13:43,533 ♪ 239 00:13:43,566 --> 00:13:45,533 {\an1}And I was starting to think about, like, 240 00:13:45,566 --> 00:13:47,266 {\an1}"Well, where's the next area?" 241 00:13:47,300 --> 00:13:50,066 {\an1}I was getting ready to give up. 242 00:13:50,100 --> 00:13:55,766 NARRATOR: But then, Tyler gets a job-- and another shot-- 243 00:13:55,800 --> 00:13:58,300 in Colorado. 244 00:14:00,000 --> 00:14:05,266 {\an1}He joins up with Ian Miller, an expert in plant fossils 245 00:14:05,300 --> 00:14:08,600 {\an1}at the Denver Museum of Nature and Science. 246 00:14:08,633 --> 00:14:14,766 {\an1}Ian shares an interest in the extinction and its aftermath, 247 00:14:14,800 --> 00:14:18,366 {\an1}and knows Colorado is a great place to search. 248 00:14:18,400 --> 00:14:20,033 ♪ 249 00:14:20,066 --> 00:14:23,866 {\an7}We have this really unparalleled record of this period of time 250 00:14:23,900 --> 00:14:25,233 {\an7}here in Western North America. 251 00:14:25,266 --> 00:14:28,833 {\an1}But the best place is right here. 252 00:14:28,866 --> 00:14:33,566 NARRATOR: Together, they start exploring locations around the state. 253 00:14:33,600 --> 00:14:35,700 ♪ 254 00:14:35,733 --> 00:14:38,600 {\an1}One, called Corral Bluffs, 255 00:14:38,633 --> 00:14:43,733 {\an1}offers 400 feet of exposed rock rising above the boundary. 256 00:14:49,933 --> 00:14:53,266 {\an1}Tyler begins by scanning the ground for bits of bone. 257 00:14:55,500 --> 00:14:57,566 LYSON: That's how we're trained to find fossils-- 258 00:14:57,600 --> 00:15:02,166 {\an1}looking for actual scraps of bone on the surface, 259 00:15:02,200 --> 00:15:03,833 or to see bones sticking out of the ground. WEBVTT X-TIMESTAMP-MAP=MPEGTS:198018, LOCAL:00:00:00.000 260 00:15:10,633 --> 00:15:14,366 NARRATOR: But at Corral Bluffs, this approach yields 261 00:15:14,400 --> 00:15:16,400 {\an1}just a few scattered fragments. 262 00:15:16,433 --> 00:15:20,800 LYSON: I really didn't find a whole lot. 263 00:15:20,833 --> 00:15:24,166 {\an1}You can only look for fossils for so long 264 00:15:24,200 --> 00:15:28,700 {\an1}before you get really frustrated and decide to go home. 265 00:15:31,700 --> 00:15:33,833 NARRATOR: What Tyler doesn't know 266 00:15:33,866 --> 00:15:35,166 {\an1}is that a museum volunteer 267 00:15:35,200 --> 00:15:38,400 {\an1}had already found the key to his quest 268 00:15:38,433 --> 00:15:40,100 {\an1}in this same spot. 269 00:15:40,133 --> 00:15:45,166 ♪ 270 00:15:45,200 --> 00:15:48,766 {\an1}Long before Tyler arrived in Colorado, 271 00:15:48,800 --> 00:15:51,833 {\an1}Sharon Milito set off to look for fossils 272 00:15:51,866 --> 00:15:55,466 from the plateau atop the bluffs. 273 00:15:55,500 --> 00:15:56,900 MILITO: When we first came out, 274 00:15:56,933 --> 00:15:59,833 {\an1}we were just looking for whatever we could find. 275 00:16:01,700 --> 00:16:03,833 {\an1}The important thing we wanted to find 276 00:16:03,866 --> 00:16:05,533 were mammal jaws and mammal teeth, 277 00:16:05,566 --> 00:16:07,066 {\an1}but they were elusive. 278 00:16:07,100 --> 00:16:10,233 So, one day, I was walking along in an area 279 00:16:10,266 --> 00:16:12,200 {\an1}I'd been many times before, 280 00:16:12,233 --> 00:16:13,366 {\an1}and I saw this white, round rock 281 00:16:13,400 --> 00:16:16,833 {\an1}sitting there on kind of its own little pedestal. 282 00:16:18,566 --> 00:16:22,700 {\an8}♪ 283 00:16:22,733 --> 00:16:24,333 {\an7}And I picked it up and looked at it, 284 00:16:24,366 --> 00:16:28,566 {\an7}and as soon as I looked at it, I saw these teeth 285 00:16:28,600 --> 00:16:31,866 {\an7}that were just smiling out at me. 286 00:16:31,900 --> 00:16:36,133 {\an7}And I just almost had a heart attack. 287 00:16:36,166 --> 00:16:39,800 NARRATOR: She'd found part of a mammal skull-- 288 00:16:39,833 --> 00:16:42,466 {\an1}one that could fit in the palm of her hand. 289 00:16:42,500 --> 00:16:43,933 MILITO: I was so excited, 290 00:16:43,966 --> 00:16:47,500 {\an1}because it was really, really well preserved. 291 00:16:47,533 --> 00:16:49,533 ♪ 292 00:16:49,566 --> 00:16:53,800 NARRATOR: She brought the fossil to the museum, 293 00:16:53,833 --> 00:16:56,766 {\an1}where it was catalogued and filed away. 294 00:17:00,533 --> 00:17:03,966 ♪ 295 00:17:04,000 --> 00:17:07,500 It was years before Tyler happened across it. 296 00:17:11,733 --> 00:17:15,366 {\an8}LYSON: I was downstairs, just looking through the collection, 297 00:17:15,400 --> 00:17:19,333 {\an7}pulling open drawers, and there, sitting right in the front, 298 00:17:19,366 --> 00:17:24,166 {\an7}was the palate of a mammal. 299 00:17:24,200 --> 00:17:27,233 {\an1}And I was absolutely astonished; I couldn't believe it. 300 00:17:27,266 --> 00:17:30,733 {\an1}And so I was sort of thinking to myself, like, 301 00:17:30,766 --> 00:17:32,900 {\an1}"If there's this complete of a skull here, 302 00:17:32,933 --> 00:17:36,200 {\an1}there's got to be more." 303 00:17:36,233 --> 00:17:40,600 NARRATOR: Sharon's fossil had been found in a particular kind of rock 304 00:17:40,633 --> 00:17:44,533 {\an1}called a concretion. 305 00:17:44,566 --> 00:17:48,633 {\an1}Sometimes, concretions can form around organic material, 306 00:17:48,666 --> 00:17:51,133 like bone. 307 00:17:51,166 --> 00:17:53,266 {\an1}And if conditions are right, 308 00:17:53,300 --> 00:17:58,433 {\an1}they protect the fossil inside for eons. 309 00:17:58,466 --> 00:18:00,200 LYSON: Sharon's skull was incredibly lucky 310 00:18:00,233 --> 00:18:05,366 {\an1}because it showed that, yes, there are fossils inside, WEBVTT X-TIMESTAMP-MAP=MPEGTS:198018, LOCAL:00:00:00.000 311 00:18:00,233 --> 00:18:05,366 {\an1}because it showed that, yes, there are fossils inside, 312 00:18:05,400 --> 00:18:08,033 {\an1}and this is the type of rock to look for. 313 00:18:08,066 --> 00:18:09,833 ♪ 314 00:18:09,866 --> 00:18:12,333 NARRATOR: Tyler decides to change his game 315 00:18:12,366 --> 00:18:15,933 {\an1}and look for concretions to crack open. 316 00:18:15,966 --> 00:18:18,933 (Tom Petty's "Runnin' Down a Dream" playing) 317 00:18:18,966 --> 00:18:22,566 LYSON: It was absolutely a light bulb moment. 318 00:18:22,600 --> 00:18:24,633 {\an1}That was the game changer. 319 00:18:24,666 --> 00:18:27,500 (song continues) 320 00:18:27,533 --> 00:18:30,666 PETTY: ♪ It was a beautiful day 321 00:18:30,700 --> 00:18:33,466 {\an1}♪ The sun beat down 322 00:18:33,500 --> 00:18:36,433 {\an1}♪ I had the radio on 323 00:18:36,466 --> 00:18:40,066 {\an1}♪ I was drivin' 324 00:18:40,100 --> 00:18:42,233 {\an1}♪ The trees went by 325 00:18:42,266 --> 00:18:47,266 {\an1}♪ Me and Del were singin' "Little Runaway" ♪ 326 00:18:47,300 --> 00:18:50,533 ♪ I was flyin' 327 00:18:50,566 --> 00:18:53,900 {\an1}♪ Yeah, runnin' down a dream 328 00:18:53,933 --> 00:18:55,400 {\an1}♪ That never would come to me 329 00:18:55,433 --> 00:18:57,466 MILLER: Tyler started to put these pieces together, 330 00:18:57,500 --> 00:19:00,800 {\an1}thinking about this new lens to look for these concretions. 331 00:19:00,833 --> 00:19:02,833 (song continues) 332 00:19:02,866 --> 00:19:05,366 PETTY: ♪ Runnin' down a dream 333 00:19:05,400 --> 00:19:06,566 {\an1}Just saying, like, "We're going to go down there, 334 00:19:06,600 --> 00:19:07,666 {\an1}blow the doors off this thing." 335 00:19:07,700 --> 00:19:08,700 {\an1}Nobody believes him, right? 336 00:19:08,733 --> 00:19:10,100 {\an1}And even me, who, his colleague, 337 00:19:10,133 --> 00:19:13,566 {\an1}I'm just, like, "That sounds good, that sounds good, man." 338 00:19:13,600 --> 00:19:15,833 (song continues) 339 00:19:15,866 --> 00:19:18,500 (song ends) 340 00:19:21,466 --> 00:19:24,000 NARRATOR: They hit the bluffs, 341 00:19:24,033 --> 00:19:26,600 {\an1}their eyes peeled for promising rocks. 342 00:19:26,633 --> 00:19:28,333 ♪ 343 00:19:28,366 --> 00:19:32,666 {\an1}There's a whole hillside of choices. 344 00:19:32,700 --> 00:19:34,766 {\an1}One catches Tyler's eye. 345 00:19:34,800 --> 00:19:38,366 LYSON: I see this rock, this concretion on the ground, 346 00:19:38,400 --> 00:19:40,633 {\an7}the very first one that I pick up, and I crack it, 347 00:19:40,666 --> 00:19:42,933 {\an7}and it was amazing. 348 00:19:42,966 --> 00:19:46,500 {\an1}I just found a mammal skull! (laughs) 349 00:19:46,533 --> 00:19:49,233 NARRATOR: And that was just the beginning. 350 00:19:49,266 --> 00:19:51,000 MILLER: It was, it was crazy the way it happened. 351 00:19:51,033 --> 00:19:53,066 {\an1}I mean, you could go your entire career 352 00:19:53,100 --> 00:19:55,600 {\an1}as a mammal paleontologist 353 00:19:55,633 --> 00:19:56,866 {\an1}and not find a skull from this time period-- 354 00:19:56,900 --> 00:19:57,800 {\an1}that's how rare they are. 355 00:19:57,833 --> 00:19:59,866 LYSON: We found, I think, 356 00:19:59,900 --> 00:20:01,166 {\an1}five or six mammal skulls 357 00:20:01,200 --> 00:20:04,966 {\an1}within about a ten-minute time span. 358 00:20:05,000 --> 00:20:06,666 MILLER: We were just laughing on the outcrop. 359 00:20:06,700 --> 00:20:08,333 {\an1}Nothing like that's ever happened to me before. 360 00:20:08,366 --> 00:20:10,500 I mean, amazing. 361 00:20:10,533 --> 00:20:13,333 NARRATOR: They'd cracked the case... 362 00:20:13,366 --> 00:20:15,900 ♪ 363 00:20:15,933 --> 00:20:19,300 {\an1}...and unearthed a trove of time capsules filled with clues. 364 00:20:19,333 --> 00:20:21,466 ♪ 365 00:20:21,500 --> 00:20:25,266 JOHNSON: It was like opening a door into a new world. 366 00:20:29,700 --> 00:20:34,000 NARRATOR: In the months that follow, Tyler and Ian scour the bluff 367 00:20:34,033 --> 00:20:36,066 and discover thousands of fossils, 368 00:20:36,100 --> 00:20:39,133 {\an1}including plants, 369 00:20:39,166 --> 00:20:43,300 {\an1}reptiles, and dozens of mammals. 370 00:20:43,333 --> 00:20:45,000 (laughing) 371 00:20:45,033 --> 00:20:50,300 NARRATOR: All of them lived here just after the mass extinction. 372 00:20:50,333 --> 00:20:51,633 GOSWAMI: Most of the time, you know, 373 00:20:51,666 --> 00:20:55,033 {\an7}we're pretty happy if we find some nice teeth 374 00:20:55,066 --> 00:20:58,000 {\an7}from an area that's that close to the boundary. 375 00:20:58,033 --> 00:21:01,366 {\an1}Having this kind of record is really rare. 376 00:21:01,400 --> 00:21:03,566 You got the other side a little bit, too? 377 00:21:03,600 --> 00:21:07,033 NARRATOR: They had found their quarry at last. WEBVTT X-TIMESTAMP-MAP=MPEGTS:198018, LOCAL:00:00:00.000 378 00:21:03,600 --> 00:21:07,033 NARRATOR: They had found their quarry at last. 379 00:21:07,066 --> 00:21:11,466 {\an1}But the really hard work now lay ahead-- 380 00:21:11,500 --> 00:21:17,300 {\an1}figuring out how mammals and their world rose from the ashes. 381 00:21:17,333 --> 00:21:23,533 ♪ 382 00:21:23,566 --> 00:21:28,200 What creatures had they unearthed? 383 00:21:28,233 --> 00:21:30,133 {\an1}What was their strange world like? 384 00:21:30,166 --> 00:21:32,066 ♪ 385 00:21:32,100 --> 00:21:34,333 {\an1}And how did they establish a foothold 386 00:21:34,366 --> 00:21:35,733 {\an1}in a planetary wasteland? 387 00:21:35,766 --> 00:21:37,533 ♪ 388 00:21:37,566 --> 00:21:39,733 {\an1}To answer these questions, 389 00:21:39,766 --> 00:21:44,100 {\an1}Tyler and Ian needed to assemble a crack team of experts. 390 00:21:44,133 --> 00:21:48,533 ZANNO: The fossils are not just the biological remains of animals. 391 00:21:48,566 --> 00:21:50,700 {\an1}They are also buried in a geological system, 392 00:21:50,733 --> 00:21:55,733 {\an1}and so no one person can really understand all the data 393 00:21:55,766 --> 00:21:57,133 {\an1}that we can get from a fossil. 394 00:21:57,166 --> 00:21:58,166 We need experts 395 00:21:58,200 --> 00:21:59,666 {\an7}to really be able to piece together 396 00:21:59,700 --> 00:22:01,600 {\an7}what the entire ecosystem would have looked like. 397 00:22:03,000 --> 00:22:06,600 NARRATOR: Each fossil contains a wealth of information, 398 00:22:06,633 --> 00:22:10,366 {\an1}but it's hidden in the rock. 399 00:22:10,400 --> 00:22:14,233 {\an1}The first step is to free it. 400 00:22:16,866 --> 00:22:20,266 {\an1}So, they reach out to a virtuoso. 401 00:22:21,433 --> 00:22:23,900 ROBERT MASEK: I love working on fossils. 402 00:22:23,933 --> 00:22:26,300 {\an1}It's so rewarding when you start a fossil and, 403 00:22:26,333 --> 00:22:28,666 {\an1}that you really can't see. 404 00:22:28,700 --> 00:22:31,800 {\an7}It's, it's almost like a piece of art, sometimes, 405 00:22:31,833 --> 00:22:35,666 {\an7}and it also is contributing to scientific knowledge. 406 00:22:35,700 --> 00:22:39,666 (tool buzzing) 407 00:22:39,700 --> 00:22:43,200 NARRATOR: Bob Masek spent his early career working in factories, 408 00:22:43,233 --> 00:22:45,066 {\an1}but he found he had a knack 409 00:22:45,100 --> 00:22:48,433 {\an1}for releasing captives from rocks. 410 00:22:48,466 --> 00:22:52,133 MASEK: When I was little, I used to work on models. 411 00:22:52,166 --> 00:22:55,666 {\an1}So, I did learn to do detailed work. 412 00:22:55,700 --> 00:22:57,500 {\an1}It was sort of in me. 413 00:23:00,833 --> 00:23:02,800 {\an1}My contribution as a preparator 414 00:23:02,833 --> 00:23:09,433 {\an1}is to make the fossil readable so it can be used for science. 415 00:23:09,466 --> 00:23:11,300 GOSWAMI: And you can imagine, you have to be incredibly careful 416 00:23:11,333 --> 00:23:13,533 {\an1}that you don't break your fossils while you're doing that, 417 00:23:13,566 --> 00:23:15,833 {\an1}or even shape them with your own ideas 418 00:23:15,866 --> 00:23:17,033 {\an1}of what they should look like. 419 00:23:18,566 --> 00:23:22,933 NARRATOR: The painstaking process can take months for a single fossil. 420 00:23:22,966 --> 00:23:29,566 {\an1}But it reveals secrets held tight for millions of years. 421 00:23:29,600 --> 00:23:32,500 MASEK: As you're working, you do start to realize 422 00:23:32,533 --> 00:23:36,200 {\an1}that this was a living animal, a living thing. 423 00:23:36,233 --> 00:23:39,833 {\an1}I'm bringing it sort of back to life. 424 00:23:39,866 --> 00:23:44,033 ♪ 425 00:23:44,066 --> 00:23:47,833 NARRATOR: One by one, the fossils emerge. 426 00:23:47,866 --> 00:23:51,366 {\an1}Each is exquisitely preserved. 427 00:23:51,400 --> 00:23:54,666 {\an1}But what are they, and what do they reveal 428 00:23:54,700 --> 00:23:57,766 {\an1}about the mammals' rise? 429 00:23:57,800 --> 00:24:03,633 ♪ WEBVTT X-TIMESTAMP-MAP=MPEGTS:198018, LOCAL:00:00:00.000 430 00:24:04,966 --> 00:24:07,166 LYSON: Stephen Chester is a vertebrate paleontologist 431 00:24:07,200 --> 00:24:10,433 {\an1}who specializes in mammals. 432 00:24:10,466 --> 00:24:14,333 {\an1}So when I made this discovery, I needed to bring him on board 433 00:24:14,366 --> 00:24:18,400 {\an1}to help me identify all these mammals that I was finding. 434 00:24:20,466 --> 00:24:24,800 NARRATOR: Stephen examines each fossil to find details that reveal 435 00:24:24,833 --> 00:24:27,400 {\an1}what it's related to. 436 00:24:27,433 --> 00:24:32,100 {\an1}Not an easy job so far back on the mammalian family tree. 437 00:24:33,333 --> 00:24:36,533 CHESTER: We're talking about species that can be 438 00:24:36,566 --> 00:24:39,300 {\an7}very difficult to identify, 439 00:24:39,333 --> 00:24:42,233 {\an7}because they don't look exactly like what you might expect 440 00:24:42,266 --> 00:24:44,566 {\an1}for, for living mammals. 441 00:24:44,600 --> 00:24:46,900 ♪ 442 00:24:46,933 --> 00:24:51,533 NARRATOR: It's a common problem in tracing ancestry. 443 00:24:51,566 --> 00:24:56,700 {\an1}Consider how different an elephant is from a hyrax, 444 00:24:56,733 --> 00:24:59,700 or a manatee. 445 00:24:59,733 --> 00:25:01,633 GOSWAMI: You might not think that they are closely related. 446 00:25:01,666 --> 00:25:04,066 {\an1}They are incredibly different animals. 447 00:25:04,100 --> 00:25:05,933 {\an1}But their DNA shows us 448 00:25:05,966 --> 00:25:07,800 {\an1}that they are actually really closely related. 449 00:25:07,833 --> 00:25:09,900 ♪ 450 00:25:09,933 --> 00:25:11,666 {\an8}NARRATOR: Descendants of a common ancestor 451 00:25:11,700 --> 00:25:16,033 {\an7}don't always look like each other, or the ancestor, 452 00:25:16,066 --> 00:25:18,333 {\an7}because they've evolved in their own directions 453 00:25:18,366 --> 00:25:21,366 {\an7}for millions of years. 454 00:25:21,400 --> 00:25:25,966 {\an7}But they're bound to share some common traits. 455 00:25:26,000 --> 00:25:31,633 {\an1}That's why Stephen examines each skull feature by feature. 456 00:25:33,600 --> 00:25:35,633 {\an1}His first task is to figure out 457 00:25:35,666 --> 00:25:39,233 {\an1}what kind of mammal they've unearthed. 458 00:25:39,266 --> 00:25:43,833 (birds chirping) 459 00:25:43,866 --> 00:25:47,266 {\an1}All mammals share a few key features. 460 00:25:47,300 --> 00:25:48,800 {\an1}They're warm-blooded, 461 00:25:48,833 --> 00:25:52,566 grow hair, 462 00:25:52,600 --> 00:25:57,500 {\an1}and have bigger brains than other animals their size. 463 00:25:58,600 --> 00:26:01,566 {\an1}They also give their young a jump start in life 464 00:26:01,600 --> 00:26:05,500 by nursing them. 465 00:26:05,533 --> 00:26:09,866 {\an1}But how they have these babies sets them apart. 466 00:26:11,666 --> 00:26:15,433 {\an7}Some, like kangaroos and opossums, use a pouch 467 00:26:15,466 --> 00:26:18,233 {\an7}to bring their embryos to term. 468 00:26:19,833 --> 00:26:23,800 {\an1}A handful-- platypuses and echidnas-- lay eggs. 469 00:26:25,833 --> 00:26:28,533 (chitters) 470 00:26:28,566 --> 00:26:32,866 {\an1}But what about the biggest group of mammals alive today-- 471 00:26:32,900 --> 00:26:37,500 {\an1}those that carry their offspring in the mother's womb? 472 00:26:37,533 --> 00:26:40,400 Like us, 473 00:26:40,433 --> 00:26:44,066 {\an1}they're called placentals. 474 00:26:44,100 --> 00:26:47,466 {\an1}And they include the mammal Stephen examines 475 00:26:47,500 --> 00:26:49,500 {\an1}from Corral Bluffs. 476 00:26:52,200 --> 00:26:56,000 {\an1}It's one of the oldest placental fossils ever discovered. 477 00:26:57,566 --> 00:27:01,666 {\an1}A creature called loxolophus. 478 00:27:01,700 --> 00:27:07,166 {\an1}It's not yet clear if it has any living descendants. WEBVTT X-TIMESTAMP-MAP=MPEGTS:198018, LOCAL:00:00:00.000 479 00:27:01,700 --> 00:27:07,166 {\an1}It's not yet clear if it has any living descendants. 480 00:27:07,200 --> 00:27:13,000 {\an1}But the fossil hints at a highly adaptable creature. 481 00:27:13,033 --> 00:27:16,366 CHESTER: This mammal is probably about the size of a skunk. 482 00:27:16,400 --> 00:27:18,700 {\an1}It has teeth in the front of its mouth 483 00:27:18,733 --> 00:27:20,900 {\an1}that are probably good for tearing meat, 484 00:27:20,933 --> 00:27:23,633 {\an1}but the back of its mouth has other teeth 485 00:27:23,666 --> 00:27:26,033 {\an1}that would be better at processing plants. 486 00:27:26,066 --> 00:27:28,933 {\an1}It's probably eating a mixed diet. 487 00:27:31,133 --> 00:27:33,366 NARRATOR: This versatility would have been a great advantage 488 00:27:33,400 --> 00:27:35,200 {\an1}in a recovering world, 489 00:27:35,233 --> 00:27:39,400 {\an1}where the types of food were probably limited. 490 00:27:41,433 --> 00:27:43,633 {\an1}Team member Karen Cuevas 491 00:27:43,666 --> 00:27:45,633 {\an1}finds other insights about how it lived 492 00:27:45,666 --> 00:27:48,166 {\an1}by peering inside the fossil. 493 00:27:48,200 --> 00:27:50,133 CUEVAS: When I first heard 494 00:27:50,166 --> 00:27:53,666 {\an7}about how mammals became what they are today, 495 00:27:53,700 --> 00:27:55,300 {\an1}I was really excited to see 496 00:27:55,333 --> 00:27:58,500 {\an1}how much we could deduce from these fossils 497 00:27:58,533 --> 00:28:02,733 {\an1}and paint this picture from so many million years ago. 498 00:28:02,766 --> 00:28:06,100 {\an1}One of the things that we can do with the CT scan 499 00:28:06,133 --> 00:28:09,233 {\an1}is view the inner anatomy. 500 00:28:10,633 --> 00:28:12,633 ZANNO: CT reconstructions give us insight 501 00:28:12,666 --> 00:28:14,100 into tissues that aren't preserved, 502 00:28:14,133 --> 00:28:16,766 {\an1}and teach us a lot 503 00:28:16,800 --> 00:28:18,466 {\an1}about what those animals were really like 504 00:28:18,500 --> 00:28:20,066 {\an1}as living, breathing creatures. 505 00:28:22,333 --> 00:28:26,866 NARRATOR: The data help the team imagine what the living animal was like. 506 00:28:26,900 --> 00:28:32,433 CHESTER: Based on CT scans, this animal had a hole underneath its eye. 507 00:28:33,700 --> 00:28:38,100 NARRATOR: A passage for nerves from sensitive whiskers. 508 00:28:38,133 --> 00:28:40,866 CHESTER: It also has a large portion of its brain 509 00:28:40,900 --> 00:28:43,633 {\an1}dedicated to the sense of smell. 510 00:28:43,666 --> 00:28:46,133 ♪ 511 00:28:46,166 --> 00:28:48,800 {\an8}NARRATOR: These senses would have been key to its lifestyle 512 00:28:48,833 --> 00:28:52,300 {\an7}in this new world. 513 00:28:52,333 --> 00:28:57,733 {\an7}Details from related species suggest how it walked. 514 00:28:57,766 --> 00:29:00,700 {\an8}CHESTER: We would assume that this animal was moving around on the ground 515 00:29:00,733 --> 00:29:04,000 {\an7}on all fours, probably something like a raccoon. 516 00:29:04,033 --> 00:29:07,033 (chittering) 517 00:29:08,533 --> 00:29:10,100 NARRATOR: It's a lot to have learned 518 00:29:10,133 --> 00:29:13,200 {\an1}about one of the creatures that roamed the new world. 519 00:29:17,166 --> 00:29:20,666 {\an1}But Corral Bluffs is about to reveal something even bigger. 520 00:29:23,066 --> 00:29:25,533 LYSON: The discovery here extends 521 00:29:25,566 --> 00:29:28,600 well beyond any one particular fossil. 522 00:29:28,633 --> 00:29:32,733 {\an1}Here, we're dealing with the recovery of an entire ecosystem. 523 00:29:32,766 --> 00:29:35,133 ♪ 524 00:29:35,166 --> 00:29:39,700 NARRATOR: If the team can determine the age of each fossil, 525 00:29:39,733 --> 00:29:44,900 {\an1}they can start to see how the mammals evolved over time, 526 00:29:44,933 --> 00:29:49,733 {\an1}and how their world changed alongside them. 527 00:29:49,766 --> 00:29:51,233 GOSWAMI: When we find some interesting fossils, 528 00:29:51,266 --> 00:29:53,300 {\an1}then the next thing that we do is spend a huge amount of effort 529 00:29:53,333 --> 00:29:56,633 {\an1}trying to figure out exactly how old they are. 530 00:29:56,666 --> 00:30:01,900 {\an1}But getting accurate dates on fossil sites is incredibly hard. 531 00:30:01,933 --> 00:30:04,866 NARRATOR: To estimate the age of their fossils, WEBVTT X-TIMESTAMP-MAP=MPEGTS:198018, LOCAL:00:00:00.000 532 00:30:01,933 --> 00:30:04,866 NARRATOR: To estimate the age of their fossils, 533 00:30:04,900 --> 00:30:07,966 {\an1}Tyler and Ian reach out to specialists. 534 00:30:08,000 --> 00:30:10,233 {\an1}(people talking in background) 535 00:30:10,266 --> 00:30:14,933 {\an1}Geologists Will Clyde and Anthony Fuentes. 536 00:30:14,966 --> 00:30:19,500 {\an1}Their goal: determine the age of each layer in the rock 537 00:30:19,533 --> 00:30:23,633 {\an1}by building a timeline up the cliff. 538 00:30:23,666 --> 00:30:28,933 {\an1}To do it, they'll rely on clues forged by planetary forces. 539 00:30:28,966 --> 00:30:32,466 ♪ 540 00:30:32,500 --> 00:30:35,800 {\an1}Earth is surrounded by a magnetic field, 541 00:30:35,833 --> 00:30:41,500 {\an1}which creates north and south magnetic poles. 542 00:30:41,533 --> 00:30:45,300 {\an1}These may seem permanent, but they're not. 543 00:30:45,333 --> 00:30:49,966 {\an1}From time to time, the field reverses. 544 00:30:50,000 --> 00:30:51,400 {\an7}And so what is today 545 00:30:51,433 --> 00:30:52,833 {\an7}the magnetic north for the Earth 546 00:30:52,866 --> 00:30:54,766 {\an7}sometimes flips and becomes the magnetic south. 547 00:30:54,800 --> 00:30:56,900 ♪ 548 00:30:56,933 --> 00:31:00,400 NARRATOR: Some rocks can record the direction of the magnetic field 549 00:31:00,433 --> 00:31:05,166 {\an1}at the time they form. 550 00:31:05,200 --> 00:31:07,733 {\an1}As these build up on top of each other, 551 00:31:07,766 --> 00:31:12,566 {\an1}they can capture a record of magnetic reversals over time. 552 00:31:12,600 --> 00:31:16,066 {\an1}The date of each flip has been firmly established 553 00:31:16,100 --> 00:31:18,100 {\an1}in rocks across the world. 554 00:31:18,133 --> 00:31:19,833 CLYDE: Four, five... 555 00:31:19,866 --> 00:31:21,466 Four, five. 556 00:31:21,500 --> 00:31:22,900 CLYDE: So if we can find 557 00:31:22,933 --> 00:31:26,333 {\an7}certain flip-flop in the polarity in the rocks here, 558 00:31:26,366 --> 00:31:30,300 {\an1}then we know the date of that change. 559 00:31:30,333 --> 00:31:32,700 Six-four. 560 00:31:32,733 --> 00:31:34,833 To the east. 561 00:31:34,866 --> 00:31:37,133 NARRATOR: To look for these flips, 562 00:31:37,166 --> 00:31:39,700 {\an1}they collect rocks along the bottom of the bluffs, 563 00:31:39,733 --> 00:31:42,300 {\an1}where the impact boundary is, 564 00:31:42,333 --> 00:31:45,100 {\an1}and work their way up. 565 00:31:47,100 --> 00:31:49,533 {\an1}They then bring each sample back to their lab 566 00:31:49,566 --> 00:31:52,400 to measure its magnetic orientation. 567 00:31:54,866 --> 00:31:56,600 NARRATOR: Near the bottom of the bluffs, 568 00:31:56,633 --> 00:32:01,900 they find a flip from 350,000 years after impact, 569 00:32:01,933 --> 00:32:04,233 {\an1}and trace it across the land. 570 00:32:06,500 --> 00:32:09,933 {\an1}But a single date isn't enough. 571 00:32:09,966 --> 00:32:13,200 MILLER: If you get one date in a pile of rocks, 572 00:32:13,233 --> 00:32:14,933 {\an1}you know where that one date is. 573 00:32:14,966 --> 00:32:18,400 {\an1}But above it, you don't know how fast the rocks are accumulating. 574 00:32:18,433 --> 00:32:20,233 {\an7}There could be a ton of rock in a short period of time, 575 00:32:20,266 --> 00:32:23,200 {\an7}or it could be a small amount of rock in a long period of time. 576 00:32:23,233 --> 00:32:25,633 ♪ 577 00:32:25,666 --> 00:32:28,433 NARRATOR: Most of the bluffs, and the team's discoveries, 578 00:32:28,466 --> 00:32:31,600 {\an1}lie above the flip they've found. 579 00:32:31,633 --> 00:32:36,300 {\an1}They need a second one higher up to bracket the dates 580 00:32:36,333 --> 00:32:38,566 {\an1}of their fossils. 581 00:32:40,433 --> 00:32:44,700 {\an1}They work their way up, one layer after another. 582 00:32:45,866 --> 00:32:47,200 MILLER: As we went up the hill, 583 00:32:47,233 --> 00:32:48,666 {\an1}you know, you're sampling, you're sampling, 584 00:32:48,700 --> 00:32:49,833 {\an1}but there's no flip, there's nothing, 585 00:32:49,866 --> 00:32:52,233 {\an1}and we're just running out of rock. 586 00:32:52,266 --> 00:32:56,233 NARRATOR: They test samples right up to the top. 587 00:32:56,266 --> 00:32:58,400 Still... 588 00:32:58,433 --> 00:33:00,433 No flip. 589 00:33:00,466 --> 00:33:04,700 No way to place their discoveries in time. 590 00:33:04,733 --> 00:33:07,000 ♪ WEBVTT X-TIMESTAMP-MAP=MPEGTS:198018, LOCAL:00:00:00.000 591 00:33:04,733 --> 00:33:07,000 ♪ 592 00:33:07,033 --> 00:33:09,833 Then, they find a small outcrop 593 00:33:09,866 --> 00:33:13,100 perched above the rest of the bluffs. 594 00:33:13,133 --> 00:33:17,600 {\an1}It's one last chance to catch the flip. 595 00:33:17,633 --> 00:33:22,533 ♪ 596 00:33:22,566 --> 00:33:24,700 And it delivers. 597 00:33:24,733 --> 00:33:27,400 {\an8}♪ 598 00:33:27,433 --> 00:33:31,433 {\an8}They've found the second date they need. 599 00:33:31,466 --> 00:33:33,233 {\an8}MILLER: That allowed us to place all these fossils 600 00:33:33,266 --> 00:33:35,233 {\an7}in this incredible time frame. 601 00:33:36,333 --> 00:33:37,533 {\an7}We had the whole thing, 602 00:33:37,566 --> 00:33:39,900 {\an7}and that was a shock. 603 00:33:39,933 --> 00:33:41,633 {\an1}We didn't expect that. 604 00:33:41,666 --> 00:33:43,366 {\an1}We thought we might be missing a part of the record, 605 00:33:43,400 --> 00:33:44,700 {\an1}but it's all there. 606 00:33:44,733 --> 00:33:47,100 ♪ 607 00:33:47,133 --> 00:33:49,066 NARRATOR: The towering face of the bluffs 608 00:33:49,100 --> 00:33:53,100 {\an1}chronicles the first one million years of the recovery. 609 00:33:53,133 --> 00:33:54,566 SHUBIN: If you were to choose 610 00:33:54,600 --> 00:33:57,633 {\an7}any one-million-year sliver of time 611 00:33:57,666 --> 00:34:00,833 {\an7}in the four-and-a-half- billion-year history of Earth, 612 00:34:00,866 --> 00:34:03,000 {\an1}it's an enormously lucky event to have one that happens 613 00:34:03,033 --> 00:34:04,766 {\an1}right after a giant asteroid impact. 614 00:34:04,800 --> 00:34:07,200 {\an1}It's like winning the lottery. 615 00:34:07,233 --> 00:34:08,733 ♪ 616 00:34:08,766 --> 00:34:12,033 NARRATOR: Now all the extraordinary fossils of Corral Bluffs 617 00:34:12,066 --> 00:34:17,233 {\an1}can be placed in time. 618 00:34:17,266 --> 00:34:20,833 {\an1}But what story do they tell? 619 00:34:20,866 --> 00:34:24,133 Another fossil reveals a turning point. 620 00:34:24,166 --> 00:34:27,766 ♪ 621 00:34:27,800 --> 00:34:30,200 LYSON: In the middle part of the bluffs, 622 00:34:30,233 --> 00:34:33,466 {\an1}I found a much larger skull. 623 00:34:33,500 --> 00:34:37,600 NARRATOR: This creature lived 300,000 years into the recovery. 624 00:34:39,366 --> 00:34:40,866 LYSON: What's interesting about it 625 00:34:40,900 --> 00:34:46,000 is that it has these really large teeth. 626 00:34:46,033 --> 00:34:51,766 NARRATOR: Mammals today use teeth like these to grind leaves and stems. 627 00:34:51,800 --> 00:34:57,366 {\an1}It suggests this creature dined mostly on plants. 628 00:34:57,400 --> 00:35:00,133 LYSON: And this is really the first major specialization that we see 629 00:35:00,166 --> 00:35:02,833 {\an7}in the mammal fossil record 630 00:35:02,866 --> 00:35:04,966 {\an7}right after the extinction of the dinosaurs. 631 00:35:06,733 --> 00:35:09,966 NARRATOR: Just after the impact, the mammals that survived 632 00:35:10,000 --> 00:35:13,600 {\an1}had been opportunistic scavengers. 633 00:35:13,633 --> 00:35:18,066 {\an1}But now, mammals were specializing in eating plants 634 00:35:18,100 --> 00:35:21,600 {\an1}and seizing a niche long held by dinosaurs. 635 00:35:21,633 --> 00:35:24,900 ♪ 636 00:35:24,933 --> 00:35:28,066 {\an1}It's a major milestone. 637 00:35:28,100 --> 00:35:30,433 {\an1}But how did it happen? 638 00:35:33,133 --> 00:35:38,533 {\an1}The answer could lie in the story of the plants themselves. 639 00:35:38,566 --> 00:35:44,266 {\an1}And Colorado's rocks are packed with clues. 640 00:35:49,566 --> 00:35:51,300 MILLER: A lot of leaves. 641 00:35:51,333 --> 00:35:54,100 {\an1}But just two species right here. 642 00:35:54,133 --> 00:35:57,100 NARRATOR: Some leaves are so beautifully preserved, 643 00:35:57,133 --> 00:35:59,833 {\an1}they look as if they had just fallen. 644 00:35:59,866 --> 00:36:01,666 ♪ 645 00:36:01,700 --> 00:36:06,533 {\an1}But other telling fossils are invisible to the naked eye. WEBVTT X-TIMESTAMP-MAP=MPEGTS:198018, LOCAL:00:00:00.000 646 00:36:01,700 --> 00:36:06,533 {\an1}But other telling fossils are invisible to the naked eye. 647 00:36:06,566 --> 00:36:09,933 Like pollen. 648 00:36:09,966 --> 00:36:12,500 {\an1}A thimble-sized chunk of rock, 649 00:36:12,533 --> 00:36:16,033 {\an1}it might have 100,000 pollen grains in it. 650 00:36:16,066 --> 00:36:19,366 {\an1}Each of the different kinds of trees, the little shrubs, 651 00:36:19,400 --> 00:36:24,033 {\an1}produce different kinds of pollen based on who they are. 652 00:36:24,066 --> 00:36:28,166 NARRATOR: Ian and scientists around the world have documented 653 00:36:28,200 --> 00:36:30,300 {\an1}the microscopic record from this time. 654 00:36:30,333 --> 00:36:32,233 ♪ 655 00:36:32,266 --> 00:36:33,366 MILLER: Take a chunk of rock, 656 00:36:33,400 --> 00:36:34,666 you dissolve it, 657 00:36:34,700 --> 00:36:36,166 {\an1}you take all the pollen spores out of it, 658 00:36:36,200 --> 00:36:39,466 {\an1}put it on a slide, and you see many different types of plants. 659 00:36:39,500 --> 00:36:41,366 {\an1}And then you can sort of paint this image 660 00:36:41,400 --> 00:36:44,833 {\an1}of what these worlds were like. 661 00:36:44,866 --> 00:36:46,333 ♪ 662 00:36:46,366 --> 00:36:48,700 {\an1}And so right at that mark where we see the evidence 663 00:36:48,733 --> 00:36:49,833 {\an1}of this extraterrestrial impact, 664 00:36:49,866 --> 00:36:53,233 {\an1}the pollen just dives right off. 665 00:36:53,266 --> 00:36:55,533 {\an1}Everything seems to die. 666 00:36:55,566 --> 00:36:57,366 NARRATOR: After the impact, 667 00:36:57,400 --> 00:37:00,166 {\an1}one primitive form of life resurges, 668 00:37:00,200 --> 00:37:04,433 and it's a sign of a devastated world. 669 00:37:04,466 --> 00:37:05,900 MILLER: Right after the boundary, 670 00:37:05,933 --> 00:37:11,266 {\an1}there's an explosion of fungal spores. 671 00:37:11,300 --> 00:37:14,766 {\an1}The thing is that fungus grows on things that are dead. 672 00:37:14,800 --> 00:37:17,800 {\an1}So most of the world must have been rotting. 673 00:37:19,733 --> 00:37:23,966 NARRATOR: Forests destroyed by heat and darkness 674 00:37:24,000 --> 00:37:28,900 decompose beneath this fungal carpet. 675 00:37:28,933 --> 00:37:32,133 {\an1}But then some plants rebound. 676 00:37:32,166 --> 00:37:36,066 ♪ 677 00:37:36,100 --> 00:37:38,766 MILLER: Following immediately on top of the fungal world, 678 00:37:38,800 --> 00:37:40,600 {\an1}we see a spike in fern spores. 679 00:37:40,633 --> 00:37:43,600 ♪ 680 00:37:43,633 --> 00:37:48,433 {\an1}Ferns are this group of plants that come back after disasters 681 00:37:48,466 --> 00:37:52,933 {\an1}before the rest of the forest is able to re-establish itself. 682 00:37:52,966 --> 00:37:56,366 {\an1}First thing that comes back are a blanket of ferns. 683 00:37:56,400 --> 00:38:00,200 {\an1}And that probably lasts for a few thousand years. 684 00:38:00,233 --> 00:38:02,500 ♪ 685 00:38:02,533 --> 00:38:05,066 NARRATOR: The world is green again, 686 00:38:05,100 --> 00:38:09,266 {\an1}but ferns are a limited source of food. 687 00:38:12,866 --> 00:38:17,166 {\an1}New options arise as the landscape evolves, 688 00:38:17,200 --> 00:38:20,233 {\an1}and long-dormant seeds spring to life... 689 00:38:23,333 --> 00:38:26,733 A new forest. 690 00:38:26,766 --> 00:38:29,000 MILLER: One of the big surprises was this incredible abundance 691 00:38:29,033 --> 00:38:32,866 of palm pollen. 692 00:38:32,900 --> 00:38:38,800 {\an1}And we get tons of palm fronds-- huge, beautiful palm fronds. 693 00:38:38,833 --> 00:38:43,833 {\an1}They're so dominant, it feels like the world is all palms. 694 00:38:43,866 --> 00:38:49,700 {\an1}And it probably lasts about 100,000 years. 695 00:38:49,733 --> 00:38:52,233 {\an1}What I'm thinking right now is that if you were a mammal, 696 00:38:52,266 --> 00:38:56,233 {\an1}there would have been a big canopy of palms above your head. 697 00:38:56,266 --> 00:38:59,700 {\an1}But there still wasn't that great source of food. 698 00:38:59,733 --> 00:39:02,433 {\an1}(insects chirping) 699 00:39:02,466 --> 00:39:08,966 NARRATOR: The habitat looks lush, but still lacks diversity. WEBVTT X-TIMESTAMP-MAP=MPEGTS:198018, LOCAL:00:00:00.000 700 00:39:02,466 --> 00:39:08,966 NARRATOR: The habitat looks lush, but still lacks diversity. 701 00:39:09,000 --> 00:39:12,666 {\an1}That, in turn, limits the variety of animals, 702 00:39:12,700 --> 00:39:16,133 as a close look at the team's fossils reveals. 703 00:39:20,233 --> 00:39:22,033 {\an7}When there's an extinction, 704 00:39:22,066 --> 00:39:24,866 {\an7}it kind of ripples from the bottom of the ecosystem, 705 00:39:24,900 --> 00:39:29,966 {\an1}starting from the plants, up into all of the other levels. 706 00:39:30,000 --> 00:39:33,766 NARRATOR: Gussie Maccracken deciphers what happened 707 00:39:33,800 --> 00:39:35,933 {\an1}to some of the smallest creatures: 708 00:39:35,966 --> 00:39:39,233 insects. 709 00:39:39,266 --> 00:39:43,166 {\an1}Insects don't fossilize well, 710 00:39:43,200 --> 00:39:46,066 {\an1}but what they do to plants can. 711 00:39:46,100 --> 00:39:48,166 MACCRACKEN: Insect damage on a leaf can tell us 712 00:39:48,200 --> 00:39:51,466 {\an1}about the ecology of the ecosystem in the past 713 00:39:51,500 --> 00:39:56,700 {\an1}in a way that no other types of fossils can. 714 00:39:56,733 --> 00:39:59,333 NARRATOR: Some insects are generalists, 715 00:39:59,366 --> 00:40:03,033 {\an1}and feed on many types of leaves. 716 00:40:03,066 --> 00:40:06,766 {\an1}They carve signature marks that can be preserved in fossils. 717 00:40:06,800 --> 00:40:08,700 ♪ 718 00:40:08,733 --> 00:40:10,466 Simple holes, 719 00:40:10,500 --> 00:40:14,100 or chunks bitten from the leaf's edge. 720 00:40:14,133 --> 00:40:16,533 ♪ 721 00:40:16,566 --> 00:40:19,700 {\an1}But other kinds of damage are caused by insects 722 00:40:19,733 --> 00:40:22,933 that specialize in certain plants. 723 00:40:22,966 --> 00:40:27,000 {\an8}MACCRACKEN: They leave these wild patterns 724 00:40:27,033 --> 00:40:30,633 {\an7}and we can tell things like if it's a moth, 725 00:40:30,666 --> 00:40:34,066 {\an7}or if it's a fly, 726 00:40:34,100 --> 00:40:36,866 {\an7}or sometimes a beetle. 727 00:40:36,900 --> 00:40:38,866 NARRATOR: Before the asteroid struck, 728 00:40:38,900 --> 00:40:42,733 {\an1}the insect world was filled with specialists. 729 00:40:42,766 --> 00:40:47,333 {\an1}But that changes abruptly. 730 00:40:47,366 --> 00:40:52,566 MACCRACKEN: During recovery, a lot of the specialist insect damage types, 731 00:40:52,600 --> 00:40:56,933 {\an1}like from leaf miners and galling insects, 732 00:40:56,966 --> 00:40:58,300 just disappear. 733 00:40:58,333 --> 00:41:00,033 ♪ 734 00:41:00,066 --> 00:41:03,833 NARRATOR: The specialists were doomed. 735 00:41:03,866 --> 00:41:08,566 {\an1}In a world with only a few kinds of plants, 736 00:41:08,600 --> 00:41:12,033 {\an1}insects that can live on anything have an advantage 737 00:41:12,066 --> 00:41:14,566 {\an1}over pickier eaters. 738 00:41:14,600 --> 00:41:20,466 {\an1}It echoes what happened to the mammals. 739 00:41:20,500 --> 00:41:23,466 {\an1}Only the generalists survive. 740 00:41:23,500 --> 00:41:25,866 ZANNO: At the time of an extinction event, 741 00:41:25,900 --> 00:41:28,933 {\an7}any species that's highly dependent on a single lifestyle 742 00:41:28,966 --> 00:41:32,066 {\an7}or a single location or a single food source 743 00:41:32,100 --> 00:41:35,900 {\an1}is likely going to go extinct when those ecosystems collapse. 744 00:41:35,933 --> 00:41:38,766 ♪ 745 00:41:38,800 --> 00:41:41,166 NARRATOR: But in time, new plants arise 746 00:41:41,200 --> 00:41:44,500 {\an1}and chances to specialize return. 747 00:41:44,533 --> 00:41:48,433 MILLER: The forests become more and more diverse. 748 00:41:48,466 --> 00:41:52,433 {\an7}We get different kinds of trees growing on the landscape. 749 00:41:52,466 --> 00:41:56,666 {\an8}♪ 750 00:41:58,966 --> 00:42:02,133 {\an8}NARRATOR: 300,000 years after its collapse, 751 00:42:02,166 --> 00:42:04,366 {\an7}the forest has recovered. 752 00:42:04,400 --> 00:42:08,200 {\an8}♪ WEBVTT X-TIMESTAMP-MAP=MPEGTS:198018, LOCAL:00:00:00.000 753 00:42:04,400 --> 00:42:08,200 {\an8}♪ 754 00:42:08,233 --> 00:42:10,633 {\an8}MILLER: And it's right there when the animals can specialize 755 00:42:10,666 --> 00:42:13,400 {\an7}in eating certain kinds of plants. 756 00:42:13,433 --> 00:42:16,233 {\an8}NARRATOR: And get bigger. 757 00:42:16,266 --> 00:42:19,700 {\an7}These new plant-eaters were now larger 758 00:42:19,733 --> 00:42:21,066 {\an7}than mammals had ever been 759 00:42:21,100 --> 00:42:25,333 {\an1}in over 100 million years on the planet. 760 00:42:25,366 --> 00:42:27,733 ♪ 761 00:42:27,766 --> 00:42:32,800 {\an1}They've shattered their record in just a fraction of that time. 762 00:42:32,833 --> 00:42:36,033 {\an1}And their growth spurt was just beginning. 763 00:42:41,966 --> 00:42:44,100 LYSON: In the very upper part of the bluffs, 764 00:42:44,133 --> 00:42:51,000 {\an1}I started to find a whole array of large and diverse mammals. 765 00:42:56,633 --> 00:43:00,400 {\an1}One of the mammals that we found is called taeniolabis. 766 00:43:00,433 --> 00:43:05,100 {\an1}This is about 80 pounds, so really a large animal. 767 00:43:06,900 --> 00:43:09,166 NARRATOR: It was ten times the size 768 00:43:09,200 --> 00:43:13,433 of the omnivore they'd found earlier. 769 00:43:13,466 --> 00:43:16,833 LYSON: It had these really big incisors, 770 00:43:16,866 --> 00:43:19,066 {\an1}much like modern-day beavers have. 771 00:43:21,933 --> 00:43:25,500 {\an1}We think this animal was living in or near the rivers, 772 00:43:25,533 --> 00:43:30,266 {\an1}because we only find this animal in riverine sediments. 773 00:43:30,300 --> 00:43:33,633 ♪ 774 00:43:36,100 --> 00:43:37,700 NARRATOR: Near this fossil, 775 00:43:37,733 --> 00:43:42,300 {\an1}Tyler finds the skull of an even bigger mammal. 776 00:43:42,333 --> 00:43:47,433 LYSON: This is a large animal that was about 100 pounds, 777 00:43:47,466 --> 00:43:50,533 {\an1}so almost the size of a wolf. 778 00:43:50,566 --> 00:43:54,966 {\an1}And this animal had really big, flat back teeth, 779 00:43:55,000 --> 00:43:59,500 {\an1}and it seems to be eating seeds and other plants. 780 00:43:59,533 --> 00:44:02,933 NARRATOR: In less than a million years since the extinction, 781 00:44:02,966 --> 00:44:07,866 {\an1}mammals have exploded from just a couple of pounds. 782 00:44:07,900 --> 00:44:10,266 {\an1}Some are 50 times bigger. 783 00:44:13,466 --> 00:44:20,066 {\an1}It would take nearly 20 million years to make such a leap again. 784 00:44:20,100 --> 00:44:23,800 {\an1}But what might have fueled this dramatic change? 785 00:44:27,466 --> 00:44:30,000 {\an1}An intriguing clue lay just a few feet 786 00:44:30,033 --> 00:44:32,300 {\an1}from the beasts' remains. 787 00:44:32,333 --> 00:44:36,466 {\an1}(kids talking in distance) 788 00:44:36,500 --> 00:44:38,633 {\an1}Ian was leading a group of teens 789 00:44:38,666 --> 00:44:41,433 {\an1}studying at the museum for the summer. 790 00:44:41,466 --> 00:44:44,433 {\an1}Probably about... I'd say about the same... 791 00:44:47,933 --> 00:44:49,333 MILLER: We were doing all kinds of different things, 792 00:44:49,366 --> 00:44:52,433 {\an1}and it wasn't a terribly exciting site. 793 00:44:52,466 --> 00:44:55,600 {\an1}A lot of fossils people hand you are just sticks. 794 00:44:55,633 --> 00:44:56,766 {\an1}So, a lot of people are just, like, 795 00:44:56,800 --> 00:44:57,866 {\an8}"Oh, this is an incredible fossil!" 796 00:44:57,900 --> 00:44:58,900 {\an8}I'm, like, "Yeah, it's just a stick," 797 00:44:58,933 --> 00:45:00,000 {\an7}you know, "throw that back." 798 00:45:00,033 --> 00:45:04,700 {\an1}But this one student, her name is Aeon. 799 00:45:04,733 --> 00:45:06,800 {\an1}We're thinking about moving on, and going somewhere else, WEBVTT X-TIMESTAMP-MAP=MPEGTS:198018, LOCAL:00:00:00.000 800 00:45:04,733 --> 00:45:06,800 {\an1}We're thinking about moving on, and going somewhere else, 801 00:45:06,833 --> 00:45:11,000 {\an1}and she hands me this rock and she's, like, "What's this?" 802 00:45:11,033 --> 00:45:14,800 Did you get something? I don't know. 803 00:45:14,833 --> 00:45:15,866 {\an1}And so I took it up, looked at it in the light, 804 00:45:15,900 --> 00:45:17,166 {\an1}and lo and behold, 805 00:45:17,200 --> 00:45:19,933 {\an1}it was the middle part of a bean pod. 806 00:45:19,966 --> 00:45:22,800 {\an7}Um, I found this legume two seconds ago 807 00:45:22,833 --> 00:45:24,733 {\an7}from this rock that's sitting in my lap. 808 00:45:24,766 --> 00:45:28,800 MILLER: Right here, 700,000 years into the recovery. 809 00:45:28,833 --> 00:45:31,566 {\an1}This is the earliest record of the legume family ever 810 00:45:31,600 --> 00:45:33,066 in the fossil record. 811 00:45:33,100 --> 00:45:36,600 {\an1}So that's pretty cool. 812 00:45:40,866 --> 00:45:43,333 {\an8}NARRATOR: Aeon's legume was alive right at the time 813 00:45:43,366 --> 00:45:48,066 {\an7}when mammals' size was exploding. 814 00:45:48,100 --> 00:45:51,000 {\an1}A new food for a new world. 815 00:45:51,033 --> 00:45:54,433 ♪ 816 00:45:54,466 --> 00:45:59,000 {\an1}Legumes are very special plants. 817 00:45:59,033 --> 00:46:02,400 {\an1}Today, there are almost 20,000 species of them, 818 00:46:02,433 --> 00:46:07,266 {\an1}including peanuts, lentils, and soybeans. 819 00:46:07,300 --> 00:46:11,366 {\an1}Their signature pods are packed with nutrients. 820 00:46:11,400 --> 00:46:14,900 ♪ 821 00:46:14,933 --> 00:46:16,200 MILLER: Legumes are like 822 00:46:16,233 --> 00:46:19,066 {\an1}these protein bars for the mammals on the landscape, 823 00:46:19,100 --> 00:46:24,500 {\an1}and at that same moment, we see all these new and large mammals, 824 00:46:24,533 --> 00:46:25,966 and we think that they're taking advantage 825 00:46:26,000 --> 00:46:27,766 {\an1}of this new food source. 826 00:46:31,200 --> 00:46:34,966 NARRATOR: Taken together, the many fossils of Corral Bluffs 827 00:46:35,000 --> 00:46:40,366 {\an1}suggest plants were helping to drive mammal evolution. 828 00:46:40,400 --> 00:46:44,966 {\an1}And a final piece of evidence reveals how plants, in turn, 829 00:46:45,000 --> 00:46:47,600 {\an1}were being driven by something else. 830 00:46:47,633 --> 00:46:49,266 ♪ 831 00:46:49,300 --> 00:46:53,600 {\an1}Ian uncovers clues to one of the planet's most powerful forces-- 832 00:46:53,633 --> 00:46:56,333 climate. 833 00:46:56,366 --> 00:47:01,133 {\an1}He zeroes in on the shape of the leaves he's unearthed. 834 00:47:01,166 --> 00:47:03,200 MILLER: The more species you have with serrations, 835 00:47:03,233 --> 00:47:04,800 {\an1}the cooler it is; 836 00:47:04,833 --> 00:47:08,533 {\an1}the more smooth leaves you have, the warmer it is. 837 00:47:08,566 --> 00:47:11,066 {\an1}And so we can use that to tell temperature in the past. 838 00:47:11,100 --> 00:47:13,133 ♪ 839 00:47:13,166 --> 00:47:16,300 NARRATOR: The size of the leaves can reveal rainfall. 840 00:47:16,333 --> 00:47:18,866 (thunder booms) 841 00:47:18,900 --> 00:47:21,066 MILLER: If you've got a really big leaf, 842 00:47:21,100 --> 00:47:23,733 {\an1}it means that you're growing in a world that rained a lot, 843 00:47:23,766 --> 00:47:25,700 {\an1}and so the forest was really dense. 844 00:47:27,533 --> 00:47:30,566 NARRATOR: Most of the fossil leaves from Corral Bluffs 845 00:47:30,600 --> 00:47:32,933 {\an1}are smooth and large. 846 00:47:35,633 --> 00:47:39,733 {\an1}Together, they paint a picture of a very different Colorado 847 00:47:39,766 --> 00:47:42,233 {\an1}65 million years ago. 848 00:47:42,266 --> 00:47:46,600 ♪ 849 00:47:48,733 --> 00:47:52,833 MILLER: We're probably looking at a world that's more like Florida. 850 00:47:52,866 --> 00:47:55,833 {\an1}It's pretty wet, pretty humid, and pretty darn warm. 851 00:47:58,433 --> 00:48:02,400 NARRATOR: This climate shaped the plants and the creatures 852 00:48:02,433 --> 00:48:03,733 {\an1}that evolved here. 853 00:48:03,766 --> 00:48:07,833 ♪ WEBVTT X-TIMESTAMP-MAP=MPEGTS:198018, LOCAL:00:00:00.000 854 00:48:03,766 --> 00:48:07,833 ♪ 855 00:48:07,866 --> 00:48:11,900 GOSWAMI: No organism evolves or lives in isolation, right? 856 00:48:11,933 --> 00:48:15,000 {\an7}Everything about them really reflects their interactions 857 00:48:15,033 --> 00:48:16,633 {\an7}with their environment, with other species. 858 00:48:16,666 --> 00:48:20,966 {\an1}We really need to understand those relationships. 859 00:48:21,000 --> 00:48:24,766 {\an1}We want to build up a picture of how life evolved in this period. 860 00:48:24,800 --> 00:48:27,466 ♪ 861 00:48:27,500 --> 00:48:33,166 NARRATOR: In the first two years after Tyler and Ian made their find, 862 00:48:33,200 --> 00:48:37,133 {\an1}their team collected over 1,000 vertebrate fossils. 863 00:48:37,166 --> 00:48:39,733 ♪ 864 00:48:39,766 --> 00:48:42,033 {\an1}Some 6,000 plants. 865 00:48:42,066 --> 00:48:43,733 ♪ 866 00:48:43,766 --> 00:48:46,066 {\an1}And the end is nowhere in sight. 867 00:48:46,100 --> 00:48:50,900 ♪ 868 00:48:50,933 --> 00:48:54,833 LYSON: The discovery at Corral Bluffs is remarkable for many reasons. 869 00:48:54,866 --> 00:48:56,933 {\an1}We have the whole ecosystem, 870 00:48:56,966 --> 00:48:58,933 and we have it at different intervals of time. 871 00:48:58,966 --> 00:49:02,100 {\an1}I mean, we're dealing with the entire story here. 872 00:49:03,633 --> 00:49:06,933 NARRATOR: So far, that story includes 873 00:49:06,966 --> 00:49:11,033 {\an1}16 different mammal species they've found. 874 00:49:11,066 --> 00:49:15,433 {\an1}It's an extraordinary record that unites plants, animals, 875 00:49:15,466 --> 00:49:17,533 {\an1}climate, and time 876 00:49:17,566 --> 00:49:19,766 {\an1}in a single picture. 877 00:49:19,800 --> 00:49:22,800 ♪ 878 00:49:22,833 --> 00:49:27,066 SHUBIN: So, what Tyler and Ian have discovered is a Rosetta Stone. 879 00:49:27,100 --> 00:49:29,866 {\an1}And Corral Bluffs is telling us something very important. 880 00:49:29,900 --> 00:49:33,300 {\an7}It's telling us about ourselves, how we got to be here. 881 00:49:36,566 --> 00:49:38,266 {\an1}(rock cracks loudly) 882 00:49:38,300 --> 00:49:40,900 ♪ 883 00:49:40,933 --> 00:49:44,266 NARRATOR: The team's discoveries, along with other evidence, 884 00:49:44,300 --> 00:49:48,766 {\an1}trace the beginning of the mammals' fateful rise. 885 00:49:48,800 --> 00:49:49,933 ♪ 886 00:49:49,966 --> 00:49:52,100 {\an1}(explosion booms) 887 00:49:52,133 --> 00:49:55,833 {\an1}Few survived the impact winter. 888 00:49:55,866 --> 00:50:01,433 {\an1}But as the climate warmed, plants regained lost ground. 889 00:50:01,466 --> 00:50:06,233 {\an1}Small creatures endured, eating whatever they could find. 890 00:50:06,266 --> 00:50:08,866 {\an1}Forests recovered, 891 00:50:08,900 --> 00:50:13,666 {\an1}and fueled mammals as they exploded in size 892 00:50:13,700 --> 00:50:17,100 {\an1}and took on new forms... 893 00:50:17,133 --> 00:50:20,000 All in less than a million years. 894 00:50:20,033 --> 00:50:24,266 ♪ 895 00:50:24,300 --> 00:50:28,566 {\an1}In the ages that followed, mammals seized empty niches. 896 00:50:28,600 --> 00:50:30,566 {\an1}(large cat growls) 897 00:50:30,600 --> 00:50:35,533 {\an1}Our ancestors scaled the trees. 898 00:50:35,566 --> 00:50:38,500 {\an1}Others took to the air, 899 00:50:38,533 --> 00:50:42,966 {\an1}or became giants of the seas. 900 00:50:43,000 --> 00:50:46,433 Mammals rose to dominate the planet. 901 00:50:46,466 --> 00:50:49,366 ♪ 902 00:50:49,400 --> 00:50:51,700 {\an1}All this diversity 903 00:50:51,733 --> 00:50:55,733 {\an1}sprang from the band of humble creatures 904 00:50:55,766 --> 00:50:58,600 {\an1}that emerged from the cataclysm. 905 00:50:58,633 --> 00:51:01,133 ♪ 906 00:51:01,166 --> 00:51:03,866 JOHNSON: They inherited a whole world 907 00:51:03,900 --> 00:51:05,533 {\an1}and they had the planet to play in. WEBVTT X-TIMESTAMP-MAP=MPEGTS:198018, LOCAL:00:00:00.000 908 00:51:03,900 --> 00:51:05,533 {\an1}and they had the planet to play in. 909 00:51:05,566 --> 00:51:10,733 And that moment of rapid mammal evolution 910 00:51:10,766 --> 00:51:12,566 {\an1}is effectively the trigger 911 00:51:12,600 --> 00:51:14,533 {\an1}to our existence here on planet Earth. 912 00:51:14,566 --> 00:51:17,300 ♪ 913 00:51:17,333 --> 00:51:21,133 NARRATOR: By unveiling the start of the mammals' explosion, 914 00:51:21,166 --> 00:51:24,933 {\an1}Corral Bluffs seems destined to join the ranks 915 00:51:24,966 --> 00:51:28,166 {\an1}of other celebrated fossil sites, 916 00:51:28,200 --> 00:51:31,800 {\an1}like Tyler's back yard in North Dakota. 917 00:51:31,833 --> 00:51:33,700 LYSON: I can trace those same questions 918 00:51:33,733 --> 00:51:36,000 {\an1}that I'm asking today out on the bluffs 919 00:51:36,033 --> 00:51:39,366 {\an1}all the way back to when I was six or seven years old, 920 00:51:39,400 --> 00:51:43,466 {\an1}running around the badlands looking for fossils. 921 00:51:47,266 --> 00:51:49,166 NARRATOR: By pursuing those questions, 922 00:51:49,200 --> 00:51:52,500 {\an1}Tyler and his colleagues are helping us understand 923 00:51:52,533 --> 00:51:57,266 {\an1}how the planet recovered from catastrophe. 924 00:51:57,300 --> 00:52:02,700 {\an1}They're illuminating the dawn of a new world. 925 00:52:02,733 --> 00:52:04,933 Our world. 926 00:52:06,733 --> 00:52:09,700 ♪ 927 00:52:31,400 --> 00:52:36,200 ♪ 928 00:52:51,033 --> 00:52:53,466 {\an7}To order this "NOVA" program on DVD, 929 00:52:53,500 --> 00:52:58,100 {\an8}visit ShopPBS or call 1-800-PLAY-PBS. 930 00:52:58,133 --> 00:53:01,833 {\an7}This program is also available on Amazon Prime Video. 931 00:53:01,866 --> 00:53:01,800 {\an8}♪