1 00:00:28,640 --> 00:00:31,280 Just look at that. 2 00:00:31,280 --> 00:00:34,080 It's awesome, isn't it? If not a little terrifying. 3 00:00:36,720 --> 00:00:41,400 A massive tsunami of ice, cascading down the valley. 4 00:00:47,000 --> 00:00:50,440 Try to imagine that, though, not just happening here, 5 00:00:50,440 --> 00:00:53,080 but happening all over the world. 6 00:00:57,720 --> 00:01:00,560 Well, 700 million years ago... 7 00:01:02,520 --> 00:01:05,400 ..that's exactly what did happen. 8 00:01:06,960 --> 00:01:08,840 Ferocious forces... 9 00:01:13,280 --> 00:01:16,040 ..created a climate emergency. 10 00:01:17,880 --> 00:01:23,560 And from pole to pole, across all of the lands and oceans... 11 00:01:25,840 --> 00:01:27,280 ..our world... 12 00:01:29,240 --> 00:01:31,000 ..froze. 13 00:01:34,560 --> 00:01:40,240 The story of this extraordinary time is written in the rocks, 14 00:01:40,240 --> 00:01:44,240 and as the latest evidence helps us piece together what happened... 15 00:01:45,560 --> 00:01:49,760 ..we know this disaster hit at the worst possible time. 16 00:01:53,160 --> 00:01:59,200 Just as the earliest forms of animal life were evolving, the ice 17 00:01:59,200 --> 00:02:05,600 threatened to destroy them, and the world as we know it, forever. 18 00:02:15,560 --> 00:02:19,920 The thing is, this moment in our planet's history is also 19 00:02:19,920 --> 00:02:24,920 a story of resilience, because this climatic 20 00:02:24,920 --> 00:02:29,040 and environmental catastrophe lead to something miraculous. 21 00:02:29,040 --> 00:02:33,560 You see, this new life on Earth didn't just survive the ice 22 00:02:33,560 --> 00:02:36,640 and its aftermath, it thrived. 23 00:02:36,640 --> 00:02:41,120 The deep freeze saw a new age on Earth, 24 00:02:41,120 --> 00:02:43,520 an age of complex life, 25 00:02:43,520 --> 00:02:47,760 of a greater size and diversity than ever seen before. 26 00:02:47,760 --> 00:02:50,600 Life that would go on to dominate the oceans 27 00:02:50,600 --> 00:02:53,240 and the land to this very day. 28 00:03:20,080 --> 00:03:23,480 Our story begins in Earth's ancient past... 29 00:03:26,160 --> 00:03:29,520 ..850 million years ago... 30 00:03:37,000 --> 00:03:40,880 ..when the face of our planet was unrecognisable. 31 00:03:47,560 --> 00:03:52,160 Almost all the land that existed was gathered into one, 32 00:03:52,160 --> 00:03:55,840 giant continent, called Rodinia. 33 00:04:05,280 --> 00:04:08,600 Thousands of kilometres, coast to coast, 34 00:04:08,600 --> 00:04:12,440 this rocky landmass dominates the planet. 35 00:04:15,480 --> 00:04:19,160 For all its scale, from its jagged peaks... 36 00:04:22,000 --> 00:04:24,200 ..across its desolate plains... 37 00:04:26,160 --> 00:04:28,440 ..there are no plants 38 00:04:28,440 --> 00:04:30,280 and no animals. 39 00:04:34,480 --> 00:04:36,000 But there is life here. 40 00:04:39,960 --> 00:04:41,800 In shallow, coastal waters... 41 00:04:45,360 --> 00:04:47,200 ..bacteria clump together 42 00:04:47,200 --> 00:04:50,400 into living mats that cover the seafloor. 43 00:04:52,640 --> 00:04:57,760 For nearly three billion years, this has been the limit of life on Earth. 44 00:05:01,240 --> 00:05:06,240 A planet that couldn't be more different from the world we live in. 45 00:05:29,520 --> 00:05:34,040 Even in Iceland, with its harsh winters, so hostile to life... 46 00:05:37,480 --> 00:05:42,600 ..once the warmth returns, so do a host of plants and animals. 47 00:05:45,680 --> 00:05:49,440 It's honestly hard to imagine that up until very recently, 48 00:05:49,440 --> 00:05:54,280 this was a dark, desolate and frigid place, because now look at it. 49 00:05:54,280 --> 00:05:59,040 It's bright, it's busy, it's warm, it's busy with life doing 50 00:05:59,040 --> 00:06:04,000 what it needs to do at this time of year, which is flower and fruit. 51 00:06:04,000 --> 00:06:08,480 And look at this lovely, delicate little harebell here. 52 00:06:09,720 --> 00:06:12,920 And these are the fruits of the crowberry. 53 00:06:13,960 --> 00:06:15,560 And they're meant to be edible. 54 00:06:18,400 --> 00:06:20,040 Best left for the birds. 55 00:06:20,040 --> 00:06:26,240 But aside from the taste, look at that, it's a perfect little package. 56 00:06:26,240 --> 00:06:30,760 It's exquisite. But what interests me more, what's more incredible, 57 00:06:30,760 --> 00:06:36,280 more important, is how this fits into the grander scheme of things. 58 00:06:41,000 --> 00:06:44,360 All the life here has evolved in partnership 59 00:06:44,360 --> 00:06:45,880 with everything around it. 60 00:06:51,320 --> 00:06:57,080 Each individual is just one strand in an intricate web of life. 61 00:06:58,160 --> 00:07:04,320 Every part connected to, and reliant upon, all the others to survive. 62 00:07:08,600 --> 00:07:13,200 Large, complex life in the modern world can only really make it 63 00:07:13,200 --> 00:07:16,840 if it's part of a bigger, interconnected ecosystem, like 64 00:07:16,840 --> 00:07:23,040 this one here, an ecosystem which is as complex as the life it supports. 65 00:07:24,320 --> 00:07:28,320 But the staggering thing is, the truly staggering thing is, 66 00:07:28,320 --> 00:07:33,000 that until recently, none of this existed. 67 00:07:33,000 --> 00:07:36,560 You see, for over four billion years, 68 00:07:36,560 --> 00:07:40,920 that's pretty much our entire planet's existence, large, 69 00:07:40,920 --> 00:07:44,240 intricate life like this was nowhere to be found. 70 00:07:48,280 --> 00:07:52,400 All the animal life that now exists in the world can 71 00:07:52,400 --> 00:07:56,120 trace its origin back to what was happening off the shores 72 00:07:56,120 --> 00:08:01,600 of Rodinia, 850 million years ago. 73 00:08:19,040 --> 00:08:22,440 In the coastal waters, amongst the bacteria, 74 00:08:22,440 --> 00:08:24,720 something new has appeared. 75 00:08:33,640 --> 00:08:37,280 Giant cells tower over the living mats. 76 00:08:40,920 --> 00:08:45,520 These strange microbes are the distant ancestors of animal life. 77 00:08:48,800 --> 00:08:53,240 They're not bacteria, but eukaryotes - bigger, 78 00:08:53,240 --> 00:08:54,760 more complicated... 79 00:08:56,520 --> 00:08:59,640 ..the first cells with a nucleus. 80 00:09:01,520 --> 00:09:06,960 The bacterial mats here get their energy from sunlight, but like 81 00:09:06,960 --> 00:09:11,040 you and me, they eukaryotes rely on food from their surroundings. 82 00:09:14,120 --> 00:09:18,240 And in this basic ecosystem, there were slim pickings, 83 00:09:18,240 --> 00:09:21,040 bacteria floating in the water, 84 00:09:21,040 --> 00:09:25,360 and the slow flow of minerals from the eroding land. 85 00:09:29,800 --> 00:09:32,040 Enough to survive, 86 00:09:32,040 --> 00:09:35,800 but far from what they need to thrive. 87 00:09:44,720 --> 00:09:49,120 These new life forms seem destined to live out a meagre existence 88 00:09:49,120 --> 00:09:50,840 stuck on the sidelines... 89 00:09:52,360 --> 00:09:56,680 ..never able to evolve into the vibrant ecosystems of today. 90 00:09:59,240 --> 00:10:03,760 But the planet was about to deliver a colossal shock to the system... 91 00:10:07,200 --> 00:10:11,040 ..thanks to powerful forces that are still at work today... 92 00:10:13,280 --> 00:10:16,400 ..and can be witnessed in places like Thingvellir, 93 00:10:16,400 --> 00:10:18,280 on the western coast of Iceland. 94 00:10:25,600 --> 00:10:30,920 Walking through here, I get a real sense of raw, primal, 95 00:10:30,920 --> 00:10:36,520 brutal forces at play, and those forces certainly are at play. 96 00:10:36,520 --> 00:10:38,720 You see, every year, 97 00:10:38,720 --> 00:10:44,440 the walls of this chasm move apart by one centimetre. 98 00:10:45,560 --> 00:10:48,200 Now, I know it doesn't sound like much, but that's 99 00:10:48,200 --> 00:10:52,760 because we've got to start thinking about this in geological time, 100 00:10:52,760 --> 00:10:57,520 so that's hundreds of millions of years, not hundreds of years. 101 00:10:57,520 --> 00:11:01,760 The rock beneath my feet is quite literally splitting in two, 102 00:11:01,760 --> 00:11:07,320 along a fracture which runs for thousands of kilometres. 103 00:11:18,520 --> 00:11:21,880 Iceland sits on a boundary between two giant 104 00:11:21,880 --> 00:11:24,640 chunks of the Earth's crust, 105 00:11:24,640 --> 00:11:27,240 known as tectonic plates. 106 00:11:31,760 --> 00:11:35,120 Heat churning within the mantle of our planet 107 00:11:35,120 --> 00:11:37,760 is driving these plates apart. 108 00:11:44,360 --> 00:11:45,680 As they spread... 109 00:11:47,800 --> 00:11:50,440 ..the land above stretches 110 00:11:50,440 --> 00:11:52,320 and then tears... 111 00:11:56,760 --> 00:11:59,640 ..creating great rifts through the landscape. 112 00:12:06,200 --> 00:12:10,760 These forces have been moving the world's greatest landmasses, 113 00:12:10,760 --> 00:12:16,000 creating and destroying them, for more than three billion years, and 114 00:12:16,000 --> 00:12:21,520 nothing can resist them, not even a giant supercontinent like Rodinia. 115 00:12:29,800 --> 00:12:31,360 Deep beneath Rodinia... 116 00:12:37,640 --> 00:12:43,000 ..swirling currents of heat cause tectonic plates to shift. 117 00:12:52,800 --> 00:12:54,200 They begin to move apart... 118 00:12:57,640 --> 00:13:01,320 ..and great chasms gape open across the landscape. 119 00:13:04,960 --> 00:13:09,920 This great continent is ripping itself apart. 120 00:13:18,000 --> 00:13:22,400 Earth is the only planet in the solar system to have active 121 00:13:22,400 --> 00:13:23,640 tectonic plates. 122 00:13:25,960 --> 00:13:30,920 And they're constantly reshaping our world and its life. 123 00:13:33,640 --> 00:13:36,960 In many ways, we can think of the history of our Earth 124 00:13:36,960 --> 00:13:41,760 as about the interplay between life and geology, 125 00:13:41,760 --> 00:13:44,960 and sometimes, the great planetary process have given life 126 00:13:44,960 --> 00:13:47,080 a bit of a leg up. 127 00:13:47,080 --> 00:13:50,280 On others, they've knocked it right back down again. 128 00:13:50,280 --> 00:13:53,480 One of these moments was about to play out, 129 00:13:53,480 --> 00:13:57,680 and what happened next would ultimately defy the entire 130 00:13:57,680 --> 00:14:00,680 living world that we experience today. 131 00:14:07,240 --> 00:14:10,440 As the rifting continues for millions of years... 132 00:14:14,520 --> 00:14:17,000 ..it creates deep valleys... 133 00:14:19,360 --> 00:14:21,080 ..powerful rivers... 134 00:14:24,040 --> 00:14:26,920 ..and hundreds of kilometres of new coastline... 135 00:14:31,880 --> 00:14:34,760 ..all greatly increasing erosion, 136 00:14:34,760 --> 00:14:40,160 and causing a flood of minerals to pour from the land into the oceans. 137 00:14:52,880 --> 00:14:59,200 Thanks to this boost in minerals, the eukaryote population explodes. 138 00:15:06,000 --> 00:15:08,920 They build numerous colonies, 139 00:15:08,920 --> 00:15:13,760 a crucial step towards forming multi-celled animals. 140 00:15:18,600 --> 00:15:22,120 And some organisms now have enough energy 141 00:15:22,120 --> 00:15:23,840 to produce protective spikes... 142 00:15:26,320 --> 00:15:29,680 ..built from all those minerals washed off the land... 143 00:15:32,400 --> 00:15:34,120 ..and vital defences, 144 00:15:34,120 --> 00:15:39,440 as there were now predators taking advantage of the boom in numbers... 145 00:15:42,200 --> 00:15:45,120 ..in this newly energised ecosystem. 146 00:15:55,920 --> 00:16:01,080 We've witnessed this dramatic change with our own eyes, 147 00:16:01,080 --> 00:16:03,600 thank to recent discoveries made 148 00:16:03,600 --> 00:16:07,840 in 700 million year-old rocks from the Grand Canyon. 149 00:16:12,440 --> 00:16:15,200 Scientists have discovered these... 150 00:16:16,640 --> 00:16:22,560 ..tiny micro-fossils of marine life, each smaller than a grain of sand. 151 00:16:25,480 --> 00:16:29,720 What shocked them were the holes in the outer shell, 152 00:16:29,720 --> 00:16:34,920 most likely created when they were attacked and eaten. 153 00:16:36,320 --> 00:16:39,120 Now, the predators weren't preserved, 154 00:16:39,120 --> 00:16:42,320 but the best guess is that they were something like... 155 00:16:43,520 --> 00:16:44,840 ..this... 156 00:16:47,880 --> 00:16:51,920 ..a single celled amoeba called Vampyrella. 157 00:16:54,720 --> 00:16:58,280 This predator punches holes in its victims 158 00:16:58,280 --> 00:17:00,880 before sucking out their inners... 159 00:17:01,880 --> 00:17:05,880 ..leaving behind holes near identical 160 00:17:05,880 --> 00:17:08,600 to those found on the micro-fossils. 161 00:17:17,200 --> 00:17:23,000 This is the earliest evidence of predators and prey ever found. 162 00:17:25,880 --> 00:17:30,880 That element of everyday life, so key to our modern world. 163 00:17:37,720 --> 00:17:42,040 The vast tectonic processes at work provided complex life with 164 00:17:42,040 --> 00:17:43,680 the spark that it needed, 165 00:17:43,680 --> 00:17:47,720 an environmental revolution which allowed it to move towards 166 00:17:47,720 --> 00:17:51,760 the interconnected ecosystems that we see around us today. 167 00:17:52,840 --> 00:17:57,040 But just as life was taking this great leap forwards, 168 00:17:57,040 --> 00:17:59,600 disaster struck. 169 00:17:59,600 --> 00:18:03,640 The forces tearing the ancient supercontinent apart were about 170 00:18:03,640 --> 00:18:09,840 to plunge the entire world into a seemingly endless, desolate winter. 171 00:18:38,800 --> 00:18:43,000 On Rodinia, events take a catastrophic turn for the worse. 172 00:18:47,120 --> 00:18:51,040 Superheated magma bursts through the surface, 173 00:18:51,040 --> 00:18:54,560 as rifting thins the crust in multiple places. 174 00:18:58,360 --> 00:19:02,080 Molten rock swamps two million square kilometres 175 00:19:02,080 --> 00:19:03,440 of the continent... 176 00:19:05,840 --> 00:19:10,000 ..one of the largest outpourings in Earth's history. 177 00:19:17,480 --> 00:19:21,720 The lava cools and forms the dark rock basalt... 178 00:19:23,920 --> 00:19:28,680 ..creating a vast black stain across the heart of the continent. 179 00:19:31,840 --> 00:19:35,880 You see, the great freeze begins not with ice... 180 00:19:37,560 --> 00:19:38,840 ..but with fire. 181 00:20:04,520 --> 00:20:07,280 Fresh basalt is quite incredible stuff. 182 00:20:07,280 --> 00:20:09,840 This is about ten months old. 183 00:20:09,840 --> 00:20:13,320 Now, it's not terribly easy to walk over, and you certainly 184 00:20:13,320 --> 00:20:14,960 wouldn't want to stumble. 185 00:20:14,960 --> 00:20:19,440 It's extremely jagged, ripping your boots to pieces, 186 00:20:19,440 --> 00:20:22,280 and you wouldn't want to fall on that, would you? 187 00:20:22,280 --> 00:20:26,800 But what's really incredible about this rock is that it has 188 00:20:26,800 --> 00:20:30,640 the capacity to change our planet's atmosphere. 189 00:20:34,560 --> 00:20:39,840 As rain forms, it absorbs carbon dioxide gas from that atmosphere. 190 00:20:45,320 --> 00:20:49,240 When that rain flows over basalt, there's a chemical reaction 191 00:20:49,240 --> 00:20:53,080 that draws carbon dioxide out of the water 192 00:20:53,080 --> 00:20:57,240 and binds it to the surface of the rock, locking it away. 193 00:21:13,280 --> 00:21:18,720 We know that carbon dioxide is a very potent greenhouse gas, 194 00:21:18,720 --> 00:21:23,600 has the capacity to lock lots of heat into our atmosphere, 195 00:21:23,600 --> 00:21:26,600 and the more of it that we pump into the air, 196 00:21:26,600 --> 00:21:30,560 the more we see our global temperatures rising. 197 00:21:30,560 --> 00:21:33,760 But then, I don't need to tell you about global warming. 198 00:21:33,760 --> 00:21:37,960 What's interesting is that the reverse is also true. 199 00:21:37,960 --> 00:21:43,280 If we take carbon dioxide out of the atmosphere, temperatures fall. 200 00:21:46,520 --> 00:21:51,600 The erosion of millions upon millions of tons of basalt, 201 00:21:51,600 --> 00:21:57,320 spewed up when Rodinia broke apart, sucked that warming 202 00:21:57,320 --> 00:22:00,920 blanket of carbon dioxide out of the atmosphere. 203 00:22:03,720 --> 00:22:06,720 And it flicked the Earth's thermostat 204 00:22:06,720 --> 00:22:10,000 from a comfortable stasis to chill. 205 00:22:16,280 --> 00:22:18,600 Falling levels of carbon dioxide... 206 00:22:20,600 --> 00:22:22,440 ..pushed down temperatures... 207 00:22:25,280 --> 00:22:27,400 ..awakening a sinister force. 208 00:22:36,560 --> 00:22:37,880 Ice... 209 00:22:43,000 --> 00:22:46,760 ..something not seen here on the planet for a billion years. 210 00:22:56,360 --> 00:22:59,040 For now, it's limited to the poles. 211 00:23:01,560 --> 00:23:03,680 But it's spreading. 212 00:23:28,560 --> 00:23:33,280 Whether you're a microscopic or more human-sized, 213 00:23:33,280 --> 00:23:35,680 most life loves the warmth... 214 00:23:37,920 --> 00:23:42,200 ..especially here in Iceland, where the winters are so harsh. 215 00:23:45,320 --> 00:23:50,200 Summers here are truly amazing - look how verdant, how green, 216 00:23:50,200 --> 00:23:52,360 how lush it is. 217 00:23:52,360 --> 00:23:55,760 And there's also a tremendous diversity of plants - 218 00:23:55,760 --> 00:23:58,600 flowers, mosses, dwarf trees. 219 00:24:00,080 --> 00:24:05,000 And, of course, on a day like today, blue sky, sunshine - it's lovely. 220 00:24:06,160 --> 00:24:11,400 But the lingering cold of winter is never too far away. 221 00:24:23,800 --> 00:24:26,320 Venture up into that lingering cold... 222 00:24:29,920 --> 00:24:34,160 ..and it's possible to see how life suffers as temperatures fall. 223 00:24:38,040 --> 00:24:42,840 I've only travelled about a mile, but I've climbed in altitude, 224 00:24:42,840 --> 00:24:46,920 and the difference in the landscape is really rather stark. 225 00:24:46,920 --> 00:24:48,880 Look at it. 226 00:24:48,880 --> 00:24:52,120 It's principally barren rock 227 00:24:52,120 --> 00:24:55,200 and the plants here are scattered few and far between. 228 00:24:58,240 --> 00:25:00,720 You see, up here, the temperature only 229 00:25:00,720 --> 00:25:04,280 gets above five degrees Centigrade for a few weeks of the year, 230 00:25:04,280 --> 00:25:06,800 and when the temperature drops below that, 231 00:25:06,800 --> 00:25:10,360 plants can't produce structural tissues. 232 00:25:14,360 --> 00:25:18,880 You can give them all the water, all the nutrients they want, 233 00:25:18,880 --> 00:25:23,520 but at lower temperatures, they just can't build their own bodies. 234 00:25:31,360 --> 00:25:35,440 Across the world, whenever temperatures drop low enough, 235 00:25:35,440 --> 00:25:37,360 for long enough, 236 00:25:37,360 --> 00:25:42,120 plants and life slowly fade away. 237 00:25:45,200 --> 00:25:51,080 Temperature is the natural limiter for complex life in our world, 238 00:25:51,080 --> 00:25:56,360 and those rich, interconnected ecosystems, 239 00:25:56,360 --> 00:26:00,840 which can thrive down there can't even survive up here. 240 00:26:00,840 --> 00:26:04,880 When it gets cold, the web of life unravels. 241 00:26:14,000 --> 00:26:18,680 On the ancient Earth, as temperatures continue to fall, 242 00:26:18,680 --> 00:26:22,720 the cold advances on early life from all sides. 243 00:26:28,440 --> 00:26:32,520 Armadas of sea ice march out from the North and South Poles... 244 00:26:37,320 --> 00:26:41,560 ..as on land, immense glaciers surge forth from the mountains. 245 00:26:46,320 --> 00:26:50,280 The places life can hold on are rapidly shrinking. 246 00:26:55,640 --> 00:27:02,720 The ancient Earth teeters on the edge of a climate catastrophe, 247 00:27:02,720 --> 00:27:05,520 as the ice tightens its grip. 248 00:27:24,680 --> 00:27:29,720 Today, ice covers a tenth of all the land on the planet. 249 00:27:31,880 --> 00:27:34,240 Vast sheets blanket the poles... 250 00:27:39,200 --> 00:27:42,520 ..and the high mountains of all of the continents. 251 00:27:48,080 --> 00:27:53,320 Nearly 10% of Iceland is covered by a single sheet of ice. 252 00:27:59,400 --> 00:28:02,280 The icecap here is vast. 253 00:28:02,280 --> 00:28:06,160 It stretches for 100 kilometres in that direction. 254 00:28:06,160 --> 00:28:11,760 It's 140 kilometres wide and nearly a kilometre thick in some places. 255 00:28:12,800 --> 00:28:16,560 But in the modern world, ice is limited. 256 00:28:16,560 --> 00:28:18,960 It comes to a grinding stop down there. 257 00:28:23,080 --> 00:28:26,520 And that's not just because of human-induced climate change. 258 00:28:28,880 --> 00:28:31,480 The world is simply too warm. 259 00:28:36,640 --> 00:28:41,680 The idea that ice could smother the whole world 260 00:28:41,680 --> 00:28:44,120 seems incomprehensible. 261 00:28:51,240 --> 00:28:54,320 But just over 710 million years ago, 262 00:28:54,320 --> 00:28:57,800 the Earth was a much more vulnerable place, 263 00:28:57,800 --> 00:29:02,640 and when the ice started marching, there was very little to stop it. 264 00:29:07,760 --> 00:29:10,920 We now know just how far it reached. 265 00:29:14,320 --> 00:29:17,840 Look under the leading edge of this icecap 266 00:29:17,840 --> 00:29:22,720 and you can see the evidence of its raw power in the countless 267 00:29:22,720 --> 00:29:27,120 chunks of rock ripped up and dumped by the ice. 268 00:29:31,680 --> 00:29:36,440 Glaciers are so destructive, they leave scars in the rock record. 269 00:29:39,840 --> 00:29:42,200 Like these stones and boulders, 270 00:29:42,200 --> 00:29:46,280 a completely different type or rock to the layers around them. 271 00:29:48,240 --> 00:29:53,160 Called drop stones, the flowing ice picked them up and dropped them 272 00:29:53,160 --> 00:29:56,240 hundreds of kilometres from where they originated. 273 00:29:57,360 --> 00:30:01,640 Scientists have found these in rock layers that were sat over 274 00:30:01,640 --> 00:30:04,640 the equator 700 million years ago... 275 00:30:09,160 --> 00:30:14,240 ..hinting at an event of an astonishing scale and reach. 276 00:30:24,320 --> 00:30:26,880 The ice is winning. 277 00:30:29,720 --> 00:30:33,320 A band of warmth still holds out around the equator... 278 00:30:34,960 --> 00:30:37,960 ..the last refuge for life. 279 00:30:41,080 --> 00:30:44,120 But as the white expanse spreads, 280 00:30:44,120 --> 00:30:48,120 more and more heat is reflected back into space... 281 00:30:49,840 --> 00:30:54,120 ..and the freeze becomes a runaway process. 282 00:30:59,680 --> 00:31:03,520 Ice surges over almost all of the remaining oceans. 283 00:31:09,520 --> 00:31:13,280 Even at the equator, hope slowly fades. 284 00:31:17,440 --> 00:31:22,360 And finally, this last stretch succumbs... 285 00:31:25,160 --> 00:31:29,080 ..leaving the planet a frozen, white marble... 286 00:31:33,080 --> 00:31:37,800 ..floating in the darkness of space. 287 00:31:51,200 --> 00:31:53,360 Ice had claimed the world... 288 00:31:55,960 --> 00:31:58,720 ..in an event known as Snowball Earth. 289 00:32:04,640 --> 00:32:06,840 It's almost impossible to imagine, 290 00:32:06,840 --> 00:32:10,960 but pretty much all of the planet was just like this. 291 00:32:13,080 --> 00:32:17,560 The whole world was plunged into a deep Ice Age, wrapped in sheets 292 00:32:17,560 --> 00:32:23,400 of ice sometimes kilometres thick, choking our land and our oceans. 293 00:32:25,000 --> 00:32:28,800 It was a global winter with no end in sight. 294 00:32:33,200 --> 00:32:35,160 Modelling suggests that it was 295 00:32:35,160 --> 00:32:38,600 minus 70 degrees Centigrade at the poles... 296 00:32:40,800 --> 00:32:44,440 ..that it never got above freezing anywhere on the planet. 297 00:32:46,240 --> 00:32:48,000 It would have been pretty sterile. 298 00:32:51,040 --> 00:32:54,400 It would have stressed or stalled the water cycle. 299 00:33:00,120 --> 00:33:02,560 There would have been little or no evaporation... 300 00:33:04,520 --> 00:33:06,440 ..hence no rain, 301 00:33:06,440 --> 00:33:08,600 no snow, 302 00:33:08,600 --> 00:33:11,080 very few clouds. 303 00:33:11,080 --> 00:33:15,080 If there were clouds, some would have been clouds of carbon dioxide. 304 00:33:18,880 --> 00:33:22,280 This was an incredibly hostile place. 305 00:33:26,480 --> 00:33:30,080 It couldn't have been more different than the beautiful, vibrant, 306 00:33:30,080 --> 00:33:32,480 dynamic planet that we have today. 307 00:33:49,280 --> 00:33:53,800 The triumph of the ice is a disaster for life. 308 00:33:57,240 --> 00:34:01,360 The ocean is almost entirely cut off from the atmosphere. 309 00:34:04,440 --> 00:34:06,320 It's dark, cold. 310 00:34:10,160 --> 00:34:13,640 And the flow of minerals from the land slows to a trickle. 311 00:34:17,000 --> 00:34:19,360 The food web begins to fall apart. 312 00:34:22,320 --> 00:34:24,960 And the predecessors of animal life... 313 00:34:26,440 --> 00:34:27,640 ..falter. 314 00:34:30,360 --> 00:34:32,880 A mass dying is under way. 315 00:34:43,920 --> 00:34:48,800 This was no short cold snap life could easily ride out. 316 00:34:49,800 --> 00:34:53,040 OK, the ice would have waxed and waned a little, 317 00:34:53,040 --> 00:34:57,400 with the changing of the seasons, but the cold persisted, 318 00:34:57,400 --> 00:35:02,160 unending, for millions upon millions of years, 319 00:35:02,160 --> 00:35:04,600 with no hope of release. 320 00:35:22,800 --> 00:35:25,120 I know it looks like a massive, muddy field, 321 00:35:25,120 --> 00:35:29,920 but I'm actually walking on top of a glacier, albeit a dirty one. 322 00:35:31,000 --> 00:35:35,520 And out here, in the biting face of the cold, it's easy to 323 00:35:35,520 --> 00:35:40,520 imagine that the endless winter put pay to complex life on Earth. 324 00:35:41,560 --> 00:35:43,720 But of course, it didn't. Live survived. 325 00:35:43,720 --> 00:35:46,400 You and I are living, breathing proof of that. 326 00:35:46,400 --> 00:35:49,400 But when it comes to looking for the clues that might tell us 327 00:35:49,400 --> 00:35:52,960 how it pulled off its great survival trick, these wild, 328 00:35:52,960 --> 00:35:55,960 frozen places are a top place to look. 329 00:35:59,720 --> 00:36:04,480 You see, even on the exposed top of the glacier, it's possible 330 00:36:04,480 --> 00:36:07,640 to find chinks in the ice's armour, 331 00:36:07,640 --> 00:36:10,960 just big enough for life to exploit. 332 00:36:17,280 --> 00:36:21,120 Here we are. This is what we're looking for. 333 00:36:21,120 --> 00:36:22,640 This, we think, 334 00:36:22,640 --> 00:36:27,480 is very similar to what might have formed way back then. 335 00:36:27,480 --> 00:36:31,960 Some dust blew out onto the glacier, was warmed up by the sun, 336 00:36:31,960 --> 00:36:36,600 it melted the surface of the ice and formed this puddle. 337 00:36:36,600 --> 00:36:42,160 They're called cryoconites, and it's this simple combination of dust 338 00:36:42,160 --> 00:36:47,120 and water which proved to be life's saviour. 339 00:36:47,120 --> 00:36:51,240 Now, I know it doesn't look like much, but this is, in fact, 340 00:36:51,240 --> 00:36:57,040 a beautiful little oasis out here on top of this vast glacier. 341 00:37:04,320 --> 00:37:09,440 Yes, in this one small pool of water, there's abundant 342 00:37:09,440 --> 00:37:14,960 minerals from the dust, and plenty of exposure to the air and sunlight. 343 00:37:17,200 --> 00:37:20,040 As astonishing as it sounds, 344 00:37:20,040 --> 00:37:24,520 that means it's possible to find life 345 00:37:24,520 --> 00:37:26,840 in muddy puddles like this. 346 00:37:31,160 --> 00:37:35,120 The simplest would be single celled algae and bacteria, 347 00:37:35,120 --> 00:37:36,720 but there are others. 348 00:37:36,720 --> 00:37:40,800 These are images that have come from an actual cryoconite. 349 00:37:40,800 --> 00:37:43,680 You've got things like this rotifer here, 350 00:37:43,680 --> 00:37:46,960 and here, our favourite little water bear, the tardigrade. 351 00:37:48,040 --> 00:37:51,760 And they would be feeding on those smaller organisms. 352 00:37:51,760 --> 00:37:55,560 And, all together, a soup here of different animals 353 00:37:55,560 --> 00:37:57,920 and plants in a simple food web. 354 00:37:58,920 --> 00:38:02,520 Now, I've got to tell you, I've seen life in some pretty amazing 355 00:38:02,520 --> 00:38:07,800 places in my time, but the idea that there could be a functional 356 00:38:07,800 --> 00:38:13,240 ecosystem living in a puddle, on top of Europe's largest glacier? 357 00:38:14,600 --> 00:38:17,040 Well, that is quite extraordinary. 358 00:38:20,440 --> 00:38:24,560 It's thought that during Snowball Earth, there would have been 359 00:38:24,560 --> 00:38:28,400 enough patches of exposed rock and land to generate dust. 360 00:38:31,480 --> 00:38:37,320 Not as much dirt as this, but enough to create many similar puddles. 361 00:38:37,320 --> 00:38:42,360 And, what's more, scientists have exposed these tiny oases 362 00:38:42,360 --> 00:38:45,960 in the laboratory to conditions found on Snowball Earth... 363 00:38:47,960 --> 00:38:51,000 ..and the life inside survived. 364 00:39:10,720 --> 00:39:15,640 For no less than 50 million years, 50 million years, that's 365 00:39:15,640 --> 00:39:22,280 a long time, life clung on in such places throughout the deep freeze. 366 00:39:22,280 --> 00:39:27,640 Let's be clear, this was a tough place to exist, 367 00:39:27,640 --> 00:39:31,160 but if life wanted to do more than survive, if it wanted to 368 00:39:31,160 --> 00:39:36,000 flourish, then the Earth would have to escape its icy prison. 369 00:39:47,640 --> 00:39:50,600 There was no easy route out. 370 00:39:52,320 --> 00:39:55,520 The ice prevented almost any change on the planet... 371 00:39:58,640 --> 00:40:00,440 ..with one exception. 372 00:40:09,680 --> 00:40:15,200 Even an endless winter can't stop the planet creating volcanoes. 373 00:40:19,880 --> 00:40:25,440 Each eruption punching through the planet's frozen shell. 374 00:40:35,560 --> 00:40:38,480 Ever since our planet first formed, 375 00:40:38,480 --> 00:40:41,960 the heat in its mantle has fuelled volcanoes. 376 00:40:44,360 --> 00:40:48,320 Today, there are over 1,000 active across the world. 377 00:40:52,960 --> 00:40:56,440 And there would have been at least as many during Snowball Earth. 378 00:41:00,720 --> 00:41:05,880 But even the ferocious heat of all that molten rock was too 379 00:41:05,880 --> 00:41:10,440 fleeting to break the grip of the global Ice Age. 380 00:41:15,640 --> 00:41:19,880 What did offer a slim chance of escape was something else. 381 00:41:23,160 --> 00:41:27,040 Something invisible that came with each eruption. 382 00:41:40,600 --> 00:41:44,360 As each eruption tore through the ice, 383 00:41:44,360 --> 00:41:49,840 it released a great slug of volcanic gases, 384 00:41:49,840 --> 00:41:55,640 including the carbon dioxide stripped from the atmosphere 385 00:41:55,640 --> 00:41:57,240 all those years ago. 386 00:42:05,240 --> 00:42:09,760 With the land and ocean covered in ice, there's nothing to stop 387 00:42:09,760 --> 00:42:14,120 the slow build up of this powerful greenhouse gas. 388 00:42:17,880 --> 00:42:22,200 And it begins to finally bring some warmth to the frozen planet. 389 00:42:34,280 --> 00:42:36,920 The world stood on a knife edge. 390 00:42:38,360 --> 00:42:42,080 If enough carbon dioxide could build up, there was 391 00:42:42,080 --> 00:42:44,000 a chance of breaking the freeze. 392 00:42:47,120 --> 00:42:51,600 What would finally decide the planet's fate is a process 393 00:42:51,600 --> 00:42:53,880 we're all too familiar with today. 394 00:42:59,520 --> 00:43:03,920 This glacier has been melting for the last 130 years, 395 00:43:03,920 --> 00:43:06,840 and the evidence of that melt is all around us. 396 00:43:06,840 --> 00:43:10,880 Look at this vast, glacial lagoon here, full of bergs 397 00:43:10,880 --> 00:43:15,400 and brash ice, and there's meltwater draining out into the sea. 398 00:43:15,400 --> 00:43:17,080 This is global warming. 399 00:43:19,680 --> 00:43:21,560 And the key thing is that this 400 00:43:21,560 --> 00:43:26,320 process has accelerated in the last 30 years. 401 00:43:26,320 --> 00:43:31,800 You see, just as freezing is a runaway process, so too is melting. 402 00:43:40,080 --> 00:43:45,560 Rising temperatures drive more water vapour into the atmosphere. 403 00:43:45,560 --> 00:43:48,080 It has a powerful greenhouse effect. 404 00:43:49,440 --> 00:43:51,640 And, as ice melts, 405 00:43:51,640 --> 00:43:55,640 the exposed dark surfaces absorb yet more warmth from the sun. 406 00:44:00,280 --> 00:44:03,320 Changes like these feed into each other 407 00:44:03,320 --> 00:44:08,920 and create tipping points, beyond which warming becomes explosive. 408 00:44:11,440 --> 00:44:13,640 To limit climate change today, 409 00:44:13,640 --> 00:44:16,920 we must avoid reaching these tipping points. 410 00:44:20,160 --> 00:44:24,360 But for Snowball Earth, they couldn't have come soon enough. 411 00:44:43,200 --> 00:44:45,280 What started as a trickle... 412 00:44:47,720 --> 00:44:49,560 ..has become a torrent. 413 00:45:02,360 --> 00:45:07,040 As the ice starts to melt, the exposed dark surfaces 414 00:45:07,040 --> 00:45:09,520 suck in ever more warmth from the sun. 415 00:45:10,840 --> 00:45:13,400 The melt becomes unstoppable. 416 00:45:15,840 --> 00:45:21,120 A runaway train that releases a staggering deluge of water. 417 00:45:26,760 --> 00:45:30,560 Sea levels rise two metres every decade, 418 00:45:30,560 --> 00:45:34,040 swallowing great chunks of coastline. 419 00:45:39,240 --> 00:45:45,120 After a total of over 50 million gruelling years in deep freeze... 420 00:45:46,920 --> 00:45:49,400 ..the world is finally reborn. 421 00:46:18,640 --> 00:46:23,640 Snowball Earth was an unprecedented assault on our planet. 422 00:46:27,440 --> 00:46:32,200 An astonishing moment that left no corner of the world unscathed. 423 00:46:35,400 --> 00:46:41,320 You and I are here because, through it all, life survived. 424 00:46:46,600 --> 00:46:52,560 But as tenacious as it was, that life was still single-celled 425 00:46:52,560 --> 00:46:57,200 and still trapped in the microscopic world. 426 00:47:02,200 --> 00:47:05,680 But this is more than just a tale of simple survival. 427 00:47:07,360 --> 00:47:12,080 In the shattered remains of the great freeze, the stage was 428 00:47:12,080 --> 00:47:18,440 set for a revolution that would change beyond all recognition. 429 00:47:27,280 --> 00:47:31,800 It's easy to assume that life progresses in a straight line, 430 00:47:31,800 --> 00:47:35,320 steadily becoming more complex, more advanced. 431 00:47:35,320 --> 00:47:41,120 But in reality, it's often not like that. Often it relies upon a great 432 00:47:41,120 --> 00:47:47,120 shock to the system, a state change, to flip life onto another path. 433 00:47:48,680 --> 00:47:52,800 After which, that life and the world in which it lives, 434 00:47:52,800 --> 00:47:54,520 are never the same again. 435 00:47:59,680 --> 00:48:03,120 Snowball Earth was just such a moment. 436 00:48:20,800 --> 00:48:22,440 The ice of the great freeze 437 00:48:22,440 --> 00:48:25,120 had shredded the surface of our planet... 438 00:48:27,440 --> 00:48:31,320 ..ripping up millions upon millions of tons of rock 439 00:48:31,320 --> 00:48:33,200 and dumping it into the oceans. 440 00:48:38,200 --> 00:48:43,040 This sudden flood of resources causes single-celled algae 441 00:48:43,040 --> 00:48:46,320 and bacteria to flourish throughout the waters of the world. 442 00:48:49,360 --> 00:48:53,600 Their vivid blooms so large they're visible from space... 443 00:48:56,800 --> 00:48:59,720 ..stretching across entire oceans. 444 00:49:01,360 --> 00:49:06,160 Growth on such a staggering scale has the power to change 445 00:49:06,160 --> 00:49:08,120 the entire ecosystem. 446 00:49:12,240 --> 00:49:15,800 All this photosynthesising greatly increases 447 00:49:15,800 --> 00:49:18,040 levels of oxygen in the water, 448 00:49:18,040 --> 00:49:21,720 an element vital for complex life. 449 00:49:28,160 --> 00:49:32,280 When the algae and bacteria eventually die, billions upon 450 00:49:32,280 --> 00:49:35,440 billions drift down to the bottom, 451 00:49:35,440 --> 00:49:38,440 a rain of organic matter... 452 00:49:43,200 --> 00:49:47,400 ..adding to millions of years worth of dead things that have built 453 00:49:47,400 --> 00:49:49,440 up over the history of the oceans. 454 00:49:52,680 --> 00:49:56,480 And bacteria living at the bottom of the ocean gorged 455 00:49:56,480 --> 00:49:58,640 themselves on this dead matter... 456 00:50:02,760 --> 00:50:07,200 ..reprocessing it and releasing a steady stream of minerals 457 00:50:07,200 --> 00:50:08,680 back into the water column... 458 00:50:13,480 --> 00:50:19,000 ..giving our ancient ancestors a plentiful, sustained source 459 00:50:19,000 --> 00:50:24,480 of food, oxygen and nutrients, 460 00:50:24,480 --> 00:50:28,880 all supplied by life itself. 461 00:50:43,040 --> 00:50:47,920 At this moment, for the first time ever, life and the planet 462 00:50:47,920 --> 00:50:52,880 come together to become complimentary cogs spinning in 463 00:50:52,880 --> 00:50:57,760 a great nutrient recycling machine, which is providing life with 464 00:50:57,760 --> 00:51:02,840 exactly what it wants in quantities that it's never had before. 465 00:51:02,840 --> 00:51:07,400 And as a consequence, life explodes. 466 00:51:07,400 --> 00:51:12,360 And after around half a billion years of struggle, 467 00:51:12,360 --> 00:51:17,040 Earth's fledgling spring is set to become a glorious summer. 468 00:51:30,560 --> 00:51:36,520 In shallow coastal waters across the planet, life blossoms. 469 00:51:40,000 --> 00:51:45,520 These may look like plants, but they are the first animals. 470 00:51:49,920 --> 00:51:53,960 Leaf-shaped Charnia feed on passing nutrients... 471 00:51:57,200 --> 00:52:00,480 ..whilst Attenborites float freely on the tides. 472 00:52:02,920 --> 00:52:08,680 They're the descendants of those first tiny eukaryote pioneers, 473 00:52:08,680 --> 00:52:13,000 now evolved into myriad strange forms, 474 00:52:13,000 --> 00:52:18,280 all of which have finally broken free of the microscopic world. 475 00:52:20,400 --> 00:52:26,400 These are creatures of a complexity and size that we could see, 476 00:52:26,400 --> 00:52:28,240 could reach out and touch. 477 00:52:30,320 --> 00:52:35,360 All living with, and supported by, an ecosystem 478 00:52:35,360 --> 00:52:40,680 just as intricate and remarkable as any on Earth today. 479 00:52:55,000 --> 00:52:59,400 These first truly complex living creatures 480 00:52:59,400 --> 00:53:01,360 are now long gone. 481 00:53:06,680 --> 00:53:10,840 But they were the first to take this great leap, 482 00:53:10,840 --> 00:53:16,000 and once they had, for life, there was no looking back. 483 00:53:17,760 --> 00:53:22,840 All thanks to Snowball Earth lighting the fuse. 484 00:53:29,440 --> 00:53:33,160 Snowball Earth was an astonishing period, 485 00:53:33,160 --> 00:53:39,240 when life, land and the climate were in conflict like never before. 486 00:53:39,240 --> 00:53:42,360 When that long winter ended, 487 00:53:42,360 --> 00:53:46,680 the stage was set for evolution to run riot. 488 00:53:48,120 --> 00:53:54,040 And finally, it's created all of the fantastic scale, the 489 00:53:54,040 --> 00:54:00,080 remarkable diversity and the amazing beauty of life on Earth today. 490 00:54:24,400 --> 00:54:29,680 How do scientists study the bizarre animal life of the Ediacaran, 491 00:54:29,680 --> 00:54:33,320 which lived more than 500 million years ago? 492 00:54:34,960 --> 00:54:39,280 So, this is a wonderful fossil from Charnwood Forest in Leicestershire 493 00:54:39,280 --> 00:54:42,720 in the UK, and it was found by schoolchildren in the '50s. 494 00:54:44,440 --> 00:54:46,840 While it looks superficially like a plant, 495 00:54:46,840 --> 00:54:49,680 because it lived in very deep water, we know it can't have lived 496 00:54:49,680 --> 00:54:53,480 off the light, been photosynthetic. Instead, it fed from the little 497 00:54:53,480 --> 00:54:57,600 bacteria and the dissolved organic carbon that were floating past it. 498 00:55:00,920 --> 00:55:03,680 These creatures are so unusual, 499 00:55:03,680 --> 00:55:07,120 understanding how they interact with each other can be difficult. 500 00:55:15,000 --> 00:55:17,960 Now, thanks to advanced laser technology, 501 00:55:17,960 --> 00:55:21,480 scientists can learn more about them than ever before. 502 00:55:24,240 --> 00:55:26,680 So, by laser scanning these fossils, we've got 503 00:55:26,680 --> 00:55:31,640 a three-dimensional surface, and what this means is, you have 504 00:55:31,640 --> 00:55:36,120 essentially a snap-shot of Ediacaran life captured on the rock surfaces. 505 00:55:39,960 --> 00:55:43,800 To date, we have over 20,000 fossils that we've laser scanned, 506 00:55:43,800 --> 00:55:47,120 and using different sorts of statistics 507 00:55:47,120 --> 00:55:50,360 and mathematical approaches, we can then work out what 508 00:55:50,360 --> 00:55:53,800 they were doing and how they were interacting with each other. 509 00:55:53,800 --> 00:55:58,320 And analysing spatial patterns within the scans has revealed 510 00:55:58,320 --> 00:56:00,880 why some of these creatures grew so big. 511 00:56:02,320 --> 00:56:05,520 For a long time, we thought that the reason they got large 512 00:56:05,520 --> 00:56:09,560 and grew things like stems was to get food without having to compete, 513 00:56:09,560 --> 00:56:13,840 and what we found is that, actually, competition's very, very rare. 514 00:56:13,840 --> 00:56:16,720 Being big wasn't an advantage for getting food, 515 00:56:16,720 --> 00:56:20,000 but what it was an advantage for was ensuring 516 00:56:20,000 --> 00:56:22,920 that your offspring got to go as far as possible, because the taller 517 00:56:22,920 --> 00:56:26,360 you are, the further your offspring will travel in the water column. 518 00:56:28,320 --> 00:56:33,000 And the scans have also led to the discovery that some organisms 519 00:56:33,000 --> 00:56:34,520 had unexpected behaviours. 520 00:56:36,120 --> 00:56:39,600 We actually found something rather surprising. They don't always 521 00:56:39,600 --> 00:56:43,600 reproduce sexually. Instead, some of them reproduce little clones 522 00:56:43,600 --> 00:56:46,560 of themselves that are attached by filaments or runners, a bit like 523 00:56:46,560 --> 00:56:49,760 strawberry plants or spider plants, and so the fossils you see are 524 00:56:49,760 --> 00:56:53,280 actually clones of their parents, and even grandparents sometimes. 525 00:56:54,800 --> 00:56:58,360 After Snowball Earth, the evolution of complex life 526 00:56:58,360 --> 00:57:00,360 occurred at a rate never seen before. 527 00:57:01,640 --> 00:57:05,600 We've gone from these tiny, microscopic, little fossils, 528 00:57:05,600 --> 00:57:08,480 that we can only see with microscopes, all the way to these 529 00:57:08,480 --> 00:57:14,120 large, complex organisms which show signs of having animal features. 530 00:57:14,120 --> 00:57:17,640 There's always a possibility that without Snowball Earth, 531 00:57:17,640 --> 00:57:19,600 life wouldn't have evolved into the complex, 532 00:57:19,600 --> 00:57:22,280 large organisms that we see around us today. 533 00:57:24,360 --> 00:57:25,840 Next time... 534 00:57:28,440 --> 00:57:31,920 The story of how the Earth turned green, 535 00:57:31,920 --> 00:57:35,200 as plants rose from the oceans... 536 00:57:37,680 --> 00:57:40,040 ..to conquer a hostile land... 537 00:57:44,000 --> 00:57:48,600 ..but whose domination almost wiped out all life on the planet. 538 00:57:55,000 --> 00:57:57,800 If the Earth could talk, what would it tell us? 539 00:57:57,800 --> 00:58:00,920 Well, the Open University imagined how it might answer 540 00:58:00,920 --> 00:58:04,720 some of our questions. To experience this interactive presentation, go to 541 00:58:04,720 --> 00:58:08,360 the website on the screen and follow the links to the Open University.