1 00:00:28,900 --> 00:00:31,540 Just look at that. 2 00:00:31,540 --> 00:00:34,340 It's awesome, isn't it? If not a little terrifying. 3 00:00:36,980 --> 00:00:41,660 A massive tsunami of ice, cascading down the valley. 4 00:00:47,260 --> 00:00:50,700 Try to imagine that, though, not just happening here, 5 00:00:50,700 --> 00:00:53,340 but happening all over the world. 6 00:00:57,980 --> 00:01:00,820 Well, 700 million years ago... 7 00:01:02,780 --> 00:01:05,660 ..that's exactly what did happen. 8 00:01:07,220 --> 00:01:09,100 Ferocious forces... 9 00:01:13,540 --> 00:01:16,300 ..created a climate emergency. 10 00:01:18,140 --> 00:01:23,820 And from pole to pole, across all of the lands and oceans... 11 00:01:26,100 --> 00:01:27,540 ..our world... 12 00:01:29,500 --> 00:01:31,260 ..froze. 13 00:01:34,820 --> 00:01:40,500 The story of this extraordinary time is written in the rocks, 14 00:01:40,500 --> 00:01:44,500 and as the latest evidence helps us piece together what happened... 15 00:01:45,820 --> 00:01:50,020 ..we know this disaster hit at the worst possible time. 16 00:01:53,420 --> 00:01:59,460 Just as the earliest forms of animal life were evolving, the ice 17 00:01:59,460 --> 00:02:05,860 threatened to destroy them, and the world as we know it, forever. 18 00:02:15,820 --> 00:02:20,180 The thing is, this moment in our planet's history is also 19 00:02:20,180 --> 00:02:25,180 a story of resilience, because this climatic 20 00:02:25,180 --> 00:02:29,300 and environmental catastrophe lead to something miraculous. 21 00:02:29,300 --> 00:02:33,820 You see, this new life on Earth didn't just survive the ice 22 00:02:33,820 --> 00:02:36,900 and its aftermath, it thrived. 23 00:02:36,900 --> 00:02:41,380 The deep freeze saw a new age on Earth, 24 00:02:41,380 --> 00:02:43,780 an age of complex life, 25 00:02:43,780 --> 00:02:48,020 of a greater size and diversity than ever seen before. 26 00:02:48,020 --> 00:02:50,860 Life that would go on to dominate the oceans 27 00:02:50,860 --> 00:02:53,500 and the land to this very day. 28 00:03:20,340 --> 00:03:23,740 Our story begins in Earth's ancient past... 29 00:03:26,420 --> 00:03:29,780 ..850 million years ago... 30 00:03:37,260 --> 00:03:41,140 ..when the face of our planet was unrecognisable. 31 00:03:47,820 --> 00:03:52,420 Almost all the land that existed was gathered into one, 32 00:03:52,420 --> 00:03:56,100 giant continent, called Rodinia. 33 00:04:05,540 --> 00:04:08,860 Thousands of kilometres, coast to coast, 34 00:04:08,860 --> 00:04:12,700 this rocky landmass dominates the planet. 35 00:04:15,740 --> 00:04:19,420 For all its scale, from its jagged peaks... 36 00:04:22,260 --> 00:04:24,460 ..across its desolate plains... 37 00:04:26,420 --> 00:04:28,700 ..there are no plants 38 00:04:28,700 --> 00:04:30,540 and no animals. 39 00:04:34,740 --> 00:04:36,260 But there is life here. 40 00:04:40,220 --> 00:04:42,060 In shallow, coastal waters... 41 00:04:45,620 --> 00:04:47,460 ..bacteria clump together 42 00:04:47,460 --> 00:04:50,660 into living mats that cover the seafloor. 43 00:04:52,900 --> 00:04:58,020 For nearly three billion years, this has been the limit of life on Earth. 44 00:05:01,500 --> 00:05:06,500 A planet that couldn't be more different from the world we live in. 45 00:05:29,780 --> 00:05:34,300 Even in Iceland, with its harsh winters, so hostile to life... 46 00:05:37,740 --> 00:05:42,860 ..once the warmth returns, so do a host of plants and animals. 47 00:05:45,940 --> 00:05:49,700 It's honestly hard to imagine that up until very recently, 48 00:05:49,700 --> 00:05:54,540 this was a dark, desolate and frigid place, because now look at it. 49 00:05:54,540 --> 00:05:59,300 It's bright, it's busy, it's warm, it's busy with life doing 50 00:05:59,300 --> 00:06:04,260 what it needs to do at this time of year, which is flower and fruit. 51 00:06:04,260 --> 00:06:08,740 And look at this lovely, delicate little harebell here. 52 00:06:09,980 --> 00:06:13,180 And these are the fruits of the crowberry. 53 00:06:14,220 --> 00:06:15,820 And they're meant to be edible. 54 00:06:18,660 --> 00:06:20,300 Best left for the birds. 55 00:06:20,300 --> 00:06:26,500 But aside from the taste, look at that, it's a perfect little package. 56 00:06:26,500 --> 00:06:31,020 It's exquisite. But what interests me more, what's more incredible, 57 00:06:31,020 --> 00:06:36,540 more important, is how this fits into the grander scheme of things. 58 00:06:41,260 --> 00:06:44,620 All the life here has evolved in partnership 59 00:06:44,620 --> 00:06:46,140 with everything around it. 60 00:06:51,580 --> 00:06:57,340 Each individual is just one strand in an intricate web of life. 61 00:06:58,420 --> 00:07:04,580 Every part connected to, and reliant upon, all the others to survive. 62 00:07:08,860 --> 00:07:13,460 Large, complex life in the modern world can only really make it 63 00:07:13,460 --> 00:07:17,100 if it's part of a bigger, interconnected ecosystem, like 64 00:07:17,100 --> 00:07:23,300 this one here, an ecosystem which is as complex as the life it supports. 65 00:07:24,580 --> 00:07:28,580 But the staggering thing is, the truly staggering thing is, 66 00:07:28,580 --> 00:07:33,260 that until recently, none of this existed. 67 00:07:33,260 --> 00:07:36,820 You see, for over four billion years, 68 00:07:36,820 --> 00:07:41,180 that's pretty much our entire planet's existence, large, 69 00:07:41,180 --> 00:07:44,500 intricate life like this was nowhere to be found. 70 00:07:48,540 --> 00:07:52,660 All the animal life that now exists in the world can 71 00:07:52,660 --> 00:07:56,380 trace its origin back to what was happening off the shores 72 00:07:56,380 --> 00:08:01,860 of Rodinia, 850 million years ago. 73 00:08:19,300 --> 00:08:22,700 In the coastal waters, amongst the bacteria, 74 00:08:22,700 --> 00:08:24,980 something new has appeared. 75 00:08:33,900 --> 00:08:37,540 Giant cells tower over the living mats. 76 00:08:41,180 --> 00:08:45,780 These strange microbes are the distant ancestors of animal life. 77 00:08:49,060 --> 00:08:53,500 They're not bacteria, but eukaryotes - bigger, 78 00:08:53,500 --> 00:08:55,020 more complicated... 79 00:08:56,780 --> 00:08:59,900 ..the first cells with a nucleus. 80 00:09:01,780 --> 00:09:07,220 The bacterial mats here get their energy from sunlight, but like 81 00:09:07,220 --> 00:09:11,300 you and me, they eukaryotes rely on food from their surroundings. 82 00:09:14,380 --> 00:09:18,500 And in this basic ecosystem, there were slim pickings, 83 00:09:18,500 --> 00:09:21,300 bacteria floating in the water, 84 00:09:21,300 --> 00:09:25,620 and the slow flow of minerals from the eroding land. 85 00:09:30,060 --> 00:09:32,300 Enough to survive, 86 00:09:32,300 --> 00:09:36,060 but far from what they need to thrive. 87 00:09:44,980 --> 00:09:49,380 These new life forms seem destined to live out a meagre existence 88 00:09:49,380 --> 00:09:51,100 stuck on the sidelines... 89 00:09:52,620 --> 00:09:56,940 ..never able to evolve into the vibrant ecosystems of today. 90 00:09:59,500 --> 00:10:04,020 But the planet was about to deliver a colossal shock to the system... 91 00:10:07,460 --> 00:10:11,300 ..thanks to powerful forces that are still at work today... 92 00:10:13,540 --> 00:10:16,660 ..and can be witnessed in places like Thingvellir, 93 00:10:16,660 --> 00:10:18,540 on the western coast of Iceland. 94 00:10:25,860 --> 00:10:31,180 Walking through here, I get a real sense of raw, primal, 95 00:10:31,180 --> 00:10:36,780 brutal forces at play, and those forces certainly are at play. 96 00:10:36,780 --> 00:10:38,980 You see, every year, 97 00:10:38,980 --> 00:10:44,700 the walls of this chasm move apart by one centimetre. 98 00:10:45,820 --> 00:10:48,460 Now, I know it doesn't sound like much, but that's 99 00:10:48,460 --> 00:10:53,020 because we've got to start thinking about this in geological time, 100 00:10:53,020 --> 00:10:57,780 so that's hundreds of millions of years, not hundreds of years. 101 00:10:57,780 --> 00:11:02,020 The rock beneath my feet is quite literally splitting in two, 102 00:11:02,020 --> 00:11:07,580 along a fracture which runs for thousands of kilometres. 103 00:11:18,780 --> 00:11:22,140 Iceland sits on a boundary between two giant 104 00:11:22,140 --> 00:11:24,900 chunks of the Earth's crust, 105 00:11:24,900 --> 00:11:27,500 known as tectonic plates. 106 00:11:32,020 --> 00:11:35,380 Heat churning within the mantle of our planet 107 00:11:35,380 --> 00:11:38,020 is driving these plates apart. 108 00:11:44,620 --> 00:11:45,940 As they spread... 109 00:11:48,060 --> 00:11:50,700 ..the land above stretches 110 00:11:50,700 --> 00:11:52,580 and then tears... 111 00:11:57,020 --> 00:11:59,900 ..creating great rifts through the landscape. 112 00:12:06,460 --> 00:12:11,020 These forces have been moving the world's greatest landmasses, 113 00:12:11,020 --> 00:12:16,260 creating and destroying them, for more than three billion years, and 114 00:12:16,260 --> 00:12:21,780 nothing can resist them, not even a giant supercontinent like Rodinia. 115 00:12:30,060 --> 00:12:31,620 Deep beneath Rodinia... 116 00:12:37,900 --> 00:12:43,260 ..swirling currents of heat cause tectonic plates to shift. 117 00:12:53,060 --> 00:12:54,460 They begin to move apart... 118 00:12:57,900 --> 00:13:01,580 ..and great chasms gape open across the landscape. 119 00:13:05,220 --> 00:13:10,180 This great continent is ripping itself apart. 120 00:13:18,260 --> 00:13:22,660 Earth is the only planet in the solar system to have active 121 00:13:22,660 --> 00:13:23,900 tectonic plates. 122 00:13:26,220 --> 00:13:31,180 And they're constantly reshaping our world and its life. 123 00:13:33,900 --> 00:13:37,220 In many ways, we can think of the history of our Earth 124 00:13:37,220 --> 00:13:42,020 as about the interplay between life and geology, 125 00:13:42,020 --> 00:13:45,220 and sometimes, the great planetary process have given life 126 00:13:45,220 --> 00:13:47,340 a bit of a leg up. 127 00:13:47,340 --> 00:13:50,540 On others, they've knocked it right back down again. 128 00:13:50,540 --> 00:13:53,740 One of these moments was about to play out, 129 00:13:53,740 --> 00:13:57,940 and what happened next would ultimately define the entire 130 00:13:57,940 --> 00:14:00,940 living world that we experience today. 131 00:14:07,500 --> 00:14:10,700 As the rifting continues for millions of years... 132 00:14:14,780 --> 00:14:17,260 ..it creates deep valleys... 133 00:14:19,620 --> 00:14:21,340 ..powerful rivers... 134 00:14:24,300 --> 00:14:27,180 ..and hundreds of kilometres of new coastline... 135 00:14:32,140 --> 00:14:35,020 ..all greatly increasing erosion, 136 00:14:35,020 --> 00:14:40,420 and causing a flood of minerals to pour from the land into the oceans. 137 00:14:53,140 --> 00:14:59,460 Thanks to this boost in minerals, the eukaryote population explodes. 138 00:15:06,260 --> 00:15:09,180 They build numerous colonies, 139 00:15:09,180 --> 00:15:14,020 a crucial step towards forming multi-celled animals. 140 00:15:18,860 --> 00:15:22,380 And some organisms now have enough energy 141 00:15:22,380 --> 00:15:24,100 to produce protective spikes... 142 00:15:26,580 --> 00:15:29,940 ..built from all those minerals washed off the land... 143 00:15:32,660 --> 00:15:34,380 ..and vital defences, 144 00:15:34,380 --> 00:15:39,700 as there were now predators taking advantage of the boom in numbers... 145 00:15:42,460 --> 00:15:45,380 ..in this newly energised ecosystem. 146 00:15:56,180 --> 00:16:01,340 We've witnessed this dramatic change with our own eyes, 147 00:16:01,340 --> 00:16:03,860 thank to recent discoveries made 148 00:16:03,860 --> 00:16:08,100 in 700 million year-old rocks from the Grand Canyon. 149 00:16:12,700 --> 00:16:15,460 Scientists have discovered these... 150 00:16:16,900 --> 00:16:22,820 ..tiny micro-fossils of marine life, each smaller than a grain of sand. 151 00:16:25,740 --> 00:16:29,980 What shocked them were the holes in the outer shell, 152 00:16:29,980 --> 00:16:35,180 most likely created when they were attacked and eaten. 153 00:16:36,580 --> 00:16:39,380 Now, the predators weren't preserved, 154 00:16:39,380 --> 00:16:42,580 but the best guess is that they were something like... 155 00:16:43,780 --> 00:16:45,100 ..this... 156 00:16:48,140 --> 00:16:52,180 ..a single celled amoeba called Vampyrella. 157 00:16:54,980 --> 00:16:58,540 This predator punches holes in its victims 158 00:16:58,540 --> 00:17:01,140 before sucking out their inners... 159 00:17:02,140 --> 00:17:06,140 ..leaving behind holes near identical 160 00:17:06,140 --> 00:17:08,860 to those found on the micro-fossils. 161 00:17:17,460 --> 00:17:23,260 This is the earliest evidence of predators and prey ever found. 162 00:17:26,140 --> 00:17:31,140 That element of everyday life, so key to our modern world. 163 00:17:37,980 --> 00:17:42,300 The vast tectonic processes at work provided complex life with 164 00:17:42,300 --> 00:17:43,940 the spark that it needed, 165 00:17:43,940 --> 00:17:47,980 an environmental revolution which allowed it to move towards 166 00:17:47,980 --> 00:17:52,020 the interconnected ecosystems that we see around us today. 167 00:17:53,100 --> 00:17:57,300 But just as life was taking this great leap forwards, 168 00:17:57,300 --> 00:17:59,860 disaster struck. 169 00:17:59,860 --> 00:18:03,900 The forces tearing the ancient supercontinent apart were about 170 00:18:03,900 --> 00:18:10,100 to plunge the entire world into a seemingly endless, desolate winter. 171 00:18:39,060 --> 00:18:43,260 On Rodinia, events take a catastrophic turn for the worse. 172 00:18:47,380 --> 00:18:51,300 Superheated magma bursts through the surface, 173 00:18:51,300 --> 00:18:54,820 as rifting thins the crust in multiple places. 174 00:18:58,620 --> 00:19:02,340 Molten rock swamps two million square kilometres 175 00:19:02,340 --> 00:19:03,700 of the continent... 176 00:19:06,100 --> 00:19:10,260 ..one of the largest outpourings in Earth's history. 177 00:19:17,740 --> 00:19:21,980 The lava cools and forms the dark rock basalt... 178 00:19:24,180 --> 00:19:28,940 ..creating a vast black stain across the heart of the continent. 179 00:19:32,100 --> 00:19:36,140 You see, the great freeze begins not with ice... 180 00:19:37,820 --> 00:19:39,100 ..but with fire. 181 00:20:04,780 --> 00:20:07,540 Fresh basalt is quite incredible stuff. 182 00:20:07,540 --> 00:20:10,100 This is about ten months old. 183 00:20:10,100 --> 00:20:13,580 Now, it's not terribly easy to walk over, and you certainly 184 00:20:13,580 --> 00:20:15,220 wouldn't want to stumble. 185 00:20:15,220 --> 00:20:19,700 It's extremely jagged, ripping your boots to pieces, 186 00:20:19,700 --> 00:20:22,540 and you wouldn't want to fall on that, would you? 187 00:20:22,540 --> 00:20:27,060 But what's really incredible about this rock is that it has 188 00:20:27,060 --> 00:20:30,900 the capacity to change our planet's atmosphere. 189 00:20:34,820 --> 00:20:40,100 As rain forms, it absorbs carbon dioxide gas from that atmosphere. 190 00:20:45,580 --> 00:20:49,500 When that rain flows over basalt, there's a chemical reaction 191 00:20:49,500 --> 00:20:53,340 that draws carbon dioxide out of the water 192 00:20:53,340 --> 00:20:57,500 and binds it to the surface of the rock, locking it away. 193 00:21:13,540 --> 00:21:18,980 We know that carbon dioxide is a very potent greenhouse gas, 194 00:21:18,980 --> 00:21:23,860 has the capacity to lock lots of heat into our atmosphere, 195 00:21:23,860 --> 00:21:26,860 and the more of it that we pump into the air, 196 00:21:26,860 --> 00:21:30,820 the more we see our global temperatures rising. 197 00:21:30,820 --> 00:21:34,020 But then, I don't need to tell you about global warming. 198 00:21:34,020 --> 00:21:38,220 What's interesting is that the reverse is also true. 199 00:21:38,220 --> 00:21:43,540 If we take carbon dioxide out of the atmosphere, temperatures fall. 200 00:21:46,780 --> 00:21:51,860 The erosion of millions upon millions of tons of basalt, 201 00:21:51,860 --> 00:21:57,580 spewed up when Rodinia broke apart, sucked that warming 202 00:21:57,580 --> 00:22:01,180 blanket of carbon dioxide out of the atmosphere. 203 00:22:03,980 --> 00:22:06,980 And it flicked the Earth's thermostat 204 00:22:06,980 --> 00:22:10,260 from a comfortable stasis to chill. 205 00:22:16,540 --> 00:22:18,860 Falling levels of carbon dioxide... 206 00:22:20,860 --> 00:22:22,700 ..pushed down temperatures... 207 00:22:25,540 --> 00:22:27,660 ..awakening a sinister force. 208 00:22:36,820 --> 00:22:38,140 Ice... 209 00:22:43,260 --> 00:22:47,020 ..something not seen here on the planet for a billion years. 210 00:22:56,620 --> 00:22:59,300 For now, it's limited to the poles. 211 00:23:01,820 --> 00:23:03,940 But it's spreading. 212 00:23:28,820 --> 00:23:33,540 Whether you're a microscopic or more human-sized, 213 00:23:33,540 --> 00:23:35,940 most life loves the warmth... 214 00:23:38,180 --> 00:23:42,460 ..especially here in Iceland, where the winters are so harsh. 215 00:23:45,580 --> 00:23:50,460 Summers here are truly amazing - look how verdant, how green, 216 00:23:50,460 --> 00:23:52,620 how lush it is. 217 00:23:52,620 --> 00:23:56,020 And there's also a tremendous diversity of plants - 218 00:23:56,020 --> 00:23:58,860 flowers, mosses, dwarf trees. 219 00:24:00,340 --> 00:24:05,260 And, of course, on a day like today, blue sky, sunshine - it's lovely. 220 00:24:06,420 --> 00:24:11,660 But the lingering cold of winter is never too far away. 221 00:24:24,060 --> 00:24:26,580 Venture up into that lingering cold... 222 00:24:30,180 --> 00:24:34,420 ..and it's possible to see how life suffers as temperatures fall. 223 00:24:38,300 --> 00:24:43,100 I've only travelled about a mile, but I've climbed in altitude, 224 00:24:43,100 --> 00:24:47,180 and the difference in the landscape is really rather stark. 225 00:24:47,180 --> 00:24:49,140 Look at it. 226 00:24:49,140 --> 00:24:52,380 It's principally barren rock 227 00:24:52,380 --> 00:24:55,460 and the plants here are scattered few and far between. 228 00:24:58,500 --> 00:25:00,980 You see, up here, the temperature only 229 00:25:00,980 --> 00:25:04,540 gets above five degrees Centigrade for a few weeks of the year, 230 00:25:04,540 --> 00:25:07,060 and when the temperature drops below that, 231 00:25:07,060 --> 00:25:10,620 plants can't produce structural tissues. 232 00:25:14,620 --> 00:25:19,140 You can give them all the water, all the nutrients they want, 233 00:25:19,140 --> 00:25:23,780 but at lower temperatures, they just can't build their own bodies. 234 00:25:31,620 --> 00:25:35,700 Across the world, whenever temperatures drop low enough, 235 00:25:35,700 --> 00:25:37,620 for long enough, 236 00:25:37,620 --> 00:25:42,380 plants and life slowly fade away. 237 00:25:45,460 --> 00:25:51,340 Temperature is the natural limiter for complex life in our world, 238 00:25:51,340 --> 00:25:56,620 and those rich, interconnected ecosystems, 239 00:25:56,620 --> 00:26:01,100 which can thrive down there can't even survive up here. 240 00:26:01,100 --> 00:26:05,140 When it gets cold, the web of life unravels. 241 00:26:14,260 --> 00:26:18,940 On the ancient Earth, as temperatures continue to fall, 242 00:26:18,940 --> 00:26:22,980 the cold advances on early life from all sides. 243 00:26:28,700 --> 00:26:32,780 Armadas of sea ice march out from the North and South Poles... 244 00:26:37,580 --> 00:26:41,820 ..as on land, immense glaciers surge forth from the mountains. 245 00:26:46,580 --> 00:26:50,540 The places life can hold on are rapidly shrinking. 246 00:26:55,900 --> 00:27:02,980 The ancient Earth teeters on the edge of a climate catastrophe, 247 00:27:02,980 --> 00:27:05,780 as the ice tightens its grip. 248 00:27:24,940 --> 00:27:29,980 Today, ice covers a tenth of all the land on the planet. 249 00:27:32,140 --> 00:27:34,500 Vast sheets blanket the poles... 250 00:27:39,460 --> 00:27:42,780 ..and the high mountains of all of the continents. 251 00:27:48,340 --> 00:27:53,580 Nearly 10% of Iceland is covered by a single sheet of ice. 252 00:27:59,660 --> 00:28:02,540 The icecap here is vast. 253 00:28:02,540 --> 00:28:06,420 It stretches for 100km in that direction. 254 00:28:06,420 --> 00:28:12,020 It's 140km wide and nearly a kilometre thick in some places. 255 00:28:13,060 --> 00:28:16,820 But in the modern world, ice is limited. 256 00:28:16,820 --> 00:28:19,220 It comes to a grinding stop down there. 257 00:28:23,340 --> 00:28:26,780 And that's not just because of human-induced climate change. 258 00:28:29,140 --> 00:28:31,740 The world is simply too warm. 259 00:28:36,900 --> 00:28:41,940 The idea that ice could smother the whole world 260 00:28:41,940 --> 00:28:44,380 seems incomprehensible. 261 00:28:51,500 --> 00:28:54,580 But just over 710 million years ago, 262 00:28:54,580 --> 00:28:58,060 the Earth was a much more vulnerable place, 263 00:28:58,060 --> 00:29:02,900 and when the ice started marching, there was very little to stop it. 264 00:29:08,020 --> 00:29:11,180 We now know just how far it reached. 265 00:29:14,580 --> 00:29:18,100 Look under the leading edge of this icecap 266 00:29:18,100 --> 00:29:22,980 and you can see the evidence of its raw power in the countless 267 00:29:22,980 --> 00:29:27,380 chunks of rock ripped up and dumped by the ice. 268 00:29:31,940 --> 00:29:36,700 Glaciers are so destructive, they leave scars in the rock record. 269 00:29:40,100 --> 00:29:42,460 Like these stones and boulders, 270 00:29:42,460 --> 00:29:46,540 a completely different type or rock to the layers around them. 271 00:29:48,500 --> 00:29:53,420 Called drop stones, the flowing ice picked them up and dropped them 272 00:29:53,420 --> 00:29:56,500 hundreds of kilometres from where they originated. 273 00:29:57,620 --> 00:30:01,900 Scientists have found these in rock layers that were sat over 274 00:30:01,900 --> 00:30:04,900 the equator 700 million years ago... 275 00:30:09,420 --> 00:30:14,500 ..hinting at an event of an astonishing scale and reach. 276 00:30:24,580 --> 00:30:27,140 The ice is winning. 277 00:30:29,980 --> 00:30:33,580 A band of warmth still holds out around the equator... 278 00:30:35,220 --> 00:30:38,220 ..the last refuge for life. 279 00:30:41,340 --> 00:30:44,380 But as the white expanse spreads, 280 00:30:44,380 --> 00:30:48,380 more and more heat is reflected back into space... 281 00:30:50,100 --> 00:30:54,380 ..and the freeze becomes a runaway process. 282 00:30:59,940 --> 00:31:03,780 Ice surges over almost all of the remaining oceans. 283 00:31:09,780 --> 00:31:13,540 Even at the equator, hope slowly fades. 284 00:31:17,700 --> 00:31:22,620 And finally, this last stretch succumbs... 285 00:31:25,420 --> 00:31:29,340 ..leaving the planet a frozen, white marble... 286 00:31:33,340 --> 00:31:38,060 ..floating in the darkness of space. 287 00:31:51,460 --> 00:31:53,620 Ice had claimed the world... 288 00:31:56,220 --> 00:31:58,980 ..in an event known as Snowball Earth. 289 00:32:04,900 --> 00:32:07,100 It's almost impossible to imagine, 290 00:32:07,100 --> 00:32:11,220 but pretty much all of the planet was just like this. 291 00:32:13,340 --> 00:32:17,820 The whole world was plunged into a deep Ice Age, wrapped in sheets 292 00:32:17,820 --> 00:32:23,660 of ice sometimes kilometres thick, choking our land and our oceans. 293 00:32:25,260 --> 00:32:29,060 It was a global winter with no end in sight. 294 00:32:33,460 --> 00:32:35,420 Modelling suggests that it was 295 00:32:35,420 --> 00:32:38,860 minus 70 degrees Centigrade at the poles... 296 00:32:41,060 --> 00:32:44,700 ..that it never got above freezing anywhere on the planet. 297 00:32:46,500 --> 00:32:48,260 It would have been pretty sterile. 298 00:32:51,300 --> 00:32:54,660 It would have stressed or stalled the water cycle. 299 00:33:00,380 --> 00:33:02,820 There would have been little or no evaporation... 300 00:33:04,780 --> 00:33:06,700 ..hence no rain, 301 00:33:06,700 --> 00:33:08,860 no snow, 302 00:33:08,860 --> 00:33:11,340 very few clouds. 303 00:33:11,340 --> 00:33:15,340 If there were clouds, some would have been clouds of carbon dioxide. 304 00:33:19,140 --> 00:33:22,540 This was an incredibly hostile place. 305 00:33:26,740 --> 00:33:30,340 It couldn't have been more different than the beautiful, vibrant, 306 00:33:30,340 --> 00:33:32,740 dynamic planet that we have today. 307 00:33:49,540 --> 00:33:54,060 The triumph of the ice is a disaster for life. 308 00:33:57,500 --> 00:34:01,620 The ocean is almost entirely cut off from the atmosphere. 309 00:34:04,700 --> 00:34:06,580 It's dark, cold. 310 00:34:10,420 --> 00:34:13,900 And the flow of minerals from the land slows to a trickle. 311 00:34:17,260 --> 00:34:19,620 The food web begins to fall apart. 312 00:34:22,580 --> 00:34:25,220 And the predecessors of animal life... 313 00:34:26,700 --> 00:34:27,900 ..falter. 314 00:34:30,620 --> 00:34:33,140 A mass dying is under way. 315 00:34:44,180 --> 00:34:49,060 This was no short cold snap life could easily ride out. 316 00:34:50,060 --> 00:34:53,300 OK, the ice would have waxed and waned a little, 317 00:34:53,300 --> 00:34:57,660 with the changing of the seasons, but the cold persisted, 318 00:34:57,660 --> 00:35:02,420 unending, for millions upon millions of years, 319 00:35:02,420 --> 00:35:04,860 with no hope of release. 320 00:35:23,060 --> 00:35:25,380 I know it looks like a massive, muddy field, 321 00:35:25,380 --> 00:35:30,180 but I'm actually walking on top of a glacier, albeit a dirty one. 322 00:35:31,260 --> 00:35:35,780 And out here, in the biting face of the cold, it's easy to 323 00:35:35,780 --> 00:35:40,780 imagine that the endless winter put pay to complex life on Earth. 324 00:35:41,820 --> 00:35:43,980 But of course, it didn't. Live survived. 325 00:35:43,980 --> 00:35:46,660 You and I are living, breathing proof of that. 326 00:35:46,660 --> 00:35:49,660 But when it comes to looking for the clues that might tell us 327 00:35:49,660 --> 00:35:53,220 how it pulled off its great survival trick, these wild, 328 00:35:53,220 --> 00:35:56,220 frozen places are a top place to look. 329 00:35:59,980 --> 00:36:04,740 You see, even on the exposed top of the glacier, it's possible 330 00:36:04,740 --> 00:36:07,900 to find chinks in the ice's armour, 331 00:36:07,900 --> 00:36:11,220 just big enough for life to exploit. 332 00:36:17,540 --> 00:36:21,380 Here we are. This is what we're looking for. 333 00:36:21,380 --> 00:36:22,900 This, we think, 334 00:36:22,900 --> 00:36:27,740 is very similar to what might have formed way back then. 335 00:36:27,740 --> 00:36:32,220 Some dust blew out onto the glacier, was warmed up by the sun, 336 00:36:32,220 --> 00:36:36,860 it melted the surface of the ice and formed this puddle. 337 00:36:36,860 --> 00:36:42,420 They're called cryoconites, and it's this simple combination of dust 338 00:36:42,420 --> 00:36:47,380 and water which proved to be life's saviour. 339 00:36:47,380 --> 00:36:51,500 Now, I know it doesn't look like much, but this is, in fact, 340 00:36:51,500 --> 00:36:57,300 a beautiful little oasis out here on top of this vast glacier. 341 00:37:04,580 --> 00:37:09,700 Yes, in this one small pool of water, there's abundant 342 00:37:09,700 --> 00:37:15,220 minerals from the dust, and plenty of exposure to the air and sunlight. 343 00:37:17,460 --> 00:37:20,300 As astonishing as it sounds, 344 00:37:20,300 --> 00:37:24,780 that means it's possible to find life 345 00:37:24,780 --> 00:37:27,100 in muddy puddles like this. 346 00:37:31,420 --> 00:37:35,380 The simplest would be single celled algae and bacteria, 347 00:37:35,380 --> 00:37:36,980 but there are others. 348 00:37:36,980 --> 00:37:41,060 These are images that have come from an actual cryoconite. 349 00:37:41,060 --> 00:37:43,940 You've got things like this rotifer here, 350 00:37:43,940 --> 00:37:47,220 and here, our favourite little water bear, the tardigrade. 351 00:37:48,300 --> 00:37:52,020 And they would be feeding on those smaller organisms. 352 00:37:52,020 --> 00:37:55,820 And, all together, a soup here of different animals 353 00:37:55,820 --> 00:37:58,180 and plants in a simple food web. 354 00:37:59,180 --> 00:38:02,780 Now, I've got to tell you, I've seen life in some pretty amazing 355 00:38:02,780 --> 00:38:08,060 places in my time, but the idea that there could be a functional 356 00:38:08,060 --> 00:38:13,500 ecosystem living in a puddle, on top of Europe's largest glacier? 357 00:38:14,860 --> 00:38:17,300 Well, that is quite extraordinary. 358 00:38:20,700 --> 00:38:24,820 It's thought that during Snowball Earth, there would have been 359 00:38:24,820 --> 00:38:28,660 enough patches of exposed rock and land to generate dust. 360 00:38:31,740 --> 00:38:37,580 Not as much dirt as this, but enough to create many similar puddles. 361 00:38:37,580 --> 00:38:42,620 And, what's more, scientists have exposed these tiny oases 362 00:38:42,620 --> 00:38:46,220 in the laboratory to conditions found on Snowball Earth... 363 00:38:48,220 --> 00:38:51,260 ..and the life inside survived. 364 00:39:10,980 --> 00:39:15,900 For no less than 50 million years, 50 million years, that's 365 00:39:15,900 --> 00:39:22,540 a long time, life clung on in such places throughout the deep freeze. 366 00:39:22,540 --> 00:39:27,900 Let's be clear, this was a tough place to exist, 367 00:39:27,900 --> 00:39:31,420 but if life wanted to do more than survive, if it wanted to 368 00:39:31,420 --> 00:39:36,260 flourish, then the Earth would have to escape its icy prison. 369 00:39:47,900 --> 00:39:50,860 There was no easy route out. 370 00:39:52,580 --> 00:39:55,780 The ice prevented almost any change on the planet... 371 00:39:58,900 --> 00:40:00,700 ..with one exception. 372 00:40:09,940 --> 00:40:15,460 Even an endless winter can't stop the planet creating volcanoes. 373 00:40:20,140 --> 00:40:25,700 Each eruption punching through the planet's frozen shell. 374 00:40:35,820 --> 00:40:38,740 Ever since our planet first formed, 375 00:40:38,740 --> 00:40:42,220 the heat in its mantle has fuelled volcanoes. 376 00:40:44,620 --> 00:40:48,580 Today, there are over 1,000 active across the world. 377 00:40:53,220 --> 00:40:56,700 And there would have been at least as many during Snowball Earth. 378 00:41:00,980 --> 00:41:06,140 But even the ferocious heat of all that molten rock was too 379 00:41:06,140 --> 00:41:10,700 fleeting to break the grip of the global Ice Age. 380 00:41:15,900 --> 00:41:20,140 What did offer a slim chance of escape was something else. 381 00:41:23,420 --> 00:41:27,300 Something invisible that came with each eruption. 382 00:41:40,860 --> 00:41:44,620 As each eruption tore through the ice, 383 00:41:44,620 --> 00:41:50,100 it released a great slug of volcanic gases, 384 00:41:50,100 --> 00:41:55,900 including the carbon dioxide stripped from the atmosphere 385 00:41:55,900 --> 00:41:57,500 all those years ago. 386 00:42:05,500 --> 00:42:10,020 With the land and ocean covered in ice, there's nothing to stop 387 00:42:10,020 --> 00:42:14,380 the slow build up of this powerful greenhouse gas. 388 00:42:18,140 --> 00:42:22,460 And it begins to finally bring some warmth to the frozen planet. 389 00:42:34,540 --> 00:42:37,180 The world stood on a knife edge. 390 00:42:38,620 --> 00:42:42,340 If enough carbon dioxide could build up, there was 391 00:42:42,340 --> 00:42:44,260 a chance of breaking the freeze. 392 00:42:47,380 --> 00:42:51,860 What would finally decide the planet's fate is a process 393 00:42:51,860 --> 00:42:54,140 we're all too familiar with today. 394 00:42:59,780 --> 00:43:04,180 This glacier has been melting for the last 130 years, 395 00:43:04,180 --> 00:43:07,100 and the evidence of that melt is all around us. 396 00:43:07,100 --> 00:43:11,140 Look at this vast, glacial lagoon here, full of bergs 397 00:43:11,140 --> 00:43:15,660 and brash ice, and there's meltwater draining out into the sea. 398 00:43:15,660 --> 00:43:17,340 This is global warming. 399 00:43:19,940 --> 00:43:21,820 And the key thing is that this 400 00:43:21,820 --> 00:43:26,580 process has accelerated in the last 30 years. 401 00:43:26,580 --> 00:43:32,060 You see, just as freezing is a runaway process, so too is melting. 402 00:43:40,340 --> 00:43:45,820 Rising temperatures drive more water vapour into the atmosphere. 403 00:43:45,820 --> 00:43:48,340 It has a powerful greenhouse effect. 404 00:43:49,700 --> 00:43:51,900 And, as ice melts, 405 00:43:51,900 --> 00:43:55,900 the exposed dark surfaces absorb yet more warmth from the sun. 406 00:44:00,540 --> 00:44:03,580 Changes like these feed into each other 407 00:44:03,580 --> 00:44:09,180 and create tipping points, beyond which warming becomes explosive. 408 00:44:11,700 --> 00:44:13,900 To limit climate change today, 409 00:44:13,900 --> 00:44:17,180 we must avoid reaching these tipping points. 410 00:44:20,420 --> 00:44:24,620 But for Snowball Earth, they couldn't have come soon enough. 411 00:44:43,460 --> 00:44:45,540 What started as a trickle... 412 00:44:47,980 --> 00:44:49,820 ..has become a torrent. 413 00:45:02,620 --> 00:45:07,300 As the ice starts to melt, the exposed dark surfaces 414 00:45:07,300 --> 00:45:09,780 suck in ever more warmth from the sun. 415 00:45:11,100 --> 00:45:13,660 The melt becomes unstoppable. 416 00:45:16,100 --> 00:45:21,380 A runaway train that releases a staggering deluge of water. 417 00:45:27,020 --> 00:45:30,820 Sea levels rise two metres every decade, 418 00:45:30,820 --> 00:45:34,300 swallowing great chunks of coastline. 419 00:45:39,500 --> 00:45:45,380 After a total of over 50 million gruelling years in deep freeze... 420 00:45:47,180 --> 00:45:49,660 ..the world is finally reborn. 421 00:46:18,900 --> 00:46:23,900 Snowball Earth was an unprecedented assault on our planet. 422 00:46:27,700 --> 00:46:32,460 An astonishing moment that left no corner of the world unscathed. 423 00:46:35,660 --> 00:46:41,580 You and I are here because, through it all, life survived. 424 00:46:46,860 --> 00:46:52,820 But as tenacious as it was, that life was still single-celled 425 00:46:52,820 --> 00:46:57,460 and still trapped in the microscopic world. 426 00:47:02,460 --> 00:47:05,940 But this is more than just a tale of simple survival. 427 00:47:07,620 --> 00:47:12,340 In the shattered remains of the great freeze, the stage was 428 00:47:12,340 --> 00:47:18,700 set for a revolution that would change beyond all recognition. 429 00:47:27,540 --> 00:47:32,060 It's easy to assume that life progresses in a straight line, 430 00:47:32,060 --> 00:47:35,580 steadily becoming more complex, more advanced. 431 00:47:35,580 --> 00:47:41,380 But in reality, it's often not like that. Often it relies upon a great 432 00:47:41,380 --> 00:47:47,380 shock to the system, a state change, to flip life onto another path. 433 00:47:48,940 --> 00:47:53,060 After which, that life and the world in which it lives, 434 00:47:53,060 --> 00:47:54,780 are never the same again. 435 00:47:59,940 --> 00:48:03,380 Snowball Earth was just such a moment. 436 00:48:21,060 --> 00:48:22,700 The ice of the great freeze 437 00:48:22,700 --> 00:48:25,380 had shredded the surface of our planet... 438 00:48:27,700 --> 00:48:31,580 ..ripping up millions upon millions of tons of rock 439 00:48:31,580 --> 00:48:33,460 and dumping it into the oceans. 440 00:48:38,460 --> 00:48:43,300 This sudden flood of resources causes single-celled algae 441 00:48:43,300 --> 00:48:46,580 and bacteria to flourish throughout the waters of the world. 442 00:48:49,620 --> 00:48:53,860 Their vivid blooms so large they're visible from space... 443 00:48:57,060 --> 00:48:59,980 ..stretching across entire oceans. 444 00:49:01,620 --> 00:49:06,420 Growth on such a staggering scale has the power to change 445 00:49:06,420 --> 00:49:08,380 the entire ecosystem. 446 00:49:12,500 --> 00:49:16,060 All this photosynthesising greatly increases 447 00:49:16,060 --> 00:49:18,300 levels of oxygen in the water, 448 00:49:18,300 --> 00:49:21,980 an element vital for complex life. 449 00:49:28,420 --> 00:49:32,540 When the algae and bacteria eventually die, billions upon 450 00:49:32,540 --> 00:49:35,700 billions drift down to the bottom, 451 00:49:35,700 --> 00:49:38,700 a rain of organic matter... 452 00:49:43,460 --> 00:49:47,660 ..adding to millions of years worth of dead things that have built 453 00:49:47,660 --> 00:49:49,700 up over the history of the oceans. 454 00:49:52,940 --> 00:49:56,740 And bacteria living at the bottom of the ocean gorged 455 00:49:56,740 --> 00:49:58,900 themselves on this dead matter... 456 00:50:03,020 --> 00:50:07,460 ..reprocessing it and releasing a steady stream of minerals 457 00:50:07,460 --> 00:50:08,940 back into the water column... 458 00:50:13,740 --> 00:50:19,260 ..giving our ancient ancestors a plentiful, sustained source 459 00:50:19,260 --> 00:50:24,740 of food, oxygen and nutrients, 460 00:50:24,740 --> 00:50:29,140 all supplied by life itself. 461 00:50:43,300 --> 00:50:48,180 At this moment, for the first time ever, life and the planet 462 00:50:48,180 --> 00:50:53,140 come together to become complimentary cogs spinning in 463 00:50:53,140 --> 00:50:58,020 a great nutrient recycling machine, which is providing life with 464 00:50:58,020 --> 00:51:03,100 exactly what it wants in quantities that it's never had before. 465 00:51:03,100 --> 00:51:07,660 And as a consequence, life explodes. 466 00:51:07,660 --> 00:51:12,620 And after around half a billion years of struggle, 467 00:51:12,620 --> 00:51:17,300 Earth's fledgling spring is set to become a glorious summer. 468 00:51:30,820 --> 00:51:36,780 In shallow coastal waters across the planet, life blossoms. 469 00:51:40,260 --> 00:51:45,780 These may look like plants, but they are the first animals. 470 00:51:50,180 --> 00:51:54,220 Leaf-shaped Charnia feed on passing nutrients... 471 00:51:57,460 --> 00:52:00,740 ..whilst Attenborites float freely on the tides. 472 00:52:03,180 --> 00:52:08,940 They're the descendants of those first tiny eukaryote pioneers, 473 00:52:08,940 --> 00:52:13,260 now evolved into myriad strange forms, 474 00:52:13,260 --> 00:52:18,540 all of which have finally broken free of the microscopic world. 475 00:52:20,660 --> 00:52:26,660 These are creatures of a complexity and size that we could see, 476 00:52:26,660 --> 00:52:28,500 could reach out and touch. 477 00:52:30,580 --> 00:52:35,620 All living with, and supported by, an ecosystem 478 00:52:35,620 --> 00:52:40,940 just as intricate and remarkable as any on Earth today. 479 00:52:55,260 --> 00:52:59,660 These first truly complex living creatures 480 00:52:59,660 --> 00:53:01,620 are now long gone. 481 00:53:06,940 --> 00:53:11,100 But they were the first to take this great leap, 482 00:53:11,100 --> 00:53:16,260 and once they had, for life, there was no looking back. 483 00:53:18,020 --> 00:53:23,100 All thanks to Snowball Earth lighting the fuse. 484 00:53:29,700 --> 00:53:33,420 Snowball Earth was an astonishing period, 485 00:53:33,420 --> 00:53:39,500 when life, land and the climate were in conflict like never before. 486 00:53:39,500 --> 00:53:42,620 When that long winter ended, 487 00:53:42,620 --> 00:53:46,940 the stage was set for evolution to run riot. 488 00:53:48,380 --> 00:53:54,300 And finally, it's created all of the fantastic scale, the 489 00:53:54,300 --> 00:54:00,340 remarkable diversity and the amazing beauty of life on Earth today. 490 00:54:24,660 --> 00:54:29,940 How do scientists study the bizarre animal life of the Ediacaran, 491 00:54:29,940 --> 00:54:33,580 which lived more than 500 million years ago? 492 00:54:35,220 --> 00:54:39,540 - So, this is a wonderful fossil from Charnwood Forest in Leicestershire 493 00:54:39,540 --> 00:54:42,980 in the UK, and it was found by schoolchildren in the '50s. 494 00:54:44,700 --> 00:54:47,100 While it looks superficially like a plant, 495 00:54:47,100 --> 00:54:49,940 because it lived in very deep water, we know it can't have lived 496 00:54:49,940 --> 00:54:53,740 off the light, been photosynthetic. Instead, it fed from the little 497 00:54:53,740 --> 00:54:57,860 bacteria and the dissolved organic carbon that were floating past it. 498 00:55:01,180 --> 00:55:03,940 - These creatures are so unusual, 499 00:55:03,940 --> 00:55:07,380 understanding how they interact with each other can be difficult. 500 00:55:15,260 --> 00:55:18,220 Now, thanks to advanced laser technology, 501 00:55:18,220 --> 00:55:21,740 scientists can learn more about them than ever before. 502 00:55:24,500 --> 00:55:26,940 - So, by laser scanning these fossils, we've got 503 00:55:26,940 --> 00:55:31,900 a three-dimensional surface, and what this means is, you have 504 00:55:31,900 --> 00:55:36,380 essentially a snap-shot of Ediacaran life captured on the rock surfaces. 505 00:55:40,220 --> 00:55:44,060 To date, we have over 20,000 fossils that we've laser scanned, 506 00:55:44,060 --> 00:55:47,380 and using different sorts of statistics 507 00:55:47,380 --> 00:55:50,620 and mathematical approaches, we can then work out what 508 00:55:50,620 --> 00:55:54,060 they were doing and how they were interacting with each other. 509 00:55:54,060 --> 00:55:58,580 - And analysing spatial patterns within the scans has revealed 510 00:55:58,580 --> 00:56:01,140 why some of these creatures grew so big. 511 00:56:02,580 --> 00:56:05,780 - For a long time, we thought that the reason they got large 512 00:56:05,780 --> 00:56:09,820 and grew things like stems was to get food without having to compete, 513 00:56:09,820 --> 00:56:14,100 and what we found is that, actually, competition's very, very rare. 514 00:56:14,100 --> 00:56:16,980 Being big wasn't an advantage for getting food, 515 00:56:16,980 --> 00:56:20,260 but what it was an advantage for was ensuring 516 00:56:20,260 --> 00:56:23,180 that your offspring got to go as far as possible, because the taller 517 00:56:23,180 --> 00:56:26,620 you are, the further your offspring will travel in the water column. 518 00:56:28,580 --> 00:56:33,260 - And the scans have also led to the discovery that some organisms 519 00:56:33,260 --> 00:56:34,780 had unexpected behaviours. 520 00:56:36,380 --> 00:56:39,860 - We actually found something rather surprising. They don't always 521 00:56:39,860 --> 00:56:43,860 reproduce sexually. Instead, some of them reproduce little clones 522 00:56:43,860 --> 00:56:46,820 of themselves that are attached by filaments or runners, a bit like 523 00:56:46,820 --> 00:56:50,020 strawberry plants or spider plants, and so the fossils you see are 524 00:56:50,020 --> 00:56:53,540 actually clones of their parents, and even grandparents sometimes. 525 00:56:55,060 --> 00:56:58,620 - After Snowball Earth, the evolution of complex life 526 00:56:58,620 --> 00:57:00,620 occurred at a rate never seen before. 527 00:57:01,900 --> 00:57:05,860 - We've gone from these tiny, microscopic, little fossils, 528 00:57:05,860 --> 00:57:08,740 that we can only see with microscopes, all the way to these 529 00:57:08,740 --> 00:57:14,380 large, complex organisms which show signs of having animal features. 530 00:57:14,380 --> 00:57:17,900 - There's always a possibility that without Snowball Earth, 531 00:57:17,900 --> 00:57:19,860 life wouldn't have evolved into the complex, 532 00:57:19,860 --> 00:57:22,540 large organisms that we see around us today. 533 00:57:24,620 --> 00:57:26,100 - Next time... 534 00:57:28,700 --> 00:57:32,180 The story of how the Earth turned green, 535 00:57:32,180 --> 00:57:35,460 as plants rose from the oceans... 536 00:57:37,940 --> 00:57:40,300 ..to conquer a hostile land... 537 00:57:44,260 --> 00:57:48,860 ..but whose domination almost wiped out all life on the planet. 538 00:57:55,260 --> 00:57:58,060 If the Earth could talk, what would it tell us? 539 00:57:58,060 --> 00:58:01,180 Well, the Open University imagined how it might answer 540 00:58:01,180 --> 00:58:04,980 some of our questions. To experience this interactive presentation, go to 541 00:58:04,980 --> 00:58:08,620 the website on the screen and follow the links to the Open University.