1 00:00:28,683 --> 00:00:31,338 Just look at that. 2 00:00:31,363 --> 00:00:34,098 It's awesome, isn't it? If not a little terrifying. 3 00:00:36,803 --> 00:00:41,418 A massive tsunami of ice, cascading down the valley. 4 00:00:47,083 --> 00:00:50,458 Try to imagine that, though, not just happening here, 5 00:00:50,483 --> 00:00:53,098 but happening all over the world. 6 00:00:57,763 --> 00:01:00,578 Well, 700 million years ago... 7 00:01:02,563 --> 00:01:05,418 ...that's exactly what did happen. 8 00:01:07,003 --> 00:01:08,858 Ferocious forces... 9 00:01:13,323 --> 00:01:16,058 ...created a climate emergency. 10 00:01:17,963 --> 00:01:23,578 And from pole to pole, across all of the lands and oceans... 11 00:01:25,883 --> 00:01:27,298 ...our world... 12 00:01:29,283 --> 00:01:31,018 .froze. 13 00:01:34,643 --> 00:01:40,298 The story of this extraordinary time is written in the rocks, 14 00:01:40,323 --> 00:01:44,258 and as the latest evidence helps us piece together what happened... 15 00:01:45,643 --> 00:01:49,778 ...we know this disaster hit at the worst possible time. 16 00:01:53,243 --> 00:01:59,258 Just as the earliest forms of animal life were evolving, the ice 17 00:01:59,283 --> 00:02:05,618 threatened to destroy them, and the world as we know it, forever. 18 00:02:15,643 --> 00:02:19,978 The thing is, this moment in our planet's history is also 19 00:02:20,003 --> 00:02:24,978 a story of resilience, because this climatic 20 00:02:25,003 --> 00:02:29,098 and environmental catastrophe lead to something miraculous. 21 00:02:29,123 --> 00:02:33,578 You see, this new life on Earth didn't just survive the ice 22 00:02:33,603 --> 00:02:36,698 and its aftermath, it thrived. 23 00:02:36,723 --> 00:02:41,138 The deep freeze saw a new age on Earth, 24 00:02:41,163 --> 00:02:43,578 an age of complex life, 25 00:02:43,603 --> 00:02:47,818 of a greater size and diversity than ever seen before. 26 00:02:47,843 --> 00:02:50,618 Life that would go on to dominate the oceans 27 00:02:50,643 --> 00:02:53,258 and the land to this very day. 28 00:03:20,163 --> 00:03:23,498 Our story begins in Earth's ancient past... 29 00:03:26,203 --> 00:03:29,538 ...850 million years ago... 30 00:03:37,083 --> 00:03:40,898 ...when the face of our planet was unrecognisable. 31 00:03:47,643 --> 00:03:52,178 Almost all the land that existed was gathered into one, 32 00:03:52,203 --> 00:03:55,858 giant continent, called Rodinia. 33 00:04:05,363 --> 00:04:08,658 Thousands of kilometres, coast to coast, 34 00:04:08,683 --> 00:04:12,458 this rocky landmass dominates the planet. 35 00:04:15,563 --> 00:04:19,178 For all its scale, from its jagged peaks... 36 00:04:22,043 --> 00:04:24,218 ...across its desolate plains... 37 00:04:26,203 --> 00:04:28,458 ...there are no plants 38 00:04:28,483 --> 00:04:30,298 and no animals. 39 00:04:34,523 --> 00:04:36,018 But there is life here. 40 00:04:40,003 --> 00:04:41,818 In shallow, coastal waters... 41 00:04:45,403 --> 00:04:47,258 ...bacteria clump together 42 00:04:47,283 --> 00:04:50,418 into living mats that cover the seafloor. 43 00:04:52,723 --> 00:04:57,778 For nearly three billion years, this has been the limit of life on Earth. 44 00:05:01,323 --> 00:05:06,258 A planet that couldn't be more different from the world we live in. 45 00:05:29,603 --> 00:05:34,058 Even in Iceland, with its harsh winters, so hostile to life... 46 00:05:37,563 --> 00:05:42,618 ...once the warmth returns, so do a host of plants and animals. 47 00:05:45,763 --> 00:05:49,498 It's honestly hard to imagine that up until very recently, 48 00:05:49,523 --> 00:05:54,338 this was a dark, desolate and frigid place, because now look at it. 49 00:05:54,363 --> 00:05:59,098 It's bright, it's busy, it's warm, it's busy with life doing 50 00:05:59,123 --> 00:06:04,058 what it needs to do at this time of year, which is flower and fruit. 51 00:06:04,083 --> 00:06:08,498 And look at this lovely, delicate little harebell here. 52 00:06:09,803 --> 00:06:12,938 And these are the fruits of the crowberry. 53 00:06:14,003 --> 00:06:15,578 And they're meant to be edible. 54 00:06:18,443 --> 00:06:20,098 Best left for the birds. 55 00:06:20,123 --> 00:06:26,298 But aside from the taste, look at that, it's a perfect little package. 56 00:06:26,323 --> 00:06:30,818 It's exquisite. But what interests me more, what's more incredible, 57 00:06:30,843 --> 00:06:36,298 more important, is how this fits into the grander scheme of things. 58 00:06:41,083 --> 00:06:44,378 All the life here has evolved in partnership 59 00:06:44,403 --> 00:06:45,898 with everything around it. 60 00:06:51,403 --> 00:06:57,098 Each individual is just one strand in an intricate web of life. 61 00:06:58,243 --> 00:07:04,338 Every part connected to, and reliant upon, all the others to survive. 62 00:07:08,683 --> 00:07:13,258 Large, complex life in the modern world can only really make it 63 00:07:13,283 --> 00:07:16,898 if it's part of a bigger, interconnected ecosystem, like 64 00:07:16,923 --> 00:07:23,058 this one here, an ecosystem which is as complex as the life it supports. 65 00:07:24,403 --> 00:07:28,378 But the staggering thing is, the truly staggering thing is, 66 00:07:28,403 --> 00:07:33,058 that until recently, none of this existed. 67 00:07:33,083 --> 00:07:36,618 You see, for over four billion years, 68 00:07:36,643 --> 00:07:40,978 that's pretty much our entire planet's existence, large, 69 00:07:41,003 --> 00:07:44,258 intricate life like this was nowhere to be found. 70 00:07:48,363 --> 00:07:52,458 All the animal life that now exists in the world can 71 00:07:52,483 --> 00:07:56,138 trace its origin back to what was happening off the shores 72 00:07:56,163 --> 00:08:01,618 of Rodinia, 850 million years ago. 73 00:08:19,123 --> 00:08:22,458 In the coastal waters, amongst the bacteria, 74 00:08:22,483 --> 00:08:24,738 something new has appeared. 75 00:08:33,723 --> 00:08:37,298 Giant cells tower over the living mats. 76 00:08:41,003 --> 00:08:45,538 These strange microbes are the distant ancestors of animal life. 77 00:08:48,883 --> 00:08:53,258 They're not bacteria, but eukaryotes - bigger, 78 00:08:53,283 --> 00:08:54,778 more complicated... 79 00:08:56,563 --> 00:08:59,658 ...the first cells with a nucleus. 80 00:09:01,603 --> 00:09:07,018 The bacterial mats here get their energy from sunlight, but like 81 00:09:07,043 --> 00:09:11,058 you and me, they eukaryotes rely on food from their surroundings. 82 00:09:14,203 --> 00:09:18,258 And in this basic ecosystem, there were slim pickings, 83 00:09:18,283 --> 00:09:21,098 bacteria floating in the water, 84 00:09:21,123 --> 00:09:25,378 and the slow flow of minerals from the eroding land. 85 00:09:29,843 --> 00:09:32,098 Enough to survive, 86 00:09:32,123 --> 00:09:35,818 but far from what they need to thrive. 87 00:09:44,803 --> 00:09:49,138 These new life forms seem destined to live out a meagre existence 88 00:09:49,163 --> 00:09:50,858 stuck on the sidelines... 89 00:09:52,443 --> 00:09:56,698 ...never able to evolve into the vibrant ecosystems of today. 90 00:09:59,323 --> 00:10:03,778 But the planet was about to deliver a colossal shock to the system... 91 00:10:07,283 --> 00:10:11,058 ...thanks to powerful forces that are still at work today... 92 00:10:13,363 --> 00:10:16,418 ...and can be witnessed in places like Thingvellir, 93 00:10:16,443 --> 00:10:18,298 on the western coast of Iceland. 94 00:10:25,683 --> 00:10:30,978 Walking through here, I get a real sense of raw, primal, 95 00:10:31,003 --> 00:10:36,538 brutal forces at play, and those forces certainly are at play. 96 00:10:36,563 --> 00:10:38,778 You see, every year, 97 00:10:38,803 --> 00:10:44,458 the walls of this chasm move apart by one centimetre. 98 00:10:45,643 --> 00:10:48,258 Now, I know it doesn't sound like much, but that's 99 00:10:48,283 --> 00:10:52,818 because we've got to start thinking about this in geological time, 100 00:10:52,843 --> 00:10:57,578 so that's hundreds of millions of years, not hundreds of years. 101 00:10:57,603 --> 00:11:01,818 The rock beneath my feet is quite literally splitting in two, 102 00:11:01,843 --> 00:11:07,338 along a fracture which runs for thousands of kilometres. 103 00:11:18,603 --> 00:11:21,898 Iceland sits on a boundary between two giant 104 00:11:21,923 --> 00:11:24,658 chunks of the Earth's crust, 105 00:11:24,683 --> 00:11:27,258 known as tectonic plates. 106 00:11:31,843 --> 00:11:35,138 Heat churning within the mantle of our planet 107 00:11:35,163 --> 00:11:37,778 is driving these plates apart. 108 00:11:44,403 --> 00:11:45,698 As they spread... 109 00:11:47,843 --> 00:11:50,458 ...the land above stretches 110 00:11:50,483 --> 00:11:52,338 and then tears... 111 00:11:56,843 --> 00:11:59,658 ...creating great rifts through the landscape. 112 00:12:06,283 --> 00:12:10,818 These forces have been moving the world's greatest landmasses, 113 00:12:10,843 --> 00:12:16,058 creating and destroying them, for more than three billion years, and 114 00:12:16,083 --> 00:12:21,538 nothing can resist them, not even a giant super continent like Rodinia. 115 00:12:29,843 --> 00:12:31,378 Deep beneath Rodinia... 116 00:12:37,723 --> 00:12:43,018 ...swirling currents of heat cause tectonic plates to shift. 117 00:12:52,843 --> 00:12:54,218 They begin to move apart... 118 00:12:57,723 --> 00:13:01,338 ...and great chasms gape open across the landscape. 119 00:13:05,043 --> 00:13:09,938 This great continent is ripping itself apart. 120 00:13:18,083 --> 00:13:22,418 Earth is the only planet in the solar system to have active 121 00:13:22,443 --> 00:13:23,658 tectonic plates. 122 00:13:26,043 --> 00:13:30,938 And they're constantly reshaping our world and its life. 123 00:13:33,723 --> 00:13:37,018 In many ways, we can think of the history of our Earth 124 00:13:37,043 --> 00:13:41,818 as about the interplay between life and geology, 125 00:13:41,843 --> 00:13:44,978 and sometimes, the great planetary process have given life 126 00:13:45,003 --> 00:13:47,138 a bit of a leg up. 127 00:13:47,163 --> 00:13:50,338 On others, they've knocked it right back down again. 128 00:13:50,363 --> 00:13:53,538 One of these moments was about to play out, 129 00:13:53,563 --> 00:13:57,738 and what happened next would ultimately defy the entire 130 00:13:57,763 --> 00:14:00,698 living world that we experience today. 131 00:14:07,323 --> 00:14:10,458 As the rifting continues for millions of years... 132 00:14:14,563 --> 00:14:17,018 ...it creates deep valleys... 133 00:14:19,403 --> 00:14:21,098 ...powerful rivers... 134 00:14:24,123 --> 00:14:26,938 ...and hundreds of kilometres of new coastline... 135 00:14:31,923 --> 00:14:34,818 ...all greatly increasing erosion, 136 00:14:34,843 --> 00:14:40,178 and causing a flood of minerals to pour from the land into the oceans. 137 00:14:52,963 --> 00:14:59,218 Thanks to this boost in minerals, the eukaryote population explodes. 138 00:15:06,043 --> 00:15:08,978 They build numerous colonies, 139 00:15:09,003 --> 00:15:13,778 a crucial step towards forming multi-celled animals. 140 00:15:18,683 --> 00:15:22,138 And some organisms now have enough energy 141 00:15:22,163 --> 00:15:23,858 to produce protective spikes... 142 00:15:26,403 --> 00:15:29,698 ...built from all those minerals washed off the land... 143 00:15:32,443 --> 00:15:34,178 ...and vital defences, 144 00:15:34,203 --> 00:15:39,458 as there were now predators taking advantage of the boom in numbers... 145 00:15:42,243 --> 00:15:45,138 ...in this newly energised ecosystem. 146 00:15:56,003 --> 00:16:01,098 We've witnessed this dramatic change with our own eyes, 147 00:16:01,123 --> 00:16:03,658 thank to recent discoveries made 148 00:16:03,683 --> 00:16:07,858 in 700 million year-old rocks from the Grand Canyon. 149 00:16:12,483 --> 00:16:15,218 Scientists have discovered these... 150 00:16:16,723 --> 00:16:22,578 ...tiny micro-fossils of marine life, each smaller than a grain of sand. 151 00:16:25,563 --> 00:16:29,778 What shocked them were the holes in the outer shell, 152 00:16:29,803 --> 00:16:34,938 most likely created when they were attacked and eaten. 153 00:16:36,403 --> 00:16:39,178 Now, the predators weren't preserved, 154 00:16:39,203 --> 00:16:42,338 but the best guess is that they were something like... 155 00:16:43,563 --> 00:16:44,858 .this... 156 00:16:47,963 --> 00:16:51,938 ...a single celled amoeba called Vampyrella. 157 00:16:54,803 --> 00:16:58,338 This predator punches holes in its victims 158 00:16:58,363 --> 00:17:00,898 before sucking out their inners... 159 00:17:01,963 --> 00:17:05,938 ...leaving behind holes near identical 160 00:17:05,963 --> 00:17:08,618 to those found on the micro-fossils. 161 00:17:17,283 --> 00:17:23,018 This is the earliest evidence of predators and prey ever found. 162 00:17:25,963 --> 00:17:30,898 That element of everyday life, so key to our modern world. 163 00:17:37,803 --> 00:17:42,058 The vast tectonic processes at work provided complex life with 164 00:17:42,083 --> 00:17:43,738 the spark that it needed, 165 00:17:43,763 --> 00:17:47,778 an environmental revolution which allowed it to move towards 166 00:17:47,803 --> 00:17:51,778 the interconnected ecosystems that we see around us today. 167 00:17:52,923 --> 00:17:57,058 But just as life was taking this great leap forwards, 168 00:17:57,083 --> 00:17:59,658 disaster struck. 169 00:17:59,683 --> 00:18:03,698 The forces tearing the ancient super continent apart were about 170 00:18:03,723 --> 00:18:09,858 to plunge the entire world into a seemingly endless, desolate winter. 171 00:18:38,883 --> 00:18:43,018 On Rodinia, events take a catastrophic turn for the worse. 172 00:18:47,203 --> 00:18:51,098 Superheated magma bursts through the surface, 173 00:18:51,123 --> 00:18:54,578 as rifting thins the crust in multiple places. 174 00:18:58,443 --> 00:19:02,098 Molten rock swamps two million square kilometres 175 00:19:02,123 --> 00:19:03,458 of the continent... 176 00:19:05,923 --> 00:19:10,018 ...one of the largest outpourings in Earth's history. 177 00:19:17,563 --> 00:19:21,738 The lava cools and forms the dark rock basalt... 178 00:19:24,003 --> 00:19:28,698 ...creating a vast black stain across the heart of the continent. 179 00:19:31,923 --> 00:19:35,898 You see, the great freeze begins not with ice... 180 00:19:37,603 --> 00:19:38,858 ...but with fire. 181 00:20:04,603 --> 00:20:07,298 Fresh basalt is quite incredible stuff. 182 00:20:07,323 --> 00:20:09,898 This is about ten months old. 183 00:20:09,923 --> 00:20:13,338 Now, it's not terribly easy to walk over, and you certainly 184 00:20:13,363 --> 00:20:15,018 wouldn't want to stumble. 185 00:20:15,043 --> 00:20:19,498 It's extremely jagged, ripping your boots to pieces, 186 00:20:19,523 --> 00:20:22,338 and you wouldn't want to fall on that, would you? 187 00:20:22,363 --> 00:20:26,858 But what's really incredible about this rock is that it has 188 00:20:26,883 --> 00:20:30,658 the capacity to change our planet's atmosphere. 189 00:20:34,643 --> 00:20:39,858 As rain forms, it absorbs carbon dioxide gas from that atmosphere. 190 00:20:45,403 --> 00:20:49,298 When that rain flows over basalt, there's a chemical reaction 191 00:20:49,323 --> 00:20:53,138 that draws carbon dioxide out of the water 192 00:20:53,163 --> 00:20:57,258 and binds it to the surface of the rock, locking it away. 193 00:21:13,363 --> 00:21:18,778 We know that carbon dioxide is a very potent greenhouse gas, 194 00:21:18,803 --> 00:21:23,658 has the capacity to lock lots of heat into our atmosphere, 195 00:21:23,683 --> 00:21:26,658 and the more of it that we pump into the air, 196 00:21:26,683 --> 00:21:30,618 the more we see our global temperatures rising. 197 00:21:30,643 --> 00:21:33,818 But then, I don't need to tell you about global warming. 198 00:21:33,843 --> 00:21:38,018 What's interesting is that the reverse is also true. 199 00:21:38,043 --> 00:21:43,298 If we take carbon dioxide out of the atmosphere, temperatures fall. 200 00:21:46,603 --> 00:21:51,658 The erosion of millions upon millions of tons of basalt, 201 00:21:51,683 --> 00:21:57,378 spewed up when Rodinia broke apart, sucked that warming 202 00:21:57,403 --> 00:22:00,938 blanket of carbon dioxide out of the atmosphere. 203 00:22:03,803 --> 00:22:06,738 And it flicked the Earth's thermostat 204 00:22:06,763 --> 00:22:10,018 from a comfortable stasis to chill. 205 00:22:16,323 --> 00:22:18,618 Falling levels of carbon dioxide... 206 00:22:20,643 --> 00:22:22,458 ...pushed down temperatures... 207 00:22:25,323 --> 00:22:27,418 ...awakening a sinister force. 208 00:22:36,603 --> 00:22:37,898 Ice... 209 00:22:43,083 --> 00:22:46,778 ...something not seen here on the planet for a billion years. 210 00:22:56,403 --> 00:22:59,058 For now, it's limited to the poles. 211 00:23:01,603 --> 00:23:03,698 But it's spreading. 212 00:23:28,643 --> 00:23:33,298 Whether you're a microscopic or more human-sized, 213 00:23:33,323 --> 00:23:35,698 most life loves the warmth... 214 00:23:38,003 --> 00:23:42,218 ...especially here in Iceland, where the winters are so harsh. 215 00:23:45,403 --> 00:23:50,218 Summers here are truly amazing - look how verdant, how green, 216 00:23:50,243 --> 00:23:52,418 how lush it is. 217 00:23:52,443 --> 00:23:55,778 And there's also a tremendous diversity of plants - 218 00:23:55,803 --> 00:23:58,618 flowers, mosses, dwarf trees. 219 00:24:00,163 --> 00:24:05,018 And, of course, on a day like today, blue sky, sunshine - it's lovely. 220 00:24:06,243 --> 00:24:11,418 But the lingering cold of winter is never too far away. 221 00:24:23,883 --> 00:24:26,338 Venture up into that lingering cold... 222 00:24:30,003 --> 00:24:34,178 ...and it's possible to see how life suffers as temperatures fall. 223 00:24:38,123 --> 00:24:42,898 I've only travelled about a mile, but I've climbed in altitude, 224 00:24:42,923 --> 00:24:46,938 and the difference in the landscape is really rather stark. 225 00:24:46,963 --> 00:24:48,898 Look at it. 226 00:24:48,923 --> 00:24:52,178 It's principally barren rock 227 00:24:52,203 --> 00:24:55,218 and the plants here are scattered few and far between. 228 00:24:58,323 --> 00:25:00,778 You see, up here, the temperature only 229 00:25:00,803 --> 00:25:04,338 gets above five degrees Centigrade for a few weeks of the year, 230 00:25:04,363 --> 00:25:06,858 and when the temperature drops below that, 231 00:25:06,883 --> 00:25:10,378 plants can't produce structural tissues. 232 00:25:14,443 --> 00:25:18,938 You can give them all the water, all the nutrients they want, 233 00:25:18,963 --> 00:25:23,538 but at lower temperatures, they just can't build their own bodies. 234 00:25:31,443 --> 00:25:35,458 Across the world, whenever temperatures drop low enough, 235 00:25:35,483 --> 00:25:37,378 for long enough, 236 00:25:37,403 --> 00:25:42,138 plants and life slowly fade away. 237 00:25:45,283 --> 00:25:51,138 Temperature is the natural limiter for complex life in our world, 238 00:25:51,163 --> 00:25:56,418 and those rich, interconnected ecosystems, 239 00:25:56,443 --> 00:26:00,898 which can thrive down there can't even survive up here. 240 00:26:00,923 --> 00:26:04,898 When it gets cold, the web of life unravels. 241 00:26:14,083 --> 00:26:18,738 On the ancient Earth, as temperatures continue to fall, 242 00:26:18,763 --> 00:26:22,738 the cold advances on early life from all sides. 243 00:26:28,523 --> 00:26:32,538 Armadas of sea ice march out from the North and South Poles... 244 00:26:37,403 --> 00:26:41,578 ...as on land, immense glaciers surge forth from the mountains. 245 00:26:46,403 --> 00:26:50,298 The places life can hold on are rapidly shrinking. 246 00:26:55,723 --> 00:27:02,738 The ancient Earth teeters on the edge of a climate catastrophe, 247 00:27:02,763 --> 00:27:05,538 as the ice tightens its grip. 248 00:27:24,763 --> 00:27:29,738 Today, ice covers a tenth of all the land on the planet. 249 00:27:31,923 --> 00:27:34,258 Vast sheets blanket the poles... 250 00:27:39,283 --> 00:27:42,538 ...and the high mountains of all of the continents. 251 00:27:48,163 --> 00:27:53,338 Nearly 10% of Iceland is covered by a single sheet of ice. 252 00:27:59,443 --> 00:28:02,338 The icecap here is vast. 253 00:28:02,363 --> 00:28:06,218 It stretches for 100 kilometres in that direction. 254 00:28:06,243 --> 00:28:11,778 It's 140 kilometres wide and nearly a kilometre thick in some places. 255 00:28:12,883 --> 00:28:16,618 But in the modern world, ice is limited. 256 00:28:16,643 --> 00:28:18,978 It comes to a grinding stop down there. 257 00:28:23,163 --> 00:28:26,538 And that's not just because of human-induced climate change. 258 00:28:28,923 --> 00:28:31,498 The world is simply too warm. 259 00:28:36,723 --> 00:28:41,698 The idea that ice could smother the whole world 260 00:28:41,723 --> 00:28:44,138 seems incomprehensible. 261 00:28:51,283 --> 00:28:54,378 But just over 710 million years ago, 262 00:28:54,403 --> 00:28:57,858 the Earth was a much more vulnerable place, 263 00:28:57,883 --> 00:29:02,658 and when the ice started marching, there was very little to stop it. 264 00:29:07,803 --> 00:29:10,938 We now know just how far it reached. 265 00:29:14,403 --> 00:29:17,898 Look under the leading edge of this icecap 266 00:29:17,923 --> 00:29:22,778 and you can see the evidence of its raw power in the countless 267 00:29:22,803 --> 00:29:27,138 chunks of rock ripped up and dumped by the ice. 268 00:29:31,763 --> 00:29:36,458 Glaciers are so destructive, they leave scars in the rock record. 269 00:29:39,883 --> 00:29:42,258 Like these stones and boulders, 270 00:29:42,283 --> 00:29:46,298 a completely different type or rock to the layers around them. 271 00:29:48,323 --> 00:29:53,218 Called drop stones, the flowing ice picked them up and dropped them 272 00:29:53,243 --> 00:29:56,258 hundreds of kilometres from where they originated. 273 00:29:57,443 --> 00:30:01,658 Scientists have found these in rock layers that were sat over 274 00:30:01,683 --> 00:30:04,658 the equator 700 million years ago... 275 00:30:09,243 --> 00:30:14,258 ...hinting at an event of an astonishing scale and reach. 276 00:30:29,803 --> 00:30:33,338 A band of warmth still holds out around the equator... 277 00:30:35,003 --> 00:30:37,978 ...the last refuge for life. 278 00:30:41,123 --> 00:30:44,178 But as the white expanse spreads, 279 00:30:44,203 --> 00:30:48,138 more and more heat is reflected back into space... 280 00:30:49,923 --> 00:30:54,138 ...and the freeze becomes a runaway process. 281 00:30:59,763 --> 00:31:03,538 Ice surges over almost all of the remaining oceans. 282 00:31:09,603 --> 00:31:13,298 Even at the equator, hope slowly fades. 283 00:31:17,523 --> 00:31:22,378 And finally, this last stretch succumbs... 284 00:31:25,243 --> 00:31:29,098 ...leaving the planet a frozen, white marble... 285 00:31:33,123 --> 00:31:37,818 ...floating in the darkness of space. 286 00:31:51,243 --> 00:31:53,378 Ice had claimed the world... 287 00:31:56,043 --> 00:31:58,738 ...in an event known as Snowball Earth. 288 00:32:04,683 --> 00:32:06,898 It's almost impossible to imagine, 289 00:32:06,923 --> 00:32:10,978 but pretty much all of the planet was just like this. 290 00:32:13,163 --> 00:32:17,618 The whole world was plunged into a deep Ice Age, wrapped in sheets 291 00:32:17,643 --> 00:32:23,418 of ice sometimes kilometres thick, choking our land and our oceans. 292 00:32:25,083 --> 00:32:28,818 It was a global winter with no end in sight. 293 00:32:33,243 --> 00:32:35,218 Modelling suggests that it was 294 00:32:35,243 --> 00:32:38,618 minus 70 degrees Centigrade at the poles... 295 00:32:40,883 --> 00:32:44,458 ...that it never got above freezing anywhere on the planet. 296 00:32:46,283 --> 00:32:48,018 It would have been pretty sterile. 297 00:32:51,123 --> 00:32:54,418 It would have stressed or stalled the water cycle. 298 00:33:00,203 --> 00:33:02,578 There would have been little or no evaporation... 299 00:33:04,563 --> 00:33:06,458 ...hence no rain, 300 00:33:06,483 --> 00:33:08,618 no snow, 301 00:33:08,643 --> 00:33:11,138 very few clouds. 302 00:33:11,163 --> 00:33:15,098 If there were clouds, some would have been clouds of carbon dioxide. 303 00:33:18,963 --> 00:33:22,298 This was an incredibly hostile place. 304 00:33:26,563 --> 00:33:30,098 It couldn't have been more different than the beautiful, vibrant, 305 00:33:30,123 --> 00:33:32,498 dynamic planet that we have today. 306 00:33:49,363 --> 00:33:53,818 The triumph of the ice is a disaster for life. 307 00:33:57,323 --> 00:34:01,378 The ocean is almost entirely cut off from the atmosphere. 308 00:34:04,483 --> 00:34:06,338 It's dark, cold. 309 00:34:10,243 --> 00:34:13,658 And the flow of minerals from the land slows to a trickle. 310 00:34:17,043 --> 00:34:19,378 The food web begins to fall apart. 311 00:34:22,403 --> 00:34:24,978 And the predecessors of animal life... 312 00:34:26,483 --> 00:34:27,658 .falter. 313 00:34:30,403 --> 00:34:32,898 A mass dying is under way. 314 00:34:44,003 --> 00:34:48,818 This was no short cold snap life could easily ride out. 315 00:34:49,883 --> 00:34:53,098 OK, the ice would have waxed and waned a little, 316 00:34:53,123 --> 00:34:57,458 with the changing of the seasons, but the cold persisted, 317 00:34:57,483 --> 00:35:02,178 unending, for millions upon millions of years, 318 00:35:02,203 --> 00:35:04,618 with no hope of release. 319 00:35:22,883 --> 00:35:25,178 I know it looks like a massive, muddy field, 320 00:35:25,203 --> 00:35:29,938 but I'm actually walking on top of a glacier, albeit a dirty one. 321 00:35:31,083 --> 00:35:35,578 And out here, in the biting face of the cold, it's easy to 322 00:35:35,603 --> 00:35:40,538 imagine that the endless winter put pay to complex life on Earth. 323 00:35:41,643 --> 00:35:43,778 But of course, it didn't. Live survived. 324 00:35:43,803 --> 00:35:46,458 You and I are living, breathing proof of that. 325 00:35:46,483 --> 00:35:49,458 But when it comes to looking for the clues that might tell us 326 00:35:49,483 --> 00:35:53,018 how it pulled off its great survival trick, these wild, 327 00:35:53,043 --> 00:35:55,978 frozen places are a top place to look. 328 00:35:59,803 --> 00:36:04,498 You see, even on the exposed top of the glacier, it's possible 329 00:36:04,523 --> 00:36:07,658 to find chinks in the ice's arm our, 330 00:36:07,683 --> 00:36:10,978 just big enough for life to exploit. 331 00:36:17,363 --> 00:36:21,138 Here we are. This is what we're looking for. 332 00:36:21,163 --> 00:36:22,698 This, we think, 333 00:36:22,723 --> 00:36:27,538 is very similar to what might have formed way back then. 334 00:36:27,563 --> 00:36:32,018 Some dust blew out onto the glacier, was warmed up by the sun, 335 00:36:32,043 --> 00:36:36,658 it melted the surface of the ice and formed this puddle. 336 00:36:36,683 --> 00:36:42,218 They're called cryoconites, and it's this simple combination of dust 337 00:36:42,243 --> 00:36:47,178 and water which proved to be life's saviour. 338 00:36:47,203 --> 00:36:51,298 Now, I know it doesn't look like much, but this is, in fact, 339 00:36:51,323 --> 00:36:57,058 a beautiful little oasis out here on top of this vast glacier. 340 00:37:04,403 --> 00:37:09,498 Yes, in this one small pool of water, there's abundant 341 00:37:09,523 --> 00:37:14,978 minerals from the dust, and plenty of exposure to the air and sunlight. 342 00:37:17,243 --> 00:37:20,098 As astonishing as it sounds, 343 00:37:20,123 --> 00:37:24,538 that means it's possible to find life 344 00:37:24,563 --> 00:37:26,858 in muddy puddles like this. 345 00:37:31,243 --> 00:37:35,138 The simplest would be single celled algae and bacteria, 346 00:37:35,163 --> 00:37:36,778 but there are others. 347 00:37:36,803 --> 00:37:40,858 These are images that have come from an actual cryoconite. 348 00:37:40,883 --> 00:37:43,738 You've got things like this rotifer here, 349 00:37:43,763 --> 00:37:46,978 and here, our favourite little water bear, the tardigrade. 350 00:37:48,123 --> 00:37:51,818 And they would be feeding on those smaller organisms. 351 00:37:51,843 --> 00:37:55,578 And, all together, a soup here of different animals 352 00:37:55,603 --> 00:37:57,938 and plants in a simple food web. 353 00:37:59,003 --> 00:38:02,578 Now, I've got to tell you, I've seen life in some pretty amazing 354 00:38:02,603 --> 00:38:07,858 places in my time, but the idea that there could be a functional 355 00:38:07,883 --> 00:38:13,258 ecosystem living in a puddle, on top of Europe's largest glacier? 356 00:38:14,643 --> 00:38:17,058 Well, that is quite extraordinary. 357 00:38:20,523 --> 00:38:24,618 It's thought that during Snowball Earth, there would have been 358 00:38:24,643 --> 00:38:28,418 enough patches of exposed rock and land to generate dust. 359 00:38:31,563 --> 00:38:37,378 Not as much dirt as this, but enough to create many similar puddles. 360 00:38:37,403 --> 00:38:42,418 And, what's more, scientists have exposed these tiny oases 361 00:38:42,443 --> 00:38:45,978 in the laboratory to conditions found on Snowball Earth... 362 00:38:48,003 --> 00:38:51,018 ...and the life inside survived. 363 00:39:10,803 --> 00:39:15,698 For no less than 50 million years, 50 million years, that's 364 00:39:15,723 --> 00:39:22,338 a long time, life clung on in such places throughout the deep freeze. 365 00:39:22,363 --> 00:39:27,698 Let's be clear, this was a tough place to exist, 366 00:39:27,723 --> 00:39:31,218 but if life wanted to do more than survive, if it wanted to 367 00:39:31,243 --> 00:39:36,018 flourish, then the Earth would have to escape its icy prison. 368 00:39:47,683 --> 00:39:50,618 There was no easy route out. 369 00:39:52,403 --> 00:39:55,538 The ice prevented almost any change on the planet... 370 00:39:58,683 --> 00:40:00,458 ...with one exception. 371 00:40:09,763 --> 00:40:15,218 Even an endless winter can't stop the planet creating volcanoes. 372 00:40:19,963 --> 00:40:25,458 Each eruption punching through the planet's frozen shell. 373 00:40:35,603 --> 00:40:38,538 Ever since our planet first formed, 374 00:40:38,563 --> 00:40:41,978 the heat in its mantle has fuel led volcanoes. 375 00:40:44,443 --> 00:40:48,338 Today, there are over 1,000 active across the world. 376 00:40:53,043 --> 00:40:56,458 And there would have been at least as many during Snowball Earth. 377 00:41:00,803 --> 00:41:05,938 But even the ferocious heat of all that molten rock was too 378 00:41:05,963 --> 00:41:10,458 fleeting to break the grip of the global Ice Age. 379 00:41:15,723 --> 00:41:19,898 What did offer a slim chance of escape was something else. 380 00:41:23,243 --> 00:41:27,058 Something invisible that came with each eruption. 381 00:41:40,683 --> 00:41:44,418 As each eruption tore through the ice, 382 00:41:44,443 --> 00:41:49,898 it released a great slug of volcanic gases, 383 00:41:49,923 --> 00:41:55,658 including the carbon dioxide stripped from the atmosphere 384 00:41:55,683 --> 00:41:57,258 all those years ago. 385 00:42:05,323 --> 00:42:09,818 with the land and ocean covered in ice, there's nothing to stop 386 00:42:09,843 --> 00:42:14,138 the slow build up of this powerful greenhouse gas. 387 00:42:17,963 --> 00:42:22,218 And it begins to finally bring some warmth to the frozen planet. 388 00:42:34,323 --> 00:42:36,938 The world stood on a knife edge. 389 00:42:38,443 --> 00:42:42,098 If enough carbon dioxide could build up, there was 390 00:42:42,123 --> 00:42:44,018 a chance of breaking the freeze. 391 00:42:47,203 --> 00:42:51,618 What would finally decide the planet's fate is a process 392 00:42:51,643 --> 00:42:53,898 we're all too familiar with today. 393 00:42:59,603 --> 00:43:03,978 This glacier has been melting for the last 130 years, 394 00:43:04,003 --> 00:43:06,898 and the evidence of that melt is all around us. 395 00:43:06,923 --> 00:43:10,938 Look at this vast, glacial lagoon here, full of bergs 396 00:43:10,963 --> 00:43:15,418 and brash ice, and there's meltwater draining out into the sea. 397 00:43:15,443 --> 00:43:17,098 This is global warming. 398 00:43:19,723 --> 00:43:21,618 And the key thing is that this 399 00:43:21,643 --> 00:43:26,378 process has accelerated in the last 30 years. 400 00:43:26,403 --> 00:43:31,818 You see, just as freezing is a runaway process, so too is melting. 401 00:43:40,163 --> 00:43:45,618 Rising temperatures drive more water vapour into the atmosphere. 402 00:43:45,643 --> 00:43:48,098 It has a powerful greenhouse effect. 403 00:43:49,483 --> 00:43:51,698 And, as ice melts, 404 00:43:51,723 --> 00:43:55,658 the exposed dark surfaces absorb yet more warmth from the sun. 405 00:44:00,363 --> 00:44:03,378 Changes like these feed into each other 406 00:44:03,403 --> 00:44:08,938 and create tipping points, beyond which warming becomes explosive. 407 00:44:11,483 --> 00:44:13,698 To limit climate change today, 408 00:44:13,723 --> 00:44:16,938 we must avoid reaching these tipping points. 409 00:44:20,243 --> 00:44:24,378 But for Snowball Earth, they couldn't have come soon enough. 410 00:44:43,243 --> 00:44:45,298 What started as a trickle... 411 00:44:47,763 --> 00:44:49,578 ...has become a torrent. 412 00:45:02,443 --> 00:45:07,098 As the ice starts to melt, the exposed dark surfaces 413 00:45:07,123 --> 00:45:09,538 suck in ever more warmth from the sun. 414 00:45:10,883 --> 00:45:13,418 The melt becomes unstoppable. 415 00:45:15,923 --> 00:45:21,138 A runaway train that releases a staggering deluge of water. 416 00:45:26,843 --> 00:45:30,618 Sea levels rise two metres every decade, 417 00:45:30,643 --> 00:45:34,058 swallowing great chunks of coastline. 418 00:45:39,323 --> 00:45:45,138 After a total of over 50 million gruelling years in deep freeze... 419 00:45:46,963 --> 00:45:49,418 ...the world is finally reborn. 420 00:46:18,723 --> 00:46:23,658 Snowball Earth was an unprecedented assault on our planet. 421 00:46:27,523 --> 00:46:32,218 An astonishing moment that left no corner of the world unscathed. 422 00:46:35,483 --> 00:46:41,338 You and I are here because, through it all, life survived. 423 00:46:46,683 --> 00:46:52,618 But as tenacious as it was, that life was still single-celled 424 00:46:52,643 --> 00:46:57,218 and still trapped in the microscopic world. 425 00:47:02,283 --> 00:47:05,698 But this is more than just a tale of simple survival. 426 00:47:07,443 --> 00:47:12,138 In the shattered remains of the great freeze, the stage was 427 00:47:12,163 --> 00:47:18,458 set for a revolution that would change beyond all recognition. 428 00:47:27,363 --> 00:47:31,858 It's easy to assume that life progresses in a straight line, 429 00:47:31,883 --> 00:47:35,378 steadily becoming more complex, more advanced. 430 00:47:35,403 --> 00:47:41,178 But in reality, it's often not like that. Often it relies upon a great 431 00:47:41,203 --> 00:47:47,138 shock to the system, a state change, to flip life onto another path. 432 00:47:48,763 --> 00:47:52,818 After which, that life and the world in which it lives, 433 00:47:52,843 --> 00:47:54,538 are never the same again. 434 00:47:59,763 --> 00:48:03,138 Snowball Earth was just such a moment. 435 00:48:20,843 --> 00:48:22,498 The ice of the great freeze 436 00:48:22,523 --> 00:48:25,138 had shredded the surface of our planet... 437 00:48:27,523 --> 00:48:31,338 ...ripping up millions upon millions of tons of rock 438 00:48:31,363 --> 00:48:33,218 and dumping it into the oceans. 439 00:48:38,283 --> 00:48:43,098 This sudden flood of resources causes single-celled algae 440 00:48:43,123 --> 00:48:46,338 and bacteria to flourish throughout the waters of the world. 441 00:48:49,443 --> 00:48:53,618 Their vivid blooms so large they're visible from space... 442 00:48:56,843 --> 00:48:59,738 ...stretching across entire oceans. 443 00:49:01,443 --> 00:49:06,178 Growth on such a staggering scale has the power to change 444 00:49:06,203 --> 00:49:08,138 the entire ecosystem. 445 00:49:12,323 --> 00:49:15,818 All this photosynthesising greatly increases 446 00:49:15,843 --> 00:49:18,058 levels of oxygen in the water, 447 00:49:18,083 --> 00:49:21,738 an element vital for complex life. 448 00:49:28,243 --> 00:49:32,298 When the algae and bacteria eventually die, billions upon 449 00:49:32,323 --> 00:49:35,458 billions drift down to the bottom, 450 00:49:35,483 --> 00:49:38,458 a rain of organic matter... 451 00:49:43,283 --> 00:49:47,418 ...adding to millions of years worth of dead things that have built 452 00:49:47,443 --> 00:49:49,458 up over the history of the oceans. 453 00:49:52,763 --> 00:49:56,498 And bacteria living at the bottom of the ocean gorged 454 00:49:56,523 --> 00:49:58,658 themselves on this dead matter... 455 00:50:02,843 --> 00:50:07,218 ...reprocessing it and releasing a steady stream of minerals 456 00:50:07,243 --> 00:50:08,698 back into the water column... 457 00:50:13,563 --> 00:50:19,018 ...giving our ancient ancestors a plentiful, sustained source 458 00:50:19,043 --> 00:50:24,498 of food, oxygen and nutrients, 459 00:50:24,523 --> 00:50:28,898 all supplied by life itself. 460 00:50:43,123 --> 00:50:47,978 At this moment, for the first time ever, life and the planet 461 00:50:48,003 --> 00:50:52,938 come together to become complimentary cogs spinning in 462 00:50:52,963 --> 00:50:57,818 a great nutrient recycling machine, which is providing life with 463 00:50:57,843 --> 00:51:02,898 exactly what it wants in quantities that it's never had before. 464 00:51:02,923 --> 00:51:07,458 And as a consequence, life explodes. 465 00:51:07,483 --> 00:51:12,418 And after around half a billion years of struggle, 466 00:51:12,443 --> 00:51:17,058 Earth's fledgling spring is set to become a glorious summer. 467 00:51:30,643 --> 00:51:36,538 In shallow coastal waters across the planet, life blossoms. 468 00:51:40,083 --> 00:51:45,538 These may look like plants, but they are the first animals. 469 00:51:50,003 --> 00:51:53,978 Leaf-shaped Charnia feed on passing nutrients... 470 00:51:57,283 --> 00:52:00,498 ...whilst Attenborites float freely on the tides. 471 00:52:03,003 --> 00:52:08,738 They're the descendants of those first tiny eukaryote pioneers, 472 00:52:08,763 --> 00:52:13,058 now evolved into myriad strange forms, 473 00:52:13,083 --> 00:52:18,298 all of which have finally broken free of the microscopic world. 474 00:52:20,483 --> 00:52:26,418 These are creatures of a complexity and size that we could see, 475 00:52:26,443 --> 00:52:28,258 could reach out and touch. 476 00:52:30,403 --> 00:52:35,418 All living with, and supported by, an ecosystem 477 00:52:35,443 --> 00:52:40,698 just as intricate and remarkable as any on Earth today. 478 00:52:55,083 --> 00:52:59,418 These first truly complex living creatures 479 00:52:59,443 --> 00:53:01,378 are now long gone. 480 00:53:06,763 --> 00:53:10,898 But they were the first to take this great leap, 481 00:53:10,923 --> 00:53:16,018 and once they had, for life, there was no looking back. 482 00:53:17,843 --> 00:53:22,858 All thanks to Snowball Earth lighting the fuse. 483 00:53:29,523 --> 00:53:33,218 Snowball Earth was an astonishing period, 484 00:53:33,243 --> 00:53:39,258 when life, land and the climate were in conflict like never before. 485 00:53:39,283 --> 00:53:42,418 When that long winter ended, 486 00:53:42,443 --> 00:53:46,698 the stage was set for evolution to run riot. 487 00:53:48,203 --> 00:53:54,098 And finally, it's created all of the fantastic scale, the 488 00:53:54,123 --> 00:54:00,098 remarkable diversity and the amazing beauty of life on Earth today. 489 00:54:24,483 --> 00:54:29,738 How do scientists study the bizarre animal life of the Ediacaran, 490 00:54:29,763 --> 00:54:33,338 which lived more than 500 million years ago? 491 00:54:35,043 --> 00:54:39,338 So, this is a wonderful fossil from Charnwood Forest in Leicestershire 492 00:54:39,363 --> 00:54:42,738 in the UK, and it was found by schoolchildren in the '50s. 493 00:54:44,523 --> 00:54:46,898 While it looks superficially like a plant, 494 00:54:46,923 --> 00:54:49,738 because it lived in very deep water, we know it can't have lived 495 00:54:49,763 --> 00:54:53,538 off the light, been photosynthetic. Instead, it fed from the little 496 00:54:53,563 --> 00:54:57,618 bacteria and the dissolved organic carbon that were floating past it. 497 00:55:00,963 --> 00:55:03,738 These creatures are so unusual, 498 00:55:03,763 --> 00:55:07,138 understanding how they interact with each other can be difficult. 499 00:55:15,083 --> 00:55:18,018 Now, thanks to advanced laser technology, 500 00:55:18,043 --> 00:55:21,498 scientists can learn more about them than ever before. 501 00:55:24,323 --> 00:55:26,738 So, by laser scanning these fossils, we've got 502 00:55:26,763 --> 00:55:31,698 a three-dimensional surface, and what this means is, you have 503 00:55:31,723 --> 00:55:36,138 essentially a snap-shot of Ediacaran life captured on the rock surfaces. 504 00:55:40,043 --> 00:55:43,858 To date, we have over 20,000 fossils that we've laser scanned, 505 00:55:43,883 --> 00:55:47,178 and using different sorts of statistics 506 00:55:47,203 --> 00:55:50,418 and mathematical approaches, we can then work out what 507 00:55:50,443 --> 00:55:53,858 they were doing and how they were interacting with each other. 508 00:55:53,883 --> 00:55:58,378 And analysing spatial patterns within the scans has revealed 509 00:55:58,403 --> 00:56:00,898 why some of these creatures grew so big. 510 00:56:02,403 --> 00:56:05,578 For a long time, we thought that the reason they got large 511 00:56:05,603 --> 00:56:09,618 and grew things like stems was to get food without having to compete, 512 00:56:09,643 --> 00:56:13,898 and what we found is that, actually, competition's very, very rare. 513 00:56:13,923 --> 00:56:16,778 Being big wasn't an advantage for getting food, 514 00:56:16,803 --> 00:56:20,058 but what it was an advantage for was ensuring 515 00:56:20,083 --> 00:56:22,978 that your offspring got to go as far as possible, because the taller 516 00:56:23,003 --> 00:56:26,378 you are, the further your offspring will travel in the water column. 517 00:56:28,403 --> 00:56:33,018 And the scans have also led to the discovery that some organisms 518 00:56:33,043 --> 00:56:34,538 had unexpected behaviours. 519 00:56:36,203 --> 00:56:39,658 We actually found something rather surprising. They don't always 520 00:56:39,683 --> 00:56:43,658 reproduce sexually. Instead, some of them reproduce little clones 521 00:56:43,683 --> 00:56:46,618 of themselves that are attached by filaments or runners, a bit like 522 00:56:46,643 --> 00:56:49,818 strawberry plants or spider plants, and so the fossils you see are 523 00:56:49,843 --> 00:56:53,298 actually clones of their parents, and even grandparents sometimes. 524 00:56:54,883 --> 00:56:58,418 After Snowball Earth, the evolution of complex life 525 00:56:58,443 --> 00:57:00,378 occurred at a rate never seen before. 526 00:57:01,723 --> 00:57:05,658 We've gone from these tiny, microscopic, little fossils, 527 00:57:05,683 --> 00:57:08,538 that we can only see with microscopes, all the way to these 528 00:57:08,563 --> 00:57:14,178 large, complex organisms which show signs of having animal features. 529 00:57:14,203 --> 00:57:17,698 There's always a possibility that without Snowball Earth, 530 00:57:17,723 --> 00:57:19,658 life wouldn't have evolved into the complex, 531 00:57:19,683 --> 00:57:22,298 large organisms that we see around us today. 532 00:57:24,403 --> 00:57:25,858 Next time... 533 00:57:28,523 --> 00:57:31,938 The story of how the Earth turned green, 534 00:57:31,963 --> 00:57:35,218 as plants rose from the oceans... 535 00:57:37,723 --> 00:57:40,058 ...to conquer a hostile land... 536 00:57:44,083 --> 00:57:48,618 ...but whose domination almost wiped out all life on the planet. 537 00:57:55,083 --> 00:57:57,858 If the Earth could talk, what would it tell us? 538 00:57:57,883 --> 00:58:00,978 Well, the Open University imagined how it might answer 539 00:58:01,003 --> 00:58:04,778 some of our questions. To experience this interactive presentation, go to 540 00:58:04,803 --> 00:58:08,378 the website on the screen and follow the links to the Open University.