What Was The Earth Like 1 Billion Years Ago?

Less than a kilometre off the western coast of Scotland, a small, low-lying island languishes in the calm, blue-grey waters of a protected bay. The mid-morning sun gives the heath and grass a velvety smoothness, the calm only punctuated by the bleating of sheep drifting across the narrow stretch to the mainland. It is 1942, the height of the Second World War. There is a flash, and several seconds later a boom crackles and pierces the highland quiet. A faint brown cloud rises and drifts with the prevailing wind, obscuring for a while the crisp island horizon. From the mainland shore, scientists peer at the dispersing stain intently through binoculars, praying silently that the wind will not turn and blow the deadly cloud towards them. For this cloud, now so thinned to be almost invisible, is not smoke or a chemical gas, but a fine, bacterial dust. The bacteria are Bacillus anthracis, and this grignard island is the site of Britain's first and only test of anthrax in biological warfare. Anthrax can be deadly to all mammals, and indeed all 80 sheep left grazing on the island soon perished from the infection. In this sense, the test was a success, proving that anthrax delivered by bomb would be potent enough to lay waste to entire German cities. But while the cloud of brown dust may have been quick to disappear, the bacteria themselves proved more tenacious. Grignard Island was thoroughly contaminated with this deadly microbe, unable to support any mammalian life, either sheep or human. Decades passed with no change to the toxic exclusion zone, with not even the bleating of sheep to disturb the abandoned silence. The island stood alone for 50 years as an extreme unlivable environment within an otherwise green and pleasant modern world. Only after intense campaigning did the government finally take steps to decontaminate the island of its anthrax infestation. But while the soil was made livable again after half a century, the rocks that make up the island and mainland nearby date back to a time when almost the entire globe was a toxic exclusion zone. One billion years ago, there were entire hemispheres where certain life forms simply couldn't survive, with exotic microbes disturbing the status quo. Just as we couldn't live on corrupted Grignard Island, so too would we perish on the billion-year-old earth. A time traveler would find themselves disoriented by shorter days, asphyxiated by a cocktail of noxious gases in the atmosphere, bombarded by ultraviolet rays, and horrified by a hellscape of black, sludgy oceans and barren land. And while Grignard's horrors lasted only 50 years, the earth was condemned for much longer. For one billion years the earth entered a new, geological age. The Neo-Proterozoic. But this is a boundary in name alone, chosen only to mark the passing of a comfortably round number of millions of years. For in reality, the planet is still mired in stasis, a period of tedium that began 800 million years before and is destined to last for another 200 million years. This bizarre chapter of earth's history, affectionately termed the Boring Billion, sees land, ocean, atmosphere and life all stuck in a rut. Nothing changes, nothing revolutionary happens to break the planet out of its toxic slump for a full thousand million years. But at this turn of a new era, all is not as it seems. Grignard Island, once the toxic exception to the habitable rule, was at one time home to a miraculous Neo-Proterozoic paradise. When all else on earth was putrid and hostile, the clouds break to let the sun shine onto a green and pleasant refuge, cradled, protected from the global murk. Tantalising winds of change blow in the Neo-Proterozoic air. Could this be a sign that things are about to change? Is this the answer to the end of the Boring Billion and the beginning of our world? A billion years ago, life lived almost entirely under the ocean, and that diversity has continued to the present day. Head over to our sponsor's CuriosityStream to check out David Attenborough explaining and exploring the bizarre, fascinating world of the deep ocean. Seven miles below the surface in the Mariana Trench, an incredible ecosystem thrives. It's like an alien planet on the surface of the earth. And that's just one of CuriosityStream's more than 3,000 documentaries to choose from. It's like a huge Netflix for So, head over to curiositystream.com forward slash history of the earth to sign up, and using the promo code historyoftheearth will save you 25%, bringing a full year down to $14.99, just over a dollar a month. Thanks. When French explorer Étienne Brûlé set foot on the island of the Minang in the northern reaches of Lake Superior in 1622, he was not the first to do so. Indeed, it was the Native American tribes who had told him of the island and taught him the ways of the lake, which had allowed him to paddle safely to it in the cross-cutting winds and currents. The natives had long used the bays and inlets as fertile fishing grounds, but in thrashing through the wilderness, the Frenchman saw that activity on the island long predated that of his guides. There were mounds and pits, scrapes in the bare surface of the rock, exposing seams and streaks of lurid blue-green, and every now and then, a glimpse of metallic orange. Later explorers gave the natives Minang a new name, Isle Royale, and more thorough investigations of the curious earthworks revealed their remarkable antiquity. These were mines and excavations dating back some four and a half thousand years, to some of the very first indigenous peoples who would colonize the area after the last great ice age. Here, the prehistoric aborigines had uncovered huge and miraculous deposits of pure copper metal within the basaltic rocks, and had worked over hundreds of years to extract it with little more than fire and simple stone tools. The copper had been forged into knives for hunting and jewelry for trading, helping the nameless ancestral natives to secure their dominance within the wilds of America. Isle Royale and the shores of Lake Superior are now known to contain the most important native copper deposits in the world. Copper can be found in huge quantities in its pure metallic form, making it an attractive prospect for miners from prehistoric times to today. And all that copper came to be concentrated around the Great Lake thanks to an event one billion years ago that nearly ripped the American continent… in half. One billion years ago, our planet has already spent three and a half thousand million years under the glow of our sun. The globe's spin has slowed, and now some 18 hours passes between one sunrise and the next. The moon, which for so long has loomed large in the young planet's skies, has robbed the earth of angular momentum to drift imperceptibly further from us with each passing month, and is now just 30,000 miles from its modern position. Every full moon appears as a supermoon in the Neo-Proterozoic. From a molten hellscape, earth has gradually cooled. Crust has formed and differentiated, water has been delivered, concentrated, cycled. Atmospheric gases accumulate and are too cycled by chemistry and the seemingly novel terrestrial innovation, biology. As the maturing sun brightens and warms, it delivers more heat to our world, offsetting the loss of greenhouse gases to the hungry biological and chemical factories. The climate warms and cools in step with internal transformations and feedbacks, bringing icy deserts and tropical storms in equal measure. Air, ocean and land are under a state of constant flux and reconfiguration as plate tectonics, after a stumbling start, now reshapes the surface in earnest. By 1 billion years ago, the majority of the continental crust on earth has assembled into a single, concentrated mass, but spanning both hemispheres as far as the northern and southern sub-arctic. This single supercontinent is Rodinia. Rodinia is merely the latest in a sequence of supercontinents formed when buoyant and long-lasting continental crust comes together and then tears itself apart under the titanic and unstoppable forces of plate tectonics. It follows the first, Columbia, which reigned from the end of the Archean through to the earliest years of the Proterozoic, and it will be followed by Pernosha, Gondwana and Pangaea, but not before the end of the Boring Billion. Large-scale trends suggesting that the But while this may be broadly true, Rodinia itself has not continued unchanged for all this time. Tectonic forces born in the churning interior of the planet do not simply grind to a halt, despite the congested clot of continents on the surface. The ancient terrains that make up the supercontinent slide, shuffle and exploit lines of weakness to try and accommodate the Leviathan molten forces beneath. One of these shuffles saw the ancient continental plate of Laurentia, which contains the bulk of modern North America, collide with the Rio Plateau and Amazonia, which now makes up the heart of South America. This slow-motion collision saw the first subduction of an ancient ocean basin, stretching and bending the crust either side and building crumpled volcanic mountain ranges, very much like the modern-day Andes. In the hearts of the growing mountains, rocks are superheated to change their composition and are folded like so many soft pastry layers. These are the same processes that occur deep below the surface of the modern-day Himalayas. As the Indian subcontinent forces its way into Eurasia, it becomes impossible to say where one continent ends and gives way to the next. This fusing of vast continental masses is known as the Grenville Orogeny, and it occurs along a battlefront that spans the entirety of modern-day North America. The rocks and structures created during these tumultuous ages one billion years ago now persist in a belt that runs from Labrador down to Mexico, in the heart of the Appalachians, the Adirondacks and the Laurentian Mountains of Canada. But there is another surprising remnant of this billion-year-old Redinian reshuffle to be found in the eastern part of America. At a time when the dominant tectonic forces were clear in their intention to fuse Laurentia with its neighbours, other forces were contriving to tear Laurentia itself apart. As the ancient Grenville Ocean is swallowed beneath the Laurentian continent, the oceanic crust at its base sinks deep into the mantle, where it releases water and eventually melts. This new injection of hot material rises until it encounters the base of the continental slab, where it has no choice but to spread out, dragging adjacent parts of overlying continent in opposite directions, with immense friction. And under this continual, relentless pull, the solid rock cracks. A deep and widening tear forms in the landscape, a huge, rift valley, much like the one threatening to rip Ethiopia, Kenya and Tanzania in two in eastern Africa today. Sometimes, cracks form that are large enough to allow molten rock to gush up to the surface, filling the floor of the valley with black, igneous basaltic rocks. But magma doesn't always make it to the open air. It flows into cracks and fills voids deep underground where it is still warm. Here, the igneous cocktail gradually matures and its constituent minerals separate until they can travel independent of the mantle rocks that gave them birth. Forcing their way up through the ever-evolving plumbing system of the rift valley, they deposit treasures of gemstones like amethyst and valuable metals like raw, native copper. This mid-continent rift system was a truly immense rip in the fabric of ancient Laurentia, the largest of its kind to ever threaten the integrity of the long-lived American Craton. Its expansion continued for around 20 million years, and had almost reached the edge of the continent to allow the waters of the global ocean to burst through and fill the rift valley. If they had, then the Grenville Belt and its associated mountains could have been rent violently from the rest of Laurentia. The present-day North American continent would have been reduced to perhaps two-thirds of its current size, with the USA deprived of the entire east coast. Florida to Maine would belong to another continent entirely, or be left adrift as an island on its own, and the American Midwest would be drowned, ripped in two, and relegated to the continental shelves of a new mid-continental ocean. But it was not to be. Before irreparable damage could be done, the forces that fed the nascent rift system suddenly, and decisively, came to an end. This mid-continent rift, that promised so much, simply failed. It never grew any larger, and it never reached the sea, but it did remain as a hole in the heart of the continent, part of which was eventually filled by river water and runoff to form the immense waters of Lake Superior. This lake, the largest freshwater body in the world by surface area, occupies just a fraction of the vast mid-continental rift system. And today, all around its shore, as well as on the Isle Royale, the treasures of the deep can be found. The copper that was once exploited by Native American ancestors owes its existence to the little rift that couldn't, and is a testament to the sheer tectonic power that creaks and So, Laurentia stayed in one piece, suffering only at its edge with the collision and dissimilation of Amazonia and Rio Plateau. On the scale of the entire Rodinian supercontinent, this was little more than a cosmetic adjustment, compared to what could have been had the mid-continent rift sustained. It seems the rut of the Boring Billion is too deep to escape, even with all the tectonic might that the Earth can muster. But the supercontinent is less than half of the global story. There is air and water and life elsewhere on our Neo-Proterozoric world. Could conditions here promise any relief from the monotony? Some 2,000 meters below the shimmering surface of the Black Sea, 80 kilometers from the coast of Bulgaria, a small remote-operated submarine descends in silence. It is dark here, much further than sunlight from the surface can penetrate, and so the little submersible rover must rely on its powerful headlights to document its progress towards the sea floor. A fine rain of dead plankton drifts down around it, shining brightly in the artificial glare, looking just like snow. Otherwise, there is nothing to mark its descent through the blackness. Without warning, the headlights, tilted slightly down, illuminate the sea floor, and the submersible thrusters switch direction, churning up the floating sea snow, in order to keep the craft from ploughing into the deep, smooth ooze. Through its camera lenses, scientists on the sunlit research ship at the surface see what the rover craft sees as it strafes along in sight of the bottom. And before long, their search is rewarded. The velvety silt of the sea floor embraces the unmistakable curve of a ship's bow, and beyond it, the diffuse lamp beam reveals a mast, still standing proudly from a deck, with rowing benches, along with twin rudders at the rear. The wreck of this wooden ship is remarkably well-preserved, it looks like it fell to the bottom of the Black Sea less than a decade ago, but its design betrays a great antiquity. It bears striking resemblance to boats depicted in classical artworks that decorate ancient Greek vases, such as the one that carried Odysseus on his long and eventful voyage. And indeed, when the submersible extracts a splinter of wood for carbon dating, the shipwreck is confirmed to be nearly two and a half thousand years old. This is the oldest intact shipwreck ever discovered, and it owes its remarkable preservation to the unique conditions of the Black Sea. Covering an area of nearly half a million square kilometres, the Black Sea is likely to be so named in English because of the dark colour of its waters, while its name in Greek derives from the phrase inhospitable sea. Many seas around the world are treacherous, but the Black Sea's peril extends deep below the waves. Descend more than about 200 metres, and just when the light begins to run out, so too does the oxygen. More than 90% of the Black Sea's volume is entirely anoxic, excluding anything that needs oxygen to live. In the sea's deep water mass, no fish or seaweed can survive. Only bacteria capable of turning food into energy without oxygen are to be found below in the deepest, darkest depths. It is this immense exclusion zone that allows such intricate shipwrecks to be preserved over millennia. Without oxygen, the kinds of creatures that would normally colonise and destroy the energy-rich wood are kept at bay. The Greek ship, along with more than 60 others spanning the Black Sea's long history, have been pickled and mummified in the black ooze of The unique conditions of the Black Sea basin are possible today because, even while the global ocean is homogenised by the exchange of water between the icy poles and steamy tropics, the Black Sea is shut off from this global mixing bowl by the narrowest of inlets. But one billion years ago, in the Neo-Proterozoic, it was the entire ocean that was subjected to the bizarre anoxic stratification. Without ice at the poles to help mix upper and lower water layers, the vast superocean that spanned the opposite hemisphere to Rodinia stagnated, and oxygen, if it had ever penetrated the abyssal plains, was gradually excluded. This strange chemical situation may be hard to imagine, given that life capable of photosynthesis had almost certainly been on the scene for one and a half billion years, pumping out its waste oxygen into the atmosphere. With photosynthetic organisms spreading around the globe, it would seem straightforward to chart a course from the carbon dioxide-rich, oxygen-poor world of before, to the oxygen-rich, carbon dioxide-poor world of today. Indeed, the air exchanges its chemistry with the ocean, so there had surely been more than enough time for oxygen to accumulate throughout the entire water column. But on a global scale, things are never so straightforward. Before the world could transform into the one we know now, the one that allows the plants, animals and modern day microbes to thrive, it first had to pass through a very ugly, greasy and stinky adolescence. The explosion of photosynthetic organisms in the shallow sunlit waters sees huge quantities of When these floating plankton eventually die, they sink into the dark ocean depths like the marine snow falling through the Black Sea's murk. There, it provides the perfect energy source for scavenger microbes, which decay and consume the organic matter, using up oxygen in the process, just like we digest our food with the help of oxygen we breathe. Thus, what little oxygen makes it into the deeper parts of the ocean is used up, while other bacteria, which don't need oxygen to digest their food, use exotic, metabolic chemistry to get their energy, transforming sulfate into hydrogen sulfide and driving not only anoxic, but sulfur-rich eugzenic conditions worldwide. The result is an eerie dark purple, or even black, superocean that stretches for half the entire globe. These sulfurous deep waters would be deadly to the majority of modern marine life. Even the simple microbes that exist at this time, and which have reigned throughout the oceans for billions of years, now find themselves quarantined to the ocean layers that can support them. Photosynthesis still reigns supreme in the surface waters. The inexhaustible wash of light energy is too bountiful a resource to shirk. But not all that photosynthesis is as we know it. When anoxic waters swell up into the ocean's top 200 sunlit meters, it encourages exotic lifeforms that can make the best of both worlds. Photosynthesis without producing oxygen, and a metabolism without needing it either. This oddly layered ocean, with its native lifeforms isolated among the chemical conditions they can withstand, helps to explain why oxygen levels continue to remain low well into the Neoproterozoic, despite the gas's first appearance 1.5 billion years earlier. Life could survive, but it was hardly a comfortable, boundless existence. Oxygen may have stayed low throughout the Boring Billion and into the Neoproterozoic, but other atmospheric gases, waste products of the exotic chemistry in the ocean, were in healthy abundance. Carbon dioxide levels are lower than they have been since the atmosphere's creation, as it is gobbled up by photosynthesizers and drawn down into seafloor sediments. But its warming effects are more than made up for by other, more potent greenhouse gases. Exotic metabolisms release methane and nitrous dioxide into the air, which help to keep the entire globe about 4 degrees Celsius warmer than today, despite the younger sun being as much as 10% dimmer. Modern day global warming has highlighted the difference that just a few degrees of global temperature can make on the climate, and 1 billion years ago, the impacts of such warmth were no different. The continent of Rodinia spanned the equator, but failed to reach either pole, and without land to stabilize ice sheets, it's unlikely that any ice persisted all year round. Perhaps the dark polar winters would see the ocean freeze over with transient ice, and perhaps temperatures could drop low enough high in the Grenville mountains to allow glaciers and snow-capped ranges to survive. But for the large part, the climate is hot, wet, and very, very energetic. The superocean is a vast breeding ground for tropical storms. As the sun warms the equatorial regions and the potent greenhouse gases lock in that warmth, the surface ocean evaporates, pouring ever more warmth and more energy into the atmosphere. Coriolis forces curl and twist air currents into powerful, self-sustaining whirls that race angrily across the blackened waves, gaining strength with every passing mile. Eventually, with winds that reach several hundred miles an hour, rains that fill the skies with water, and storm surges that inundate the cliff tops, these immense cyclones hurl themselves against the Rodinian shoreline. They continually batter and erode, bringing with them the unmistakable stench of rotten eggs, as hydrogen sulphide from the eugzenic ocean depths is whipped up and into the stormy air, black sludge dredged from the deep. And so, the air and oceans are still, just as disagreeable as the Rodinian continent itself. Desolate land, stinking oceans, steamy, roiling atmosphere all contribute to a Neo-Proterozoic Earth that is no different to the age that has gone before. But, somewhere on this miserable planet, there is a glimmer. It is small, isolated and precarious, but it could just be the Eden from which our habitable world is built anew. On Christmas Day 2021, an Ariane rocket lifted off from the spaceport in French Guiana, carrying with it an extraordinarily expensive and precious payload. The James Webb Space Telescope. In development for over 30 years and costing more than 10 billion dollars, this innovative space telescope promises to herald the next generation of space exploration, using its incredibly sensitive infrared sensors to probe the universe for clues to its birth and evolution. It will study some of the cosmos' earliest moments, charting the lives and deaths of stars and galaxies. And it will probe the atmospheres of exoplanets with unprecedented detail, searching for signs of extraterrestrial life. As the rocket faded into the brightening morning sky, scientists all over the world breathed a cautious sigh of relief. The most perilous stage of its journey was complete. Nearly 1,500 people were involved in the design, build and deployment of the James Webb Space Telescope. But NASA's ranks boast more than 10 times that number. There are the rocket scientists, the engineers, the planetary scientists, the planetary protection officers, and then there are the exobiologists. Film and television usually depict their jobs as glamorous and exciting. Listening to cryptic signals from little green men, or poring over photos from Mars rovers, looking for signs of alien civilisation. Indeed, it will be these exobiologists who will analyse Webb's exoplanet data for the kinds of molecules only life can produce. But most of the time, the exobiologist's job is much more mundane. We have not, to date, discovered life on any planet other than Earth, and so if we hope to find it, or even to know where to look in the vast expanse of space, we must first understand what constrains life. Right here. Where can living things thrive? Where might they eke out a living? Where could they not possibly hang on? And so, a summer afternoon finds a small group of exobiologists on a field trip from NASA Ames, the administration centre in California's Silicon Valley. Their destination is a slough, a river delta turned tidal flat on the state's Pacific coast. As they park up and head out along the braided streams, music from a roadside diner blares out, and the smell of barbecue ribs floats over the faintly stagnant air. It is not the most alien of environments, but it nevertheless has what they are looking for. Close to the water's edge, the soft brown ooze is covered with a woven and tufted mat of green. It is the perfect environment for photosynthetic algae. A flat, stable surface, nice and moist, and continuously exposed to the sun. But thrusting a spade through this yielding biofilm into the compacted sediments beneath reveals a spectacular rainbow of colours. This sedimentary spectrum is created by layers of algae and bacteria, neatly stacked and layered, organised according to their metabolic needs and preferences, Oxygenic photosynthesizers at the top give way to bacteria that still need oxygen, but do not require light. Deeper, where the oxygen from the surface can't penetrate or is all used up, there are myriad anoxygenic forms, each utilising a particular chemical compound, and producing waste products which the bacteria in the lower echelons can use. This colourful hierarchy fills the tidal mudflats out of sight, making best use of every possible geological resource. It is a useful analogy for thinking how life might survive on a nutrient-starved exoplanet. Or indeed, on the neoproterozoic Earth. The billion-year-old ocean may seem like a stinking, toxic waste ground to us, but just like the layered communities of the Californian tidal flats, it is actually an ideal environment in which to breed diversity. Living things persisted on Earth for more than a billion years before the appearance of any oxygen at all, so its scarcity in the deep dark oceans is no great loss. There are still minerals washed from the supercontinent's surface, still nutrients being pumped in via deep hydrothermal vents. There is plenty of energy in the water, if you know how to use it. Complex eukaryotic cells appeared sometime in the last billion years as just such a response to the ocean's frugal living conditions. Every multicellular organism alive on Earth today is a eukaryote, and can trace its ancestry back to a moment, sometime in the early proterozoic, when simpler prokaryotic cells combined in mutual cooperation. Compared with the simple bacterium, eukaryotes are spectacularly complex, containing within them the equivalent of several of their prokaryotic brethren. But these larger cells correspondingly have much higher energy and nutrient requirements, they need more nitrogen and phosphorus to help build their larger and more convoluted cell machinery. And yet these are the compounds that are in shortest supply. So, despite being more efficient and more adaptable to different environments, eukaryotes still find themselves elbowed out of many parts of the stratified ocean. The environment instead favours lifeforms that are able to supply their own nitrogen and phosphorus, like the prokaryotic cyanobacteria. There are still places where eukaryotes can thrive, however, and the relative stasis of the Boring Billion has allowed them to experiment with new forms, new metabolisms, new cellular architecture. Slowly, gradually and hidden in the shadows, eukaryotes are developing the adaptations that will help them dominate and shape the world we see today. Billion-year-old rocks exposed by melting ice retreating from Somerset Island in Arctic Canada reveal exceptionally preserved fossils of remarkable new eukaryotic forms. And these glassy tombs contain more complex cellular forms than have ever been seen on Earth before. Moreover, they are almost identical to the modern-day red algae that can be found colonising the shoreline rocks and tidal flats of Somerset Island and elsewhere. The modern algae is called Bangia, and its fossil counterpart, preserved in intricate detail, is Bangiomorpha. The fossils of Bangiomorpha reveal an association of disc-shaped cells, creating long filaments that are rooted to an ancient surface. They grow upwards to the light, and at their tips they bloom and expand into bulbous masses with many more cells. They look provocatively similar to the fruiting, reproductive bodies of modern-day algae and seaweed. This, paleontologists believe, is evidence of something special happening among these early eukaryotes. It appears that Bangiomorpha has developed an efficient strategy for reproducing sexually. Until now, primitive prokaryotes have reproduced largely through the simple act of cloning. Genetic variation is introduced through mutations, and through a complex trading of genetic material that is totally unrelated to reproduction. But eukaryotes have much more advanced cellular machinery, and so now have the ability and incentive to invent a much more involved reproductive dance. It is less efficient than the prokaryotic way, requiring two parents to make a single offspring, but properly executed it brings with it the possibility of much greater variation, and correspondingly, better adaptation and faster evolution. Today, bacteria may be able to trade the information needed to evade a certain antibiotic, but only sexually reproducing eukaryotes are able to evolve entire new body parts, simply by the recombination of genes in a generation. Sex with the differentiation of gendered forms of a given organism helps Bangiomorpha to innovate faster, to avoid the perils of error-prone cloning, and to stay one step ahead of their prokaryotic brethren. It is the beginning of a glorious, if complicated dance, that will come to define the lives of all eukaryotes, for a billion years. Meanwhile, the Rodinian supercontinent is still barren. Despite a bounty of minerals ripe for the taking in the newly crumpled Grenville mountains and elsewhere, the sun is still a deadly laser, beaming damaging UV rays across the land's surface. There is not yet enough oxygen in the atmosphere to create an effective ozone barrier, and so the only production to be found is beneath water. Since its beginnings in the deep oceans, life has dominated there, but it is not particular about which bodies of water it chooses to colonise. And so, as the earth rotates, a little faster than today, and the sun rises rapidly over the east coast of Rodinia, the morning light washes inland from the shore, slowly suffusing the undulating foothills with a soft, golden glow. And among the pale pastel blush is a piercing highlight, a bright, sinuous gleam as the early sun reflects in a calm, winding river. Higher in the newborn Grenville mountains the shadows linger a little longer, but the shining ribbon pierces the darkness as it winds up, leading the eye eventually to a still, golden pond, a lake nestled among the snow-covered mountain peaks. It is just one of the freshwater Torridon lakes, the sediments of which now make up much of the rocks of the western Scottish coast, including the anthrax-poisoned Grinyard Island. Here it is high enough in altitude and latitude for the lake to freeze over in the winter and re-thaw each summer. It is large enough in area and depth to persist for tens of millions of years. And it is here that we will find the ingredients for remaking our world. The Torridon lakes are completely isolated from the global ocean, and so they are not forced to share its stratified fate. The regular flow of water and the seasonal cooling and warming are enough to keep the lake waters mixed and oxygenated, keeping the stinking hydrogen sulphide at bay. They are more like today's oceans and lakes, even with the low oxygen in the atmosphere, and the mountains that tower over them ensure a plentiful supply of biologically important nitrogen and phosphorus. As a result, these lakes are full of life. The lake microbes' ancestors may have followed the river courses upstream to their new home, or they may have been blown in on the powerful cyclone winds, but once there they found the Torridon lakes to be a veritable Eden. There was so much phosphate in the water that it formed a glassy gel that trapped some of the abundant lifeforms before they could decay away, preserving for a billion years a picture of the remarkable diversity of these isolated lakes. And so, paleontologists have discovered more than 20 species of fossils, from cyanobacterial filaments to larger complex cells with protective outer coverings, and even to tiny scavenger bacteria, hoovering up the spare organic matter that falls to the lake bottom. And there is another new and curious form among them, a fossil that its discoverers have named Bicellum. Like Bangiomorpha in the oceans, it contains different cell types within a single, discrete body. Bicellum has a mass of equidimensional cells packed into a ball, surrounded by a shell of elongated sausage-shaped cells around the outside. Several examples of this species have been recovered, showing variations in the numbers of elongated versus spherical shells around the outside. But in every case, Bicellum retains its spherical shape. This implies that unlike with the algal Bangiomorpha, the change in cell shape doesn't result in the change in shape of the overall organism. The individual cells that make it up must morph and flow over one another to accommodate the growth of certain cells over the others and keep an overall spherical body. The cells themselves must not be rigid, but fluid and flexible, much like the cells that make up our own and every other animal's bodies. And indeed, Bicellum has been interpreted as a multicellular holozoan, a brand new kind of organism that is a stepping stone on the road to true animals. It is a remarkable evolutionary innovation, and one that was potentially only possible in this isolated Eden, far away from the stratified austerity of the global ocean. And so, as the door closes on one chapter of Earth's history and opens onto the Neoproterozoic, change is in the air. There is still a lot of bizarre and unrecognisable chemistry, painting the oceans black and the endless continent red, but this is the last time in Earth's history that our planet would appear quite so alien to us. In an inconspicuous lake behind a snow-covered mountain range, a tiny slice of paradise appears as a flash of golden green. And it is beneath these waters one billion years ago that we can finally glimpse the wonders of complex life that are soon to sweep the globe. You've been watching the entire history of the Earth. 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