The Human Planet: How We Created the Anthropocene

By Simon L. Lewis and Mark A. Maslin

An exploration of the Anthropocene and “a relentless reckoning of how we, as a species, got ourselves into the mess we’re in today” (The Wall Street Journal).

Meteorites, mega-volcanoes, and plate tectonics—the old forces of nature—have transformed Earth for millions of years. They are now joined by a new geological force—humans. Our actions have driven Earth into a new geological epoch, the Anthropocene. For the first time in our home planet's 4.5-billion-year history a single species is increasingly dictating Earth’s future.

To some the Anthropocene symbolizes a future of superlative control of our environment. To others it is the height of hubris, the illusion of our mastery over nature. Whatever your view, just below the surface of this odd-sounding scientific word—the Anthropocene—is a heady mix of science, philosophy, history, and politics linked to our deepest fears and utopian visions.

Tracing our environmental impacts through time, scientists Simon Lewis and Mark Maslin reveal a new view of human history and a new outlook for the future of humanity in the unstable world we have created.

• Language: English
• Publisher: Yale University Press
• Release date: Apr 12, 2022
• ISBN: 9780300243031

Book preview

The Human Planet

SIMON L. LEWIS AND MARK A. MASLIN

The Human Planet

How We Created the Anthropocene

With a New Preface

First published in the United States in 2018 by Yale University Press.

First published in Great Britain in 2018 by Penguin Books Ltd., London.

Original edition first published by Penguin Books Ltd., London.

Text copyright © Simon L. Lewis and Eco-Climate Ltd. 2018.

Preface to the paperback edition copyright © Simon L. Lewis and Eco-Climate Ltd., 2022.

The moral rights of the authors have been asserted.

All rights reserved.

This book may not be reproduced, in whole or in part, including illustrations, in any form (beyond that copying permitted by Sections 107 and 108 of the U.S. Copyright Law and except by reviewers for the public press), without written permission from the publishers.

Yale University Press books may be purchased in quantity for educational, business, or promotional use. For information, please e-mail [e-mail] (U.S. office) or [e-mail] (U.K. office).

Book design by Matthew Young.

Set in 10/14.664 pt Freight Text Pro

Library of Congress Control Number: 2018935049

ISBN 978-0-300-23217-2 (hardcover : alk. paper)

ISBN 978-0-300-26477-7 (paperback)

A catalogue record for this book is available from the British Library.

Contents

LIST OF FIGURES

PREFACE TO THE PAPERBACK EDITION

ACKNOWLEDGEMENTS

INTRODUCTION

The Meaning of the Anthropocene

CHAPTER 1

The Hidden History of the Anthropocene

CHAPTER 2

How to Divide Geological Time

CHAPTER 3

Down from the Trees

CHAPTER 4

Farming, the First Energy Revolution

CHAPTER 5

Globalization 1.0, the Modern World

CHAPTER 6

Fossil Fuels, the Second Energy Revolution

CHAPTER 7

Globalization 2.0, the Great Acceleration

CHAPTER 8

Living in Epoch-Making Times

CHAPTER 9

Defining the Anthropocene

CHAPTER 10

How We Become a Force of Nature

CHAPTER 11

Can Homo dominatus Become Wise?

NOTES

INDEX

List of Figures

2.1 Major biological and geological events in the 4.54 billion-year history of the Earth

2.2 Official Geologic Time Scale for the past 541 million years

2.3 Length of Epochs or Periods over the past half-billion years

3.1 Summary of the main hominin species over the past 7 million years

3.2 Spread of Homo neanderthalensis, Homo erectus and Homo sapiens across the world

3.3 Extinct megafauna from the Americas compared to a human

4.1 Independent centres of plant and animal domestication

4.2 How changes in Earth’s orbit create feedbacks within the climate system

4.3 Historical trends of atmospheric carbon dioxide and methane levels

5.1 Globalization of species

5.2 Eighteenth- and nineteenth-century shipping routes

5.3 Decline in atmospheric carbon dioxide after 1520

6.1 Spread of the Industrial Revolution across Europe

6.2 Locations of sediment cores in which carbonaceous particles have been counted

7.1 Rising global energy consumption, 1830–2010

7.2 Changes to the human component of Earth system between 1900 and 2010

7.3 Changes to the atmosphere of the Earth system between 1900 and 2010

7.4 Changes to the oceans within the Earth system between 1900 and 2010

7.5 Changes to the land surface and biosphere within the Earth system between 1900 and 2010

7.6 The planetary doughnut

8.1 Summary of the major human technological advances and impacts on the Earth system

9.1 Summary of changes to the Earth system and suggested dates or golden spikes to mark the beginning of the Anthropocene Epoch

9.2 Geological records showing globally correlated changes to define the base of the Anthropocene at the 1610 Orbis Spike

9.3 The last 23 million years of the current official Geologic Time Scale and three options to allow the addition of the Anthropocene Epoch

10.1 Positive and negative feedbacks

10.2 How a complex adaptive system moves between two stable states over time

10.3 Summary of the five modes of living

10.4 Modes of living and energy levels

11.1 The undersea cables of the Internet

11.2 Possible carbon dioxide emissions over the twenty-first century

11.3 Fraction of global gross domestic product and population in each continent in 2015

11.4 Future fossil fuel emission pathways

PREFACE TO THE PAPERBACK EDITION

In the worlds of science and ideas, things change. New data become available, new understandings emerge. This preface to the paperback edition provides key updates since the first edition of The Human Planet was published in 2018. We focus on two areas: updates on the science describing the escalating climate crisis, and new ideas about defining the geological time in which we live.

The world experienced many dramatic climate impacts in the northern hemisphere in summer of 2021. In the Pacific Northwest of Canada and the northwestern United States, a heat wave obliterated temperature records, resulting in hundreds of people dying suddenly from heat stress, while a billion shellfish boiled alive in the ocean. In a much less well-documented heat wave in the Middle East, five countries had temperatures exceeding 50°C. The extreme heat reached Pakistan, where in one classroom twenty children fell unconscious and survived only thanks to hospital treatment for heat stress. Extreme heat also affected eastern Europe and Siberia, with the latter reaching temperatures over 30°C. Later in the summer the Mediterranean experienced extreme heat, with Greece and Turkey most affected. In Africa, Madagascar endured the most acute drought seen in forty years, compounded by locust outbreaks, culminating in up to 60 per cent of loss of crops in the hardest-hit areas, and over a million people facing starvation.¹

The intense heat and dry conditions meant record fires. More carbon was released into the atmosphere from forest fires in July 2021 than in any month since satellite records began in 2003. Fires raged across Siberia, Italy, Greece, Turkey, the United States and Canada. In Canada, towns burnt; in Greece, islands were evacuated; and in the Siberian city of Yakutsk, the fires caused record pollution.²

Meanwhile, when it was not dangerously hot, it was dangerously wet. In Germany, homes were swept into rivers, with flooding that led to 184 deaths, after two months’ worth of rain fell in twenty-four hours. The same extreme rainfall led to 200,000 people being advised to evacuate Liège, Belgium. Later in the summer, a year’s worth of rain fell in just three days in Zhengzhou, China. Subway trains flooded, full of people. Dangerous flash floods occurred in both London and New York. Floods have affected parts of East Africa, particularly Ethiopia, Sudan, South Sudan and the Shabelle River basin in Somalia.³

These events are part of long-term trends, as global temperatures rise due to greenhouse gas emissions and as warmer air holds more moisture, meaning that more heat waves and more extreme rainfall events and accompanying flooding are possible. Overall, weather-related disasters have increased by a factor of five over the past fifty years.⁴

The perception of summer began to change in the summer of 2021, from a time of fun and holidays to one of trepidation and increasing danger. Climate concerns were crystallized by the August 2021 publication of the first installment of the Intergovernmental Panel on Climate Change’s (IPCC) Sixth Assessment Report, some seven years since the Fifth Assessment, providing a global update from the world’s scientists on our collective understanding of climate change. Commissioned and agreed to by 196 governments and written by 751 independent scientists from 66 countries, it is a landmark study. The report’s summary, formally agreed by the world’s governments, concludes: ‘It is unequivocal that human influence has warmed the atmosphere, ocean and land. … Widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred. … Many changes due to past and future greenhouse gas emissions are irreversible for centuries to millennia, especially changes in the ocean, ice sheets and global sea level.’ UN Secretary-General Antonio Guterres described the report as ‘code red’ for humanity.⁵

Today, global temperature is 1.1°C above preindustrial levels – a level not seen for more than 100,000 years – and the report confirms that every region in the world has experienced increased impacts of climate change. The IPCC notes that the lower global average surface air temperature target of 1.5°C above preindustrial levels may be breached within the next two decades. It warns that temperature rises above 2.0°C will cause strong and negative impacts on food production across Europe, North and South America, and Africa. Estimates of the greenhouse gas emissions from countries imply warming on the order of 2.5–3°C, which would severely affect food production, greatly increase the number and strength of extreme weather events, and increase water and food insecurity for billions of people.

Clearly, without immediate, rapid and large-scale reductions in greenhouse gas emissions, limiting warming to close to 1.5°C or even 2°C will be beyond reach. Critically, for any temperature, emissions of carbon dioxide must fall to zero, with steep reductions in other greenhouse gases. Any remaining emissions must be neutralized by removing an equivalent amount of carbon from the atmosphere. To meet the 1.5°C goal, we will need to slash year-on-year emissions to net-zero emissions for carbon dioxide by 2050 and reduce emissions of all greenhouse gases to net zero by the late 2060s.

Two reports spell out what this means in terms of policies. First, researchers from University College London showed that for a 50 per cent chance of limiting warming to 1.5°C, 90 per cent of coal must remain in the ground, as well as nearly 60 per cent of oil and gas. Put another way, the International Energy Agency recently modelled reaching net-zero emissions by 2050, outlining 400 milestone actions to decarbonise the world economy in three decades. One action is ensuring no investment in any new extraction of fossil fuels. The IEA also notes that there should be low use of carbon dioxide removal as part of any achievable plan.⁶

Although the outlook for the climate and wider environmental crisis can seem bleak, change is happening. For the first time, the three largest global economic blocs are aligned when it comes to reducing emissions. The European Union has put in place the legal target of reaching net-zero greenhouse gas emissions by 2050. In September 2020, China’s president Xi Jinping announced via video link to the UN General Assembly in New York that his country would reach peak emissions before 2030, within the context of a longterm target to reduce all greenhouse gases to net zero by 2060. At the beginning of 2021, the United States pledged to cut its current emissions in half by 2030 and achieve net-zero greenhouse gases by 2050. These pledges represent progress, but the devil is always in the details. These countries are still working out just how to deliver a net-zero economy, and there are still many other countries yet to set off on the path to greenhouse gas neutrality who will need support and encouragement.

The major hope for a swift global energy transition to renewables is public pressure, regulation and cost. Since the Paris Agreement was signed in December 2015, the market for coal has collapsed. Some 76 per cent of proposed coal-fired power stations have been cancelled since 2015, bringing an end to coal in sight. And in September 2021, China announced that it would not fund coal-fired power stations overseas, which will result in the elimination of a further forty-seven planned coal-fired power stations.⁷

There is also good news on cost: a new report from Oxford University shows that, after accounting for inflation, the costs of fossil fuels, which are subject to large price swings, have not changed in 140 years. By contrast, costs of renewables have been rapidly declining over the past fifty years. The researchers conclude that investing in renewables and retiring costly fossil fuel use can deliver a global net-zero energy system within just twenty-five years, at a saving of trillions of dollars compared to a slower transition.⁸

Looking at the changes to our climate alone strongly suggests we are in a new period of human history. Yet, the much-debated idea of the Anthropocene, the unit of geological time when human actions constitute a force of nature, remains formally undefined. This is just as it was when the first edition of The Human Planet was published. Although there have been no significant breakthroughs from the formal group working on a definition of the Anthropocene – the Anthropocene Working Group – another working group has, to the surprise of the world, newly defined the time we live in.

In 2017, we formally lived in the Holocene Epoch, the warm period that began 11,700 years ago after the last ice age. But now we live not only in the Holocene, but also in a new age – the Meghalayan Age – which began 4,250 years ago.⁹ The ratification of the Meghalayan Age, on 14 July 2018, by the International Union of Geological Sciences confused and angered scientists all around the world.¹⁰ People were expecting an announcement on the Anthropocene Epoch, not the unheard-of Meghalayan Age.

The Holocene Working Group has formally subdivided the Holocene Epoch into three ages. First is the Greenlandian Age, which is from 11,700 to 8,236 years ago; followed by the Northgrippian Age, which lasted until 4,250 years ago; and the Meghalayan Age, which began 4,250 years ago and encompasses the present day.¹¹ What happened behind the scenes was a race between two ‘committees’, with some scientists wedded to the idea of the Holocene and others backing the Anthropocene. The Holocene committee, which has been around longer, has won the first round. The geologists’ competitive committee structure that presides over formalizing geological time is causing rancor and shows no sign of ending soon.

Geologists can formalize novel names for the time in which we live, but they cannot make people use them. The Anthropocene as a term, an idea and a way of thinking is here to stay – adopted by many academic fields, journalists and increasingly the public. It will remain in use, because it is very clear that the world humans have built over decades, centuries and even millennia is not fit for the planet we have now made. The brutal reality of 2021 is that every single achievement of every human society on Earth occurred under a climate that no longer exists. The Anthropocene is here, and how we respond to this new period of human history will have consequences for billions of people and every other life form with which we share this planet.

Simon L. Lewis and Mark A. Maslin, 27 September 2021

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NOTES

1. Canadian Broadcasting Corporation (2021), ‘Seventy percent of sudden deaths recorded during the British Columbia heat wave were due to extreme temperatures, coroner confirms’, 29 July; L. Cecco (2021), ‘ Heat dome probably killed 1bn marine animals on Canada coast, experts say’, Guardian, 8 July; M. Cappuchi (2021), ‘Record heat bakes Middle East as temperatures top 125 degrees’, Washington Post, 7 June; R. Nazir (2021), ‘Heatwave scorches Pakistan, cities record sweltering temperatures’, Xinhua, 11 June; L. M. Lombrana (2021), ‘Record heatwaves are scorching Eastern Europe and Siberia’, Bloomberg Green, 25 June; W. Mathis (2021), ‘Heatwave scorches Mediterranean in latest sign of climate change impacts’, Bloomberg Green, 12 August.

2. J. Watts (2021), ‘Last month was worst July for wildfires on record, say scientists’, Guardian, 6 August; A. Roth (2021), ‘ Everything is on fire: Siberia hit by unprecedented burning’, Guardian, 20 July; World Meteorological Organization (2021), Atlas of Mortality and Economic Losses from Weather, Climate and Water Extremes (1970–2019), Geneva; United Nations Office for the Coordination of Humanitarian Affairs (UN OCHA) (2021), Madagascar Snapshot, July 2021.

3. Die Welt (2021), ‘Hochwasser aktuell: Zahl der Toten in Rheinland-Pfalz steigt auf 135 – Mindestens 184 Opfer durch Flut in Deutschland’, 22 July; M. Cappucci (2021), ‘Eight inches in one hour: How a deadly downpour flooded Zhengzhou, China’, Washington Post, 21 July; H. Sullivan (2021), ‘14 dead in New York region amid historic flooding caused by Ida remnants’, Guardian, 2 September; EU Joint Research Council (2021), Anomaly Hotspots of Agricultural Production (ASAP) Assessment, August 2021.

4. World Meteorological Organization (2021), Atlas of Mortality and Economic Losses from Weather, Climate and Water Extremes (1970–2019).

5. The Intergovernmental Panel on Climate Change’s Sixth Assessment Report Working Group I, Climate Change 2021: The Physical Science Basis, is available at https://www.ipcc.ch/report/ar6/wg1/. The Summary for Policy Makers sets out the main conclusions.

6. D. Welsby et al. (2021), ‘Unextractable fossil fuels in a 1.5°C world’, Nature 597: 230–34; International Energy Agency (2021), Net Zero by 2050: A Roadmap for the Global Energy Sector, 18 May.

7. C. Littlecott et al. (2021), ‘The collapse of the global coal pipeline’, E3G, September 2021; V. Ni (2021), ‘ Big line in the sand: China promises no new coal-fired power projects abroad’, Guardian, 22 September.

8. R. Way et al. (2021), Empirically Grounded Technology Forecasts and the Energy Transition, Oxford University Institute for New Economic Thinking Oxford Working Paper No. 2021-01.

9. All dates are years ago from the year 2000. The Meghalayan Age announcement is available at http://quaternary.stratigraphy.org/iugs-ratifies-holocene-subdivision/.

10. For the controversy, see R. Meyer (2018), ‘Geology’s timekeepers are feuding’, The Atlantic, June 20; M. A. Maslin and S. L. Lewis (2018), ‘Anthropocene vs Meghalayan: Why geologists are fighting over whether humans are a force of nature’, The Conversation, 8 August.

11. The Meghalayan is named after the northeast Indian state of Meghalaya, the location of the Mawmluh Cave housing the speleothem (cave deposits including stalactite and stalagmites) that provide the record of changing drought conditions. The Greenlandian is named after the location of the ice core that defines the Holocene and Greenlandian boundary, and the Northgrippian is named after a scientific project, the North Greenland Ice Core Project, known as NorthGRIP. That these are named after a colonial name of a country and a European scientific project shows how far decolonisation of academia has to go. In our view it would have been better to use the name of the people of Greenland in their language, Kalaallit Nunaat, the KalaallitNunaatian Age, followed by the Greenlandian Age, as this name came later.

ACKNOWLEDGEMENTS

This book is the product of two scientists attempting to make sense of the question: Why is the world like it is today? But the spark was a much narrower question. Back in 2012, one of us (Simon), was worrying about the enormous changes humans have wrought on the planet, while looking at a graph of the ever-rising amount of carbon dioxide in the atmosphere after the Industrial Revolution. A kind of epiphany occurred: the beginning of a new epoch – the Anthropocene – cannot be pinned on carbon dioxide emissions following the Industrial Revolution, as usually argued, since this goes against the basic scientific definition of a geological epoch. Unsure, Simon walked down the corridor to see Mark, who had trained as a marine geologist under the late great stratigraphy expert Nick Shackleton, for a much-needed second opinion. He concurred. And so began our collaboration. We wrote to the leading science journal Nature asking to write an overarching review of the evidence with which to define the Anthropocene, which seemed to be missing from the scientific literature. They agreed, and in 2015 our paper featured on the front cover, gaining worldwide media coverage. Following this, we were asked if we might write a more general book on the Anthropocene, what it is, and what it means for the future of humanity and life on Earth. This is our attempt, having received a great deal of help along the way.

We thank our UCL colleagues Jason Blackstock, Chris Brierley, Anson Mackay, Neil Rose and Chronis Tzedakis, experts from a wide range of fields, Noel Castree, Dipesh Chakrabarty, Erle Ellis, Phil Gibbard, Clive Hamilton, Bruno Latour, Glen Peters and Kathryn Yusoff, plus Julian Mossinger at Nature and UCL PhD student Alex Koch, for sharpening our ideas over the years prior to getting down to writing. Experts read the book, parts of it, or provided other important inputs, as did a number of professional writers. Our sincere thanks to: Merrick Badger, Andrew Barry, Alice Bell, Mary-Elena Carr, Paul Dukes, Jean-Baptiste Fressoz, Dorian Fuller, Garry Glass, Emma Gifford, Ellie Mae O’Hagan, David Harvie, Ellie Julings, Tim Lenton, Charles C. Mann, Oliver Morton, Robert Newman, Ella Ravilious, David Robertshaw, Ben Stewart, Chris Turney and Bob Ward, plus the three anonymous peer reviewers of the book, including two from the Anthropocene Working Group. Also, thanks to Miles Irving for his excellent illustrations. The book is much improved by this input. Any errors in the book are, of course, wholly ours.

We thank our editor, Casiana Ionita at Penguin in London for encouraging us to write in the first place, and Joe Calamia at Yale University Press, our US publisher, for many excellent suggestions. Thanks from Simon also go to the Arvon Centre staff and their science writing course tutors, Michael Brooks and Aarathi Prasad, and classmates Frances Bell, Aylar Farrokhzad, Sam Henry, Ali Manuchehri, Tony Martyr, Paul Moynagh and Peter Stott. Being a student trying to learn a new craft was rewarding, and perhaps more importantly, hopefully some of the lessons have been deployed to good effect in the book. Thanks from Mark also go to Will de Freitas at The Conversation for the many articles that he has kindly commissioned and beautifully edited and in doing so refined and improved Mark’s writing – and of course got us over 1 million reads.

Our greatest thanks are to our families, who have had to put up with us spending even more time in front of a computer screen than usual: Sophie Allain and Laurie May Lewis (born mid-final edits), and Johanna, Alexandra and Abbie Maslin.

INTRODUCTION

The Meaning of the Anthropocene

‘What it lies in our power to do, it lies in our power not to do.’

ARISTOTLE, NICOMACHEAN ETHICS, c. 350 BC

‘The conquest of the earth … is not a pretty thing when you look into it …’

JOSEPH CONRAD, HEART OF DARKNESS, 1899

If you compressed the whole of Earth’s unimaginably long history into a single day, the first humans that look like us would appear at less than four seconds to midnight. From our origins in Africa, we spread and settled on all the continents except Antarctica. Earth now supports 7.5 billion people living, on average, longer and physically healthier lives than at any time in our history. In this brief time we have created a globally integrated network of cultures of immense power.

On this journey we have also exterminated wildlife, cleared forests, planted crops, domesticated animals, released pollution, created new species, and even delayed the next ice age. Although geologically recent, our presence has had a profound impact on our home planet.

We humans are not just influencing the present. For the first time in Earth’s 4.5 billion year history, a single species is increasingly dictating its future. In the past, meteorites, super-volcanoes and the slow tectonic movement of the continents radically altered the climate of Earth and the life-forms that populate it. Now there is a new force of nature changing Earth: Homo sapiens, the so-called ‘wise’ people.

The influence of human actions is more profound than many of us realize. Globally, human activities move more soil, rock and sediment each year than is transported by all other natural processes combined. The total amount of concrete ever produced by humans is enough to cover the entire Earth’s surface with a layer two millimetres thick. We have manufactured so much plastic that it has made its way as tiny fibres into almost all of the water we drink.

We are disrupting the global cycling of the elements necessary for life. Factories and farming remove as much nitrogen from the atmosphere as all Earth’s natural processes do. Since the dawn of the Industrial Revolution we have released 2.2 trillion metric tonnes of carbon dioxide into the atmosphere, increasing levels by 44 per cent. This is acidifying the world’s oceans and raising the Earth’s temperature.

We are also directly changing life on Earth. Today, there are about 3 trillion trees on Earth, down from 6 trillion at the dawn of agriculture. This farmland annually produces 4.8 billion head of livestock and a further 4.8 billion tonnes of our top five crops: sugar cane, maize, rice, wheat and potatoes. We also extract 80 million tonnes of fish a year from the oceans, with another 80 million tonnes being farmed.

Almost every living creature is affected by human actions. Populations of fish, amphibians, reptiles, birds and mammals have declined by an average of 58 per cent over the last forty years. Extinctions are commonplace, running at 1,000 times the typical rate seen before humans walked the Earth. On land, if you weighed all the large mammals on the planet today, just 3 per cent of that mass is living in the wild. The rest is made up of human flesh, some 30 per cent of the total, with domesticated animals that feed us contributing the remaining 67 per cent. In the oceans, low-oxygen dead zones have appeared across 245,000 square kilometres of coastal waters. We live on a human-dominated planet.¹

The implications of these statements are profound. The cumulative impacts of human activity rank alongside other planetary-scale geological events in Earth’s history. And for us, the unusually stable environmental conditions that began about 10,000 years ago, when farming emerged and increasingly complex civilizations developed, are over. We have entered a time of greater variability and extremes, the repercussions of which are only now beginning to be understood. Can humans flourish on a rapidly changing planet, or is the future one of grim survival, or even our own extinction?

Combining the Greek words for ‘humans’ and ‘recent time’, scientists have named this new period of time the Anthropocene. It describes when Homo sapiens became a geological superpower, setting Earth on a new path in its long development. The Anthropocene is a turning point in the history of humanity, the history of life, and the history of the Earth itself. It is a new chapter in the chronicle of life and a new chapter of the human story.

The stakes could not be higher. Yet the idea of the Anthropocene is so immense it can be debilitating. It is hard to comprehend a geological epoch. Each successive epoch in Earth’s history marks an important change to the Earth, usually encoded in the life-forms that live at that time. Epochs typically last for millions of years. It is doubly difficult to grasp the reality of a human epoch. Can we even conceive of environmental changes driven by us that will last longer than our species has existed?

Although many people use the Anthropocene as a synonym for climate change or global environmental change, it is much more than these critical threats. People began to change the planet long ago, and these impacts run deeper than just our use of fossil fuels. And so our responses to living in this new epoch will have to be more far-reaching.

As Naomi Klein said of rapid global climate change: this changes everything.² The Anthropocene embraces even more than this, encapsulating all the immense and far-reaching impacts of human actions on Earth. It says: this changes everything, for ever.

There is no single entity called ‘humanity’ that drives the changes to our home planet: specific groups of people cause each impact. Nevertheless, an analysis of these behaviours raises the question of whether humans, as a particular type of animal, are special. Other species consume resources until natural limits stop that growth – whether food supplies, nesting sites, or some other essential need. With access to vast new resources – think of the uncontrollable growth of bacteria in a Petri dish or an algal bloom in a lake – these communities grow exponentially and then collapse as resources are exhausted.

Although anatomically modern humans had emerged by about 200,000 years ago, it wasn’t until 1804 that our numbers reached one billion. It then took only a single century to pass two billion people. The sixth to seventh billion was added in just twelve years. Over the long run the human population has grown faster than exponentially – the amount of time taken to double the population has been getting shorter – although rates have slowed since the 1960s. Of course, our impacts also relate to what, and how much, people produce and consume. In the past fifty years the global economy increased six-fold, whereas the human population only doubled. The resulting explosion in resource use and environmental impacts is out of all proportion to our numbers. So can the human enterprise, the economy included, continue to expand indefinitely given the vulnerabilities of the land, oceans and atmosphere that constitute our planetary life support system? Can we escape the exponential growth–collapse cycle of other species? Or is the Anthropocene the terminal phase of human development?

This is only one story that acknowledging the Anthropocene can tell. To some a new human epoch symbolizes a future of superlative control of our environment and our destiny. Perhaps we have become a ‘god species’, Homo deus, with the clever deployment of technologies solving our problems. To others a human-driven epoch is the height of hubris, the ultimate folly of the illusion of our mastery over nature. Perhaps we have prodded Earth one too many times and awoken a monster. Whatever our view, just beneath the surface of this odd-sounding scientific name, the Anthropocene, is a heady mix of science, politics, philosophy and religion linked to our deepest fears and utopian visions of what humanity, and the planet we live on, might become.

These are not abstract concerns: the story we choose to tell matters. At one extreme, if the Anthropocene began when people first began using fire or farming crops, environmental change is merely part of the human condition. At the other extreme, if human activity transformed Earth only in recent decades, we need to question the role of technology and the development of consumer capitalism. More concretely, the changes we are making to the planet needs a response. This is because the release of carbon dioxide from fossil fuel use has already pushed Earth outside the 10,000 year period of relatively stable climate. The resulting increasing variability and extremes of weather will increasingly affect people’s health, security and prosperity. What should our response be?

One answer is to stop using fossil fuels. Another could be to use geoengineering – deliberate major interventions in how our planet functions – to stabilize Earth’s climate. But might such intentional large-scale interference with Earth’s natural processes, such as reflecting some of the energy coming from the sun back into space, have severe unintended consequences? Could other solutions that stabilize Earth’s climate, with differing planetary impacts, be better? There are no easy answers, but increasingly society will be confronted with questions like these. Once we recognize ourselves as a force of nature, we will need to address who directs this immense power, and to what ends.

Our home planet functions as a single integrated system: the oceans, atmosphere and land-surface are all interlinked. This ‘Earth system’ can be thought of as consisting of physical, chemical and biological components. The biological component, beginning some 4 billion years ago when life first emerged, has had planet-changing impacts which continue today. First micro-organisms, and later plants have radically altered Earth’s development, with Homo sapiens being a recent biological addition. This book charts the rising environmental impact of this large-brained animal, from our pre-human ancestors to the present day. The chapters proceed chronologically, beginning with the birth of Earth and ending with a look into the future.

The book is based around four main themes integral to the Anthropocene. Firstly, that the environmental changes caused by human activity have increased to a point that today human actions constitute a new force of nature, increasingly determining the future of the only planet known to harbour life. And as in past episodes in Earth’s long history, this new human epoch is captured in Earth’s natural data storage devices, geological sediments, that will become the rocks of the future. These changes and the resulting indelible markings, when carefully compared to past changes in Earth’s history, show that the Anthropocene is a genuinely new and important phase. This is the usual focus for scientific investigations of the Anthropocene.

Yet understanding this new chapter in Earth’s history requires a deeper investigation than merely comparing today’s planetary changes to those of the distant past. The Anthropocene is the interlacing of human history and Earth’s history. To understand the creation of the human-dominated planet we live on, we also need to take a fresh look at our history of changing the environment around us, and the legacy of these changes. As scientists, we re-interpret human history in a new way, looking through the lens of Earth system science.

This brings us to our second theme in the book. As we trace human societies from our march out of East Africa through to today’s globally connected network of cultures, there are four major transitions – a pair relating to patterns of energy use and a pair relating to the scale of human social organization – that fundamentally altered both human societies and our environmental impacts on the Earth system. We call this the ‘human development double two-step’, with each transition leading to ever larger impacts on the Earth system.

Human societies spread worldwide as hunter-gatherers. The first transition, beginning roughly 10,500 years ago, resulted from learning to farm. By domesticating other species to serve human ends people captured more of the sun’s energy. Within a few thousand years foraging had been replaced by agriculture almost everywhere. These farmers transformed landscapes, and over time changed the chemistry of the atmosphere so much that they stabilized Earth’s climate. Serendipitously, farming created environmental conditions across our home planet that were unusually stable. This gave time for large-scale civilizations to develop.

The second of the four transitions was organizational: in the early sixteenth century Western Europeans began colonizing large areas of the rest of the world, creating the first globalized economy. A new world order driven by the search for private profit was born. These new trade routes linked the world as