Anthropocene

Based on Wikipedia: Anthropocene

In March 2024, after fifteen years of deliberation, a committee of geologists voted down one of the most ambitious proposals in the history of their field. The question before them was deceptively simple: Should we officially declare that human beings have ended one geological epoch and begun another?

The vote wasn't even close. Twelve to four against, with two abstentions.

But here's the strange thing: the scientists who rejected the proposal didn't disagree that humans have fundamentally altered the planet. They rejected it because the evidence of our impact is too sprawling, too varied, too impossible to pin to a single moment in time. We've changed Earth so thoroughly, in so many ways, across so many centuries, that the geologists couldn't figure out where to draw the line.

What the Anthropocene Actually Means

The word Anthropocene combines two Greek roots: anthropo, meaning human, and cene, meaning new or recent. It's meant to describe a new chapter in Earth's history—one defined not by asteroid impacts or volcanic eruptions or the slow drift of continents, but by us.

Think about what that claim implies. Geological epochs typically last millions of years. The dinosaurs roamed Earth for roughly 165 million years. The epoch we're supposedly replacing—the Holocene—began just 11,700 years ago, when the last ice age ended. That's a blink in geological time. And now we're proposing that humans have ended even that brief chapter and started something new?

The audacity is breathtaking. But so is the evidence.

The Fingerprints We Leave

When future geologists dig through the rocks that are forming right now, they'll find things that have never existed in Earth's 4.5-billion-year history. Plastics that didn't exist before the twentieth century are now embedded in sediments on every continent and in every ocean. Radioactive isotopes from nuclear bomb tests in the 1950s and 1960s have left a distinct chemical signature in ice cores, lake beds, and coral reefs worldwide.

Concrete—that mundane material we barely notice—has become one of the most significant geological deposits of our era. Humans have produced so much of it that if you spread all the concrete ever made evenly across Earth's surface, it would form a layer two millimeters thick over the entire planet.

Then there's the nitrogen. For billions of years, nitrogen cycled through Earth's ecosystems at a relatively steady pace, fixed from the atmosphere by bacteria and lightning, returned through decomposition. In 1909, a German chemist named Fritz Haber figured out how to pull nitrogen directly from the air and convert it into ammonia for fertilizer. Today, humans fix more nitrogen than all natural processes combined. We've doubled the amount of biologically available nitrogen on Earth in less than a century.

The carbon signature is even more dramatic. By burning fossil fuels, we've released carbon that was locked away for hundreds of millions of years, changing the chemical composition of the atmosphere faster than at any point since the asteroid that killed the dinosaurs.

When Did This Begin?

This is where the geologists ran into trouble. To formally define a new epoch, you need what they call a Global Boundary Stratotype Section and Point—mercifully abbreviated as GSSP, and informally called a "golden spike." It's a specific location where you can point to a layer of rock or sediment and say: here. This is where the old epoch ends and the new one begins.

The working group that spent fifteen years studying the Anthropocene eventually proposed Crawford Lake in Ontario, Canada. It's a small, deep lake with unusually still water—so still that sediments settle in undisturbed annual layers, like tree rings. In those layers, you can see a sharp spike in plutonium beginning in 1950, fallout from hydrogen bomb tests. You can see carbon particles from fossil fuel combustion. You can see nitrates from synthetic fertilizers.

The proposed start date was 1950. The first age of the Anthropocene would have been called the Crawfordian.

But other scientists looked at this proposal and saw a problem. Human transformation of Earth didn't begin in 1950. It didn't even begin with the Industrial Revolution.

The Deep Roots of Human Impact

Consider what happened when humans first migrated out of Africa more than 60,000 years ago. Everywhere we went, large animals started disappearing. In Australia, roughly 85 percent of mammals weighing more than 44 kilograms went extinct shortly after humans arrived. In the Americas, the pattern repeated: mammoths, giant ground sloths, saber-toothed cats, all gone within a few thousand years of human arrival.

This wasn't climate change. The climate had fluctuated wildly for millions of years and these species had survived. What was different was us.

Then came agriculture, about 12,000 years ago. Humans began clearing forests, draining wetlands, and reshaping landscapes on a massive scale. Some scientists argue that this is when the Anthropocene really began—when we stopped merely living in ecosystems and started engineering them.

By the time Europeans arrived in the Americas, indigenous peoples had been managing the land for thousands of years through controlled burning, selective planting, and other techniques. When European diseases killed roughly 90 percent of the indigenous population in the sixteenth and seventeenth centuries, so much farmland reverted to forest that it may have affected global climate. Ice core records show atmospheric carbon dioxide and methane dipping to unusual lows around 1610.

One scientist, Vincent Gauci, has even proposed 1592 as the start of the Anthropocene, based on evidence that atmospheric methane reached a minimum that year—possibly because of the catastrophic depopulation of the Americas and the resulting reforestation.

Why the Vote Failed

The geologists who rejected the Anthropocene proposal weren't climate skeptics. They weren't dismissing human impact on the planet. Their objection was more subtle and, in its way, more profound.

The problem, they argued, is that human transformation of Earth is what scientists call "diachronous"—it happened at different times in different places, spreading at different rates. The megafauna extinctions happened tens of thousands of years ago. The agricultural revolution happened twelve thousand years ago. The Industrial Revolution began in England in the late 1700s but didn't reach many parts of the world until the twentieth century. Nuclear fallout is global, but it marks a process of transformation that was already well underway.

Picking 1950 as the start date, they argued, obscures more than it reveals. It makes it seem like human impact on Earth began with the atomic bomb, when in fact we'd been reshaping the planet for millennia. It privileges one kind of evidence—radioactive isotopes—over equally significant transformations like deforestation, species extinction, and soil degradation.

Some of the dissenting scientists proposed an alternative: rather than treating the Anthropocene as an epoch with a definite start date, we should think of it as an ongoing "event"—a transformation comparable to other great transitions in Earth's history.

The Great Oxidation Event

The comparison is illuminating. About 2.4 billion years ago, something happened that makes human climate change look modest. Cyanobacteria—simple photosynthetic organisms—had been releasing oxygen as a waste product for hundreds of millions of years. For a long time, that oxygen reacted with iron and other elements before it could accumulate in the atmosphere. But eventually, the sinks filled up. Oxygen began to build.

For most life on Earth at the time, oxygen was poison. The Great Oxidation Event was a mass extinction on a scale we can barely imagine. But it also made possible all complex life that would follow, including us.

The key point is that the Great Oxidation Event didn't happen on a single day or in a single year. It unfolded over hundreds of millions of years. If we're going to compare human impact to transformations on that scale, maybe we shouldn't expect to pin it to a precise date either.

The Sixth Extinction

Whatever we call this era, one thing is clear: we are living through a mass extinction event. Scientists estimate that current extinction rates are somewhere between 100 and 1,000 times higher than the natural background rate—the rate at which species would be going extinct without human interference.

In 2021, the economist Partha Dasgupta published a review for the UK government concluding that "biodiversity is declining faster than at any time in human history." A 2022 scientific review in the journal Biological Reviews confirmed that we are in the midst of what researchers call the sixth mass extinction.

The previous five mass extinctions were caused by volcanic eruptions, asteroid impacts, and other catastrophic events. This one is caused by habitat destruction, pollution, climate change, overhunting, and invasive species—all driven by human activity. We are the asteroid.

The rate of extinction has been accelerating. It was already elevated above background levels by 1500. It accelerated in the nineteenth century with industrialization. It accelerated again in the twentieth century with population growth and economic expansion. A 2022 study in Frontiers in Ecology traced these patterns in detail.

The Great Acceleration

Scientists have a name for what happened after World War II: the Great Acceleration. Starting around 1950, nearly every measure of human impact on Earth began climbing at unprecedented rates. Population growth. Economic output. Energy consumption. Water use. Fertilizer application. Plastics production. International tourism. The number of McDonald's restaurants.

Plot these trends on a graph and they all show the same pattern: relatively flat lines for most of human history, then a sharp upward bend around the middle of the twentieth century. We went from one billion people in 1800 to two billion in 1930 to eight billion today. Global economic output increased more in the second half of the twentieth century than in all of prior human history combined.

This is what the Anthropocene Working Group was trying to capture with their proposed 1950 start date. Not the first human impact on Earth, but the moment when that impact went exponential.

What Happens Now?

The formal rejection of the Anthropocene epoch proposal doesn't mean the term goes away. As the International Union of Geological Sciences noted in their statement, "Anthropocene will nevertheless continue to be used not only by Earth and environmental scientists, but also by social scientists, politicians and economists, as well as by the public at large. It will remain an invaluable descriptor of human impact on the Earth system."

The term has escaped the geologists. It's become a way of talking about our moment in history, a shorthand for the recognition that we are no longer merely inhabitants of this planet but its dominant force. For better or worse—mostly worse, from the perspective of other species—we have become a geological agent.

The proposal could theoretically be raised again, but it would require starting the entire fifteen-year deliberation process from scratch. Given the divisions among scientists about when the Anthropocene should begin, that seems unlikely to produce a different result.

A Word We Need

The Italian geologist Antonio Stoppani saw it coming. In 1873—before automobiles, before plastics, before nuclear weapons—he wrote about an "anthropozoic era" and acknowledged "the increasing power and effect of humanity on the Earth's systems." Other nineteenth-century geologists proposed terms like "Psychozoic" to describe an age defined by mind, by consciousness, by intention.

The Russian scientist Vladimir Vernadsky developed the concept of the "noosphere"—the sphere of human thought—and in 1938 described "scientific thought as a geological force." Soviet scientists were apparently using the term Anthropocene as early as the 1960s.

But it was the biologist Eugene Stoermer who first coined the word in its current form, sometime in the 1980s. He used it informally, casually, in conversations with colleagues. The term might have remained obscure if not for the atmospheric chemist Paul Crutzen, who independently reinvented it in 2000 and began promoting it aggressively.

Crutzen had won the Nobel Prize for his work on the ozone hole—another way humans have altered the planet's chemistry on a global scale. He saw in the Anthropocene a way to capture the full scope of human impact, not just on climate or biodiversity but on Earth's fundamental systems.

The word caught on because we needed it. We needed a way to name what was happening, to recognize that the relationship between humans and Earth had crossed some kind of threshold. Whether or not it belongs on the official geological time scale, the Anthropocene names something real.

Living in Geological Time

There's something vertiginous about thinking of ourselves as geological actors. Geology operates on timescales so vast that individual human lives are essentially meaningless—brief flickers in an endless dark. A single volcanic eruption can deposit more material than all human construction in history. A single earthquake can release more energy than all the nuclear weapons ever detonated.

And yet. The evidence is clear that we are now operating on that scale. The carbon we're releasing will affect climate for thousands of years. The species we're driving extinct will never return. The plastics we're producing will persist in sediments for millions of years, a permanent record of our brief tenure on this planet.

The Anthropocene, whether or not it becomes an official epoch, forces us to confront a strange truth: we are both insignificant and consequential, brief and permanent, small and world-shaping. We are organisms that evolved to think on timescales of days and years, and we have accidentally become actors on timescales of millennia and eons.

The geologists couldn't agree on when this started because, in a sense, it's always been starting. Every expansion of human population, every new technology, every cleared forest and drained wetland has been part of a single long transformation. The bomb tests of the 1950s didn't begin it. The steam engines of the 1700s didn't begin it. The first farmers didn't begin it. Even the first humans hunting mammoths didn't begin it.

We are still becoming a geological force. The Anthropocene isn't a moment we can point to in the past. It's what we're living through right now.