Joe & Clair Carnegie / Libyan Soup / Getty

Looming over the new food court of the Smithsonian National Museum of Natural History is one of those creatures so massive and menacing that its mere existence in Earth’s ancient past counsels against time-travel research. It is an accurate, if unbelievable, model of the Megalodon shark—52 feet long, dagger-studded maw agape. These things ate baleen whales and, hovering here above tourists munching on artisanal grain bowls, mindlessly swiping on their phones, Megalodon accuses our modern world of decadence.

“It could have been right here, too,” the NMNH curator and paleontologist Scott Wing told me as we stood at the business end of the shark, peering into the digestive abyss.

“What do you mean?” I said.

“Well, I don’t know what the water depth would have been here, but—”

“Ah,” I understood. He meant that 16 million years ago, when the sea level of planet Earth floated tens of meters higher than today and “Washington, D.C.” was sunk beneath the waves, a Megalodon might have literally occupied the exact same physical space above us. Rumors of this ancient ocean weave under Cleveland Park, in the city’s northwest quadrant, and poke out in unstudied and unloved patches of dirt—thin ribbons of seafloor sediment that themselves sit atop volcanic rocks almost a half-billion years older, with no record of anything that ever happened here in-between.

Wing had reached out to me a few weeks after I wrote an essay that channeled the many conversations I’d had with grumpy geologists and paleontologists in recent years. In it, I was dismissive of the Anthropocene, a proposed new epoch of Earth history that has long since escaped its geoscience origins to become a dimly defined buzzword and, as such (I argued), serves to inflate humanity’s eventual geological legacy to those unfamiliar with deep time.

The past few decades will leave a bizarre boundary in the rocks, I wrote, but the reign of humans will appear as nothing compared with the mountainous stacks of rock that make up the other epochs. Humans are congratulating themselves on an unearned geological legacy before we’ve proved ourselves capable of escaping the next century with our lives. And, besides, most of our proudest creations—whole cities and manufactured landscapes—will be destroyed by the ceaseless destruction of tectonics and erosion.

Similarly, many of the synthetic markers proposed to delineate the Anthropocene, I argued, will not survive the insults of deep time. Human history, though environmentally cataclysmic and sedimentologically interesting, is not usefully described in the terms of a geological epoch on par with a yawning span of time like the Early Cretaceous, an epoch that lasted 600,000 times longer than this newly minted one.

But Wing is on the Anthropocene Working Group, a group of scientists working to define just such an epoch. He hated my essay. In his manner, though, he was extremely nice about it.

It happened that this summer I had joined Wing and his colleagues for a week of camping out in the Bighorn Basin in Wyoming to prospect for tiny teeth and fossil palm fronds, 56 million years old. By day we hiked through rattlesnake country in 100-degree weather. We crawled atop red-clay hillocks on hands and knees looking for relics, and hauled sacks of sediment through the candy-striped badlands to be screenwashed in the Bighorn River—panning for ancient curios. Arrested in this landscape were the remarkable early days of the age of mammals, who were still timorously emerging from under the shadow of vanished giants, amid a world beset by climate chaos. But the record of this age was quickly eroding here. “Someday this will all be the Cretaceous,” one of Wing’s colleagues told me as we surveyed the landscape, referring to the older dinosaur-laden layers hidden beneath us—clays and old bones that would be revealed by erosion in the fullness of time.

In the starlit hours long after fieldwork, when sunburned rockhounds slump deep into camping chairs and beer tastes better than ambrosia, the conversation followed the unhurried pace of the sunset, and shifted languidly like the wind. One night, considering the crumbling rocks before us—which held one of the only fossil records of life on land during a brief 200,000-year-long global-warming spasm—conversation turned to just how little of the globe-spanning artifact of human industrial civilization (amounting to only a few decades of stuff) would remain for geologists of the far future to discover.

All parties, cloaked by now in darkness and entering in and out of the conversation unseen like crickets, generally agreed that one would have to be very lucky indeed to ever find anything like a fossilized city, 100 million years from now. Human activity would more likely pop up in a strange layer of seafloor rock filled with isotopic oddities. After taking another swig of beer I then brazenly proposed that the Anthropocene—in comparison with the epic stacks of sediment that make up the other epochs—was therefore a ridiculous idea. It was subliminally fast in geological terms and, I argued, unless we figured out a way to persist for tens of millions of years, would not leave much in the way of a fossil record at all.

If there had been a record player to scratch, someone would have dutifully scratched it. It was as if I had insulted the very ancestral primates whose teeth we had spent all day plucking from the desert. The reaction to this provocation, especially from Wing, so surprised me that I began to rethink an essay I had just submitted to The Atlantic making similar claims. So, when I got home from Wyoming I sent the piece out to a bunch of geologists and paleontologists to make sure I had my head on straight. When the response came back enthusiastic, I swallowed hard and pressed send on the final draft.

The essay came out. Some geologists loved it. Some hated it. The Anthropocene is an oddball in Earth science. Unlike other settled issues, like climate change, there is no objective data set to point to and say, “Aha, there is an Anthropocene epoch.” It is a stratigraphic unit with minimal stratigraphy, first suggested by an atmospheric chemist, and disliked by many stratigraphers. The Anthropocene is something one can have opinions about—and people do (as I painfully learned on Twitter). Anyway, the article was meant to be provocative. I moved on.

Then the dreaded email from Scott Wing landed in my inbox. He was disappointed. And so I came to the National Museum of Natural History, as if being called into the principal’s office.

In the museum lobby I reunited with Wing, a man who positively exudes kindness and reflection, and nevertheless braced for a chronostratigraphic tongue-lashing. But Wing started on an unexpected note. He wanted to talk about southern Gothic literature.

“For me the essence of a lot of Faulkner is, before you can be something new and different, slavery is always there, the legacy of slavery is not erased, ‘The past is never dead. It’s not even past,’” he said. In Faulkner’s work, memories, the dead, and the inescapable circumstance of ancestry are all as present in the room as the characters who fail to overcome them. Geology similarly destroys this priority of the present moment, and as powerfully as any close reading of Absalom, Absalom! To touch an outcrop of limestone in a highway road cut is to touch a memory, the dead, one’s very heritage, frozen in rock hundreds of millions of years ago—yet still somehow here, present. And because it’s here, it couldn’t have been any other way. This is now our world, whether we like it or not.

The Anthropocene, for Wing, simply states that humans are now a permanent part of this immutable thread of Earth history. What we’ve already done means that there’s no unspoiled Eden to which we could ever return, even if we disappeared from the face of the Earth tomorrow.

“For me that’s what the Anthropocene means. It means: Let us recognize that we have permanently deflected the course of evolution. We have left this pretty much indelible record in sediments that is very comparable to, say, if you were looking around, 100 years after the [dinosaur’s] asteroid—if you were a decent biologist you would say, ‘You know what? Given the rate at which things are blinking out right now, and the way in which systems have changed, I betcha things are never going to be remotely the way they were before.’”

It’s strange to seemingly disagree with someone with whom you agree about everything. In the particulars—the extent to which humans are destroying and have destroyed the living world, and have dramatically warped the chemistry of the oceans and atmosphere—we agreed. The difference was perspective. In my essay I framed these planetary injuries in the context of our geologically brief human history. Severe, yes, but at 75 years old (according to Wing’s group) far, far, far too fast, and stratigraphically insignificant in the long run, to earn its own epoch.

And I assumed, as many do, that the Anthropocene would end when humans did: when an inevitable Yellowstone-style eruption wipes out the last band of climate refugees huddled around the poles in a thousand years, or when a psychotic, utility-maximizing AI—having long since turned the last human resistance fighter into a paper clip—suffers its own terminal blue screen of death. Even if humanity limps on for thousands of years, our time on this Earth will have been supersonic from a geologic perspective. And when the Earth begins its long, long recovery from this strange, technological blitzkrieg in the millions of years to come—and sediment finally begins to stack up in respectable quantities—I presumed that that would be a new epoch. But for Wing the Anthropocene goes on.

Wing and his colleagues want us to look further. Despite the “Anthropo” in Anthropocene, the new epoch is not, by his lights, synonymous with the reign of humans, or the patina of technological baubles we’ve left on Earth’s surface, or under it. If we wipe ourselves out tomorrow it will still be the Anthropocene a million years from now, even if very little of our works remain.

“I could see the subtext of what you were writing, and I was thinking, ‘Well, I completely agree,’ but that’s not the way to look at this,” he said. In my essay I made hackneyed reference to Percy Bysshe Shelley’s “Ozymandias,” that evergreen parable about the hubris of civilization. “A sort of Ozymandian vision of the Anthropocene is in my view exactly wrong. It’s exactly the opposite of what the Anthropocene means to me.”

Where, in my essay, I emphasized the potential transience of civilization, Wing and colleagues on the Anthropocene Working Group emphasize the eternal mark left on the biosphere, whether our civilization is transient or not. This, they argue, is the Anthropocene.

“It doesn’t stake out a hopeful future and it doesn’t stake out a catastrophic future,” Wing said.  “It just says that if you want to be a sentient species you have to reckon with the degree to which you have already changed things.”

And that change—whether through tens of thousands of years of human-driven extinctions, our spreading of invasive species across the face of the Earth, converting half of its land surface to farmland, or warming the planet and souring the seas—is undoubtedly profound.

But such dramatic changes don’t always define epochs in the rock record. True, the asteroid at the end of the Cretaceous and the chaotic rocks it left behind mark both the instantaneous end of the age of dinosaurs and the beginning of the 10-million-year-long Paleocene epoch—the beginning of the age of mammals. And it is a decent (if, to this point, still far more devastating) analogue to humanity’s lightning-fast impact on the living world. But consider the disruption inflicted on the planet by the rise of land plants more than 300 million years earlier. In the Paleozoic, land plants conquered the continents and geoengineered the planet, possibly contributing to, or even causing, at least 10 extinction pulses over 25 million years, including one of the worst mass extinctions in Earth history. Land plants profoundly and permanently altered Earth’s geochemical cycles, underwrote the flourishing of all subsequent life on land, and might have sequestered so much carbon dioxide that they kicked off a 90-million-year ice age.

“The evolution and spread of land plants across the Earth was far greater than the human impact ever will be, and I don’t see any drive to define a [stratigraphic] unit based on that,” said Stan Finney, the outgoing chair of the International Commission on Stratigraphy, the governing body decides what is and isn’t an epoch. Finney famously dislikes the idea of the Anthropocene, referring to it as “the few millimeters of sediment deposited since 1945.”

“Isn’t the [Anthropocene] anthropocentric?” he asked at the 2015 Geological Society of America annual meeting, proposing instead that we recognize the term on the same footing as “the Renaissance,” rather than bestow it with the official sanction of geology.

Wing thinks the criticism by Finney and others misses the point. Yes, geology—a field that has developed over centuries, and has accumulated rules, and rules of thumb, as haphazardly as keepsakes in an attic—is inconsistent. There isn’t some Platonic “epoch” out there waiting to be cross-referenced with the various layers of Earth’s rocks. This is because naming units of sediment is a fundamentally human endeavor. We decide what to emphasize, and Earth history gets divided up insofar as such divisions are useful or important to scientists, and to the broader public.

“What motivates me, I confess, is not my concern for future geologists but my belief that this is philosophically a good thing to do because it makes people think about something that they otherwise wouldn’t think about,” Wing said. “I hear this idea from some of my colleagues that science is just supposed to keep its nose to the grindstone. But … like it or not, we are a pimple on the butt of society that’s supposed to do the thinking in some areas. And that places an obligation on us. If you back away from that obligation you’re not being a better scientist; you’re being a worse scientist.”

Ten million years from now, humans went extinct—give or take a few thousand years—10 million years ago. Huge grazing herbivores and cursorial predators move carbon and nitrogen around the landscape. These unfamiliar creatures evolved from survivor lineages that timidly emerged from some long-forgotten disaster now deep in their evolutionary past. A herd of grazers moves to the next patch of grass. A rainstorm comes and goes. Monsoons wobble about the equator, as the planet does so around the sun. A million more years go by. The waves beat against the shore. Humanity has as little to do with this world as Megalodon does with ours, and nothing remains of us at the surface. Though no one is alive to tell us what epoch it is, these creatures have nevertheless inherited a planet forever diverted by our legacy—as surely, in Faulkner’s words, “as Noah’s grandchildren had inherited the Flood although they had not been there to see the deluge.”

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