The Fossils of the 21st Century

By Maddie Stone on at

In 100 million years, human civilisation will have bit the dust. Perhaps a nuclear war scorched the planet, or a last-ditch bid to solve climate change backfired horribly. Or, more optimistically, we overcame the myriad challenges of the 21st century, took to the stars and evolved into new species on alien worlds. Either way, what you and I consider humans will have long since vanished, our memories lost to the grinding colossus of time.

The Earth, however, doesn’t forget so easily. Whatever eschatological fate awaits us, some of the marks we’ve left on our planet’s surface will last for aeons. We’ve flattened mountaintops; bored holes deep into Earth’s crust to extract precious fuels; drained lakes and re-routed rivers. And then there’s all the stuff we’ve churned out—trillions upon trillions of tonnes of it, from mobile phones to skyscrapers to chickens—some of which will become part of the geologic record, too.

“Most of our things... will not rot down at all easily.”

Collectively, the relics of the Anthropocene, also known as “technofossils”, will telegraph a story to the distant future. But what kind of story will that be, and how will it be interpreted? It isn’t easy to predict what the coming century will look like, much less the fossils of a future era, but a growing number of researchers and artists are now attempting to do exactly that. Some of them, at least, believe our fossil fingerprint will be stark.

“Even if all humanity were to disappear tomorrow and some aliens were to arrive 100 million years hence, there’d be a very clear marker that something unusual happened about now,” said Peter Haff, a professor emeritus of geology and civil engineering at Duke University.


For thousands of years, humans have been leaving technological artefacts behind. But since the mid-20th century, advances in industrial manufacturing, economic globalisation, and explosive population growth have conspired to exponentially increase the amount of techno-junk strewn across the Earth’s surface.

As our waste piles up in landfills, sink to lake bottoms and settles onto the seafloor, some bits will broken down, either by physical and chemical processes or biology. But a portion of our trash won’t be recycled: Instead, it’ll get buried in sediment, which over time will become squished and chemically altered to make new rocks.

Like shark teeth or dinosaur bones from eras past, our refuse won’t just be entombed in rock, it’ll become part of that rock.

Plastiglomerate samples/ready-mades collected by geologist Patricia Corcoran and sculptor Kelly Jazvac at Kamilo Beach, Hawai’i, 2012. (Photo: Jeff Elstone. Courtesy of the artist.)

“Most of our things, [if] you leave them outside in a garden, or a beach, they will not rot down at all easily,” University of Leicester professor of palaeobiology Jan Zalasiewicz, who along with colleagues in the UK and the US coined the term technofossil in 2014, told Earther. “Unless we do something drastic to them, they do have a very good chance of getting into the fossil record and forming part of our future geology.”

For Zalasiewicz, technofossils are more than a fun thought experiment. As chair of the International Commission on Stratigraphy’s Anthropocene Working Group, he’s been working for years to build and interrogate the case that humanity is a force of nature deserving of its own notch on the geologic timescale. He sees these future fossils as evidence that we are. After all, for as long as stratigraphers have been working to build Earth’s Geologic Time Scale, fossils have proven invaluable for characterising different chapters.

“The whole Geological Time Scale was founded on fossils, with each period [originally] being described by a particular fossil group,” said University of Leicester geologist Carys Bennett.

And some scientists—Zalasiewicz and Bennet included—suspect the fossil record of the Anthropocene will be profound. For one, if humans to continue to drive up extinction rates worldwide, our geologic moment will feature a sudden, dramatic pruning of the tree of life, comparable perhaps to the five major mass die-offs in Earth’s history. At the same time, our industrial takeover has resulted an explosion of new, potentially-fossilisable things, analogous to the trace fossils animals leave behind in the form of nests and footprints.

Zalasiewicz noted that the number of potential technofossil “species”, while only roughly estimated, is “at least hundreds of millions”, far in excess of the biodiversity recognisable in the rock record based on fossil shape, pattern, and structure.

“The levels of techno diversity are huge,” he said.

These potential Anthropocene fossils are not only diverse in form, but in composition. For most of life’s 4-billion-year run on this planet, fossils have formed from precious few starting materials: mainly hard-stuff like bones, shells, and wood, and in rarer cases, soft tissues. Modern civilisation has gone and expanded the stratigraphic ingredient pantry to include semi-natural substances like concrete, metals rarely seen in nature like aluminium, and things that never existed at all, including artificial glasses, plastics, and an entire family of new gems and minerals.

Of course, the traces we leave behind aren’t limited to stuff made by machines. We humans are fossils waiting to happen. So are our livestock, including cows, sheep, pigs, and chickens, which along with people now outweigh all wild land vertebrates on the planet. In fact, Bennett notes that the 66 billion-odd chickens we consume a year give the ill-fated birds “great potential to become fossils to mark this time period.”

“Broiler chickens, now unable to survive without human intervention, have a combined mass exceeding that of all other birds on Earth; this novel morphotype symbolises the unprecedented human reconfiguration of the Earth’s biosphere,” Bennett, Zalasiewicz and others noted in a commentary published Wednesday in Royal Society Open Science.

Chickens aren’t alone in their tremendous footprint. We produce close to 300 million tonnes of plastic a year, enough to cover the entire United States in a layer of shrink wrap. We’ve churned out at least half a billion tonnes of aluminium since 1950. A 2016 paper by Zalasiewicz and others pegged weight of Earth’s “technosphere”—a term Haff ginned up to describe the physical footprint of the human enterprise, including all the infrastructure supporting civilisation—at approximately 30 trillion tonnes. That is 50 kilograms of human-branded junk per square metre of Earth’s surface and growing.

“It’s very hard to find a square centimetre in the world that doesn’t have some indication of the existence of the technosphere,” Haff said. “It’s everywhere, it’s ubiquitous, it’s massive compared to the size of things we’re used to in our everyday life.”

Given these numbers, it’s easy to imagine an Anthropocene rock record strewn with techno-trash, from stashes of old CDs to fossilised libraries. Still, that picture of our future geology relies on a number of assumptions: about the long-term survivability of our stuff, about how much is getting buried in sediment and where, and about whether an epoch that commenced perhaps 70 years ago—a nanosecond in geologic time—can leave a meaningful record in the sedimentary strata.

“There’s probably no process more destructive of the fossil record of humanity than humanity. We’re constantly disrupting this record we’re creating, and re-digging it all the time.”

Nick Pyenson, Curator of Fossil Marine Mammals at the Smithsonian Museum of Natural History and author of Spying on Whales, says it’s clear humanity has become a geologic-scale force. He’s far less certain how much of a fossil record we’re leaving behind.

“If we are geologic-scale agents, then are we leaving a record that could be found in the million year time frame?” Pyenson said. “I think the answer is gonna be very tricky.”

Pyenson points out that the rock record doesn’t build up smoothly—like tree rings that can vary in thickness from year to year, some chapters of Earth’s history feature faster accumulation of new sedimentary layers, and better preservation of materials, than others. The record also varies across space: while a dead bird that sinks to a lake bottom may become entombed in sediment very quickly, that same bird left out in the Amazon rainforest will be picked apart by scavengers and digested to atoms by bacteria.

Then there’s the fact that the Anthropocene is, well, an age of human dominance. And one thing we’re really good at is digging up and destroying our old stuff.

“There’s probably no process more destructive of the fossil record of humanity than humanity,” said Erle Ellis, an environmental scientist at the University of Maryland, Baltimore County and member of the Anthropocene Working Group. “We’re constantly disrupting this record we’re creating, and re-digging it all the time.”

 

Artist’s concept of a fossilised watch. (Photo: Courtesy Erik Hagen)

One need look no further than humanity’s own archaeological record, which we’ve been steadily digging out of the ground and sticking in museums for centuries, for evidence of this. Or the fact that cities like New York and Paris are constantly being “churned up and remade into something else,” as Ellis put it.

Even where our stuff is getting buried and staying put—for instance within large river deltas or estuaries near human population centres—its long term fate remains a bit of a mystery.

Ellis and Pyenson both pointed out that two of the most prevalent modern materials, plastic and concrete, aren’t necessarily stable over geologic time. At Earth’s surface, concrete can be broken apart by acid and erosion, while plastic is susceptible to UV-degradation. Ellis did note, however, that both can leave a record if buried in the right environment, even if the material itself degrades and it’s simply a fossil impression.

“We look after the planet we live on, and we’re altering it at a rate that’s entirely unprecedented throughout the whole of Earth’s history. It’s important to understand what we’re leaving behind.”

And it’s possible our waste will get altered in ways we’ve never imagined. On the Big Island of Hawaii, for instance, there’s a beach where plastic waste has melted around campfires and bonded with pebbles and sand to form a new kind of stone. Dubbed “plastiglomerate” by the researchers who formally described the material in 2013, the substance is exceptionally hard and decay-resistant, giving it “great potential to form a marker horizon of human pollution”, as they wrote at the time.

“Plastigolomerate I find is a perfect example of humans’ influence on the natural environment,” said Patricia Corcoran, an Earth sciences professor at the University of Western Ontario who first described the material. “Not just because it contains plastic, but because plastic and natural fragments were melted together because of anthropogenic influence. It’s a human-influenced action that’s actually creating it.”

But while plastiglomerate and chickens may be compelling symbols of our influence, ultimately more data is needed to say how much of the Anthropocene will be preserved long term and in what form. We can look around the world to places where new geologic deposits are forming rapidly. Zalasiewicz pointed to an area along the northern Spanish coast where, over the past century, slag and rubble from factories have become cemented with shells and other natural materials to create what are effectively new, trash-infused outcrops. Bits of plastic can be seen poking out of the upper portion of these metres-high deposits, Zalasiewicz said.

We can also try to fast-forward time by running experiments in the lab.

That’s what Sarah Gabbott, a professor of palaeobiology at the University of Leicester, is now starting to do. Gabbott, whose prior work has mostly consisted of watching dead critters decay and seeing what gets preserved under different conditions, is now taking plastic, aluminium, and other potential future fossils and subjecting them to heat, pressure, and chemical assaults similar to what they would experience during fossilisation.

“We look after the planet we live on, and we’re altering it at a rate that’s entirely unprecedented throughout the whole of Earth’s history,” Gabbott said. “I think it’s important to understand what we’re leaving behind.”

This research is just getting started, but when all is said and done Gabbott hopes to have the first experimental data point to say how our techno-junk will be transformed over geologic time, and what will remain behind. “We know some of the variables that affect whether [things] become technofossils,” Gabbott said. “And we’re just—bit by bit, step by step—trying to build very simple experimental conditions and add layers of complexity.”


If it’s difficult to say what parts of the Anthropocene will remain to tell our story after we’re gone, what our future fossils will look like in 100 million years and how they might be interpreted are questions open to wild speculation. Naturally, some artists are beginning to take up the challenge.

Houston-based artist Eric Hagen uses mixed media to explore themes of deep time and the Anthropocene. About seven years back, he started playing the concept of Anthropocene fossils, using acrylic resin and paint, plaster, oil paints, and even plastic microbeads, to create colourful abstractions of our 21st century geology. In these pieces, the fossils themselves are often subtle, like objects in a Magic Eye trick that only pop when the viewer unfocuses her gaze.

“I try to create something that’s physically beautiful that people want to approach and then realise it’s something a little different,” Hagen said. “I like to envision how the geologic process was that buried the object. I think if you tried to make the fossil as it would [really] be, it wouldn’t be obvious.”

Image: Courtesy Erik Hagen

Hagen said he envisioned the series as a kind of cultural portrait of the Anthropocene, with coins representing commerce and phones representing communication. Focusing on objects with familiar shapes rather than, say, formless concrete, was a way of making geologic time more relatable.

But if these “fossils” are difficult for present-day humans to recognise, they may be utterly confounding to people of the distant future (who may not even be human). To illustrate that, a few years back Zalasiewicz collaborated with French artist Anne-Sophie Milon on “The Mystery of Brunaspis enigmatica”, an art project that sought to explore how a group of geologists 100 million years from now might misinterpret one 21st century fossil, the Brunaspsis enigmata, using analytical methods similar to modern-day palaeontologists.

Zalasiewicz and Milon created their strange fossils by imprinting aluminium cans into homemade cement, then proceeded to recreate the geologists’ workspace, including detailed fossil sketches and “scientific” illustrations of the life form these future scientists dreamt up from the artefact’s remains. Zalasiewicz and Milon even worked up an accompanying research paper on the mysterious creature of the “Great Crisis Stratum”.

The kicker? The scientists totally botched their interpretation, imagining the human trash to be the remains of some sort of burrowing, colony-forming sea creature. Milon noted that before the exhibit went on display at an art museum in Germany, she showed some of the fake fossils to a group of palaeontologists at the University of Leicester, and none of them could successfully identify their origin, either.

“Scientific” illustration of the Brunapsis enigmata’s imagined lifestyle. (Illustration: Anne-Sophie Milon)

Even if Anthropocene fossils are readily identifiable, Bennett cautioned they will only offer a snapshot of our time. “When I study fossil ecosystems, we’re always conscious that the majority of life living at the time probably was not preserved,” she said.

While some suspect the overall picture of what went down in the Anthropocene will be obvious even if the details are fuzzy, others are thinking about how our stratigraphic signal can be manipulated to make it clearer—or even how we can alter the geologic narrative.

Take the Pink Chicken Project, brainchild of artists and designers Leo Fidjeland and Linnea Våglund. Launched a little over a year ago, the speculative art project is premised on the idea that Anthropocene rocks will be full of chicken bones. It suggests we use gene drive, a nascent genetic engineering technology based on the genome-editing tool CRISPR that aims to force alterations through an entire population, to recolor the birds’ bones pink as a way of “re-occupying the rock strata.”

The idea, Fidjeland said, is to spark a discussion over who holds power in the Anthropocene and “who has the right to leave traces behind”.

“It’s a specific group of people who have power, who are controlling ongoing violence and destruction that we’re seeing,” Fidjeland said, noting that just a few corporations are responsible for the vast majority of chickens alive today. Technologies like CRISPR and gene drive—especially as they become more widely accessible—could allow the rest of us to exert a bit more control over our future geology.

 

Artist’s concept of what a pink-boned chicken fossil might look like. (Image: Pink Chicken Project)

Fidjeland and Våglund fleshed out the concept in collaboration of synthetic biologists and believe that, on a technical level, chickens can indeed be altered so that their bones are pink. (Other biologists have expressed scepticism, and the duo have not attempted to make a genetically-modified pink chicken, emphasising that gene drives are wildly controversial.)

But Fidjeland said that the project was more about generating discussion than creating a bonafide pink chicken. He wants “to emphasise how unknowable the future is”, and how new technologies could alter the story.

Uncertainty about the future is a sentiment most scientists and artists who think about Anthropocene fossils will echo. But where does that leave those of us who’d like some existential closure on our place in geologic history?

Perhaps the best we can hope for is that there are intelligent, curious beings roaming the Earth 100 million years hence. If we’re very lucky, perhaps as they dig through strange sedimentary layers infused with crushed concrete and molecular microplastic, they’ll begin to discover that the Anthropocene was a time of profound ecological upheaval. And, perhaps, that insight will prevent them from repeating some of the 21st century’s mistakes.

Or, maybe future geologists will conclude chickens were the real driving force of the Anthropocene—creatures as powerful as earthquakes and volcanoes—and that we bipedal primates were just another garden-variety livestock species along for the ride. The distant future is nothing if not humbling.

Featured image: Kelly Wood. Courtesy of the artist.