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What We Leave in the Rocks

I’ve been thinking a lot about the stuff I’ll leave behind lately. 

I’m not talking about which of my children is going to eventually inherit my Star Trek Blu-ray collection or that box of sentimental letters I’ve been saving for thirty years (sidebar: if you ever want to take a peek at the raw, primordial matter of your inner self, skip the meditation app and check out something you wrote when you were five).

I’m not even talking about my professional “legacy,” whose future existence I’m skeptical of but also, it’s totally going to be that viral tweet above the Voyager Probe and not one of the climate change feature articles I spent weeks painstakingly reporting.

Nah, I’m talking about the real stuff. 

The plastic Nalgene I drank from for years before panicking that my brain might be 1/3 microplastic by mass.

The plastic garments I wore, as most of my clothes are made of the stuff, too.

The discarded chicken bones from bygone summer barbeques.

The brick of glass, metal, and silicon in my pocket that contains two-thirds of the periodic table in alloys and arrangements found nowhere in nature—a mineralogical marvel that my husband and I use to discuss what brand of toilet paper to buy at the store.

The toilet paper.

If I take the long view, these are the vestiges of my existence that matter; the ones that are most likely to survive the relentless Rollo Rabbit steamroller of geology.

My squishy, meaty bits will have been long since stripped to atoms by feasting bacteria, but these assembled trinkets, or others like them, will live on as technofossils, an emerging evolutionary lineage of manufactured crap that will come to define me, and every other human being living and dying at the dawn of the Anthropocene, in the only in memoria that matters in the end: The one inscribed in fucking rock.

I’ll also be remembered by the stuff I don’t see, but that my cushy, 21st-century lifestyle depends on. The concrete foundation of my house, and the similar heaps of artificial rock buttressing the buildings around me. The copper wiring that shuttles electrons across the mid-Atlantic, allowing me to turn on my lights and type this essay. The fossil gas that heats my home.

And the unintended consequences of it all: Rising global temperatures. Mass extinction. Forever chemicals at the bottom of the sea.

Geology is very good at destroying evidence.

But scatter enough of something on the surface of the Earth, and a few lucky specimens will end up in the right environment for eonic preservation—buried beneath a sedimentary heap in a growing river delta, smushed into the mud of an anoxic lake bed, or petrified in place on a sinking tectonic plate. Even the invisible gases and molecules that define an era can be trapped and preserved through the abysses of time, their unique isotopic signatures leaving ancient chemistry puzzles for future geologists to unravel.

And we are producing a staggering amount of evidence.

According to the new book Discarded: How Technofossils Will Be Our Ultimate Legacy, we’ve produced enough copper wiring to stretch to the Sun and back a dozen times. We’ve coated Earth’s surface in half a trillion tons of concrete and manufactured enough plastic to shrink-wrap Argentina. We raise and consume so many chickens that their biomass now exceeds that of all other bird species combined. Each year, we make over 22 billion new pairs of shoes. 

But while Zalaceiwicz is convinced that we humans are leaving a distinct stratigraphic slime trail, it’s far less clear what kind of story our fossil remnants will tell.

Certain things about humanity’s industrial age may be obvious to future excavators: A sudden change in the isotopic signature of dead plants, for instance, may clue them into the fact that something, or someone, was burning fossil carbon at a feverish pace.

A radioactive haze in the rocks—the ghostly fingerprints of nuclear weapons tests—could reveal our capacity for mass destruction.

The sudden proliferation of petrified cow, pig, and chicken parts inside ancient takeout containers will suggest our dominion over life.

A stew of industrial chemical residues will raise questions about our regard for it.

But evidence of humanity’s domination and destruction of nature will only be part of our rockbound narrative.

The silicon chips inside today’s devices will reveal our capacity for marvelous engineering, especially if any of the nano-scale etchings on their surface persist through the ages.

A far future exhumation of Anthropocene graveyards may turn up skeletons with artificial parts and repaired bones, showing that we cared for our sick and injured.

The fossil remains of children’s toys may reveal our playful side, while mudstones imprinted with textured fabrics will show that we cared about aesthetics.

The mineralized scribblings of toddlers—both the cellulose molecules that make up paper and the graphite in pencils can be preserved millions, if not billions, of years—could reveal our family structures, and the strength of our bonds with each other. 

In other words, far-future excavators will be sifting through many contradictory pieces of evidence about the technological beings that lived and died in the Anthropocene.

But even if they are able to resolve this breadcrumb trail of human detritus into a somewhat coherent picture, the investigators of ages hence are bound to get some details wrong. Those fossilized toddler doodles might contain reasonably accurate pictures of human dwellings. But they could also suggest we lived with dinosaurs.

Ancient fashion could help alien visitors reconstruct our anatomy, but if they discover an ossified Walmart before finding any human remains, they’re liable to be perplexed.

Huge parts of our story may be omitted entirely from Earth’s rocky record.

Take music. We’ve invented countless devices for playing and recording it, but sound itself doesn’t fossilize. Just as the Jurassic Park writers had no real-world examples of a T. Rex roaring to go off—maybe this menacing mega-predator clucked and crowed like its descendants in the poultry aisle—our own geological legacy will be sonically impoverished.

Zalaceiwicz imagines that the only way far-future geologists will learn anything about our musical nature is if they happen to unearth some fossilized shellac from an old 78 record, with the spiral grooves still intact. But it will take a clever rockhound indeed to recognize that those etchings encoded melodies.

Considering all that might be erased by the tectonic train wrecks of tomorrow, I’ve started to wonder if there’s anything we can do—anything I can do—to send a message to the distant future.

When I asked Gabbott and Zalaceiwicz about this, their experimental paleontology training kicked in, and they immediately started suggesting materials and burial sites for a deep-time capsule.

Gabbott proposed making graphite drawings on a surface of a fine-grained clay, such as kaolinite, and sinking them to the bottom of the Black Sea (a “super duper place” for long-term preservation, as she put it).

Zalaceiwicz suggested printing humanity’s story on a skein of polyester—a sort of Nausicaä of the Valley of the Wind-style tapestry—and burying it in the sinking river delta surrounding New Orleans.

Of course, such projects require considerable time and resources, potentially including access to a deep sea-worthy submersible (hard to come by) or an autonomous underwater vehicle. For those lacking such specialized tools, perhaps the best way to try and explain things to the future is to assume that some random assortment of one’s worldly possessions will have an extended afterlife, and act accordingly. 

Personally, the message I’d like to send is pretty simple: I adore my family, my community, and this amazing rock we call home.

Maybe I should organize a neighborhood trash cleanup, in the hopes that the fossil remnants of my city’s streets show evidence of care and maintenance.

Or I could throw the local children’s park a fundraiser so that we can finally hire an artist to paint a mural there (maybe we can even consult an archaeologist to determine what kinds of paint have the best preservation potential).

Maybe all that I need to do is spend a bit more time drawing pictures with my kids and a bit less doomscrolling.

Zalaceiwicz told me he believes future geologists might “struggle to put together this evidence of extreme cleverness on the one hand and extreme stupidity” on the other. Perhaps, by putting more thought and foresight into how we live today, we can start to set the record straight.