In the original version of Planet of the Apes (1968), the astronaut played by Charlton Heston believed he was on a distant planet, only to realise that it was his old Earth, where more than 2,000 years had passed due to the time dilation effect of travelling at near-light speed. The scene in which the astronaut discovers the truth after coming across the remains of the half-buried Statue of Liberty has gone down in history as one of the most spectacular endings in cinematic history. It raises an interesting question: when our civilisation dies out, what will remain as a testament to our time on this planet?
In 2000, biologist Eugene Stoermer and atmospheric chemist Paul Crutzen proposed the declaration of a new geological epoch called the Anthropocene, a term coined by Stoermer in the 1980s. According to the current scale of geological time, we live in the Holocene—the last epoch of the Quaternary period—which began after the last ice age 11,700 years ago. Stoermer and Crutzen reviewed how humanity has become “a major geological force” that will remain “for many millennia, maybe millions of years, to come”, and that the planet is therefore no longer governed by Holocene parameters.
The declaration of the Anthropocene has not yet been officially adopted, nor have scientists agreed on its starting point: Stoermer and Crutzen put it at the end of the 18th century, the Industrial Revolution; others suggest the nuclear age in the mid-20th century, detectable in the soil by the deposition of plutonium from thermonuclear testing, coupled with an increased presence of plastics, heavy metals such as lead, ash from burning coal, and the footprint of carbon dioxide and other greenhouse gases.
The world without us
Along these lines, in 2023 the Anthropocene Working Group of the International Commission on Stratigraphy selected Crawford Lake in Canada, along with 12 other secondary locations, as the standard marker for the beginning of the Anthropocene, a kind of “golden nail” to serve as an international reference point. According to University of Southampton environmental radiochemist Andrew Cundy, a member of this working group, “the presence of plutonium gives us a stark indicator of when humanity became such a dominant force that it could leave a unique global ‘fingerprint’ on our planet.”
But if, in a post-human future, our presence here could be detected by a sediment of radioactive dust and plastics, will that be all? In 2007, journalist Alan Weisman published the book The World Without Us, in which he brought together the views of various experts to venture what would happen to the physical legacy of our civilisation and the rest of the planet if humans were to suddenly disappear.
Weisman’s book surprised many readers, first of all by pointing out the fleeting nature of our normality: in just two days, New York’s subway tunnels would be flooded, and in a few weeks the reactors of all nuclear power plants would melt down, while petrochemical plants would become flaming geysers. On the other hand, the shadow of our civilisation would be long: while wooden houses would soon disappear, the ruins of concrete or stone structures would remain for millennia. In the 2,000-year scenario of Planet of the Apes, the Statue of Liberty would be far from the only remnant of civilisation. In a million years, the flooded Channel Tunnel and bank security cameras would still bear witness to our having been here. Even seven million years from now, the faces of US presidents will still be visible on Mount Rushmore.
Chickens, the biological marker of our age
In 2020, David Farrier published Footprints: In Search of Future Fossils, which speculates on the future geological record of the Anthropocene. In 100,000 years, Farrier writes, our plastics will be encased in clays formed by the reaction of silicates with aluminium and then hardened into shale, which will preserve the “ghostly impression of plastic knife handles, light switches, or the knob of a gear stick.” Remnants of reinforced concrete pillars of skyscrapers may still be recognisable in the strata millions of years from now, and the formation of new mountains 100 million years from now would perhaps expose a layer a few metres thick in which the silhouettes of chairs, SIM cards and hair clips could be found.
As for the real fossils, those of living things, the rock record will be dominated by one species: the chicken, the “Anthropocene rat”, as Farrier puts it. We consume around 60 billion chickens every year. In 2018, geologist Carys Bennett and her collaborators proposed in a study that the broiler chicken will be the biological marker of our era. According to the scientist, “the enormous number of distinctive chicken bones discarded worldwide will leave a clear signal in the future geological record.” In another 2020 study, palaeontologist Roy Plotnick and palaeobiologist Karen Koy added other fossils that will be abundant: cows, pigs, sheep, goats, dogs, cats and, of course, us. By contrast, they write, “the chance of a wild animal becoming part of the fossil record has become small.”
That is, of course, if there is anything left at all. Some authors oppose the idea of the Anthropocene, not so much as a technical matter, but rather because of how “grandiloquent and portentous” it sounds, in the words of psychologist Matthew Adams. In the end, he says, humanity will be a tiny transition between two epochs in Earth’s long history, “a mere blip in the context of deep time.”