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Macmillan Childrens Publishing Group


In Search of Future Fossils

David Farrier





England’s eastern edge is slowly being reclaimed by the sea. At a rate of around two meters per year, the tides carry away the shallow cliffs that form the Anglian coastline. Seasonal storms gouge away the earth, mostly glacial till that was deposited when ice sheets reached as far as southern Britain 450,000 years ago; like a cheaply made wall, the coast is vulnerable to erosion and sudden collapses. One night in 1845, a farmer plowed a twelve-acre field near Happisburgh, in Norfolk, and retired to bed with the soil ready for planting the following morning. When he woke, the field had vanished. Coastal defenses built after devastating floods in 1953, which killed over three hundred people, have long since crumbled. Buildings that once stood out of sight of the coast now huddle within its reach, and homeowners watch anxiously as the margin creeps closer, eating up their lovingly tended gardens inch by inch. Occasionally, a house tumbles into the sea. The ground beneath your feet feels provisional, as though you are standing on borrowed time.

Sometimes, though, the sea gives something back. In May 2013, a spring storm uncovered the oldest traces of human passage outside Africa on Happisburgh’s claggy foreshore. Heaving seas had stripped away the sand behind the dilapidated postwar flood defenses to reveal a section of laminated silt flecked with dozens of lozenge-shaped hollows. The scooped depressions were the 850,000-year-old fossil footprints left by a group of early humans, Homo antecessor, moving along the muddy banks of an ancient river. The differently sized footprints suggested that it was a group of mixed age, adults and children, headed in a southerly direction. At the time, it was an estuarine landscape, populated by pine, spruce, and birch forests interspersed with open areas of heath and grassland. Photographs of the footprints resemble a step map of a frantic dance floor. The busy play of feet suggests a neighborly scene: adults pausing to coax tired children or turning to check the horizon for predators; arms raised to indicate points of interest or offer an encouraging hand on the shoulder. Some impressions were so well preserved that you could see the outlines of individual toes.

Briefly, startlingly, this small party of hominids walked out of the deep past and into the present. They disappeared almost as fast: within two weeks, the tide had washed away every print.

Ancient footprints, like burrows, tracks, and tooth marks, are known as trace fossils. Unlike fossilized remains, they speak of life rather than death. Though bodiless, they bear witness to a departed body’s weight, gait, and habits, telling stories about how ancient lives were lived. Trace fossils like the Happisburgh footprints are an accidental memory; where the group came from and where they were headed are beyond our knowing. But the prints offer an enchanting glimpse of ancestors whose past seems to brush against our present, whose step into our time seems like an invitation to join in a mysterious journey. Even in photographs they conjure the uncanny sensation that the group has only just left, their prints fresh and glistening—that we could catch them, if only we hurried.

In terms of traces left by early humans, the Happisburgh footprints are relatively young. The oldest known hominid prints were made 3.6 million years ago, in volcanic ash at Laetoli in what is now the Ngorongoro Conservation Area, in Tanzania. They were discovered in 1976 and embraced as marks of a Pliocene “first family,” making their way like Milton’s Adam and Eve, “hand in hand, with wand’ring steps and slow.” When the deep past arrives in the present, it is often surprising. The Laetoli footprints were found when, in high spirits during a break in their labors, a team of paleoanthropologists led by Mary Leakey began to throw elephant dung at one another. One exuberant member of the party noticed the prints only after falling on them.

But perhaps the most famous footprint, at least the one pressed most deeply in the Western imagination, was never really made at all:

It happen’d one Day about Noon going towards my Boat, I was exceedingly surpris’d with the Print of a Man’s naked Foot on the Shore, which was very plain to be seen in the Sand: I stood like one Thunder-struck, or as if I had seen an Apparition; I listen’d, I looked round me; I could hear nothing, nor see anything … There was exactly the very Print of a Foot, Toes, Heel, and every Part of a Foot; how it came thither, I knew not, nor could in the least imagine.

This discovery of a single footprint is the most iconic moment in Daniel Defoe’s Robinson Crusoe, published in 1719 and sometimes referred to as the first modern novel. Robert Louis Stevenson considered it one of four emblematic scenes in literature that, more than any other, have been “printed on the mind’s eye forever.” Friday’s impossible mark—how can there be only one, isolated in the middle of an otherwise pristine beach?—has Crusoe spooked. After enduring the solitude of his deserted island, he suddenly sees hints of human presence everywhere, “mistaking every bush and tree, and fancying every stump at a distance to be a man.”

The discoveries of Friday’s footprint and the footprints of early humans have such a vivid claim on our imagination because we have all lived a version of it at some point: the sudden feeling of being accompanied by an unseen other. Although you are alone, the air seems somehow closer, or an empty room is still thick with the presence of one only just departed. Someone or something has passed through already.

In the final part of The Waste Land, T. S. Eliot drew inspiration from accounts of the Shackleton expeditions to Antarctica, in which exhausted members of the party would hallucinate that there was always one more person present than could be counted. “When I look ahead up the white road,” complains one of the poem’s many disembodied voices, “there is always another one walking beside you.” It was recently suggested that the Laetoli footprints do not represent a pair walking side by side, as was originally thought, but sets of individual prints made at different times. New high-resolution photographic techniques have revealed a third set of toeprints obscured by the other two. The third walker seems to have favored their left foot over their right and was perhaps carrying an injury. Wherever they were going, they did not come back by the same route: there are no footprints to mark the return journey.

* * *

AS ONE SET OF FOOTPRINTS stepped out of the past, another kind stepped into the future. In May 2013, the same month that the Happisburgh footprints were uncovered, climate scientists at the Mauna Loa Observatory, in Hawaii, announced that atmospheric carbon dioxide levels had reached 400 parts per million (ppm) for the first time in all human history.

For the past eight hundred millennia, since the Happisburgh footprints were pressed in the mud to the middle of the nineteenth century, atmospheric CO2 has oscillated between 180 and 280 ppm as the planet moved between freezing ice ages and warm interglacial periods. The last time concentrations were higher than 280 ppm was during the mid-Pliocene, three and a half million years ago, when the Laetoli footprints were made and our earliest ancestors were only just beginning to diverge from apes. It was in many ways a world we would recognize: the continents were essentially in the same positions they occupy now, inhabited for the most part by similar species of plants and animals, while the same kinds of fish swam in the oceans between them. But the seas themselves were tens of meters above where they are today, and the global mean temperature was around 3 degrees Celsius higher.

If the Pliocene world resembles the one we know, it also, potentially, foreshadows what our world will become. Some scientists look to the mid-Pliocene as a form of “paleo-laboratory” to better understand the difficult and dangerous world we will live in if the planet continues to heat up. Global mean temperatures are already 1 degree Celsius higher than they were in 1850, and we could reach 1.5 degrees Celsius by the middle of this century, leaving us poised on the threshold of a world that is radically different from the one modern humans evolved in. Already, drought and flood, wildfires and storms, have become more common in many parts of the world, with fatal consequences, but beyond an increase of 1.5 degrees Celsius, we face the prospect of having to rapidly learn how to live on a planet that has become profoundly alien: where crops do not grow as they once did, equatorial cities have become uninhabitable, and low-lying islands and nations sink beneath the sea. Perhaps a fifth of the ecosystems on Earth will undergo some kind of fundamental change if we cross this threshold, but far more worryingly, it would trigger the irreversible thawing of Arctic permafrost, releasing catastrophic levels of greenhouse gases and guaranteeing a return to a Pliocene-like climate within several centuries.

The new Pliocene is not a given, yet. We can still determine a different future. Even so, signs of the changes we have already wrought abound and will be evident to those who inhabit that future, however distant. Much of the carbon dioxide that rose from the furnaces of the industrial revolution and the exhausts of the very first combustion engines still circulates unseen above our heads, while the distinctive isotopes that come from burning fossil fuels are scattered like spores over the entire planet, layered in glaciers and lake sediments. Even if we were to stop using fossil fuels immediately, traces of the carbon we have produced will still linger for time out of mind. David Archer, a climate scientist at the University of Chicago, has estimated that as much as a third of the carbon derived from burning fossil fuels will remain in the atmosphere a thousand years from now. After ten thousand years, this declines to between 10 and 15 percent, but the last of a long tail, around 7 percent of anthropogenic carbon, will still be present after one hundred thousand years, long enough to delay future ice ages. Our carbon could influence the climate for the next half a million years.

The entire atmosphere now bears the marks of our passage, like a vast geochemical trace fossil of the journeys we have taken and the energy we have consumed. When the last residue of our carbon finally leaves the atmosphere, humanity will have lived and evolved through another four thousand generations. Language and communication will have altered beyond our ken; how people in the year 102,000 C.E. talk and think, what they consider to be art or music, may well be unrecognizable to us. What it means to be human may even have changed in ways we cannot imagine, but as that change unfolds and our descendants pull away from us, like the ghostly third figure in Eliot’s poem, we will accompany them.

To produce the spike in atmospheric carbon measured by the Mauna Loa scientists, we have also made countless other deep marks, from the burrows we have dug in pursuit of fuel or minerals to the network of hard-wearing roads that carry them from pit to pump or factory. Our carbon traces won’t be directly legible without specialist knowledge and equipment, but we can already read them in the form of more frequent and intense extreme weather events. New landscapes shaped by climate change will silently bear witness. Droughts that parch the land or storms that flood it may produce trace fossils of their own, as ecosystems change or collapse altogether and rising seas make living in coastal cities untenable. A huge proportion of anthropogenic carbon isn’t in the atmosphere at all but has been absorbed by the oceans, which are becoming progressively warmer and more acidic, with severe consequences for virtually everything that lives in or depends on them.

The moment I realized the uncanny coincidence of the discoveries in Happisburgh and Hawaii was both thrilling and appalling. In part, it was the curious intimacy of a connection across such a broad stretch of time. Like Crusoe, the Happisburgh prints give us “Toes, Heel, and every Part of a Foot”—individual bodies that walked, and feared, and loved just as we do. But I wondered whether the “footprint” we have left in the atmosphere will also inspire the same sense of recognition. Will future generations feel the past rush toward them, just as 850,000 years contracted to a distance of a few meters when the Happisburgh prints were discovered? Will they, like, Crusoe, be alarmed by the realization that our presence still haunts their passage? The footprint has become one of the most widely recognized metaphors for human impact on the planet. Particularly in the West, we are urged to be mindful of how the way we live produces a deeper or shallower chemical imprint on the world’s atmosphere. Our carbon footprint is a mark of how much we care (or don’t) about the consequences of our actions. Sometimes the metaphor is literal, such as the famous exhortation that hikers “take only photographs, leave only footprints.” But the suggestion that a footprint is ephemeral, a temporary impression soon wiped clear by wind or rain, masks the reality that our marks will endure for a very long time indeed. Our trace fossils will be inscribed in the planet’s geologic, chemical, and evolutionary history, legible, in some cases, even to our most distant successors. Long after we are silent, they will speak of how life was lived in the late twentieth and early twenty-first centuries.

We can only speculate about who might notice them many years from now, if at all. Perhaps no one will be around to read our traces, but nonetheless we are, everywhere, constantly, and with the most astonishing profligacy, leaving a legacy that will endure for hundreds of thousands or even hundreds of millions of years to come. Like the Happisburgh prints, what seems most fleeting presages the most incredible leap in time. We are conjuring ourselves as ghosts who will haunt the very deep future.

* * *

I TEACH ENGLISH LITERATURE at the University of Edinburgh. In early 2013, only a few months before the Mauna Loa announcement and the discovery at Happisburgh, I began teaching a course concerned with writing about nature and place. Since then, once a week in the spring semester, my students and I gather in a small room around tables of lacquered blond wood, a surface that feels more like plastic than pine, and talk about the work of writers like Edward Thomas, Kathleen Jamie, and W. G. Sebald. One side of the room is all windows that open out onto a view of Salisbury Crags, a wave of fine-grained dolerite cliffs breaking at the foot of Arthur’s Seat, the extinct volcano around which Edinburgh has wrapped itself for more than a thousand years.

My fascination with the idea of deep time began with teaching this course in the shadow of Salisbury Crags. Like the hub of an enormous wheel, the crags are both an emblem and a point of orientation for the city of Edinburgh. The path that runs around the base of the cliffs offers spectacular views of the rampart of the Pentland Hills to the south, and to the north and west, the Georgian New Town, the Forth estuary, and beyond to the low hills of Fife. But the crags hold an even more special place in the history of time. In the eighteenth century, while Edinburgh was at the center of an extraordinary clamor of intellectual activity known as the Scottish Enlightenment, the area was a quarry. A gentleman farmer named James Hutton used the crags to demonstrate his theory that sedimentary rocks are gradually lifted into mountains by immense heat and pressure from below the ground. His discovery of a fist of reddish igneous rock closed around a paler chip of much older dolerite, now known as Hutton’s Section, proved that molten rock intruded upon older sedimentary layers. Hutton’s Theory of the Earth, published in 1788, was the first scientific work to imagine the immensely long timescales required to shape the planet.

Hutton’s ideas set him at odds with geologists today: whereas he saw the world as a machine, endlessly running through cycles of sedimentation that lifted the earth and erosion that ground it down, modern geologists acknowledge that the planet is shaped by sudden events as well as predictable processes, that cataclysms—an abrupt increase in volcanic activity, or a meteor strike—have as much influence as the orderly cycles Hutton identified. Rather, his legacy is the scope he gave others to think with. His real innovation was to fundamentally change how we look at the world around us. Such a vision, measured in grains of sand, required hundreds of millions of years, deep time beyond anything that had been envisaged before.

Hutton’s section was one of the first places where deep time was imagined, but the phrase is not his. Curiously, it first appears in a reflection on how long good writing might last. “All work is as seed sown,” wrote the Scottish polymath Thomas Carlyle in 1832, in an essay on James Boswell’s Life of Samuel Johnson that speculated on the longevity of Johnson’s writing. “It grows and spreads and sows itself, and so, in endless palingenesis”—or rebirth—“lives and works. Who shall compute what effects have been produced, and are still, and into deep Time, producing?” Just under 150 years later it was popularized by the American essayist John McPhee in Basin and Range, a book about the landscape of the southwestern United States. But like the fingers of magma that fired his imagination, Hutton’s vision of deep time intruded upon the minds of the poets and writers who followed him. We can read traces of Hutton’s thinking in Tennyson’s In Memoriam (“The hills are shadows, and they flow / From form to form”). In “On the Sea,” Keats fancies that the ocean “gluts twice ten thousand Caverns,” and in Shelley’s “Mont Blanc,” the slow violence of glaciation becomes “a flood of ruin,” producing landscapes “ghastly, and scarr’d, and riven.” For some, deep time replenished a sense of mystery depleted by the loosening bonds of religious faith. “How little do we know of the business of the earth,” wrote Edward Thomas, “not to speak of the universe; of time, not to speak of eternity.” Without Hutton’s insight into the great age of the planet, Charles Darwin would not have had the scope to conceive his theory of evolution. From the perspective of very deep time, the most intractable rocks appear as fragile as eggshells, as free-flowing as water.

Treating the planet as a succession of sinks and taps, as we have, has kept us focused on the present, concealing the fact that we also inhabit this flow. Earth’s long pulse shapes the arc of our lives, but to see this poses a tremendous challenge to our everyday imaginations. For the most part, deep time is “the strange sleep,” which, according to Shelley, “wraps all in its own deep eternity.”

One day in November 1944, standing on a “bare ocean-moulded hill” in the chalk uplands of Dorset, the Irish writer John Stewart Collis sought to peer through the veil. “I pressed my mind back through the bottomless abysses of time,” he wrote later. The effort is beyond him, but it summons a memory of when time did, briefly, stand revealed:

Once, in the middle of the Atlantic, looking at the horizon, I tried to imagine the space beyond it. For a second I had a true glimpse of that space, and of the space beyond that space. And perhaps for as much as a second now, I saw the reality of a hundred million years.

In the ocean’s immensity, the truly deep age of the earth flares for an instant with the force of a vision. In the rhetoric of ancient Greece, the term for this irruption of clarity was enargeia, and it described a speaker’s capacity to peer beyond the present moment: Aristotle wrote that enargeia allowed an audience to “see things occurring now, not hear of it as in the future.” What Collis saw as he sought to push his mind’s eye beyond the gray horizon was the enargeia of deep time, rhyming the pitch and roll of the Atlantic with an uncanny tilt of the senses. The same vision is available to us, too, if we choose to look with patience and care, and by it we can catch, as Shelley did, “gleams of a remoter world.”

Or perhaps not so remote. What enargeia reveals is not always easy to face—the poet Alice Oswald’s translation of the term is “bright unbearable reality.” Not long after the peak in May 2013, global atmospheric CO2 dropped below 400 ppm, but this was only a brief reprieve. Allowing for fluctuations, today the level of CO2 in the atmosphere is around 410 ppm, rising at around 2 ppm per year. Climate scientists at the Australian National University recently proposed that human activity is forcing changes to the Earth system 170 times faster than natural processes. By this queasy calculus, we will see ten thousand years of environmental change in fifty-eight years, less than a single lifetime.

Some geologists think that this staggering rate of change justifies the naming of a new phase in planetary history. For more than one hundred years the International Chronostratigraphic Chart, which lays down the sequence of geologic time, has culminated with the Holocene, the period of benign climate that began around 11,700 years ago with the end of the last ice age and coincided with the development of human society. But in 2009, the International Commission on Stratigraphy (ICS) charged a group of geologists, biologists, atmospheric chemists, polar and marine scientists, archaeologists, and Earth scientists with establishing whether or not the chart should be updated to reflect the onset of a new unit of geologic time: the Anthropocene, or the time of the human. The Anthropocene Working Group has focused its efforts on a search for evidence of wholesale change in the way the earth works as a system of interdependent geochemical, sedimentary, and biological processes. For the evidence to be compelling, they determined, it must produce new and distinct layers in the stratigraphic record. The group explored human-mediated acceleration in the rates of erosion and sedimentation, disturbances to the major chemical cycles (carbon, nitrogen, and phosphorus), the likelihood of significant changes in sea level, and the effect of human activity on the diversity and distribution of species across the globe. They examined the potential for synthetic materials, from artificial radionuclides produced by nuclear testing to plastic waste, to leave an identifiable signal in the strata. Many of these changes and signals, they concluded, are not only present and observable now but also effectively a permanent part of the archaeological and stratigraphic record.

When determining the boundaries of geologic time, stratigraphers search for sites where evidence of the shift from one geological age to another glitters in the dark of deep time. Such boundary sites are sometimes referred to as “golden spikes,” and marked by a bronze plaque hammered into the rock. But what the Anthropocene Working Group sought was the flash of enargeia: not the residues of worlds past, but the difficult brightness of a new world arriving. Geology is a cautious discipline: many who practice it feel that the process for introducing a new entry in the International Chronostratigraphic Chart ought to be as patient as forming a novel layer in the strata. But in 2016, at the International Geological Congress in Cape Town, the members of the ICS voted nearly unanimously that the Anthropocene was a stratigraphic reality and that it coincided with the eruption of technological innovation and material consumption in the middle of the twentieth century. The AWG is currently working on a proposal to formalize the Anthropocene as a new unit in geologic time.

Hutton learned to read the deep past in the rocks he saw every day, and according to the Anthropocene Working Group we can now read something of the deep future in even the most ordinary artifacts. The evidence of the Anthropocene is all around us, inextricably woven into the way we live our lives. But to see it, we need to face the “bright unbearable reality” of the world we have made.

Copyright © 2020 by David Farrier