Signs of Deep Time

Prefixed with the nationality of the word’s origin, Döstädning is known in English by its blunt translation as ‘Swedish Death Cleaning’. This is the practice of dealing with the material detritus of our lives while we still can. Upon entering, say, our eighth decade, we should start emptying attics, closets and basements of clutter. It is an act of anticipatory kindness to our future grieving heirs who will have enough to cope with besides our accumulations of junk. Some people have been thinking about a sort of inverted version of this for an even higher purpose: the preservation of the human race. If civilisation were wiped out by human folly or natural disaster, how could we warn our post-apocalyptic successors, for their own good, not to go rooting through the worst of the stuff we have left behind? Nuclear and biologically hazardous waste is piling up, and in the absence of reliable methods of making it safe, the means employed to keep it siloed are dependent on stewardship that would be gone.

As well as the challenge of making long-term warnings so resilient that they can see out whatever world-shattering event had taken place, and the indeterminable length of time that new communities might take to emerge, there is the matter of what our human successors would have in common with us. Some language might be assumed, but whether it would be anything like existing ones isn’t certain, and the written word might not have survived at all.

Biohazard symbol; nuclear trefoil, skull and crossbones

Could any sort of persistent sign or pictogram be an answer? The general consensus has been probably not. Without written language or the context of familiar objects these would lack any meaning. The biohazard sign and the nuclear trefoil are pure abstractions without any intrinsic symbolic value. The skull and crossbones seems like a candidate to inspire terror, but tales of ferocious seagoing pirates would have perished with us, and bare bones alone can’t be counted on to be universally terrifying. Skulls and skeletons are common mottifs in art and design, tattoos, jewellery and textiles, and by no means always as symbols of threat. In Mexico calaveras, long a traditional part of folk art and the celebrations of the Day of the Dead, can seem almost as festive Santa Claus.

‘Calaveras Zalameras de las Coquetas Meseras’ by J.G. Posada
‘Calaveras Zalameras de las Coquetas Meseras’ (‘Saucy Calaveras of the Flirty Waitresses’) by J.G. Posada

In the early 1980s the US Department of Energy and the Bechtel Corporation formed the Human Interference Task Force, a multi-disciplinary team of academics and experts, assigned to come up with methods for leaving comprehensible messages that deep time won’t erase. Unlike ordinary shibboleths, signs identifying or understood only by certain groups, these should express pan-human symbolism, be understood by everyone.

A group led by the architect Michael Brill suggested assembling ‘Deterrent Landscapes’ around waste dumps: rebarbative formations designed to look threatening and be difficult to negotiate on foot. A problem with this is that most of the likelier disasters that might have all but wiped us out will have made every landscape look pretty deterrent.

A more adorable, if technically more challenging, proposal came from the philosophers Françoise Bastide and Paolo Fabbri: ray cats, short for radiation cats. A quality rare in nature possessed by domestic cat is that they are not exactly parasitic or symbiotic, but self-domesticating. Cats have proved themselves skilled at ingratiating themselves to human communities where they are not just tolerated, but appreciated for their minor efforts at pest control, and more so for their companionable nature and appealing looks. If felis catus could be genetically modified to change colour, or perhaps even glow, in the presence of radiation, our descendants might learn that this was a prompt to grab the moggy and get the hell out of Dodge.

A ray cat
I think we should go now.

Our history of collapsed civilisations suggests that humans might not be good at very long-term planning, and it seems unlikely that any of the HITF’s schemes will be put in place. Should the worst happen, the next humans may have to learn from hard experience that invisible poisons abound in some places, and these places should be avoided. But one thing our species is good at is improvising, so perhaps warning signs do have a future, even if they will have to wait for the people of the after-times to make them. Homo Anthropoceno would probably use strategies similar to those we use now.

One way of sending a wordless message is to simply put something in a counter-intuitive position or place. These gestures aren’t always immediately obvious and sometimes need to be gently explained. In my own domestic arrangements I have been taught that a balled-up Post-It note in the hallway hasn’t necessarily been dropped by mishap, but is as likely to be an aide memoire left by my partner, reminding herself not to leave home without picking up a particular thing before she goes. For the United States armed forces, flying the stars and stripes upside down has been a way of silently communicating extreme distress (a pattern which has been co-opted in political protests).

Other configurations don’t really need to be learned, and are clear so long as one has some familiarity with the artefacts of the place where they are seen. In a British pub, a towelling bar mat covering a counter tap makes it obvious that the ale from that pump is out of stock. The raised hood of a vehicle beside the road tells us that it has broken down. This could have been a problem in London when old Routemaster double-deckers conked out: their engines are at the front, so the hood is unseeable from the rear. The improvised, universally understood solution was to lean the top of a bench seat against the back of the bus, letting anyone approaching from behind know it wasn’t going anywhere any time soon.

One of these symbolic solecisms which I’ve only come across in the past few years, is seen after closing time in the windows of some cafés and small shops.

Cash drawer tray

The written version of this is often inscribed on the trucks and vans of builders, plumbers and carpenters – No tools or valuables will be left in this vehicle overnight. The empty cash tray, a metaphorical turning out of the pockets, does the same job by literally showing potential smash-and-grab artists that, whatever else might be behind the plate glass, there’s no money to be had. Sometimes the till drawer’s sole purpose is to make this statement: a coffee shop close to where I work, which routinely has one in the window, no longer accepts cash for a croissant, an espresso or a latte. If you only have notes and coins there’s just one way to spend them there: the tip jar.

 Images. Any images included in this post may be used under the terms of the Creative Commons CC BY 4.0 license. Notes. A short documentary on the ray cat solution can be seen at