There are, of course, other historical records. Great works of art and literature are likely to survive for a fair amount of time through replication or conservation, whether or not they are stored digitally. But there are limits to physical preservation, and the destruction of intentionally conserved records tends to be down to human, rather than natural processes. Julius Caesar is thought to have (accidentally) burnt down the centuries old library at Alexandria; in modern day Greece, Iraq, and Egypt political and economic factors have allowed looters to raid important museum collections. We might put books, photographs, and even dead bodies into cold storage, but the fact is that we can’t guarantee the maintenance of such facilities indefinitely. The further into the future we go, the more likely it becomes that our unintended material remains will be the ones to survive.
In what sort of environment might such remains survive? Well, that depends to a large extent on the materials themselves, but there are certain extreme environments in which the preservation of a large number of both organic and inorganic materials is likely. Organic materials in particular are prone to degradation, so such rare finds provide an important resource for contemporary archaeologists. The greatest enemies of long-term preservation are oxygen, moisture, and variable temperature. Consistently dry environments, such as the deserts of Egypt; oxygen-free environments, such as peat bogs in Britain, Ireland, and Denmark; and environments of extreme (and persistent) cold are top of the list for long-term preservation.
In 1991, a pair of hikers in the Ötztal Alps came across a body, face down in ice and melt water. Thinking they had stumbled upon a modern murder case, they immediately contacted the authorities. It quickly became apparent, however, that what was being dealt with – though it may indeed have been a murder case – was pretty far from modern. The man, who was named Ötzi by his modern investigators, had been killed over 5,000 years ago, by an arrow in the back and a blow to the head, before his body was buried by snow and later ice, preserving him along with his tools, weapons, clothes, shoes, and backpack. Just to be clear here, no other finds of this antiquity are so well preserved. Climate change was behind the melting of the ice and, had it not been discovered in the nick of time by the hikers, Ötzi’s body and accessories would no doubt have succumbed very quickly to the effects of exposure.
One organic material that may last rather longer than most is plastic. This may not be such good news for the environment, as shown by the marine biodegradation timeline provided by the Centre for Microbial Oceanography (#mce_temp_url#): the idea of disposable nappies floating around in various stages of decay for up to 100 years is not desirable in any sense. Anybody who has seen the harrowing photographs in Chris Jordan’s project ‘Midway: message from the Gyre’ (#mce_temp_url#) will agree that contemporary plastic waste can be a hazard, but just how long will plastics last? Depending on the composition of a plastic, its degradation can be affected by factors such as heat and light, or in a buried environment pH, but most are thought to be durable enough to survive for 100s of years. There is no way of being certain, however, because the first plastics were developed just over 100 years ago, and the composition of those in use today was only developed over the last 50 years.
“Forget your mobile phone, laptop, books, clothes, and all that they say about you.”
In fact, ‘organic’ plastics are now being developed, which should biodegrade more quickly (#mce_temp_url#). All of this is rather relevant for us and our children, but in the distant future – 1,000 and more years away – it is unlikely that many plastics will survive from our time and, if they do, they may be in a state of severe corrosion. Archaeologists of the yet more distant future, two, three, or four thousand years away, may find themselves reconstructing the flesh of our material world – paper, plastics, wood – based only on surviving ceramics, the odd fossil, and certain stable metals or alloys: just as we today attempt to reconstruct the wooden hafts of stone tools, or the architecture of ancient houses based only on the holes into which supporting posts were fitted.
Inorganic materials, of course, are also vulnerable to degradation and corrosion. Early Medieval iron swords on display in the British Museum are corroded almost beyond recognition, but careful analysis with radiography and other scientific techniques shows that they were once items of outstanding beauty and terrifying functionality. Replica swords are displayed alongside these corroded remains, in order to show their complex pattern-welded designs, the work of master craftsmen, and the product of a developed understanding of the behavior of metals.
With the exception of gold, which the ancient Egyptians equated with the flesh of the gods because it resists even the faintest tarnishing over time, most metals will suffer the effects of oxygen and other chemical action on their surface. Modern metallurgy has developed various means to combat this, including non-metal coatings and various specialist alloys, but these are mainly designed for use in architectural and industrial settings. In any case they can’t protect a piece once it has suffered physical damage, such as bending. Nor do they prevent recycling: copper is today so valuable that the theft of copper piping from unused buildings is a commonplace problem.
So, forget your mobile phone, laptop, books, clothes, and all that they say about you. Ceramics (including bricks), glass, and stone are likely to form the basis of the long-term material record of your life. Ceramics – in the form of pottery – are already of incredible value to contemporary archaeologists. As well as being pretty much ubiquitous in archaeological sites of the Neolithic and later due to its resistance and functionality, pottery is an extraordinarily accurate marker of change over time. We are accustomed to thinking of the archaeologist carbon dating everything, but in fact the expense and limitations of carbon dating (it can only be performed on certain organic remains) mean that it is more commonly used as an ‘anchor’ for dating by more old-fashioned means. One of these is simply to look at the style of pottery found in a given layer, and compare it with others of known date.
Chemically speaking, modern glasses are pretty resistant and should survive for 1000s of years. It is unclear how they will be used by future archaeologists, though, given that very few glasses are likely to survive intact due to their combination of delicacy and relatively low value. Current archaeologists use the chemical signature of ancient glass to investigate where it was originally made, so perhaps glass will become one marker of international trade relations. Stone, of course, is the ultimate chemically resistant material. Where they have not been re-used or robbed, building facades and sculptures will be available for recording, and will at least show our interconnectedness in bringing together materials from many parts of the world.
This brings me onto another very important point in our consideration of the remains we will leave behind: the uniqueness of the modern situation. Although I have been rather scathing of ‘end time’ arguments, there is no doubt that we are living through a period of extraordinarily rapid growth and change. Assuming that anatomically modern Homo sapiens appeared at around 50,000 BC, the total number of people ever to have existed is estimated at 108 billion. Given that between 6.25 and 7 billion of those are alive at the current time, the current global population makes up around 6% of all the humans who have ever lived (some rather more outrageous estimates are debunked here: #mce_temp_url#). Added to this, we live – at least, in the West – in a time of unprecedented material consumption.
The effects of these factors on archaeology will depend on how far into the future we want to look. In the near future, rebuilding in urban areas will likely mean that older architectural remains will be destroyed by successive generations. Archaeologists will have to look to abandoned areas for clues to material culture and everyday life. Such sites are fascinating even to the contemporary eye, as illustrated in the extraordinary photos of abandoned parts of Detroit posted at buildingsofdetroit.com (site currently under construction: see instead #mce_temp_url#). In the long-term, however, abandoned sites are likely to yield surprisingly few remains. Even close to the centre of the Chernobyl exclusion zone, where radiation levels were still at 40ci/km2 a whole ten years after the disaster, looters and former residents are known to have started returning within a few years and even months to recover possessions and valuable items.
If urban sites are too complex, and abandoned sites are looted, where will archaeologists be able to look for our material remains? One obvious choice might be landfill sites. In the ancient Middle East, people occupied the same sites for long periods of time, and as layer upon layer of discarded material was laid down over the centuries, artificial hills known as ‘tells’ were formed. Such sites are invaluable for present day archaeologists, as are middens (discard heaps) and other disposal sites. The size of landfills, however, may prove limiting. Tells and middens have a clear stratigraphy; that is, they show change over time. The sheer quantity of modern waste means that landfill sites are rapidly filled, reflecting just a few years’ of use, and they are spatially disassociated from other sites such as houses or factory sites.
Some of the future gaps in knowledge about us may be filled in by so-called ‘time capsules’; archaeological remains of a single event, such as the burial of Pompeii under volcanic ash and pumice. Shipwrecks in particular could prove promising sources of information, as underwater environments can aid preservation due to the lack of warmth, light, and oxygen. The famous wreck of a Bronze Age trading ship at Ulu Burun, off the southern coast of Turkey, offers an insight into the luxury goods prized over 3000 years ago, including perfumes, ostrich shells, ivory, and various foodstuffs. Modern warfare may also contribute to the archaeological record, and – like it or not – much could be made of submarines, tanks, and the wreckage of fighter planes in the future.
It is admittedly rather amusing to think about the mistakes future generations might make about us, based on the foibles of the material record. Will it be assumed that in the west, people who wear large amounts of gold jewellery belong to the ruling class, for example?
Actually, I don’t think this sort of mistake very likely. Archaeologists currently recognise that what may seem ‘common sense’ to us could be completely alien to the people of the past, or even to other groups in the present. To refer to the example above, status can be determined by many factors, including where a person is buried in relation to others, and their health as determined by bone condition. What is probable, by contrast, is that we will only be understood in a limited sense: the complexity of our thoughts and beliefs will become more difficult to reconstruct as time goes on, and the finer twists and turns of history will eventually become lost against the vast timescale of human existence.
All of this, of course, supposes that archaeologists themselves will survive the test of time. That may be rather an arrogant idea, though admittedly necessary for the current thought experiment. In any case, the archaeologists of today might learn a little from considering the future as well as the past. In particular, there is a rather ‘gung ho’ attitude to archaeology in the media and in the eyes of many archaeologists themselves, leading to an over-emphasis on excavation by comparison with conservation and publication. There exist a finite number of archaeological sites, and more money must be spent on preserving them in situ wherever possible. After all, what has survived for millennia in one place is unlikely to do better in a museum store cupboard.