What will be left after us for the archaeologists of the future? – young Polish scientists wonder. A stone upon stone or maybe something more?
In 1994, the world of archaeology was shaken by the discovery of Göbekli Tepe in south-eastern Turkey, the oldest building complex in this part of the world. Some people claim that it is also the oldest sacral structure on Earth. The deepest layer of the complex contains 20 massive structures, which consist of megaliths with images of predators, connected with oval-shaped walls.
This discovery will revolutionise our perception of Neolithic cultures and suggests a possible source of the agrarian revolution.
It would not have been so well preserved had it not been for the fact that, for some unknown reason, it was entirely buried by the local people around 8,000 BC. The civilisation of that period vanished without a trace for the next 10,000 years and although modern archaeologists have been working hard for over a decade, they find more questions than answers.
One must ask, when looking at how well-preserved such places as Giza, Machu Picchu or Göbekli Tepe are: Which of the things we see now will stand the test of time and live to see the inquisitive researchers of the future?
The illusion of our world’s durability is a widespread and persistent one, and yet most of the materials that we use are susceptible to the inevitable process of degradation. The impact of atmosphere, the presence of water, light, chemical reagents, changes in temperature, the influence of plants, and finally the physicochemical characteristics of the material are the most important factors that determine the degradation rate. Entropy, which is the scientific measure of the disorder in mass and energy, is still growing.
Natural fabrics exposed to air and humidity become oxidised and start to degrade after 150 years. In an aqueous environment, they become hydrolysed and their durability will be reduced tenfold. Acid-free paper exposed to air may last up to 500 years, but the presence of light or water is enough to reduce this time to a few decades. When it comes to buried materials, the chemical composition of the soil is a very significant factor. Wool may last thousands of years in acidic soil, whereas in alkali soil it degrades in decades.
Plastics lose their macroscopic structure after a century or even earlier. However, they break down into smaller fragments, which are very durable and can last for a few hundred years.
It is also worth mentioning that they are very toxic for the environment in that form. The best and largest global example of their effect on the environment is the phenomenon of the garbage patch floating on the Pacific Ocean that stretches for a few thousand kilometres. A similar plastic island is forming closer to us on the Atlantic Ocean.
How long the City of London’s skyscrapers survive? Glass is a cooled liquid, which means that even if it isn’t mechanically damaged, the effects of its “dripping” can already be observed after half a century. The atmosphere causes its oxygen atoms to be replaced with sulphur, for example, which negatively affects its durability. However, the latest research conducted by the Hitachi corporation proves that we can use a modified quartz glass as an extremely durable data storage medium. According to the initial calculations, the durability of this material can last up to 300 million years.
Although metals are very durable, they are very susceptible to corrosion, with some exceptions such as gold or platinum.
A steel rod kept in low humidity conditions and isolated from oxidants will endure much longer than the same one submerged in sea water. One only has to look at the disparity in the amount of preserved monuments and statues made of stone and metal, the latter of which, for example, in ancient Greece, was an equally popular material. In museums, however, we can now only admire stone exhibits.
The information carved in stone has survived thousands of years. A good example of that is the Rosetta Stone (a collection of ancient Egyptian inscriptions on which Jean-François Champollion based his decryption of hieroglyphs for the first time in modern history), but also clay tablets with exercises for Babylonian children. They indicate that the number pi was already at that time calculated to four decimal places! An artificial rock e.g. concrete is also very durable, but none of these building materials is resistant to erosion.
Since most modern infrastructure components have a modular design, erosion will affect them quicker than a homogeneous rock, attacking the junctions between the materials and using their porosity. Frequent passing through the 0 °C point (which, due to water expansion, causes microscopic cracks), sudden and extreme changes in temperature (with differences in thermal expansion of the modules) and plant roots damage concrete and stone constructions. There is a reason why the best preserved finds are usually located in dry zones, where humidity and plants make little or no impact.
Mass culture has created thousands of apocalyptic visions of the future, in which currently urbanised areas are reclaimed by nature, with flocks of predators preying among the ruins of skyscrapers and shopping malls. At least some of these scenarios seem plausible from the perspective of modern science.
There are, however, some constructs that may become long lasting relics of our civilisation. Cold War bunkers and other similar shelters, for example, are massive sealed constructions that are protected against erosion and may last thousands, if not hundreds of thousands of years. Another class of objects “doomed to survive” are the remains of technology in outer space, such as probes and satellites. Other examples are seed banks, kept in a protective atmosphere and at a low temperature in the remote regions of the world (such as the one in the photograph, on Spitsbergen) and some “time capsules”.
The dynamic development of science and technology is leading not only to producing more data storage devices, but also to a dramatic increase in their information storage capacity with every passing decade. But what chances do the future archaeologists have if the majority of objects, and therefore the information stored “directly” on them as well, will most likely degrade in a few, or at most dozens of thousands of years?
Hence the growing significance of a new discipline called digital archaeology. Its pioneers are searching for and preserving websites that are significant to the evolution of the Internet. It is possible, however, that their successors will scan Earth and its surroundings in search for technological remains that will contain information about our civilisation in their very structure, even if they lose their stored information. One of the most interesting types of such findings might be microprocessors.
They are quite durable, due to the production process itself (photolithography), and at the same time they contain a lot of repetitions of the same basic construction information. Because of this, even a major, partial degradation will not stop future researchers from deciphering them. Another aspect that the digital archaeologists of the future may be interested in are modern optical storage devices that not only can provide information about the method of recording and the technological process, but also, under favourable conditions, may contain relatively intact fragments of movies or recorded music.
The rapid development of synthetic biology may also foreshadow genetic archaeology. In terms of information storage density (capacity), DNA eclipses all kinds of storage devices we can currently produce. DNA can store 10^16 bits of information in one cubic millimetre. A hard drive can only store 10^9 bits/mm3. In one milligram of a DNA particle, you might theoretically store the content from all university libraries in Poland and there would still be plenty of room for fiction.
However, the most interesting information for future archaeologists may be stored in the DNA of some of the genetically modified species of plants: our civilisation’s history of playing with genomics and the course of climate change caused by humans.
An interesting finding here may be the previously mentioned seed banks or the DNA of the distant descendants of the organisms modified by our civilisation.
What will archaeologists find then 12,000 years from now? On the one hand, things that modern researchers find – a few silent skeletons of buildings and some scattered everyday objects. Aside from that, they may also find a bunch of outdated electronic stuff that, with a little luck and creativity, may provide them with some information about our culture. Will our legacy survive in a good enough state to intrigue future generations?
We should probably focus on finding the answers to practical concerns: how, with the help of modern knowledge and technology, can we leave a durable and clear legacy of our civilisation.
Authors: Monika Koperska*, Kamil Klinowski**
*Monika A. Koperska is a PhD student of the Stability and Degradation of Paper Laboratory at the Chemistry Faculty of the Jagiellonian University.
**Kamil Klinowski is a PhD student of the Collegium for Social Studies of the Institutes of the Polish Academy of Sciences.