Image credit: Pixabay, 2017.
There are few fields that are as interdisciplinary as archeology. From radiocarbon dating to ground-penetrating radar, Archeologists use a wide range of scientific methods to gain insights into historic cultures. But which scientific methods are actually most useful to archeologists? And what kind of information do they provide? I have interviewed Professor Kerstin Lidén, an archeologist at Stockholm University, to find out more about this. According to her the three most important scientific methods for archeology are ground-penetrating radar (GPR), mass spectrometry and X-ray fluorescence (XRF).
Ground penetrating radar (GPR) is a physical method also used in geosciences. It emits radio waves into the ground and detects their reflections caused by burried structures, for example ruins of castles, temples or settlements. GPR is popular because it offers the possibility to identify the location and the form of buildings and monuments without digging them up.
Mass spectrometry is a chemical technique that normally helps to determine the composition of unknown substances, as many of us have seen in TV crime dramas. In archeology, however, it is used differently. Here, its main task is to identify different isotopes (atoms of the same element with different neutron numbers). One example is the identification of the carbon-14 isotope, a radioactive carbon isotope used for radiocarbon dating. As long as plants, animals or humans live they incorporate carbon-14 into their systems, either by photosynthesis or by eating plants. No new carbon-14 enters the organism after death and conclusions can be drawn about age from the radioactive decay of carbon-14 and its half-life.
Isotope analysis can teach us even more about long-deceased organisms. Carbon and nitrogen isotopes are used to reconstruct diets, while oxygen isotopes can help to determine geographic origins and environment. Strontium and lead isotopes, on the other hand, can give clues about population mobility which means seasonal and/or permanent migrations.
X-ray fluorescence (XRF) is popular to gain information about the chemical and elemental composition of historic artefacts made from metal, glass or ceramics. This method works by bombarding the archeological sample with X-rays or gamma-rays which causes the removal of inner-shell electrons from the sample atoms. As a response, electrons from outer-shells will ”fall” into the inner-shells and simultaneously emit energy in the form of characteristic X-rays. These can be used to identify the chemical composition of the artefact.
Besides the three techniques described here, there are many other, some pretty cool, methods in operation by archeologists. Lidén gives the example of one colleague who used laser scanning to study the writing on rune stones. This analysis showed that different people had carved on the same rune stone. According to Lidén it is like analysing hand writing, only that it is over 1000 years old.
Lidén also says that the goal of archeologists is to get ”life history details of individuals that have been dead for thousands of years”. The information from different scientific techniques has to be put together like a puzzle to gain this information. In the end, archeologists will know what an individual ate at different points in life, where he/she lived and if there was movement between different geographical areas, which diseases the person might have had and when the individual died. This kind of information is important to understand variations and similarties between different cultures and populations.
What Lidén is most proud of in her own work was showing that two archeological cultures in Sweden were really two different cultures. She and her team were able to show that they did not only use different materials and burried their dead differently, but also actually ate different foods. This had long been disputed in Sweden before.