Dental Calculus Sheds Light on Our Evolutionary History

Dental calculus are the yellowish/whitish deposits that form on our teeth. This formation is due to the crystallization of calcium phosphate crystals. The calculus can especially penetrate the biofilm layer that is located on the lingual side of the lower front teeth or the buccal side of the upper posterior teeth.

Dental calculus are one of the reasons why dentists strongly recommend using dental floss as well as tooth brushing, since calculus accumulates above and below the gum edges of most people and can cause various gum diseases. Dentists also strongly recommended to have these removed every 6-12 months. Our ancestors did not have the luxury of dental visits to have these routinely removed. So, researchers are able to use these to reveal the past dietary habit of our species and our closest relatives!

The development of a mineralized biofilm represents the dynamic process which begins with a non-mineralized biofilm layer and proceeds with the calcification procedure resulting in the production of the matter called “dental calculus”. Throughout these steps of the procedure, the bacterial biofilm is kept within the mineralized residues. It is claimed that 800 different species of bacteria (taxa) are present within this non-mineralized biofilm layer (the layer that is formed immediately following the tooth-brushing).

In addition to viral and fungal taxa, microorganisms associated with diseases of the respiratory tract have been identified both in ancient biofilms and in recent mineralized biofilms.

Southwestern Finland is not considered an ideal please for archaeologists to evaluate our ancestral remains. Pine needles that fall on the ground in the northern forests, lower the pH of the soil making it acidic which results in the destruction of organic matter including our buried ancestors. In addition, the freezing temperatures of a Finland winter is thawed by the rising temperatures that spring brings. These conditions destroy potential archaeological remains very quickly. While the region does contain valuable macro-remains, it can be very challenging to understand the behavior of the local people that lived in these soils during the time period for which we do not have any written proofs or documents.

Micro-remains have almost never been studied in the Iron Age regions of Finland. One of the only exceptions concerning this matter, was a study on the analysis of pollen collected from the teeth of those buried in that period of history. Despite the fact that they are rare studies, these pollen studies can provide valuable information concerning plants in the diets of those that lived during that period. Nowadays, many studies suggest that microfossil analysis should also be included in traditional archaeological research.

Two researches, PhD student Tytti Juhola and archaeologist Amanda Henry, knowing all the challenges described above, decided to try a novel and unexpected method in order to better understand the lifestyle for the people who lived in the Iron Age by studying the remains of the dental calculus of people that lived in that Age!

National Geographic

Every food we eat and every liquid we drink leaves traces within the biofilm, as we mentioned above. Through the biofilm crystallizing and turning into dental calculus, archaeologists gain a great opportunity to evaluate these traces that are left within the biofilm. Although the calculus analysis and the small clues hidden within the structure of the calculus are considered as a relatively new area, these techniques were applied to seek answers for many interesting archaeological questions, such as the content of the Neanderthal diet. Wall drawings, hand tools and nitrogen-carbon studies obtained during the excavation sites of our closest cousins revealed their meat-oriented diets. Besides, it has been discovered that the Neanderthals consumed plant resources, thanks to the remains of their dental calculus which was found in the archaeological site that is located in Şanidar/Iraq and Spy/Belgium.

MPI f. Evolutionary Anthropology/ R. Power

PhD student Tytti Juhola and archaeologist Amanda Henry examined thoroughly the 32 teeth samples gathered from the Luistra cemetery between 1968-1992. Furthermore, they also collected and examined a handful of sediments classified as "unidentified organic matter" or simply "dirt" in the original excavations. In these examples, phytolites, the inorganic skeleton of a fossil that has been produced by plants throughout their lifetime, have been investigated. The shape of phytolite depends on the type of plant cells. Therefore, these small shapes can often be used to define the plants growing in and around an archaeological site, or to prove that someone used to live in this particular region and has bitten the plant with his/her teeth.

However, the examination team did not come across any phytolites in the dental calculus examples gathered from the Luistra cemetery. On the other hand, the phytolites were detected in a location that is far away from teeth; the bracelet on one’s arm, the location which is considered as near the stomach instead of teeth. Even though it is assumed that these micro-remains come from a person's stomach, the scientists were unable to provide evidence for it. Despite the fact that the dental calculus that has been gathered did not contain any phytolites, it contained micro-remains of bird feathers, eggs of intestinal parasites, and animal hair fragments. Concerning the source of the feather micro-remains, it has been claimed that they could have been inhaled during breathing while tearing the feathers of a bird or it is derived from a down pillow.

The presence of intestinal parasite species indicates that the people who lived during the Iron Age, could have been suffering from some digestive health problems and were challenged to provide hygienic environment for themselves. Some animal hair has been identified as belonging to sheep or goats. It has been assumed that there may be several deer hairs coming from the traditional grave cover in Finland during the Iron Age.

Even though these details seem to be too little and vague, they have given us plenty information concerning the lifestyle of those who lived during the times of the Iron Age. It is possible that some people buried in Luistra spent their days knitting wool, or some had suffered from persistent abdominal pain. When these people passed away, they were buried with high-quality items such as elk hides, woven fabric, down pillows or bracelets that secretly contain phytolites by their mourners.

History

Despite the fact that these techniques are very valuable indicators, they actually are just a small part of the big picture, rather than being the only determinant in the elucidation of human behavior. Archaeological evidence, which at one time, was considered as meaningless, can now shed light on the past with the development of technology and perspective.