Palaeodiets

Isotopic analysis is widely used within the worlds of archaeology and anthropology. From analysing isotopes we’re able to uncover a wide range of information regarding the past; ranging from palaeoenvironments to palaeodiets, and even using isotopes to reconstruct trade routes of materials.

But first, what are isotopes?

All of the chemical elements consist of atoms which are specific to the element and the mass of an atom is dictated by the number of protons and neutrons it contains. The identity of the chemical element depends on the number of protons found within the atom’s nucleus, but the number of neutrons within the atom can vary. Atoms of the same chemical element (same number of protons), but with different masses, which is from the varying amount of neutrons, are called isotopes.

Within nature, most of the elements consist of a number of isotopes. These isotopes can be found within water, livestock, crops and plants, which can then be used to reconstruct palaeodiets and palaeoenvironments.

Within nature, most of the elements consist of a number of isotopes. For a great majority of elements these relative proportions of isotopes are fixed, but there are a group of elements which either due to chemical or biochemical processes are of variable isotopic composition. These elements are oxygen, carbon, nitrogen and sulphur. Another group of isotopes that are used for analysis are strontium, lead and neodymium. These are formed by elements which contain stable but radiogenic isotopes, which are formed by radioactive decay of another element. Carbon and nitrogen isotope composition are primarily used to reconstruct diets, and oxygen isotopes are used to determine geographic origin. Strontium and lead isotopes found within teeth and bone can sometimes be used to reconstruct migration patterns in human populations and cultural affinity

A table of the various elemental isotopes that are valuable in archaeological and anthropological research.

But how do isotopes get into skeletal remains?

Carbon isotopes are taken up through the diet of animals during their lifetime and these isotopes are deposited into teeth and bones of humans when they are consumed and digested. By studying animal bones and examining the ¹²C and ¹³C isotope ratio, it is possible to determine whether the animals ate predominately ³C or ⁴C plants. Oxygen isotopes are constantly being taken up and deposited into the body through the water a population drinks. This process ends with the organism’s death, from this point on isotopes no longer accumulate in the body, but do undergo degradation. For best result the researcher would need to know the original levels, or estimation thereof, of isotopes in the organism at the time of its death.

By creating a map of these natural occurring isotopes in different environments, rivers and areas, it is possible to identify where in an area the population lived, sourced their water or where the livestock grazed, by comparing the levels of isotopes that were obtained from skeletal remains to the environmental map. This mapping can also help identify trade routes that once existed and can also identify the migration patterns of populations.

References:

Balme, J., Paterson, A. 2006. Archaeology in Practice: A Student Guide to Archaeological Analayses. Oxford, UK: Blackwell Publishing. Pg 218.

Renfrew, C., Bahn, P. 1991. Archaeology: Theories, Methods and Practice. London, UK: Thames & Hudson. Pg 249-53.

If you’re new to the realm of archaeological, anthropological and forensic sciences (AAFS), or are a student needing sturdy and reliable references, or wondering “what archaeology or anthropology textbooks to buy?” Check out our new ‘Useful Literature’ page!

This is a Quick Tips post providing a basic answer to a commonly asked question often faced within the field of archaeology and anthropology.

An anthropologist can obtain a wide and varied collection of information from examining teeth. Information such as paleodiets and palaeoenvironments can be learnt from studying a population, or from studying an individual sample you can identify how old the person was at time of death or whether that person was pregnant/ill. These examples are just the tip of the iceberg on what you can learn from dentition.

An anthropologist can obtain a wide and varied collection of information from examining teeth, ranging from palaeodiets and palaeoenvironmental information to age of death.

From studying a large population dentition sample, a picture can be painted of their past diets, current diets and palaeoenvironments. Isotopes play a huge part in conducting research into palaeodiets and palaeoenvironments.

Isotopes are deposited into the teeth of an individual/population from food sources or environment. A tooth can provide isotopic information from the past 20yrs of the individual’s life. The enamel and dentine can be examined to analyse the isotopic values that will pinpoint an origin of a population or food sources. The carbon and nitrogen isotope compositions found within the enamel are used to reconstruct diet and the oxygen isotopes are used to determine the geographic origin of the food source. The carbon isotopes are absorbed from the diet of the animals that are sources and the oxygen isotopes from the water that the population consume. These isotopic values are vital in helping an anthropologist understand the local ecosystem a population exploited and whether a population migrated to numerous locations which caused changes in the available diet.

The cementum of a tooth can highlight important information about a person which can be used for forensic identification; this information could give an approximate age of death. An example of this application is seen in Kagerer and Grupe (2000) study where they obtained 80 freshly extracted teeth and investigated the incremental lines in acellular extrinsic fibre cementum. From studying the cementum, they were able to determine the age of the patient by comparing it to detailed queries of the patients life history. This study also identified patients who were pregnant. Kagerer and Grupe (2000) concluded that if there was a presence of hypo-mineralised incremental lines on the extracted tooth, the patient was pregnant. This is due to the pregnancies influence on calcium metabolism. A confliction with this is that hypo-mineralized lines can also appear when a skeletal trauma or renal illness was present.

By looking at the dentition of molars the age of the skeleton can be estimated. A recent study by Mesotten, et al. (2002) highlighted the application of forensic odontology. Mesotten, et al’s methodology consisted of examining 1175 orthopantomograms which belonged to patients who were of Caucasian origin and were aged between 16 and 22years. From their investigation Mesotten, et al. were able to conclude that from studying the molars, it was possible to age Caucasian individuals with a regression formula with a standard deviation of 1.52 or 1.56 years for males and females, respectively, if all four third molars were available. This could play a fundamental role in identifying a missing person by estimating the decease’s age and seeing if its estimate matches the individual.

Although the studies from Mesotten, et al (2002) and Kagerer and Grupe (2000) have been written about and applied to individual cases, their methodology and conclusions can be applied to a past population if a group of skeletons were found with preserved teeth. The individual’s age of death can be used as quantitative data, alongside other individuals from the same sample, to figure out a past population’s life expectancy.

References:

Kagerer, P. Grupe, G. 2000. Age-at-death diagnosis and determination of life-history parameters by incremental lines in human dental cementum as an identification aid. Forensic Science International. 118, 1. 75-82.

Mesotten, K. Gunst, K. Carbonez, A. Willems, G. 2002. Dental age estimation and third molars: a preliminary study. Forensic Science International. Volume 129, Issue 2, 110-115

To learn how archaeologists and anthropologists use teeth to age skeletal remains, read our Quick Tips: How To Estimate The Chronological Age of a Human Skeleton – Using Dentition to Age Subadults. Or to read more of our interesting Quick Tips, click here.