"You are what you eat", an archaeological investigation of diet

You are what you eat. This particular statement has been used time and again to encourage the modern population to move away from “unhealthy” foods and towards those currently believed to be “healthy”. This statement has also been used in a philosophical sense in an attempt to provide a corollary between the person eating and the once living thing being eaten. However, this statement has proven to be very true, especially in an archaeological context.

The consumption of food and overall diet can have radical effects on the human skeleton. These effects occur throughout the entire lifetime of an individual and are dependant on the food intake (or, in some cases, the lack of such) of the individual. These lifetime changes are preserved in the skeleton at the point of death and are thus accessible in the archaeological record.

In many cases, very obvious indications of diet were the teeth of the individual. Those with a diet that contained a lot of inorganic “grit” could expect to have a heavy wear on their teeth. This increased wear could include increased occurrences of dental caries and lesions.

Teeth may also be examined in a more technical manner to provide more information on diet. Food intake is studied by examining the lateral surfaces of the teeth. The lateral surfaces normally escape wear from inorganic material in food and show the wear from the movement of the actual organic food material. In this way, by examining the striations on the teeth, information can be gained about the types of meat and vegetables consumed by the individual.

Another important aspect in the study of human remains to ascertain diet comes from isotopic evidence. Isotopic analysis works on the fact that different plants and animals have different ratios of the carbon isotopes ¹²C and ¹³C. These different ratios occur in plants due to natural processes such as photosynthesis. As photosynthesis works differently in different species of plants, it is possible to distinguish three distinct categories of plant – marine vegetation and two terrestrial vegetation types (known as C₃ and C₄). Each of these plant types will have unique carbon isotope signatures.

Animals (including humans) that eat these plant types begin to absorb the isotopic residue. This will, in turn, alter the isotopic ratio in the consuming animals. This provides evidence, in the form of chemical signatures, about the vegetative diet of the individuals being studied as it allows broad categorisations based on their diet – for example, it may show a high amount of the marine carbon isotope, suggesting that the individual may have relied heavily upon a marine diet.

In humans, the chemical signatures are examined on tooth enamel and bone collagen. The chemical signatures provide information about the diet and environment of the people being studied. They tell of the long term dietary intake of the subjects and may be said to prove the assumption that “we are what we eat” (Renfrew & Bahn, 2004 p 313).

However, this evidence is not as certain as it may initially appear.

“the only incontrovertible proof that a particular plant or animal species was actually consumed is the presence of its traces in stomach contents or in desiccated faecal matter” (Renfrew and Bahn, 2004, p275)

Failing this evidence being present, archaeologists may settle for the presence of floral and faunal remains in the archaeological record of the individuals being studied. A study of 58 native North American adults (31male, 18 female and 9 unidentified) at Moatfield, Ontario, Canada, was able to determine a meat diet that consisted of fresh water fish, land mammals and avians. This interpretation of the isotopic analysis was backed up by the finding on the site of the remains of these types of animals. However, the exact composition of the meat diet was not calculable from the available data (van der Merwe et al. 2003).

In some cases the historical record may also provide verifiable clues about the dietary practices of an era. Historic evidence from medieval England shows that there was a strict calendar of abstinence from meat based on church teachings. This meant that there was an increased importance upon the consumption of fish as a non proscribed meat substitute. The historical evidence is borne out in the archaeological record after excavations at various sites in Northern England (Muldner & Richards, 2005, p41).

This evidence was also able to create a distinction between urban and rural diets at the time. The excavation reports, isotopic analysis and subsequent comparisons between sites at Warrington (an urban mass grave) and St Giles (a rural cemetery) North Yorkshire show that urban diets were generally better. This is accredited to a greater variety of fresh foods on offer in the urban areas.

Not everybody is happy with the assumption that collagen provides adequate isotopic evidence. RH Tykot asserts that:

“isotope studies have specifically determined that bone collagen is produced mainly from dietary protein, whereas bone apatite and tooth enamel represent the whole diet” (Tykot, 2006, p132).

Tykot believes that there are other methods that may prove to be more accurate in assessing the dietary practices of past populations. Tykot carried out controlled experiments on animal populations. The results of these experiments seemed to support his claim that bone and tooth apatite (i.e. their inorganic components) provided verifiable evidence for the whole diet being examined (Tykot, 2006, p138).

Turner et al. supported the assertion that collagen isotopic analysis was inadequate, but they also went on step further by saying that both collagen and apatite analysis could both suffer from “diagenetic alteration, which can distort biogenic isotopic signals” (Turner et al., 2006, p7).

Renfrew and Bahn repudiated both arguments by stating “that the collagen method is the only one whose validity is confirmed for the present” (Renfrew & Bahn, 2004, p314).

However, one does not need to rely upon isotopic analysis for all assessment of dietary practices. There are often other indicators of diet present in the archaeological record. This is often true in cases where humans were consuming things that proved to be detrimental to their health. In Roman England, the elite inhabitants of Poundbury were using lead based cosmetics which left very obvious traces on their bones. There were similar things happening in later populations, such as the Colonial North Americans who were eating their food off of lead glazed tableware and drinking from pewter flagons! “However, only the rich could afford to poison themselves in this way” (Renfrew & Bahn, 2004, pp454-455).

This was not the only time that unhealthy measures were taken as standard practice. For example, mercury inhalation was used as a treatment for syphilis and similar conditions. This use of mercury can be deduced from the archaeological record, and, in some cases, backed up by the historical record.

Consider the case of Isabella D’Aragone, a 15^th century Italian noblewoman and the possible inspiration for the Mona Lisa. Isabella inhaled mercury regularly in an attempt to lessen the effects of the syphilis that was afflicting her and, as a result, gained a black stain upon her teeth. This is also a case of the cure being worse than the disease as Isabella’s likely cause of death was mercury poisoning and not syphilis (Renfrew & Bahn, 2004, p455).

In dietary terms, it was not just what you ate that could affect your skeleton, but also, due to circumstances beyond the control of the individuals being studied, what was not eaten. Malnutrition, where the body does not get enough food, could have a huge effect. In adolescent and pre-adolescent human remains, malnutrition could lead to stunted growth. Malnutrition in adults could lead to the flattening of the long bones of the lower limb.

Malnutrition could also have other effects. These often included a decrease in the overall skeletal size. In particular, this was often especially apparent in the face and jaw with significant reductions in the size of both. This was due to the body attempting to resorb the calcium contained in the bones in order to sustain the body (Renfrew and Bahn, 2004, p460).

In a very real sense the statement that “you are what you eat” is true. Archaeological assessment of past populations has been able to provide indications of the diets of these populations based upon the examination of human remains. Dietary practices left clear indications on these remains which allow those studying the remains in the present to create a “menu” of the foods that were eaten. These menus can be verified by various means available to archaeologists – such as the inclusion on the sites where the remains were discovered of floral and faunal remains that match the assessment of dietary practices. In examining past populations in the historic period, archaeologists can also access the written, historical records which may also contain clues about the dietary practices of populations.

Archaeological assessment of human remains can also ascertain dietary practices that may seem silly to modern populations (who, of course, have the perspective of hindsight). Essentially, the archaeological record of human remains may contain clues for every single morsel that passed a persons’ throat – the only challenge, then, is creating the ability to access and assess this information.

Bibliography

Muldner, G and Richards, MP, Fast or Feast: reconstructing diet in later medieval England by stable isotope analysis, in Journal of Archaeological Science 32 (2005), pp39-48

Renfrew, C and Bahn, P, Archaeology: Theories, Methods and Practices, London 2004, pp 275-317, 429-468

Turner, BL; Edwards, JL; Quinn, EA; Kingston, JD and Van Gerven, DP, Age-related Variation in Isotopic Indicators of Diet at Medieval Kulubnarti, Sudanese Nubia, in International Journal of Osteoarchaeology, Atlanta 2004

Tykot, RH, Isotope Analyses and the Histories of Maize, in Staller, J; Tykot, RH and Benz, B, Histories of Maize, Florida 2006, pp130-142

van der Merwe; NJ, Williamson, RF; Pfeiffer, S; Cox Thomas, S and Oakberg Allegretto, K, The Moatfield ossuary: isotopic dietary analysis of an Iroquoian community, using dental tissue, Journal of Anthropological Archaeology 22 (2003), pp245–261