Nutritional Anthropology 1/3: Optimising Diet


Having finished my degree in medical anthropology, I thought I would post three relatively unedited essays which link nutrition, social structures, and health.  I am not posting the essays in chronological order; rather, I want to present the essays according to a more thematic progression.  The first essay therefore looks at how pre-industrial human societies create their diets not simply on the basis of what foods are local, but also around social structures and alliances.

A !Kung Community in the process of resettlement

(I)
What evidence is there that pre-industrial human societies might naturally optimise their diets to maximise both health and reproduction?

While a certain amount of evidence exists that pre-industrial societies optimise their diets to maximise both health and reproduction, that optimisation is neither spontaneous (i.e. ‘natural’) nor immune to influences from social, market, and power relations. This is particularly the case if ‘pre-industrial societies’ is understood not simply as an academic term for contemporary hunter-gatherer communities, but includes the more colloquial meaning of the pre-seventeenth century world in general. In this essay, I hope to demonstrate that the health benefits experienced by some of these societies, particularly with regard to longevity and causes of mortality, are more closely tied to egalitarian social structures and the freedom to catch or cultivate food resources of one’s own choice.

The Optimal Foraging Model is a model used to assess the cost-benefit ratio of choosing to hunt certain game over others. The theory is that communities will choose those animals which give the best energetic return for caloric investment. As Hawkes et al (1985) note, the model is used to simplify complex data in order to identify “the factors that most significantly shape subsistence behaviour,” but “are not suited to describe the interaction of all, or even a large number of the variables that might affect subsistence-related behaviour.” (Hawkes et al. 1985:401) However, in using the model, Hawkes et al. collected extensive data on the diets of the Ache of Paraguay (Hawkes et al. 1982) and the !Kung of the Kalahari (Hawkes et al.. 1985). Both groups happen to have an egalitarian social structure. A subsequent study by Cordain et al, which drew on the data gathered by Lee (1968) and Hawkes et al (1982, 1985), noted the low rates of cardiovascular diseases among the !Kung and Ache, despite the high percentage of animal based food sources in their diets, an observation which is at odds with the epidemiological data for industrialised countries (Cordain et al 2002). Cordain et al. hoped that by examining the diets of contemporary hunter-gatherer societies, some insight into a purported singular and essentialised ‘paleolithic diet’ could be gained for the purposes of designing therapeutic diets to counteract disease patterns seen in industrialised countries. Although in their concluding remarks Cordain et al noted the diets of modern hunter-gatherer societies “may have operated synergistically with other lifestyle characteristics (more exercise, less stress [sic], and no smoking) to further deter the development of CVD.” (Cordain et al 2002:S49) , they do not go into detail about these potential synergistic effects. In particular, they do not describe how the Ache and !Kung groups experience less stress, leaving one to wonder if their work is underpinned by twenty-first century remnants of a bon sauvage approach.

The Ache and !Kung are not the only groups to have been studied in relation to the ‘diseases of modern life,’ however. Looking at health from the opposite end of the spectrum, the presence of modern diseases among groups which have transitioned from hunter-gatherer food acquisition practices to industrialised wage-dependant diets has been shown in studies of Australian Aborigines (O’Dea 1991) and the Pima nation of the American Southwest (Benyshek 2001). (The Pima, however, were an agricultural people; more on this below.) Both these groups have high percentage incidences of type 2 diabetes, cardiovascular disease, and obesity. In contrast to these two groups, the Aleut, Inuit, and Dogrib, all of whom incorporated ‘western’ foods into their traditional diets without shifting to a western lifestyle or type of work, have managed to stave off the several modern chronic diseases manifested among the Pima and Aborigines (Benyshek 2001, drawing on Helm 1981 and Chance 1984).

The natural conclusion from these studies is that something about the pre-industrial diet exerts a protective health benefit. However, I would venture an additional hypothesis: something about how these societies structured social relations and food acquisition practices were key to their health. To support this claim, I will first look at how the Optimal Foraging Model (OFM) can be applied to agricultural groups, so that we can see how the same predictive factors of nutritional expenditure and input continue to work even after a transition away from foraging. Second, I will assess a critique of the OFM through a study of the Etolo of Papua New Guinea, which demonstrates how social relations can provide the impetus for both hunting and the subsequent distribution of resources. Finally, I will briefly examine three cases, one from Palaeolithic China, the second from present day Kenya, and the third from Medieval Europe, which corroborate how diet is susceptible to social, and ultimately economic, relations.

Keegan (1986) examined whether the Optimal Foraging Model could be applied to the choices horticultural communities make about what crops to grow. Horticultural communities are presented by him as a transitional point between agricultural subsistence and hunter-gatherer modes of food acquisition. As such, they provide an example of a society in the process of selecting which food items, and how much of each, to cultivate and which to disregard. Although their particular environment may never pressure them to adopt agricultural practices exclusively, and in fact may constrain such a development (Keegan 1986:102), it is assumed that most agricultural communities went through a period similar to what modern horticulturalists continue to practice. Keegan particularly looked at the diet of the Machiguenga of Eastern Peru, because the data were available, and compared it with Hawkes et al’s analysis of Ache hunting choices. The results indicated that choices about which food resources to exploit varied by resource availability as compared to all available options, and that the seasonal change in diet reflected which food resources provided the most net gain at that particular time (Keegan 1986:103). The choice of which crops to grow, therefore, was predictable using the OFM.

Postcard of Etoro or Etolo from Papua New Guinea

The Optimal Foraging Model, due to its simplicity, can easily be critiqued. The model examines principally energetic expenditure and returns; it does not take into account what happens to the food after it is obtained, how that food is distributed among the community, nor does it look at the motives which inspire a hunter to search for game on a particular day. Additionally, Robson and Kaplan, though not directly critiquing OFM, note that young hunters are not necessarily the most capable, and expend a greater amount of energy learning their craft with the expectation of higher returns in later years. Therefore, the simple numbers may not be evenly applicable for all hunters. One study which does examine the motives for going hunting and the choice of certain hunting companions over others was conducted by Dwyer among the Etolo of Papua New Guinea (Dwyer 1985). In this particular case, social relations within the community had been disrupted by a series of accidents involving the exchange of marriage-wealth. The resulting conflict pitted several houses against one another. As Keegan summarises,

Three events, or sets of events, appear as primary in motivating m2 to hunt. (i) Gifts of meat his family had received from m3 and f3 encouraged him to reciprocate. (2) The marriage of his half-sister fi encouraged him to make a prestation through her to her (and his) new kin. (3) He had been unsuccessful in an earlier attempt at easing tension between the residents of Houses III and IV and a joint hunting venture would provide another means towards that end. m2, as a key sponsor of fi’s marriage arrangements, and m4, as injured party, were focal to the difficulties that had arisen between the two households.

The choice to go hunting, in this particular instance at least, was therefore susceptible to social relations. The effect social and economic relations have on diet is also seen in other societies, ancient, medieval and modern.

Ancient China provides interesting evidence that pre-industrial health optimisation is negatively impacted by changes in social stratification. Pechenkina et al (2002) examined skeletal remains from two cultures in Neolithic China, the older Yangshao and the more recent Longshan. The Yangshao diet consisted of some agricultural products, notably millet, supplemented by game and fish. Because little evidence of social stratification has been forthcoming, scholars assume the Yangshao lived in an egalitarian society. Aenemia and carious lesions have rarely been found among their remains. The shift from Yangshao to Longshan culture coincided with climatic change, and it may be theorised that this climatic shift forced the evolution of agricultural techniques if the communities were to survive. As Pechenkina et al write, “Further agricultural intensification in response to proposed climate change increased the caloric base, which permitted rapid populatin growth at the Yangshao-Longshan transition. As people aggregated into larger centers, their access to wild food resources became even more limited and their diet narrowed.” (Pechenkina et al 2002:16) The “chiefdom-like society” of the Longshan, although they intensified pre-existing agricultural practices, paradoxically experienced poorer health, as evidenced by osteoarthritis in the jaw, more extensive indications of anemia, reduced stature (particularly evidenced in sexual dimorphism, perhaps indicating females suffered more frequently from nutritional deprivation), and growth disruption lines in tooth enamel, exacerbated by poorer hygiene from crowded living conditions. Interestingly, the Longshan period is also characterised by advances in technology, and is considered to have laid the foundations for the Zhou and Shang dynasties (Pechenkina et al 2002). The two principle changes I note are shifting social structures (egalitarian-chiefdom/ patriarchal) and the reduction of dietary breadth.

While ancient China offers some circumstantial evidence of how social structures affect dietary practices, medieval Europe offers more concrete examples. Pearson, a historian, notes that Charlemagne required a bishop to provide the palace with two cartloads of soft rind cheese per year, after Charlemagne sampled the cheese at the bishop’s table (Pearson 1997:10). This is a clear example of how food functions to preserve or augment social relations. Other examples of how social practices influence dietary choices drawn from medieval history are the rations permitted to monks, nuns, and workers in monastic communities (Pearson 1997:16). Finally, the revenues required by feudal lords of their tenant farmers to their feudal lords supply evidence that what the tenant farmers chose to grow was not always by their own choice (ibid, 20).

Finally, the ethnography by Fujita et al (2003) examines how a shift from pastoralism to sedentarisation causes nutritional deficits along wealth lines. Historical work by Adas, however, indicates pastoralism usually comes about after a shift from HG to agriculture because agricultural societies provide the springboard from which pastoralism is able to develop (Adas, 2001:75). Therefore, the Kenyan example may not be the best example to use. However, it does indicate that the relation of nutrition to social distinction(s) seem to be exacerbated under certain conditions, and that sedentarisation is one of them.

In the context of social inequality and decision making, it is interesting to note studies which have examined the impact of social relations on brain size (Aiello and Wheeler 1995:208). In contrast, Robson and Kaplan (2003; Kaplan and Robson 2002) associated brain size with an increase in intelligence, in their examination of the co-evolution of brain size and longevity. Although their association of brain size with intelligence may be problematic, when their study is combined with Aiello, a triad of relations emerges: social relations foster greater brain size, which is dependant on higher nutrient acquisition, which itself relies on social relations which are themselves benefitted by greater (post-fertility) longevity to allow the acquisition of complex foraging and hunting skills. As noted by Robson and Kaplan, “the economies of hunter-gatherers rely on skill-intensive food production strategies that would not be viable without massive intergenerational resource flows and exceptional adult life expectancy.” Robson and Kaplan also argue that resource flows between generations, because these flows continue even the period of fertility in human women ends, may be more useful than models which simply look at sheer fertility in terms of numbers of offspring, in terms of health optimisation (Robson and Kaplan 2003:157, 164).

If health is measured by an absence of chronic disease markers while alive and its absence as a cause of mortality at death, and fertility is measured not by number of offspring but by that longevity which ensures reproductive success through longer intergenerational resource flows to offspring, then hunter-gatherer communities may not be the most optimised communities to study, despite their low levels of death from neoplasms or chronic diseases (Gurven and Kaplan 2007). Gurven and Kaplan (2007) in their cross-cultural survey of longevity among hunter-gatherer societies note that “the average modal age of adult death for hunter-gatherers is 72 with a range of 68 – 78 years. This range appears to be the closest function equivalent of an ‘adaptive’ human lifespan.” They go on to point out that illnesses such as infectious and gastrointestinal diseases (less than half due to contact-related diseases) account for 70 percent of all deaths in their sample.

The chronic disease-free situation of hunter-gatherers could be fruitfully compared with ‘blue zones’, areas of the world in which a high density of centenarians live disease-free lives. These communities could be seen as continuing the evolutionary path which led to greater longevity in hominids in the first place. In particular, an examination of resource flows through the generations, and an evaluation of the egalitarianism (or lack) experienced in the work and social lives of the centenarians may provide additional insight into those factors which can promote longevity and health in industrialised societies like Okinawa, eastern Sardinia, Ikaria, and Loma Linda in the USA. Future research might ask what other social practices are shared between contemporary hunter-gatherers and blue zone communities.
While some groups seem to optimise health ‘naturally’, the reasons allowing this seem more related to egalitarian social practices than to pre-industrial status as such. As Woodburn (1982) writes about hunter-gatherer societies,

“These societies, which have economies based on immediate rather than delayed return, are assertively egalitarian. Equality is achieved through direct, individual access to resources; through direct, individual access to means of coercion and means of mobility which limit the imposition of control; through procedures which prevent saving and accumulation and impose sharing; through mechanisms which allow goods to circulate without making people dependent upon one another… The value systems of non-competitive, egalitarian hunter-gatherers limit the development of agriculture because rules of sharing restrict the investment and savings necessary for agriculture; they may limit the care provided for the incapacitated because of the controls on dependency; they may in principle, extend equality to all mankind.”
How people eat and manipulate their diets is susceptible to structural impacts. These impacts include social relations, market forces, medicine, social stratification as seen in paleographic and medieval forensic evidence. Bodily investment, mood manipulation, and the codification of medical manipulations of the health through the use of food also impact food choices. Of the pre-industrial societies mentioned above, those which are egalitarian seem better able to cultivate health (as represented by freedom from chronic disease) through diet optimisation. In contrast, hierarchilisation, government directives, and labour commodification appear to lead to ill health through the narrowing of crops produced and the curtailment of foraging practices in the local area. When peoples are left to develop their own hunting and food growing practices, and not interefered with by the demands of a centralised state’s directives to produce certain crops but not others, pre-industrial peoples, greater health seems to result.

 

References

Adas, Michael (2001). Agricultural and Pastoral Societies in the Ancient and Classical World. Philadelphia: Temple University Press.

Aiello, Leslie C., Wheeler, Peter. (1995) The Expensive-Tissue Hypothesis: The Brain and the Digestive System in Human and Primate Evolution.

Benyshek, 2001. “A reconsideration of the origins of the type 2 diabetes epidemic among native Americans and the implications for intervention policy.” Medical Anthropology, 20: 1, 25 – 64.

Cordain, L. et al (2002). The paradoxical nature of hunter-gatherer diets: meat-based, yet non-atherogenic. European Journal of Clinical Nutrition 56: Supplement 1, S1-S11.

Dwyer, Peter D. (1985) A Hunt in New Guinea: Some Difficulties for Optimal Foraging Theory. Man, New Series, Vol 20, No 2, 243—253.

Fujita, Masako, Roth, Eric A., Nathan, Martha A. and Fratkin, Elliot. (2004) Sedentism, seasonality, and economic status: A multivariate analysis of maternal dietary and health statuses between pastoral and agricultural Ariaal and Rendille communities in northern Kenya. American Journal of Physical Anthropology 123:277-291.

Gurven, Michael, Kaplan, Hillard. (2007) Longevity Among Hunter- Gatherers: A Cross-Cultural Examination. Population and Development Review 33(2):321 – 365.

Hawkes et al (1982). Why hunters gather: optimal foraging and the Ache of eastern Paraguay. American Ethnologist 9: 379-398.

Hawkes, Kristen, O’Connell, James F. (1985) Optimal Foraging Models and the Case of the !Kung

Kaplan and Robson (2002). The emergence of humans: The coevolution of intelligence and longevity with intergenerational transfers. Proceedings of the National Academy of Sciences of the United States of America.

Keegan, William F. (1986) The Optimal Foraging Analysis of Horticultural Production. American Anthropologist, New Series, Vol 88, No 1, 92-107.

O’Dea, K. (1984). Marked improvement in carbohydrate and lipid metabolism in diabetic Australian Aborigines after temporary reversion to traditional lifestyle. Diabetes 33: 596-603.

O’Dea, 1991. “Traditional Diet and Food Preferences of Australian Aboriginal Hunter-Gatherers [and Discussion]” Philosophical Transactions of the Royal Society B. 334:233-241

Pearson, Kathy L. (1997) Nutrition and the Early-Medieval Diet. Speculum, vol 72, No 1, 1-32.

Pechenkina, Ekaterina A., Benfer, Robert A. and Zhijun, Wang. (2002) Diet and health changes at the end of the Chinese neolithic: The Yangshao/Longshan transition in Shaanxi province. American Journal of Physical Anthropology 117:15-36

Prasad, C. (1998) Food, mood and health: a neurobiologic outlook. Brazilian Journal of Medical and Biological Research 31:1517-1527.

Robson and Kaplan (2003). The Evolution of Human Life Expectancy and Intelligence in Hunter-Gatherer Economies. The American Economic Review.

Woodburn, James (1982). Egalitarian Societies. Man, New Series, vol 17, No 3, 431 – 451.

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