Continuing my posts on nutritional anthropology and health, this second essay concentrates on the relationship between ‘disease transitions’ and agricultural-industrial changes in society. The key point I would like to draw attention to is that chronic disease rose dramatically when diet became linked to wage earning at the expense of self-sufficiency through gardens, hunting, or foraging.
Do current global trends in non-infectious disease fit with established frameworks of historical ‘disease transitions’ (e.g., McMichael 2001)? Why or why not?
When the established frameworks of historical ‘disease transitions’ are understood from the ecologic perspective of human-environmental equilibrium, current global trends in non-infectious diseases such as increased rates of type 2 diabetes, heart disease, and obesity not only reflect a current disequilibrium between humans and their environmental conditions (diet, technology, social structures, and materials) but also highlight additional questions of health sustainability. Evidence from ethnographies on Native American and Aboriginal populations not only highlight this process, but also show current global trends to be both reversible and often preventable. Finally, the existence of ‘Blue Zones’ (areas of high density of centenarians) demonstrate that these positive health changes are achievable in industrialised countries today.
McMichael (2001) notes three, broad-based historical infectious disease transitions, book-ended in the past by an initial emigration out of Africa, and in the contemporary world by a theorised ‘fourth transition.’ As McMichael writes,
“These three great historical transitions were processes of equilibration between, first, humans and animal species and, later, between regional human populations. As new ecological niches were created by changes in human cultural practices, microbes exploited those niches. As new contacts were made between previously isolated civilizations, infectious diseases were pooled.” (McMichael 2001:111)
According to his reading, the first disequilibrium occurred when humans began to create agriculturally and pastorally based economies with the concomitant rise of towns about 10,000 years ago. At that point, a favourable environment for the transmission of zoonotic bacteria and viruses to human hosts was created, and the age of infectious diseases was born. Because these population centres were spread out, over time a co-evolution occurred between humans and microbes in relatively contained regions which allowed human civilisation (in the sense of cities) to continue without major disruption; an equilibrium point between technology, social structure, and the microbial environment had been reached. However, with the expansion of these regions through trade and empire building, during which time previously isolated regions came into contact with one another, the second and third disease transitions came about leading to the spread of global epidemic disease, first throughout Eurasia, and then to the Americas.
The question examined by McMichael (2001) is whether the recent resurgence of infectious diseases, combined with the discovery of many new diseases in the past quarter century, are adequate evidence of disequilibration to posit a fourth great transition, in which infectious diseases become resurgent. McMichael offers the increased opportunities for the global transmission of disease as well as the niches created by new technologies in food processing and pharmaceuticals. (McMichael 2001:112-13). Additionally, he mentions changes in human behaviour brought about through changes in urbanisation patterns both with regard to sexual behaviour and to new medical interventions. Finally, he notes the role which climate change and ecological disruption (including large scale clearing of land and the loss of species biodiversity) due to human technologies continues to play in effecting this ‘fourth’ disease transition.
Olshansky (1986), in contrast, advances a different set of determinants for, as he terms them, epidemiologic transitions. Basing himself on Omran (1971), he writes, “The epidemiologic transition theory… was designed to provide a general picture of the major determinants of death that prevailed during several distinct periods in our epidemiologic history.” (Olshansky 1986:356) As such, the focus of these transition periods shifts away from ecological equilibrium factors and towards factors which preclude longevity and ‘natural death’. In Olshansky’s reconceptualization of the transitional periods, he breaks down the components examined in each period into three distinct groups: cause of death (e.g. parasitic, infectious, degenerative); age and sex of the deceased; and the effects on survival which a transition from one set of causes to another might have. In this last component, we have a concern not only with the ecological factors which can partially overlap with McMichael’s model, but also with the fundamental question “who benefits the most from mortality transitions in terms of gains in life expectancy?” (Olshansky 1986:356) This fundamental question raises concerns about the sustainability of any given health transition, and provides a link between his epidemiological approach and critical anthropology’s deconstruction of power and exploitation in capitalist world systems of health and sickness.
The common thread underlying each disease transition in both models seems to be disequilibrium caused by social change (including technology and hygiene) and nutrition, particularly in terms of its impact on both mortality and longevity. In the first period (McMichael’s first through third stages), the disequilibrium resulted from urbanisation, agriculture, and trade; likewise health gains can be attributable to the same causes. In the second period (overlapping only partially with McMichael’s fourth stage), the shift was caused by increased nutrition and clearly changing social policies towards public sanitation. The final stages, moving towards a primary concern with chronic disease, once again evince a shift in social patterns. These shifts can be seen when we look at ethnographies of indigenous populations who have recently become Westernised, as well as case studies of areas in which longevity and natural death exists in greater concentration than other areas of the world.
The limitations of a disease transition framework are that it relies on very broad and generalizable historical trends, and is therefore at the mercy of historical records (textual, archaeological, and secondary sources), which, as surviving records become more plentiful, serve to telescope the periods of transition into shorter and shorter time frames. With regard to Native Americans and Australians, however, the disease transition processes set forth above have occurred in an equally telescoped period of time. Thus, ethnographies of Native Americans and Australians are particularly helpful in testing the model of disease transitions, since these populations encountered several disease transitions within the past two or three centuries, and we can see how those populations were able to find new equilibrium points – or continued disruption – during this period of time.
The Pima nation, located in present-day Arizona, has been studied by epidemiologists because of the high rates of type 2 diabetes (around 50% of adults between 30 and 64) emerging in that community since the 1950s. While previous studies had focused on a theoretical ‘thrifty genotype’ assumed among Native populations, Benyshek et al (2001) takes a closer look at the historical emergence of type 2 diabetes among the Pima, and ultimately advances a position which favours the intrauterine environment as a predisposing factor to development of type 2 diabetes later in life. For our purposes, however, the historical element is most relevant.
From at least the 1600s through the nineteenth century, the Pima were an agricultural, settled population. Through contacts with the Spanish in the 17th century, they incorporated wheat into their diet, although they continued to cultivate the indigenous maize, beans and squash which formed the earlier backbone of their diet. They supplemented these foods with cattle, wild game, fish, and foraged plant foods. By the mid-nineteenth century, crops were plentiful enough that the Pima conducted trade with Anglo-Americans settlers. Far from being subsistence farmers, they engaged in “a flourishing commercial agriculture based on sales.” (Benyshek et al 2001:39) While they may have initially been susceptible to the epidemic diseases brought by the Spaniards (Benyshek et al does not examine this), it is obvious that the population had reached some sort of epidemiological equilibrium point by the 1800s. That equilibrium began to break down after 1870, when environmental disruption in the form of droughts and irrigation projects begun by Anglo and Mexican-American settlers led to crop failures by the turn of the century. By the early 20th century, most of the Pima had turned to “woodcutting and wages” to support themselves. Thus, following an environmental disruption, the Pima’s economic equilibrium point also shifted from self-sufficiency to dependence on employment by others. By the interwar period, the Pima were largely employed in government funded water projects. It was during this time, after reliance on locally produced indigenous foods shifted to purchased wheat flour, animal fats, coffee, and sugar, that diabetes first began to be diagnosed in increasing numbers among the Pima. (Benyshek et al 2001:40) Today, with government programmes, Pima continue to find their livelihood through wage earning work, rather than through returning to commercial small-scale agriculture, and their diabetes rates hover around 50% of the adult population.
In contrast to the economic and environmental disruption(s) experienced by the Pima, the Dogrib and Aleut peoples further north were able to maintain a pace of exchange which has allowed them not to suffer from the emergence of type 2 diabetes within their populations. After contact with European traders, the Dogrib “developed what Helm (1981) calls a ‘contact-traditional’ lifeway in which these people supplemented their traditional diet of game and fish by trading furs for food and other goods at trading posts (where they enjoyed credit). Due to their geographic isolation, this adaptation persisted into the 1950s,” after which time they began to be settled into permanent housing by the Canadian government. (Benyshek et al 2001:43) The Dogrib traditional diets had not been disrupted by trade in foodstuffs (e.g. coffee with sugar, butter), but had instead augmented through their incorporation. Even a half-century after settling into permanent communities, the diabetes rate remains low. Unfortunately, Benyshek et al does not detail what type of work is currently practiced by the Dogrib.
A similar pattern of maintained equilibrium was found among the Aleut and Eskimo of Alaska. Like the Dogrib, they also seemed to have developed a contact-traditional way of life, adding traded foodstuffs to their traditional diets of fish and game. Interestingly, “this reliance upon traditional food-getting activities (especially among Alaskan Eskimo) as late as the 1960s and 1970s was often due to high unemployment and poverty rates (Chance 1984).” In other words, unlike the Pima, they did not make a complete shift from traditional means of survival to wage-earning; or rather, they did not lose the environmental resources for maintaining that knowledge. (Benyshek et al notes that the environment had been rich enough to provide for not just Aleut, but also Russian, and Euro-American traders.) By the 1950s, however, local diets had begun to give way to imported foods, including candy and soft drinks. Although diabetes rates have remained low, obesity (based presumably on a Euro-american body type standard), had increased. (Benyshek et al 2001:45).
Benyshek et al argues that the Dogrib and Alaskans did not suffer “from extended periods of chronic protein malnutrition followed by a rapid transition to a Western diet and lifestyle.” (Benyshek et al 2001:45) My argument, however, is that the northern peoples did not experience either the environmental or the economic disruption that the Pima did. Because they were able to preserve an ecological equilibrium status, they have not suffered the development of those chronic degenerative diseases, such as type 2 diabetes, which are increasing throughout the world.
A similar pattern can be found among Aborigines in Australia. O’Dea (1991) notes that prior to westernisation, the Aborigines led a mostly hunter-gatherer, nomadic lifestyle. They were lean and fit, and “had no evidence of the chronic diseases that occur in epidemic proportions in Westernized Aboringinal communities today.” (O’Dea 1991:233) Although O’Dea points to eating behaviour and food preferences as the key component in promoting obesity among the Aborigines today, I would argue that the initial culprit was an economic disequilibrium that began when Aborigines were employed as stockmen in the Australian outback. Rather than receiving wages with which to purchase government provided supplies (in contrast to the shift in Pima work patterns), stockmen were paid in rations of meat, flour, sugar, tea, and tobacco. However, because the focus of O’Dea’s article is on the nutritional-chemical components of a traditional Aboriginal diet, this aspect of economic-dietary disequilibrium is not explored in full. Why did Aborigines work as stockmen? Were they pressed into service, or did they volunteer willingly? Why did they choose to switch to western rations instead of incorporate them into a traditional diet, as did the Dogrib or Aleut?
One of the most telling points O’Dea makes is that when Aborigines revert to their traditional lifestyle, including both diet and the steady exercise exerted by nomadic hunting and gathering, the markers of several degenerative diseases also declined. Excess weight was lost, diabetes abnormalities began to reverse, and major heart disease risk factors were reduced. (O’Dea 1991:79) That traditional lifestyle was the most recent ‘set point’ of ecological equilibrium. I would caution, however, against adding, ‘for them’, and pose instead the question of whether chronic degenerative diseases among industrialised Eurasian populations is not also a result of an ecological disequilibrium present in those societies today. The existence of Blue Zones, areas of the world with high concentrations of longevity, and in which chronic degenerative diseases are not the norm, offers a case of equilibrium points within industrialised societies which were either maintained while the rest of society changed, or which were created in contrast to it.
The Blue Zones of east-central mountains of Sardinia, a community of Seventh-Day Adventists in Los Angeles, and groups on the main island of Okinawa all serve as examples of an industrial-age equilibrium. Mostly untouched by degenerative diseases, these groups of people share four characteristics in common: they practice mild exercise embedded in daily life (kneading dough, walking up and down stairs in multi-level houses), eat plant based diets, have a sense of faith or purpose about their lives, and have close ties to family and friends. (Buettner 2010) These characteristics contrast with popular discourse about the lifestyles found in much of Euro-America, with their disruptive high-stress, cardio-emphasised exercise programmes, go-go-go work styles and consequent fast or quick food diets, and periodic waves of existentialist angst.
Both McMichael and Olshansky note that disease transitions occur as a result of disruptions to previous disease equilibrium states. These disruptions can come about through environmental change, but are equally likely to be tied to social practice (diet, trade, work) and technological development. The experiences of Native Americans and Aboriginal Australians, whose lifeways have been visibly disrupted by ‘Westernisation’ provide evidence that chronic diseases, like the epidemic diseases which preceded them, are also diseases of ecological disequilibrium.
In light of these ethnographies, an interesting health shift seems to occur when societies move from being self-sustaining to being wage earners. The Pima thus stand in stark contrast with the fur trading peoples of Canada and Alaska, who managed to maintain a dual livelihood. This particular insight also raises questions about the first disease transition: rather than look at the rise of agriculture as a turning point, why not examine also the rise in employment by others? It also questions how much current Western society’s primary economic paradigm, namely, a reliance on wage earners, and the role workplace culture plays in promoting health (dis-)equilibrium, which we ultimately see manifesting as chronic degenerative diseases.
The weakness in my argument is that non-infectious diseases have always been present in the population, perhaps previously masked by the visibility of high-mortality infectious disease. However, I would counter by observing that disease transition periods are achieved only after an equilibrium point has been found. Thus, the equilibrium state for chronic degenerative diseases has only been found in a few areas of the world, which are being identified as ‘longevity hot spots’ or ‘blue zones’.
Benyshek, D; Martin, J; and Johnston C, 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.
Buettner, 2010. Video lecture at http://www.bluezones.com/about/dan-buettner/
Daar, 2007. “Grand challenges in chronic non-communicable diseases: The top 20 policy and research priorities for conditions such as diabetes, stroke and heart disease.” Nature vol 450:494—496.
McMichael, A. J., Smith, K. R., & Corvalan, C. F. 2000. The sustainability transition: a new
challenge. Bulletin of the World Health Organization, 78, 1067.
McMichael, 2001. “Human Culture, Ecological Change, and Infectious Disease: Are We Experiencing History’s Fourth Great Transition?” Ecosystem Health Vol. 7 No. 2 June 2001.
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