Metabolic thinking deals in bounded organisms, regulated systems, and the calculated (self)-optimisation of responsible, profitable, and healthful nutritive and energetic transactions. But critical scholars have also been thinking, metabolically, about the openness of bodies, economies, and ecologies, attending to the ways in which substances – sugar and fat, DDT and insulin, guano and tortillas – move through time, space and relations of power and sociality, into and between different forms of life and life-making. The last few decades have seen something of a metabolic turn, or renaissance, across various fields, notably science and technology studies, medical anthropology, and political ecology. This body of works tracks the emergence and effects of metabolic ideas and norms, for example in the category of “metabolic syndrome”,classifications of diabetes,or biological models of autonomy and entanglement. Yet anthropologists, sociologists, historians, and geographers have also been rethinking metabolism as a capacious empirical focus and analytic that can loosen narrow framings of, say, industrial farming or chronic disease, to encompass a broader array of ingestions and depletions, as well as of generations: of value, meaning, growth and waste. Through ethnographic engagement with eating, illness and care;inspiration from emerging bioscientific attention to bodies’ plasticity and historicity (notably in epigenetics); or by reanimating older vitalist or Marxist versions, the metabolic is being fashioned as a way of thinking through unequal (re)distributions of nutritive, energizing, and harmful matter and capacities in postcolonial, post-industrial landscapes.
Inspired by, if not yet fully immersed in, this scholarship, we convene this series about metabolic relations in Africa. The contributions to the series take up, in some cases to qualify or set aside, the lens of metabolism to re-examine projects and practices of survival, (dis)ordering, and optimisation in/from Africa, as a continent where growth – of children, plants, economies – has often been particularly fragile and problematically framed as such. Some of us had already been thinking with metabolism and its scholarship. Others started considering how metaphors and materialisations of metabolism might expand or constrain our understanding of relations among persons, ecosystems, pesticides, reagents, bananas, and trees. The conversation we propose to have here seeks to be particularly attentive to the range of collateral effects – from toxic emanations to erasures of knowledge and meaning – which metabolic processes and framings might entail. We also want to be mindful of diverse valuations and epistemologies of growth, given troubled African histories with idealisations of both (homeo)stasis and development. Working across ethnography and history, informed by medical anthropology, African studies, political ecology, and science and technology studies, this series discusses what metabolic thinking might tell us about past and present politics of (re)production, extraction, and disposal in African sites, in oscillation and dialogue between poles of health-prosperity-energy and of toxicity-depletion-waste. Following Megan Vaughan, whose work on chronic illness in southern Africa inspired the instigation of this conversation, we ask how we might rethink metabolism from specific African situations, through histories and ethnographies of farming, eating, scientific collaborations, or tree planting and burning. This series, thus, grapples with the promises and limitations of metabolic thinking for understanding the predicaments of growth in Africa.
The contributions draw in different ways, and sometimes eclectically, from metabolic-themed scholarship, to deploy and critique diverse conceptions of metabolism. We nevertheless discern three themes that cut across our engagements with metabolic thinking: scale, harm, and expertise.
We were initially drawn to metabolism for its promise of expanding the scales in which we might locate relations of exchange, consumption and mutual transformation among entities. Marxist uses of metabolism have broadened the spatial reach of capitalist extraction, beyond workers’ labour, to foreground its disruption of nutrient cycling among soil, crops and eating/excreting bodies, and the subsequent disconnection between “town and country.” Seeing capitalism as a metabolic process has further illuminated how it feeds on (or “eats up”) resources and capacities nurtured within non-capitalist relations, not only in nature but also domestic domains of care and reproduction, particularly in settler colonial and migrant-labour systems – as Rosa Luxembourg point out. A recent “socio-metabolic re-reading of Marx” has brought ecological questions into political-economic frameworks. Jason Moore urges us to push our thinking of metabolism, to not only connect “society” and “nature,” but to dissolve their boundaries by following different kinds of things and forces involved in the “process of life-making.” Scaling up to the planet, and historically-attuned, such a metabolic gaze points at capitalism and imperialism as drivers of the Anthropocene, or rather the Capitalocene. From “imperial metabolism” to (more-than-human) “metabolic labour,” metabolic concepts abound to rethink how ecological, social, and economic systems are coterminous.
Similarly, and sometimes inspired by this political-ecological work, anthropologists of health and medicine have sought to rethink the metabolic, zooming out from its use as a disease label and as a calculable set of “tidy conversion[s]” between food, organisms, energy, and labour through “the atomized nutrient body.” Harry Solomon innovatively invites us to consider “metabolic living” as what happens at the “absorptive interface of bodies and surroundings,” which he defines as “an actively ongoing process people endure to survive the porosity that all life entails.” Amy Moran-Thomas similarly observes how “sugar,” as a parallel term for diabetes and as a history of slavery, agriculture, and violence in Belize, happens not just inside bodies but also between persons and across life-courses and generations, as well as in interaction with sedimented infrastructures and landscapes. Lastly, calling for a “metabolic history”, Hannah Landecker documents how, in the postwar U.S., “feed efficiency” in industrial agriculture made crop residues a cheap but impoverished food for farmed animals, whose growth was boosted by antibiotics and arsenics that now disrupt the metabolisms of microbes and human cells.
In both histories of capitalism and ethnographies of illness, metabolism has thus invited greater attention to environmental dimensions of eating, labouring and (re)producing, while also posing the question of where the environment begins and ends. We take here metabolism as a prompt to think harder about how our objects of study – guts, peanuts, genes, trees, pesticides – are environmental, as well as historical. More than just expanding the scope of analysis, thinking metabolically is then, for us, an invitation to consider the effects of scalar choices, and ask ourselves what the appropriate spatial and temporal scale(s) might be for telling particular stories.
Noémi Tousignant uses metabolism to open a carcinogenic fungal metabolite, aflatoxin, to the imperial scales in which Senegalese peanuts have been grown, eaten and traded. This locates Senegalese peanut-eaters amid broader relations of unequal exchange, protection, exposure and neglect, but also of (potential) care and taste. Véra Ehrenstein describes how the charcoal trade and its transfers of energy, matter and money between a large African city, Kinshasa, and the surrounding woody savannah have come to be connected to global climate policy and the transformation of carbon into a commodity. Sandra Calkins links the molecular scale of banana gene editing to scalar aspirations for the metabolic solution of population-wide vitamin deficiencies and of flourishing careers for Uganda scientists. Miriam Waltz sets the fantasy of closing off “skin, nose, mouth” to pesticide ingestion alongside broader scales of agricultural histories, permeable bodies, and desires for growth.
Other contributors, however, wonder whether the metabolic scales that scholars mobilize to create connections are meaningful and relevant to those to/for whom they have been applied. Branwyn Poleykett asks if scaling up the analysis of metabolic disorder, beyond global health framings, might still miss out on what quality food means for women and their babies in Dakar and how nutritious relations can be sustained despite precarity. Thomas Cousins turns to the ethnographic archive and highlights the diversity of the social and cultural meanings of the gut to decentre the western biomedical understanding of metabolism that underpins the metabolic turn.
The costs of growth
Thinking in terms of metabolism centres not only processes of production, gain and growth, but also their by-products and deviations: degradation, depletion, loss, and waste. Marxist uses of metabolism seek to expand what is counted as the costs of capitalist production. In initial formulations, these costs were the depletions of soil in the hinterlands, as fertilizing organic matter was moved to feed the city, as well as the polluting effects of wasted and dumped urban excrement. Ethnographies of metabolic illness point to the often-harmful side-effects of biomedical metabolic norms and prescriptions, but also to how bodies unevenly bear the metabolic burdens of food scarcity, urban growth, toxicants, political violence, and privatized care. Without necessarily subscribing to cyclical models of nutrient/energetic exchange, we recognise that metabolic accumulations come at a cost, depending on extractions and generating excesses.
We thus ask, in our case studies: Who and what is meant to grow, and who bears the costs, labours for, and absorbs the wastes of this growth? These questions draw attention to the unequal nutritive, regenerative and energetic exchanges that can be thought of as core metabolic processes, but also to how people and more-than-human beings involved in and transformed by these processes – as producers, workers, eaters, consumers, bystanders – are differentially valued and recognised.
In their contributions, Miriam Waltz and Branwyn Polyekett draw attention to the metabolic costs incurred by people for whom making ends meet is already difficult. The promise to grow more crops by killing pests is being sold as safe to Kenyan farmers, making them responsible for whether or not the chemicals may also end up costing them their lives. Similarly, the humiliating rituals of measurements and standardised caloric fixes of nutrition programmes in Dakar shift the blame for the malnutrition of their babies onto mothers, while simultaneously denying their agency.
Changing the scale of analysis, Thomas Cousins and Noémi Tousignant attend to the costs of ensuring the growth of an economy. In South Africa, workers, their bodies, the meanings given to bodily strength, and their relations of kin, are placed at the service of the plantation system. In Senegal, a peanut economy is developed towards exports that generates possibly toxic leftovers for domestic producers, eaters and public health authorities to deal with.
Finally, Sandra Calkins and Véra Ehrenstein examine expectations that harnessing nature and more-than-human beings would solve metabolic imbalances. Using better bananas and theories of metabolism to accumulate vitamin A in supposedly deficient Ugandan bodies overlooks ways in which the plants have long written themselves into Great Lakes histories and landscapes. Growing acacias on the Bateke Plateaux is meant to satisfy the energetic needs of urban consumers accused of depleting the landscape its forest galleries, but why farmers should be interested in bearing the cost of planting those trees is not being asked.
The ignorance of expertise
Much scholarship on metabolism, including the contributions to this series, points out what is ignored by expert approaches to problems of health, energy, nutrition, and growth. Africa has been a historical site of expert diagnoses and hubristic interventions, rife with failure and misreadings. Interventions seeking to salvage supposedly eroded soils or malnourished bodies, or to improve dietary and agricultural practices might be seen as examples of metabolic thinking that channels expert power and its intrusions, blaming Africans for mismanaging life-giving conditions. Yet, alternatively, metabolism might become a way of disrupting expert models, by continuously seeking to bring more “actants,” spaces and times into view and into play, especially if one accepts the uncertainty, limits and historicity to what can be known, modelled, delineated and calculated when thinking metabolically.
Contributors here wonder how histories of expert authority and projects shape and challenge our attempts to think metabolically. How are our approaches to molecular substances, such as aflatoxin, carbon, or vitamins, informed and constrained by the ways in which scientific practices have been enacted in African locations? What traces and sensitivities do expert practices, such as upper-arm measurements, farmer extension services or forestry management, leave in the sites we visit? What are the limits to what can be known as metabolic actors and actions, and to how that knowledge might be made commensurable across worlds and locations?
Sandra Calkins, thus, shows that scientists’ sophisticated thinking about plant metabolism does not conceive of human nutritional absorption in equally complicated ways. Thomas Cousins highlights the value of revisiting anthropological knowledge in order not to be too easily fascinated by the metabolic thinking of the life sciences. Noémi Tousignant points at the difficulties in developing locally relevant expert knowledge about the way aflatoxin may circulate in people’s diet. Miriam Waltz suggests that pesticides’ harm is the object of an information battle in which marketing is presented under the guise of expert authority. Véra Ehrenstein critically engages with the policy fads of development experts as they claim to address global environmental concerns, from woodfuel scarcity to the climate crisis. And last but not least, Branwyn Poleykett wonders, provocatively, whether we can ever step out of expert frames…
 Anthony Ryan Hatch, Blood sugar: racial pharmacology and food justice in Black America (Minneapolis: U of Minnesota Press, 2016).
 Amy Moran-Thomas, Traveling with sugar: chronicles of a global epidemic (Berkeley: University of California Press, 2019); Emma Nelson Bunkley, “Interembodiment, Inheritance, and Intergenerational Health,” Medical Anthropology Quarterly (2022), https://doi.org/10.1111/maq.12689; Lauren Carruth, Sarah Chard, Heather A. Howard, Lenore Manderson, Emily Mendenhall, Emily Vasquez and Emily Yates-Doerr, “Disaggregating diabetes: New subtypes, causes, and care,” Medicine Anthropology Theory 6 (December 2019): 119-126.
 Hannah Landecker, “Postindustrial metabolism: Fat knowledge,” Public Culture 25 (September 2013): 495-522.
 Moran-Thomas, Traveling with sugar; Emily Yates-Doerr, The Weight of Obesity (Berkeley: University of California Press, 2015); Harris Solomon, Metabolic living: Food, fat, and the absorption of illness in India, (Durham NC: Duke University Press, 2016).
 Hannah Landecker, “Food as exposure: Nutritional epigenetics and the new metabolism,” BioSocieties 6 (March 2011): 167-194.
 John Bellamy Foster, Marx’s ecology: Materialism and nature (New York: Month Review Press, 2000); Maurizio Meloni, “Provincializing Metabolism (On the Poverty of Modernism,” Somatosphere, January 28, 2020. Available at: https://somatosphere.net/2020/provincializing-metabolism.html/. Accessed July 6, 2022.
 This conversation emerged from a planned workshop – which was held online due to COVID-19 restrictions – supported by UCL (Institute of Advanced Studies and Urban Lab) as part of the 2019-2020 research theme of “waste.” Initial participants in these conversations included, in addition to the authors: Megan Vaughan, Tatiana Thieme, Treasa De Laughry, Mish Nkhata and Carlos Grijalva Eternod.
 Samir Amin, Maldevelopment: Anatomy of a global failure (Cape Town: Pambazuka Press, 2011); Frederick Cooper, Africa since 1940: the past of the present, (Cambridge: Cambridge University Press, 2019); Julie Livingston, Self-Devouring growth: a planetary parable as told from southern Africa (Durham NC: Duke University Press, 2019).
 Megan Vaughan, “Conceptualising metabolic disorder in Southern Africa: biology, history and global health,” BioSocieties 14, no. 1 (2019): 123-142.
 Foster, Marx’s ecology; see also William Cronon, Nature’s metropolis: Chicago and the Great West (London: WW Norton & Company, 1991).
 Patrick Bond, “Luxemburg’s Contemporary Resonances in South Africa,” in Creolizing Rosa Luxemburg, edsDrucilla Cornell and Jane Anna Gordon (Lanham MD: Rowman & Littlefield, 2021), 287-316.
Jason W Moore, “Metabolic rift or metabolic shift? Dialectics, nature, and the world-historical method,” Theory and Society 46 (August 2017a): 285-318, 286.
 Moore, “Metabolic rift”, 288.
 Jason W Moore, “The Capitalocene, Part I: on the nature and origins of our ecological crisis,” The Journal of peasant studies 44 (March 2017b): 594-630.
 Alf Hornborg, “Imperial Metabolism: Empire as a process of ecologically unequal exchange,” in The Oxford World History of Empire, eds Peter Fibiger Bang, C. A. Bayly and Walter Scheidel (Oxford: Oxford University Press, 2021), 437-459.
 Les Beldo, “Metabolic labor: Broiler chickens and the exploitation of vitality,” Environmental Humanities 9 (May 2017): 108-128; see also Sarah Besky and Alex Blanchette, eds, How nature works: Rethinking labor on a troubled planet (Albuquerque: University of New Mexico Press, 2019).
 Yates-Doerr, Weight of Obesity, 135.
 Solomon, Metabolic living, 9.
 Moran-Thomas, Traveling with sugar; see also Vaughan, “Conceptualising metabolic disorder” and Bunkley, “Interembodiment”.
 Hannah Landecker, “A Metabolic History of Manufacturing Waste: Food Commodities and Their Outsides,” Food, Culture and Society 22 (July 2019): 530-547, 542; see also Hannah Landecker, “Antibiotic Resistance and the Biology of History,” Body and Society 22 (March 2016):19-52; Hannah Landecker, “Trace Amounts at Industrial Scale: Arsenicals and Medicated Feed in the Production of the ‘Western Diet’,” In Risk on the Table: Food Production, Health, and the Environment, eds Angela N.H. Creager and Jean-Paul Gaudillière eds (New York: Berghahn, 2021), 187-213
 Especially Landecker, “Food as exposure”; Moore, “Metabolic rift”.
 Gabrielle Hecht, “Interscalar vehicles for an African Anthropocene: On waste, temporality, and violence,” Cultural Anthropology 33 (Feburary 2018): 109-141.
 Foster, Marx’s ecology.
 Hatch, Blood sugar.
 Yates-Doerr, Weight of Obesity; Solomon, Metabolic living; Moran-Thomas, Traveling with sugar; Vaughan, “Conceptualising metabolic disorder”; Landecker, “Metabolic History”.
 Guillaume Lachenal, The Lomidine Files: the untold story of a medical disaster in colonial Africa, (Baltimore: Johns Hopkins University Press, 2017); James Fairhead and Melissa Leach, Misreading the African landscape: society and ecology in a forest-savanna mosaic, (Cambridge: Cambridge University Press, 1996); James Ferguson, The anti-politics machine: ‘development’, depoliticization, and bureaucratic power in Lesotho (Minneapolis: University of Minnesota Press, 1994).
 Henrietta L Moore and Megan Vaughan, Cutting down trees: gender, nutrition, and agricultural change in the Northern Province of Zambia, 1890-1990 (London: James Currey Publisher, 1994); Christophe Bonneuil “Development as experiment: Science and state building in late colonial and postcolonial Africa, 1930-1970,” Osiris 15 (2000): 258-281; Diana Wylie, Starving on a full stomach: Hunger and the triumph of cultural racism in modern South Africa (Charlottesville: The University of Virginia Press, 2001); Kate B Showers, “A history of African soil: Perceptions, use and abuse,” in Soils and Societies: Perspectives from Environmental Histories, eds John R McNeill and Verena Winiwarter (Isle of Harris: The White Horse Press, 2006), 118-176; John Nott, “‘No one may starve in the British Empire’: kwashiorkor, protein and the politics of nutrition between Britain and Africa,” Social History of Medicine 34 (May 2021): 553-576.
 Landecker, “Antibiotic Resistance”.