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Fermentation is the product of microbial relations that are often treated as neutral and external to the bodies that such relations nourish. By attending to these relations directly we see the potential to upend long-standing taxonomic orders whose purpose was to create patterns out of the perceived ambiguity of the natural world. Here, we reevaluate this ordering through theorizing how microbial relations — and their connection to these ordering practices — constitute gender materially, even as they also destabilize the boundaries of these ordering categories.

As Londa Schiebinger argues in her groundbreaking work on Linnaeus’s development of the class, mammalia, gender was key to an 18th century understanding of species taxonomies that linked milk production — and women’s lactating bodies — to the animalistic nature of humans. The emphasis on the food-producing capacity of both humans’ and nonhumans’ reproductive labour supported European class ideals, thus infusing “nature with middle-class European notions of gender.”[2] The contemporary naturalization of this equation between the bodily production of milk and species differentiation illustrates the continued entanglement between such constructions of gender and sexed, or reproductive, bodies. This association with lactation aligns one gender more closely with nature and, thus, the other with culture — a subject of established feminist critique. It also leads to the conflation of the feminine with the mammalian. Finally, this structural alignment with species’ nature ignores that making food from bodies requires culture — both in the sense of culturing microbes and in being reliant on technoscientific processes. Using case studies of food made from ruminants’ stomachs and women’s vaginas, we denaturalize this expectation of mammalian capacity to explore the traction of gendered ideologies that accompany exchanges between microbial life resulting in food.

Linnaeus’s focus on female reproductive organs to group together species reflects a cultural emphasis on the significance of (breast)milk. Both cows and humans produce milk as the result of reproductive labour. However, when the public interacts with cows, they use the essentializing assumption that cows naturally produce food for humans. While dairy scientists have long characterized cow (and other ruminants) stomachs as “fermentation vat[s] par excellence” — and thus milk as an already processed food — advances in microbiology have introduced consideration of yet another set of relations to be nurtured that further obscure connections to their reproductive labour. Attempts to realign farmers’ interest in optimizing milk production by nurturing microbes in cow bodies illuminate the reordering of these relations, especially when placed alongside virtually identical discourses about the role of pro and pre-biotic food products in optimizing human health and digestion. In both cases, microbes are intermediating agents in creating these food products but, we argue, this intermediating nature is under-theorized. Tracing their enrolment in such production, we show that microbial relations with sexed bodies constitute gender materially partially through recourse to symbolic taxonomic orderings of nature and culture that cross species lines. In doing so, they destabilize the easy binaries of human and nonhuman, sexed and asexed, inside and outside, eater and eaten. In other words, we consider how microbial lives are necessarily layered inside and outside the body on their way to becoming food. This feminist analysis of atypical kinds of fermentation illuminates that a) fermentation is a form of reproduction and b) microbes’ attachments to gendered bodies shifts the nature of those bodies.

North Americans are arguably participating in a resurgence of interest in fermentation. From yogurt to sauerkraut, vinegar to kombucha, this food trend is striking for its shift from promoting consumption alone to encouraging home production: a process that requires attuning oneself to microbes’ productive role in converting one substance to another. Consumers as producers are tasked with being cognizant of this process of transformation. These explorations of fermentation focus on conversions that happen outside of bodies resulting in food. This interest feeds into popular science reporting stressing the productive role of interactive communities of microbes inside the body resulting from the food we eat. These narratives contain carefully stated promises that proper cultivation of these communities will heal or prevent modern diseases like diabetes and arthritis. The North American public, in other words, is being encouraged to reorient themselves from the inside out, to see ourselves as “more microbe than human.”[3] Fermented food products now feed us and feed our embodied colonies of bacteria, yeasts, and other microorganisms.

The public generally refers to these colonies as the “microbiome” even though the technical term for the taxonomic array is “microbiota.”[4] While this seems like an issue of concern only to scientists, this interchangeable use obfuscates the multiplicity of organisms that make up the microbiota — each with potentially different microbial relations. In microbiome science, bodies — gendered or otherwise — materialize as a series of interrelated ecosystems of organic-microbial interactions. Life sciences in the epoch of the microbiota thus rely on a model of human materiality that instantiates Karen Barad’s feminist argument about the essential dynamics between tangible material, imperceptible relations, and cultural meaning. Focused on “how matter comes to matter,” she argues for going beyond “matters of signification” to attend to how “matter is substance in its intra-active becoming — not a thing, but a doing, a congealing of activity.”[5] This argument elaborates Judith Butler’s point that discursive and symbolic orderings are central in making “bodies that matter”[6] to consider also the generative nature of material — and here, microbial — relations. Extending from these feminist contributions, we also draw on microbial relations scholarship that attends both to their potential world modelling[7] and to their capacity to destabilize the traditional binaries that make up life taxonomies.[8] Microbiome research as it has entered popular science hones in on microbes’ role as dynamic co-creators of both human health and those things that support human health, particularly fermented food. While dairy scientists have long recognized this kind of co-production in animals, this shift toward understanding microbes as entangled with our own “intra-active becoming” allows us to rethink fermentation’s transformative or (re)ordering potential in a broader sense.

Microbes’ centrality to new models of mammalian bodily materiality and vibrant participation in non-bodily intra-actions makes them compelling figures. In this context of life sciences’ re-assemblage of mammalian bodies into collective and dynamic ecosystems, our material-semiotic approach to gender foregrounds how things emerge with specific “boundaries, properties and meanings” only through attachments to discursive, symbolic, and material phenomena.[9] Feminist scholarship on gender generally works to denaturalize the conflation of sexed bodies with gendered human and nonhuman sociality.[10] Out of this tradition we are interested in inverting this process to trace the traction of sex/gender conflation in organizing the outcome of microbial relations and, in this case, define what is food and what is not. As such, we attend to how — in the course of fermentation — microbes cross boundaries to facilitate material transformations and challenge seemingly obdurate nature/culture binaries. Looking at instances when their connection to bodily context matters and other times not, we can therefore trace the symbolic attachment and detachment from sexed bodies necessary to produce food-like substances.

This analysis rests on two ostensibly orthogonal cases: 1) the everyday production of quality dairy products and 2) the extraordinary performance of fermenting yogurt from vaginal microbes. Such juxtaposition enables us to illuminate, first, the manner in which milk products of maternal nonhumans (cows and other ruminants) are disaggregated from their sexed bodies, and, second, the over-determination of sexed bodies in sorting out the work of microbes in fermentation. These cases are both intimately intertwined with the emergent science of microbial interactants. Yet what gets to be considered as food from their outcome requires the naturalization of this binary between human and nonhuman bodies. We place them together to analyze their ability to enroll gender and/or disavow gender in order to produce food. Thus, rather than posing the question “do microbes have a gender?”, we instead focus on how microbes’ capacity to move between fleshy and gastronomic domains facilitates (or obscures) particular expectations about gendered bodies.


At the 2015 World Dairy Expo in Madison, Wisconsin, the space for ruminant microbiologist Paul Weimer’s presentation on “The Secret Life of Rumen Microbes” was standing room only with a mixed crowd of varying ages. Weimar began with the bald statement: “What’s so important about rumen microbes? ... [w]ithout them the cow would die.” Passing around a clear, glass vial filled with a vaguely greenish liquid and a brownish mat of solid materials at the bottom of the tube, it was as if he wanted us to see what he knew was there — a “very dense microbial community.” Explaining to the attentive crowd, he noted “microbes… feed the cow,” and farmers are not so much feeding their cows as they are “feeding the microbes.” What happens in the rumen, in other words, builds the foundation for quality milk output vis-à-vis the fermentation of fibre, starch, sugar, and protein into fatty acids and microbial protein. His lecture closely mirrored popular science writing on the human microbiome, questioning whether or not microbes are “good” or “bad;” how fully scientists understand the microbiome even though the role of microbial fermentation in ruminants has been recognized since the late 19th century; and how the “right” communities are created inside humans and non-humans. In his lecture, Weimar responded to his own question on whether or not rumen microbes are good or bad to say, “well, sort of…”. His conclusion matched that of science writer Ed Yong in his 2014 Op-Ed in the New York Times that considered similar questions before refuting any simple, dualistic framing of the organisms that live within us.[11] What is interesting about these discussions of microbes and bodily optimization is that they are not the only site where discourses about human and animal bodies converge.

From the perspective of feminism’s relationship to fermentation, this synergy between human and animal frames is not an idle one and follows in accord with other gendered collapses, such as the argument that cows’ mammalian abilities “readily evoke thoughts of femaleness more generally,” making “the cow’s image easily trans[fer] to women” and likewise from women to cows.[12] The ability to produce milk, in other words, is gendered as feminine in a manner that circles back to the naturalized conflation of sex and gender in Linnaeus’s category building. Similarly, Kathryn Gillespie argues that even in interactions around “asexual” artificial insemination, participants draw on expectations of gendered sexuality that parallel those of normative human heterosexuality.[13] Others suggest that women’s replacement in dairying amidst technical transitions from hand-milking to mechanized systems represent classic, if essentialized, associations of women with nature and men with culture.[14] As Taija Kaarlenkaski notes, the corporeality of humans and cows are intertwined in everyday interactions that lead to the coproduction and coexistence of both emotional and instrumental relations. Cows, at a minimum then, are always already (re)productive and potentially gendered if simultaneously asexed through artificial insemination and other technologies. As production animals, cows’ bodies embody particular practices — ones to be optimized as “good” fermenters.

In what we might consider to be the over-essentialization of cow bodies, the “natural” ability to make milk makes it difficult for everyday consumers to see the centrality of reproduction: that cows need to be both female and postpartum to produce milk. To illustrate with a recent example, headlines in 2017 flashed with provocative statements like “[c]hocolate milk is too confusing for nearly half of American adults;” “[c]hocolate milk definitely doesn’t come from brown cows — but some adults think it does;” and “[p]ublic ignorance, brown cows, and the origins of chocolate milk,” in stories that derided a small percentage of American consumers for believing that chocolate milk is produced by brown cows.[15] In the reactions that followed questioning the legitimacy of the survey on which these headlines were based, one response is of particular note — that of Jenny Schlect in AGWEEK, a publication directed at farm business people and related industries.[16] Schlect took a Washington Post writer to task not for the piece’s discussion on whether or not US consumers really think chocolate milk comes from brown cows but largely for the photo that accompanied the article — a picture of a brown bull who is, of course, unable to produce milk. The author, Ilya Somin, would later retract the picture and post a brief explanation that he did not “have much knowledge of cows or bulls or much skill in telling them apart.” The irony in being unable to tell the difference between bulls (male) and cows (female) in an article on public ignorance did not pass Schlect by, but rather reinforced the broader points she was trying to make about the political consequences of our lack of agricultural knowledge. What is important about this exchange is not that some portion of Americans may believe that brown cows produce chocolate milk but that someone relatively educated — a law professor— could not tell the difference between a male and female cow where the latter is the only one that produces milk. Cows may be understood as reproductive, but the separation between consumers and producers is so vast that the former never even think to recognize that cattle have sexed, much less gendered, bodies. While dairy scientists and farmers work hard on feeding microbes to optimize milk from inside the body, consumers just care about milk and cow colour — characteristics packaged outside the body.

While we might dismiss consumers as non-experts, especially where it comes to cows, the rumen microbes lecture was aimed at turning bovine experts into microbial ones. The presentation, practical rather than academic, focused on what microbes are, what they do, and how farmers can encourage their communities inside cows’ stomachs. Representing a kind of microbiopolitics,[17] the responsibility for cultivating the “right” kind of microbial life inside cows (or humans) is placed upon individuals. In this case, the needs of the microbes supersede those of the cow so that farmers are retaught to view feed management in terms of nourishing microbial colonies rather than the cow per se. Here fermentation is not just productive; it is a reproductive “ecological, multi-organismic” process that mediates relations between bacteria, archaea, protozoa, fungi, and humans.[18] Greater attention to bovine microbiota, participants of Weimar’s lecture were told, would lead to better control in the rumen of both desirable microbial activity for more efficient nutrient capture and undesirable microbial activity like that of methane production. In other words, while all ruminants of either sex/gender ferment, only some ruminants ferment productively. Moreover, if “fermentation effects transformations in both eater and eaten,”[19] the process involved in making milk contains and produces a multiplicity of eaters, “eatens,” and transformations. Yet, who is eaten and who is eater is obscured in the densely layered materialities of fermentation and production. Milk, instead of being viewed as solely raw material that is fermentable, can be viewed as the product of cows’ and microbes’ reproductive relations.


Milk outside the body, when mixed with lively microbes and left undisturbed in a warm environment for extended fermentation, yields yogurt. In this moment of increased public attention to the interplay between feeding our human bodies and feeding our microbiomic bodies, yogurt is hailed as a key dietary participant in these exchanges. While commercial yogurt manufacturers tout the presence of particular strains of beneficial microbes, artisanal yogurt brands go further to stress that particular colonies or families of microbes come from particular places. Such crafters emphasize the doubled nature of food “culture” to describe intergenerational cultivations that sustain microbial and human communities.[20] Yet, even as yogurt-makers emphasize the centrality of heritage microbial communities and community care practices, the final product requires clear distinction between the microbial relations that ferment and the human relations that cultivate them. That is, we expect microbes to feed bodies but human bodies not to feed microbes.

The tacit expectation that microbes neutrally mediate between milk-making bodies and milk-consuming bodies while remaining detached from bodies themselves was spectacularly upended in a public culinary experiment in 2015. Cecelia Westbrook was piqued by new scientific attention to the dynamic ecosystems of vaginal microbiomes dominated by the same Lactobacillus microbes that facilitate fermentation into yogurt and similarly intrigued by the entanglements of gendered bodies and culinary assumptions as those that motivate this article. Her friend and reporter Janet Jay described the scene thus: “[A]s the disapproving ghost of Julia Child looked on, she grabbed a spoon, a pan, and a candy thermometer, and set out to create yogurt from her vagina — the ultimate in locally-sourced cuisine.”[21] Unlike Paul Photenhauer’s widely suspected performance art cookbook, Natural Harvest, in which the author advocates for using human semen as a culinary flavour, this experiment instead relied on human bodily products to produce food. Extracting microbial strains from her body, she challenged conventional notions about how gendered bodies could and should make milk-based food.

Drawing on gendered traditions of domestic crafting, Westbrook made two test batches, sampled them, and decided that this was enough data to answer the question of whether vaginal microbes could culture yogurt. She then shared this domestic experiment with Jay who wrote a now infamous article on the blog Motherboard, and for a moment the internet was abuzz with speculation about what it meant to create food-like products from vaginal material. From wry “mommy blogs” like to more mainstream digital magazine platforms like Huffington Post or Complex, this project inspired fevered public discussion about its visceral connections, at least one biohacking workshop “fusing micro-organism biology, culinary traditions and performance art”,[22] and some critique from microbiologists about technical feasibilities.[23] While it is impossible to know whether Westbrook’s experiment inspired other private fermentation projects, what is interesting is how narratives about this project reflect entrenched ideas about the symbolic excesses of the gendered body. For example, it is useful to query how such ideas enable articles to pose the question, “[w]hat are you having for breakfast tomorrow? Are you practicing patriarchy, or having a bowl of feminine worship?”[24]. Such rhetorical framing illustrates that once extracted from the vagina, microbes still retain vestiges of the over-determined sexed materiality of their bodily origin. These microbes’ connection to Westbrook’s vagina allows them to symbolically possess a gendered significance.

Dutch microbiologist Rosanne Hertzberger was one of the few public interlocutors to directly engage with the substance, rather than the symbols, of Westbrook’s experiment. Drawing on her own position as an active researcher of microbial influences on reproductive health, she challenged the usability of human microbes for yogurt cultures, and thus the science of Westbrook’s experiment. Characterizing probiotic strains as “fermentation partners,” she argues that it is only through “a beautiful duet between the two” that milk and microbes transform into yogurt.[25] Making yogurt thus requires particular eaters. Skeptical that standard human vaginal ecosystems contain the specific genetic strains needed to create yogurt rather than spoiled milk, she extracted eight strains of vaginal Lactobacillus from samples in her lab, mixed them with warm milk, and tested the results. She described the final product as “a granular substance, sour milk. … not a nice sour creamy yogurt.” On the basis of this test she argued that it was unlikely that the microbes in Westbrook’s yogurt were specifically vaginal in origin: “[i]t could be that some of those bacteria had a vaginal origin, but it could also be that some of them came out of the wooden spoon, or from the air, or from the sink, or from under her fingernails.” The body’s microbial relations in this case are less determinative than the broader microbial ecologies of Westbrook’s experimental context.

Hertzberger ends her post by noting that microbes lose attachment to any vestigial bodily origins during fermentation. Out of the body, as the microbial strains combine with milk and rapidly reproduce, she argues, they transform both the fermenting agents and the medium such that “there is no longer a molecular vagina.” However, even in this carefully detailed scientific analysis of the inextricable transformation away from connection to gendered materiality, Hertzberger is careful to note that her experiments relied on samples already collected for ongoing research by her lab, terming her own samples “private.” Her labelling suggests that contra to her own conclusion above, there is a molecular vagina that symbolically survives fermentation. If Hertzberger explicitly denies these connections while implicitly endorsing them, Westbrook concludes on the basis of her own yogurt’s taste that “eating actual pussy” [26] is not equivalent to eating yogurt made from vaginal microbes, explicitly rejecting the implication that sexed origin matters after microbial transformation.

Microbes mediate, or foment, relationships between bodies and food-like products. Extracted from bodily contexts, microbes reproduce and catalyze reactions that transform milk into yogurt or cheese. Microbes are at once instigators of these processes and enfolded into the new substance. During fermentation, they enable transformative shifts from raw to cooked that can be understood as a kind of transubstantiation. Crucially, the material nature of their component parts alters as they transverse across media: microbes are themselves transformed as they transform. Thus, understood in this fashion, Westbrook’s yogurt should not carry vestigial bodily attachments, but they still appear to, as illustrated by Hertzberger’s demurral of the private nature of using her own samples. Even as Westbrook’s extracted microbes and warm milk transformed into a fermented food-like substance, the microbes seem to have retained an essentialized and gendered residue that is at odds with the stripping of commercial food-stuffs’ bodily attachments. While the FDA’s caution against replicating this experiment emphasizes that “a food product that contains vaginal secretions or other bodily fluids is considered adulterated"[27] — we suggest that the character and quantity of public response is amplified by attachment to sexed and bodily origins. Whereas microbial relations inside cow bodies ultimately become food, microbial relations outside — but still attached to — sexed bodies are not food.


Returning to Linnaeus’s ordering principles, naming in the service of taxonomic orders matters. Latin and Greek are languages that oblige nouns to have gender; thus microbes can be inadvertently gendered — for example, the name Lactobacillus is classed as masculine. Even though microbes are not recognized to have gender on their own, this status does not preclude them from being intertwined with gender projects. Naming and ordering produces categories that further mediate the relationships between what we recognize as natural and cultured. Microbes can thus be a productive locus through which to understand fermentation’s capacity “not to create matter out of nothing but to organize matter, to direct it and to change its form.”[28] In this way, ordering matters. Extending feminist arguments that discursive, social, and political classifications make bodies matter (or not), we use fermentation to consider how the matter of bodies is entangled with such orderings.

We conclude with the proposition that microbes in the body and those outside the body are not the same thing. While Weimar emphasizes a material and productive relationship between rumen and ruminator (and the unique microfloral “signatures” of individual cows), Hertzberger suggests that the “rumen” can ruminate without ruminator (e.g. “there is no longer a molecular vagina” in yogurt). Taking Weimar and Hertzberger together suggests that fermented food has layered microbial lives. Out of the body there is only one layer of microbial life to think about — the microbes themselves, which are uneasily categorized as good or bad within the microbiopolitics of artisanal food production.[29] But, when they are inside the body, there are different kinds of life that have that to be co-fed.

Having brought these cases of fermenting milk and yogurt together, we offer two additional provocations about how fermentation organizes sex/gender as “a congealing of activity”[30] between microbial and mammalian bodies, especially in relation to their capacity to produce food products. First, recognizing milk as the product of reproductive labour from gendered — yet asexed — animals opens up new possibilities for recognizing the way that sex and gender materialize in the capacity of mammalian bodies to ferment. While it is easier to apply gender to things that are already sexed, the way that the human microbiome spatializes the human body as differentially sexed or gendered ecosystems (breast, penis, and vagina apart from gut and skin) illuminates how microbes themselves are also sexed and gendered through their material attachments. While microbes do not have reproductive organs, humans and cows do. When we locate microbes in particularly reproductive spaces, it is easy to see how they then have the possibility of becoming gendered by creating new layers of biological determinism. Focus on the co-productive work of microbes to feed and be fed thus potentially enrolls new forms of relatedness into the deeply naturalized binaries on which taxonomic classification rest.

Second, fermentation is always already a reproductive process. While mammalian bodies make milk, human ones only make food through their reproductive capacities and labours, another stubborn boundary marker between who is eating and who is eaten. While it is easy to fall back on a human/nonhuman binary that splits the capacity of mammalian bodies between those who legitimately produce food and those who do not, we want to suggest that there is something more at work that is glimpsed by centering microbial relations rather than the comestible products themselves. Even as dairy scientists have refocused attention on cultivating microbial relations rather than cows alone, so too has public interpretations of breast milk science begun to reorder human-milk relationships in ways analogous to cow-milk relationships. As one summary of scientific developments concludes, “Human milk isn't sterile — it's very much alive, filled with good bacteria, much like yogurt and naturally fermented pickles and kefir, that keep our digestive systems functioning properly. So mother's milk contains not only the bacteria necessary to help a baby break down food, but the food for the bacteria themselves to thrive.”[31] Breasts and rumens both are fermentation vats par excellence — and the maternal nurturance Linnaeus used to order the species line is now expanded to include the capacity to nourish bacteria. Like vaginal ones, narratives about the capacity of human breasts to ferment food raise questions about how participants semiotically draw on the capacity of sexed bodies.

In making this argument, we share with food studies scholars a broad interest in the social and material relations created by production and consumption practices as well as the recognition — indeed truism — that the study of food serves as a window into the intricate linkages between history, culture, identity, politics, and economics. However rather than centering food as such in our analysis, we center the intimate and microbial connections to bodies that constitute food’s materiality and its acquisition of identity through praxis. Extending food studies’ insights into how fermentation’s generative (and reproductive) transformations are integral to the ways fermented foods’ constitute heritage, gendered, and health practices, we demonstrate that questions of microbial consumption involve broader questions about the relationship between ordering food and food products and other forms of ordering bodies. We bring, in other words, a microbiological analysis of gender and food together. Microbes ferment, but they cannot ferment by themselves. The outcome of fermentation — whether it is in the rumen, in the breast, or outside the vagina — is materially and symbolically reordered relationships. The cultured product of microbial reproduction in organic matter, thus, goes beyond food conventional or otherwise. Challenging the idea that such relationships can ever be neutral or external to the bodies they nourish, instead, we argue that microbial relations are central to how gender comes to matter and nature comes to culture.