Homemaking for More-Than-Humans: Biodesign and the Redesign of Homes as Spaces for Multispecies Care

Abstract

Thinking through the expectations and experiences of biodesigners in London, this article explores how domestic politics and caring practices change as environmental entanglement becomes a basis for ethical homemaking. As this paper ethnographically explores, taking care within more-than-human homes requires new design considerations and timeframes, new homemaking practices, and new domestic relations.

KEYWORDS: :

• biodesign
• more-than-human
• home
• care

INTRODUCTION

In a home in a metropolis like London, most of the physical stuff of homemaking like food, clothes, water, fuel, and furniture starts and ends its journey elsewhere. The home, in this light, might be considered a node in long supply chains and waste chains. This article considers a growing design discipline—biodesigners—taking issue with such a flow of goods as they connect it to mounting ecological crises. Biodesigners are makers introducing living organisms within design processes (Myers 2012), in hopes of redesigning materials in a circular, regenerative manner. This paper explores how biodesigners reframe homes for, as they present it, a good home does not denote coziness, homeliness, or safety (as it does in Duque et al. 2019) but rather a new ethic of domestic production and waste that accounts for distributed more-than-human effects.

For example, each year in London¹ several Masters showcase projects feature home-related designs like appliances which grow produce or filter air, furniture grown in situ with mycelium, windows treated with alive photosynthesizing bacteria, or clothes embedded with odor-stopping microbes. Holistically, these present a future for homes that is regenerative, environmentally friendly, and pollution-free. Though metabolizing homes have been imagined before (Bonnemaison and Macy 2016), biodesigners’ work serves different ends as, for many in this community, their projects are not primarily about creating better dwellings for people but about expanding possibilities for environmental action. As my interlocutors frame it, their work might be understood as “design for planet” or “non-human centered design.” In this light, the use and care of items like metabolizing appliances should be considered in relation to more-than-human concerns.

Biodesigners’ imaginaries and engagements within more-than-human homes invite anthropological attention as they speak to questions of increasing interest such as how environmental politics or public actions translate to domestic life (Marres 2008; Knox 2018). This article ethnographically explores how domestic politics and caring practices change as environmental entanglement becomes a basis for ethical homemaking.

This article is structured in three parts. The first section briefly situates biodesigners’ imaginaries of homes as centers for environmental action within literature on eco-homes. I trace in this literature a shifting politics of space as domestic energy usage and carbon emissions are brought to bear on climate change. I contrast this energy politics to biodesigners’ material ethics. For my interlocutors, environmental crisis is tangibly and materially grounded: they evidence toxicity, waste, and environmental disasters in plastics which leach, in dyes which poison, and in fabrics which linger and clog up landfills. Accordingly, their domestic environmental ethos is based on an understanding of matter as fundamentally lively, flowing through supply chains, ecosystems, organisms, and digestive tracts.

In the second section, I argue that biodesigners’ material ethics introduce fresh criteria for the design of spaces. Instead of imagining homes for people, they reconsider human-centered spaces from the perspective of the environment. As biodesigners extend consideration to more-than-humans within their designs for the home, I see them practicing a kind of carework. Drawing on Maria Puig de la Bellacasa’s writings on permaculture farming and her definition of care as “labor/work, affect/affections, ethics/politics” (2017: 5), I see their expansion as a political and ethical act, with specific affective and practical effects.

In the third section, biodesigners’ experience of taking care of more-than-human environments comes home in a very literal way. During the Covid-19 lockdowns in London, institutional labs shut down and emerging designers brought their organisms into their flats to continue their design experimentations. For this group of designers, living within explicitly more-than-human spaces was immediately and intimately felt. As they nurtured organisms like bacteria, algae, and mycelium at home, my interlocutors found themselves affectively entangled, increasingly conscious, and responsible towards their more-than-human companions—companions which, they discovered, were more numerous than the creatures they were designing alongside. Overall, this paper traces how domestic environmental caring practices may transform and layer from indirect to direct and from collective to specific as biodesigners radically reimagine what it means to be at home with more-than-humans.

This article draws from a 19-month research project on London-based biodesigners. The project had two phases. The first phase involved an “interface ethnography” (Ortner 2010)—an ethnography of design shows, museum exhibitions, conferences, and talks, both in person and online—followed by interviews with designers encountered in those spaces. The second phase involved a corporate ethnography at a biodesign start-up in South London. This latter work indirectly feeds this paper, as the imagined futures of the things created by the start-up were also in domestic contexts. Overall, my engagement with designers was as an external observer, not as a co-designer or researcher. In total, I conducted 68 formal and informal interviews, attended 28 bio talks and panels, visited 14 design showcases, and worked within a bio-startup for 9 months. The focus on London provides a particular bent to my research: my interlocutors described feeling incapable of consuming ethically in everyday life within the city, and so framed their experiments as a direct response to these feelings.

HOMES RECONTEXTUALIZED: ECO-HOMES AND THE DYNAMICS OF DOMESTIC ENERGY USE AND WASTE

In designing homes, one is designing futures—new ways of living and dwelling within the world (Pink et al. 2017). This is apparent within a burgeoning literature on eco homes which illustrate how domestic actions acquire political dimensions as domestic energy consumption is resituated within broader climate discussions. As Kersty Hobson (2006), Noortje Marres (2008), and Hannah Knox (2018, 2020) variously note, homes are increasingly presented as spaces of environmental (ir)responsibility and guilt. In their accounts, changing lightbulbs, taking showers, shutting windows, or drying clothes take on new meanings and politics as climate change and carbon emissions are brought to bear on daily life. This changes people’s relationship with energy; as Knox writes, “practices that would otherwise have been cast in a different register—consumption oriented towards comfort, familial relations, generosity, thrift—became recast as a practice of waste avoidance” (2018: 114).

Marres (2008) makes a similar point that inhabitants are “materially implicated in collective environmental problems … by virtue of their energy habits” (Marres 2008: 34) but highlights a concern here. As homes enter conversations on emissions accountability, she writes, responsibilities that belong to the public are pushed into private domains. This may suggest a shift in the ontological basis of the home as a place of separation (Hinchcliffe 1997: 201). Yet, it is evident that a gap persists between domestic energy usage, climate ethics, and collective impacts. An illustrative example of this gap comes from Knox’s work. She describes a teenage boy riling up his eco-conscious mother by flicking lights on and off and chanting “one polar bear dead, another polar bear dead, another polar bear dead…” (2018: 122). His cynical joke points to the disconnect: turning lights off does not literally or directly equal polar bear lives saved, though they might be tangentially and imaginatively linked.

This is where biodesigners’ approach differs—and their distinctive material ethics comes to the fore. While biodesigners share the belief that everyday consumption connects to environmental disaster, they trace it physically and locate toxicity, waste, and negative consequence in the material constitution of things. Plastics leach and chemicals poison directly, and so their criteria for eco-designs is based in changed material considerations rather than on energy usage. A good example of this comes from a seminal text within biodesign, William McDonough and Michael Braungart’s (2002) Cradle to Cradle. McDonough and Braunagart instruct designers to consider the environments impacted by their choices so that a designer of a hair product should ask not only “what does the consumer want from this hair gel?” but also “what does the river into which this hair gel will eventually be discharged want from it?” (cited in Mathews 2011: 376). Materials, they suggest, have direct, causal impacts on more-than-human worlds and, to act responsibly, one must account for these impacts.

EXTENDING CARE THROUGH THINGS IN MORE-THAN-HUMAN HOMES

Accounting for more-than-human worlds within the home begins with changed design considerations. In this section, I consider how more-than-human concerns might be reflected within emerging biodesigns as I trace new possibilities for care in the forms and functions of biodesigned things within the context of the home. In contrast to researchers for whom the home is a place of identity, care, and living (Pink et al. 2017; Reimer and Leslie 2004), biodesigners redefine homes as a node in the movement of things and the things within it as temporarily owned. Overly focusing on human utility, biodesigners suggest, means ignoring the timescales and impacts of things. Such a view was articulated by Colin, co-founder of a nonprofit promoting the shift towards a circular economy, at the Applied Utopia symposium at Central Saint Martins in October 2022. “Look around you,” he said to an audience of young designers:

every single thing you see in this room—the walls, the floor, your clothes, the ceiling—every single thing was created and is going somewhere… Most of the time, the built environment was thought of in terms of use but not what happens afterwards and where it’s going. So it’s all garbage. Literally all day, we are surrounded by garbage.

Initially, Colin’s assertion seemed at odds with the surrounding polished and designed lecture theatre. However, his vision, which resonates with many biodesigners, I’ve spoken to, is predicated on objects moving through systems (Simms and Potts 2012). A similar observation is made by Tim Ingold (2017) who notes that “building is a process that is continually going on … It does not begin here, with a pre-formed plan, and end there, with a finished artefact. The ‘final form’ is but a fleeting moment in the life of any feature, when it is matched to a human purpose” (ibid: 188). Here, though, biodesigners would disagree: the final form is not that slice matched to human purpose, but the transformation and flow itself which impacts more-than-human worlds. They emphasize that their overarching goal is for the end-of-life of a thing—the point at which it becomes “waste”—to be considered during the design process. Agnes, a designer who created a particle board made from fruit waste, expressed this perspective to me in an interview: “I really like considering the full cycle of things … The fact that we overproduce and produce without thinking at all about the resources, I just felt like doing exactly the opposite.” She suggested that overly focusing on the user’s or consumer’s experience, as is common in most commercial designs, results in a world filled with “bad” products—things that were negligently designed and destined for incineration or landfill. This, she argued, makes the world “close to a dystopia … since there’s an end to every cycle.”

In biodesigners’ approach to making which reworks the end-of-life of things as a central concern, I see a rejection of the modernist formula that form follows function: rather, the form itself is the function. By this, I mean that biologically derived, benign, decomposable, and regenerative materials serve their more-than-human purpose by their very constitution. Consider an algae-based biopolymer that substitutes for single use plastics, for instance. Whether discarded into a bin or landscape, it will degrade quickly, ensuring that its users will not be (overly) polluting no matter their behavior. As biodesigners collapse form and function within things,² the stuff they make has built-in impacts and their materials attempt to make certain kinds of ethical actions more likely (cf. Latour 1992), regardless of the user’s intentions.

It takes significant effort to design in such a way. This was described to me by Valentina, a designer working on mycelium boards for construction purposes. She said that was trying to bring her design’s human utility and more-than-human life and effects into line. To achieve this, she needed to accurately predict the length of time a material would need to be in use and match the lifespan of her mycelium base material and its treatments to that timeframe. “Let’s say we want the building to last 20 years,” she explained, “so then a coating should also last for 20 years before biodegrading when we put it into the compost heap.” This was an intricate task, requiring the aid of material scientists, chemical engineers, and building experts. She said she had to explain to them the reason why her approach was important: why it was worth merging human and more-than-human needs within buildings to “mak[e] sure that our material is not harming anyone.” I see, in this effort, a kind of carework based on a distinctively more-than-human accounting of who or what matters at all stages of a design’s life.

For biodesigners, such careful more-than-human consideration is in direct contrast to how most things populating urban and Western homes have been designed. According to my interlocutors, most consumer goods are over-engineered and outlive their usefulness or their desirability. A common example of this was plastic bags. Plastic bags—containers with a fleetingly short use span—are made from resources that cannot be replaced and will linger leaching in landfills and waterways for millennia. My participants argued that the bags have “bad lifecycles” because there is a mismatch with between its form, its use, and the environment into which it will flow. Mismatches like this are the result of lack of knowledge or lack of care; for my interlocutors, they evidence a failure to apply the right consideration sets on the part of the designer. As the biodesign community presents, human-centered design (which they define as design overly focused on usefulness to humans) is prone to these errors. This is because a focus on human utility often fails to reflect the broader relations that are created by and surrounding a design.

Many biodesigners contend that pervasive mismatches between use and desire is intentional: that planned obsolescence ensures people do not form lasting or meaningful relationships with the things around them. They explain that because people do not currently care enough about the material environment—do not care enough about where things came from and where they are going—many societies are so extractivist and toxic. Such claims align with scholars writing on waste who view the proliferation of waste—be it waste products, wasted ecosystems, or wasted lives—as a consequence of a lack of care (Chapman 2009; Martínez 2017).

This informs biodesigners’ challenge as they try to make things with and for care. Emma, a biodesigner creating soft robotics with algae-based biomaterials, told me that because “everyday objects really do go undervalued,” designers must “hero the object” to change people’s relationships with things. She argued that emphasizing the activeness of materials—their ability to flow outwards and impact more-than-human lives—might be a step towards more caring relations. Caroline, a textile artist working with found natural materials like flower stems or tree shoots, told me something similar. She said the goal for her work was for people to see “something as precious” and then seek to “preserv[e it] rather than throwing it away.” Such preservation requires effort—and changed expectations for what materials might require in terms of attention and labor. Preservation and revaluing things, as Emma and Caroline presented, might be a reinvestment in care. Cindy Isenhour and Joshua Reno (2019) make a similar case as they see the removal of a thing from the “waste” category as a kind of “carework” which involves “both attention to a thing’s material qualities, as well as a concern for why and for whom they matter” (2009: 3). The concept of preservation, though, pushes further than this: it points to active participation that biodesigns encourage as they require their users to engage with more-than-human needs. Preservation thus offers a productive lens to understand how biodesigns’ affordances and forms can facilitate more-than-human caretaking.

This kind of preservation-as-carework can be very literal, as in the case of biodesigns which are still alive after they exit the design studio. For instance, consider a shirt that is treated by the London based company, Post Carbon Labs. This shirt, coated with photosynthesizing microorganisms, is literally alive and for it to remain alive, it must be carefully looked after. Its owner must engage with it repeatedly, must be made responsible for its existence, and must learn how to care for it by misting it at times or by keeping it away from too bright of lights. For the owners of such objects, preserving their vitality is key as one aspect of their worth lies in their ability to produce as much oxygen as much a young tree (Warner 2020) in new contexts. As Dj, the co-founder of Post Carbon Labs, explained, they provide “people access to take climate action within their living rooms,” a harder and harder task in “an age of reduced land liberty.”

In reconsidering the lifespans and effects of things, biodesigners bring the home into new arrangements within more-than-human worlds. I understand this as a kind of carework, which is both material and imaginative, and which has ethical, affective, and political effects (Puig de la Bellacasa 2017). As biodesigners present it, taking care within the home—taking care, for instance, of the things brought into the home and which are taken out—is a means of taking care for the environment more broadly. With their new forms and functions, things like photosynthesizing t-shirts open the aperture to more responsible domesticity—for both designers and those engaging with their designs. This speaks to the political imaginary behind their practice, which connects reframed designer considerations to new domestic caring possibilities for the environment.

AFFECTIVE ENTANGLEMENTS AND HOMEMAKING FOR MORE-THAN-HUMANS: BIODESIGN AT HOME

While more-than-human homes were presented in the previous section as the conceptual foundation for a new domestic ethos that accounts for things beyond human utility, they were also experienced firsthand by a group of emerging biodesigners. As graduate designers set up makeshift labs on their kitchen counters and under their beds during Covid-19 lockdowns, the home became a literal space of more-than-human care. This section explores the consequences of such intimate care at home as it asks, in line with Puig de la Bellacasa, “what happens when thinking about and with others is understood as living with them? When the effects of caring, or not, are brought closer?” (2017: 17).

In 2020, when most non-commercial biolabs in London shut down, emerging biodesigners brought their designs home and they quickly had to adapt to their new co-residents. While frustration, challenge, and adaptation are inherent parts of the biodesign process (Karana et al. 2020), this is especially true in the imperfect conditions of home labs. When I interviewed designers a little more than a year after they brought their work home, they emphasized their difficulties. Few places in urban homes are conducive to growth, and so creating the right conditions took significant work. Nicole, a biodesigner working with biomineralizing bacteria, told me how she had to think through the preferences of her bacteria to ensure her space was suitable. “I had to learn from the beginning how these organisms work—What do they like? What temperature do they like? What food do they like to eat?” She likened them to “little people” in that they have their own habitats and habits that needed to be catered to. “I had to observe them to understand what works and what doesn’t,” she explained. Creating the right conditions for different organisms is an iterative process of discovery. Through a gradual attunement, biodesigners learn how to observe and interpret their organism. This is similar to the refinement of sensibilities developed by other craftspeople working with microorganisms, such as cheese makers (Paxson 2008), bokashi practitioners (Kinnumen 2021), and natural winemakers (Chartier 2021).

When organisms did not grow as expected, the importance of understanding their needs and worlds came to the fore. I had this described to me by Helena, a biodesigner working on an artistic project around the biodegradation of clothing with mycelium. She described recurrent challenges to her work, and how she had to recalibrate her approach. She said that when she began her work,

I thought I had all this control over it… I had this idea that I’m going to make this garment and after a bit of time, I’m going to grow mycelium and completely decompose it. But when my first garment that was decomposing with mycelium, I had to check on it and at six weeks in I thought it would be growing but absolutely nothing was happening… I realized, I have zero control over this.

As the mycelium behaved in unexpected ways, Helena became acutely aware of the challenge of encouraging and preserving life within her home. She told me that she adjusted both her expectations and her processes accordingly. For instance, while she initially used what she thought was a “nice polyester fabric… it was clear they didn’t like it. That’s why I resorted to using materials that had zero treatments” like undyed hemp. Caring for the mycelium well, she found, involved adapting to its natural behaviors and preferences.

For biodesigners, such careful attention and caretaking at home had unintended consequences. While it may have been instigated by a desire to take care of a broader environment by the redesign of things, its affects and impacts quickly exceeded this frame. Intimate caretaking reworked both my interlocutors’ relationship to their projects and to their homes at large. For example, though Helena had embarked upon her project to explore how organisms might facilitate the disposal of things at home, she found herself invested in ways she did not anticipate. She said that project was instigated, in part, because of her relationship with things—particularly her own creations. “I’m not exactly a hoarder,” she told me, “but with all the work that I’ve done in the past, I find it hard to get rid of.” She said she had had boxes of work from her earlier degrees around her house. In creating garments designed for degradation, she was deliberately asking questions around the relationship people have with clothes and with their own creativity. She was willing—eager even—to destroy her craftwork as she told me that “I’d rather have it destroyed than have it whole.” Yet, when it came time for Helena to discard her garment, having had it consumed by mycelium, she found it difficult to let go of the organism. Instead of burying the piece as she planned, she kept some, hoping to inoculate future works with it and preserving its vitality.

Such attachment was not unique. I heard from Ruta, another designer working with mycelium, about how her behaviors and expectations quickly changed when caring for her organisms at home. She too was deeply interested in the personal ethics of disposal and her degree project had involved encouraging mycelium to consume her wasted, unwanted, and broken things in jars. Yet, Ruta’s project had a somewhat ironic afterlife following her degree show. The mycelium’s work was not to a schedule; it takes time to degrade things, and biological agents take the time they need. When Ruta and I chatted a little over a year after she graduated, she said her house remained cluttered with jars full of brightly colored scraps and white hyphae.

There are a few things worth unpacking from these two examples. First, both Ruta’s and Helena’s projects attempted to extend their homes’ capacity to consume things as a mode of environmental action. Both projects succeeded in that regard and instigated a new sense of responsibility and capability within their homes. Ruta, for instance, told me that during her project, she avoided eating food like spinach because it came in plastic bags that her mycelium could not handle. This could be seen as a first layer of more-than-human care within their homes, comparable to Post Carbon Lab’s photosynthesizing fabrics or to Agnes’ or Valentina’s construction materials as new domestic capacities called for new modes of consumption. Yet, both projects also dragged out in time and instigated unanticipated attachments. Neither Ruta nor Helena had allowed their projects to reach their “final” step—the responsible disposal of their organisms’ outputs. Instead, they felt intimately attached to their organism and to their collaborative output. As Helena put it, “this mycelium garment was my baby, my child. I was trying to take care of it. I was giving it a lot of love and attention… I wanted to keep it.” Intimate involvement with specific beings brought new dimensions to their carework.

Such emotional intimacy was common amongst my interlocutors who were working from home. Like Helena, many referred to the organisms they were working with as “babies.” Cassie, a recent graduate from Central Saint Martin’s Biodesign MA, connected this to the fact that many organisms are placed in an “incubator to keep [them] warm” and are carefully handled to ensure their safety. She described that “it’s like looking after a little baby… although it is because you want the most materials in the end—it automatically creates that sense of care with it." In Cassie’s description, care layers: she expresses a maximizing productive impulse—that, by taking care of these organisms, one might accomplish certain positive design outcomes—but it is an impulse complicated by affective entanglements.

As other scholars have noted in the context of more-than-human care, caring entanglements spread—and do so unexpectedly. Caring for creatures like earthworms (Puig de la Bellacasa 2017) or cheese-making bacteria (Paxson 2008) leads to broader considerations of ecosystems. Scales collapse in these accounts; as Paxson writes, “care of the cheese, care of the animals, care of the land, and care of the consuming self all must consider the microbe” (2008: 38). At home, my interlocutors experienced a similar expansion of care and awareness which grew from intimate engagement and attention to their organisms. Often sitting on their kitchen counters, or growing in boxes in corners of their flats, their experiments were exposed to the wild ecologies of their homes, including creatures previously unnoticed. I heard from many designers that they came to be more and more aware of other beings (algae, molds, bacteria, spiders, slimes) which had previously escaped them as they worried about potential threats and contaminants to their organisms. Some even came to seek out new collaborators around their homes. Ruth, a biodesigner working on bacterial dyes, described having a contamination issue and fuzzy green mold growing on top of her usually bright pink colonies. When she stripped the mold away, she discovered that the colonies had produced an even brighter pigment than usual. In subsequent experiments, Ruth said, she intended to deliberately experiment with contaminants to better understand—and perhaps exploit—her colonies’ responses.

Experiences of growing and caring for algae, plants, fungi, and bacteria heightened their awareness of the lively and reacting wild ecologies already present in their homes. From trying to design homes that serve more-than-humans, my interlocutors found their homes were always more-than-human. Such awareness, in turn, fed new domestic practices. I heard that as my interlocutors felt newly aware of their effects on other forms of life, and acts like washing hands, sterilizing equipment, or cooking food took on new meanings. As one designer put it to me: things changed when she realized that everything she did has “a direct intervention in an ecosystem.” Caring practices, as I explored in this section, layer as biodesigners came to personally experience the consequences of living within more-than-human homes.

CONCLUSION

In this article, I explore biodesigners’ novel approach to homemaking. This approach will interest anthropologists curious about how more-than-human care might evolve within the context of the home, and to those invested in environmental action. I argue that in biodesigners’ redefinition of homes from a more-than-human perspective, one can trace a new material ethic and mode of care that aspires to bring about a more ecologically sound future. This is not based on thermodynamics or energy usage (as is the case in many eco-homes), but on a redefinition of materials as lively and entangled within more-than-human worlds. Significantly, such care might be planned for and designed, yet still emerges in unpredictable ways as speculative ethical commitments to more-than-humans collide with lived experiences of intimately caring for more-than-humans within their homes.

As my interlocutors’ homes emerged as a more-than-human environment, as much as they are within a more-than-human world, what it meant to take care within the home expanded. Such an expansion enriches understandings of how more-than-human care might evolve as a kind of layering process. While Puig de la Bellacasa (2017) and Paxson (2008) describe how care for organism or ecosystem might expand outwards, enrolling more and more things into considerations of care, my interlocutors found that from abstract care for the environment they became intimately entangled with specific creatures. This, in turn, opened up again: from taking care of those organisms, they came to care more broadly for the immediate and vibrant ecology already in their homes.

Biodesigners’ evolving experiences and expectations of more-than-human homes also offer valuable insights into how one might reimagine domestic spaces as interconnected and mutually dependent ecosystems—and what the consequences of doing so would be. In many ways, their work serves as a corrective to conventional notions of homemaking and human-centered design which fail to account for impact of domestic choices on more-than-human worlds. It also serves as a counterpoint to more recent attempts at domestic climate action which fail to bring home the entanglement between everyday domestic life and more-than-human worlds within urban settings. Yet, as this article began to unpack, the implications of imagining and experiencing homes from more-than-human perspectives remains uncertain. Questions linger, for instance, as to whether individuals will willingly embrace the caring roles imposed upon them, or whether relationships instigated by biodesigns can lead to broader and more enduring changes in behavior.

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Katie Pfeiffer

Katie Pfeiffer recently received her PhD in Design Anthropology from University College London (UCL). She completed her fieldwork on biodesign practitioners in London in late 2022. Her broader research examines questions of ethics and value for makers in the context of climate crisis.

Notes

1 London is one of the main biodesign hubs, with four universities offering biodesign programs and many of the UK’s biodesign startups based in the city.

2 In some ways, this is a collapse of biological and designerly definitions of form: it refers to more than the aesthetic dimensions of things, but to the relationship between material and biological affordances (Norman 2004; Gibson 1979) and their physical constitution.