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John Dupré, Lecture 3: Humans and their Fellow Travelers

What is an organism? This is question that preoccupied our third Gifford lecture of the 2023 series. Dupré met an engaged audience at the Gordon Aikman Lecture Theatre, and responded enthusiastically to varied questions stemming from different disciplines. The summary and response from recent PhD Graduate Zahra Massoud is below.

The standard view: two types of organisms- single-celled and multicellular. Unlike single-celled, multicellular organisms are formed from the sum of all the interconnected cells derived from the zygote. The problem: biofilms- the most successful life form on Earth (found as plaque on our teeth and creating slimy surfaces on rocks). Biofilms are complex communities having characteristic life cycles, recruiting various kinds of members in a particular order, and eventually dispersing. They are functional wholes, and the individual cells within them usually can only flourish when in the whole. There is an excellent case for considering them as organisms. This is usually rejected because biofilms do not form identifiable lineages.

This problem is related in bacterial taxonomy. Bacteria are obligately social members of multispecies communities and cannot be held outside of a cell culture to be displayed in a museum. ‘While there are estimated to be millions of bacterial species, only about 20,000 have been named.  Something seems to have gone wrong.’

In the human body, 50-80 percent of our cells are non-human. What is important is that many of these bacteria are essential for the health of the human. ‘The healthy human is a multi-species symbiosis.’ It has become common to refer to the human and its symbiotic partners as a holobiont.

Holobionts are argued to be the best description of the human. However, they also do not form clear lineages. Some symbionts are inherited from parents, but many from the environment.

If a human is a thing that evolved, but the thing that evolved cannot function in the way a human does, we have an impasse.

Thinking in processes, the MDLC (monogenomic differentiated cell lineage), has lineages of cells to one’s liver and one’s brain are different but converge at zygote- the Universal common ancestor. The lineage of the bacterium, an obligate symbiont of the human, is embedded in the human lineage. The processes differ completely, one by cell division, the other by sexual reproduction, but both processes help to stabilize each other. Environmentally acquired symbionts likely do not require the human symbiont but still bumps into it in a mutually beneficial relationship- not constantly being intertwined. ‘. Is there any answer to exactly how much of all this is truly part of the functional whole? Surely not. But this is just what processes are often like.’ Stabilization often happens at the boundaries of the holobiont, we have continuous processes with no defined borders.

Economic processes can illustrate this, where unemployment, inflation or welfare system constitute the wider processes with which individuals engage. Dupré pointed to the ignored reality of domestic work not being included in these larger GDP processes, effecting the well-being of women.

Dupré presents this looseness of boundary present in the holobiont as a feature. Tens of trillions of bacteria are present in the human body, perhaps 7x more than there are human cells. With ten times as many viruses as bacteria. The knowledge that bacteria are beneficial (the hipster rise in kombucha comes to mind), the same thinking is influencing the positive presence of viruses. They are useful for regulating the numbers of symbiotic bacteria and also reside in dangerous places to protect from harmful external bacteria (mucus tissues in the mouth). Populations of viruses in the human if fairly stable- not increasing and decreasing as might be expected as when studying prey and predator organisms. This suggests that the virome is part of the stabilizing system.

This complex system is maintained partly through the immune system. Instead, however, of recognising human over non-human cells, attacking the later, it has been suggested that the immune system, rather than judging the intrinsic nature of cells, reacts instead to sudden changes in the chemical environment- making it a stabilizing system. There are also the cooperative construction of biofilms in the body. Humans, then, are hardly just made up of human cells, but include bacteria, viruses and perhaps protists, fungi archaea and more.

Life, as I am trying to present it, is quite generally an intertwining of parts of lineage processes to produce stable individuals. These individuals, in turn, generate new parts—organisms—to sustain the lineages that they include.

Ecological relations always help sustain these equilibriums. Humans and their livestock for instance (whether this legitimates the appalling conditions that they are reared in is up for debate) where the success of each is dependent on the other is an exmaple. More important, are the relationships between humans to sustain our equilibriums.

Here is where we come into the discussion of pregnancy. The common view is that life begins when an egg is fertilized (the bun in the oven view of pregnancy). This container view overlooks the work of the symbionts that connect the two “individuals”. Might we rather take the foetus to be a part of the mother? The relations between a foetus and mother are intimate beyond any other where all the flows of nutrients, oxygen and countless other chemicals pass through the mother to foetus. It is not autonomous, and still is not strictly autonomous once the umbilical course is cut.

Note the separation between foetus and mother

Of course, this connects to the abortion debate. The idea that life begins at fertilization, Dupré poses is ‘philosophically correct’ but there is an ‘enormous difference between a single cell and a developed human being.’ People seem less concerned when these cells are stored in liquid nitrogen. And since biological systems do not have essences, he would encourage people to disregard the essentialism found in the ethics of many religions. Another arbitrary, or as Dupré describes ‘fishy’, cut-off time (for experimentation) is at 14 days, where the embryo, after this point cannot turn into twins. Surely, Dupré argues, this should be an even stronger argument against experimentation, and the right to choose an abortion is a great deal later than two weeks.

Kingma’s definition that they become two at birth puts a lot of philosophical weight on one act. Kingma however sees difficultly with embracing the birthed individual was part of another individual. Dupré does not find issue with this. ‘If life is a flow of activity, then pregnancy is a bifurcation within that flow.’ In light of this, Dupré refuses to pinpoint the stage of ultimate separation.

Going back to his point about the important of co-operation explored in the last lecture, Dupré reflects on the ability of humans to orchestrate joint efforts for human flourishing. So why, he questions, has individualism dominated political, psychological and economic theory for the last 150 years (linking also to competition present in natural selection)? How, though, Dupré stresses, that all the town planners, architects and labourers working together on erecting a structure are merely pursuing their own personal goals? Even with the resources of a billionaire we are still dependent on human co-operation to build houses and grow food. Bezos does not grow food, so why is it considered reasonable to think that he ‘earned’ his billions?

This connects to the issue of the thing ontology. Thatcher made this famous by her belief that there is no such thing as society. Dupré ended his lecture by commenting,

Seeing the human individual as a complex process sustained in its far from equilibrium condition by countless interactions with other organisms, human and otherwise, and by a vast infrastructure also created by vast numbers of humans dead and alive, the assumption of isolated self-interested individuals seems nonsensical. Indeed, it is no surprise to find it to be an assumption that serves mainly to foster socially dysfunctional behaviour.


Response: Dr Zahra Massoud 

In the third lecture of the series, entitled ”Humans and their Fellow Travellers”, Professor John Dupré discussed whether the human organism can be defined as an discrete entity, and the implications of this in both a biological and societal context. He introduces the idea that human beings – traditionally conceptualised as a distinct organism with a solid boundary between “us” and the outside world – may be better thought of as a holobiont, or assemblage of multiple individual organisms which together form a discrete ecological unit.

The idea that the microorganisms – bacteria, viruses and others – that live on, in and around us are a necessary part of the human condition is a relatively new one. In the last decade, much work has been done to show that the bacteria within our digestive systems or on our skin provide functions such as metabolising the food we eat or fighting harmful pathogens, which are vitally important to maintaining a healthy and functional human organism. The body is able to distinguish between beneficial, symbiotic bacteria and harmful bacteria, providing evidence that these bacteria are considered “part of” their host. Between the ideas that many of these bacteria are unable to survive without a human host, and that microbial ecosystems are inherited in humans via the parental microbiome, and the harmful effects we experience if these “passengers” are lost or disrupted, we can reasonably conclude that we are more than simply discrete entities co-existing.

The line between “us” and “them” is crossed further when considering viruses. Professor Dupré touched on the idea that viruses are also members of the human organism, using their roles in protecting against pathogens and balancing beneficial bacterial populations as examples. What further complicates the relationship between human and virus is the existence of retroviruses – a class of virus which integrates its DNA into the host cells’ own genome as a necessary step of its reproductive cycle. Examples of human retroviruses are Human Immunodeficiency Virus (HIV) and Hepatitis B Virus. By integrating into the host’s DNA, the viral genes become a part of the heritable unit of human cells. The changes made are passed on to all offspring of that cell. If this affects cells involved in reproduction, such as eggs and sperm, such changes are also permanently passed on to that human’s offspring. It has been found that up to 1/10 of the human genome contains fragments of viral DNA[1]. This poses the question; to what extent is a retrovirus that integrates into a human genome a separate entity from its host?

Professor Dupré goes on to discuss the potential ramifications of this line of reasoning. Assuming there is a more fluid boundary between individual organism, symbiotic relationship and holobiosis, what does this mean for our understanding of human pregnancy, for example? It is clear that the relationship between mother and foetus is a complex one, and that there are many possible ways to define where one begins and the other ends. Aside from the intriguing biological, philosophical and religious arguments that come into play around this discussion, this example goes to show that biological definitions have a real and tangible impact on all of our lives. The example of pregnancy, and subsequently on whether abortion should be considered as ethical or permissible, and at which stage, has been a hot-button political issue among many interest groups for decades. It is a key example of how biological systems are far from straightforward, and that this can drastically impact the law, society and individuals.

This is a premise that has bled into many other political issues. Primarily in the last few years, the discussion in politics and the media around the nature of transgender identities and rights comes to mind. Some interest groups believe that biological sex is a fixed concept and cannot be changed, and that this should form the basis of a wide range of policies including sports participation, bathroom use and access to healthcare. However, we know that biology is a fluid concept on any and all levels; there is arguably no such thing as a biological absolute, even in something as apparent as the existence of the “human organism” or “biological sex”. Biology exists as a series of complex, overlapping gradients, for which different categories can be drawn depending on the questions being asked. This is true for pregnancy, as it is true for transgender identities, and as it is true for the very existence of ourselves as individual and discrete organisms.

Professor Dupré closes his lecture by warning us against individualism in politics and society. The lessons we would most benefit by learning from biology are that no man is an island – whether bacteria, biofilm or human, we cannot exist as discrete entities, and thinking of things this way often leads to disastrous consequences. Biology, as society, is a fluid and dynamic series of processes, and incorporating that understanding into our science and our lives opens doors to our understanding of each other and the world around us.


2 replies to “John Dupré, Lecture 3: Humans and their Fellow Travelers”

  1. Stewart Brown says:

    Thank you, Ms Turner and Dr Massoud, for your thoughtful and informed lead blog and comment blog, which have captured well the main themes of this lecture and how this lecture relates to the larger themes and arguments of Professor Dupré’s immensely important Gifford series. With this lecture, the major thesis of the lectures is emerging clearly, and we are seeing how a process perspective illuminates fundamental questions regarding our human condition, and how a process perspective can offer guidance on the major ethical debates concerning abortion, economic individualism and social responsibility. As Professor Dupré emphasises, the boundaries between organisms and lineages are extremely fluid, and our growing knowledge of the natural world points to interdependence and cooperation, rather than individual autonomy and competition. The extreme complexity of the human holobiont inspires a sense of awe and humility. One of the high points of each lecture has been the question period and Professor Dupré’s generous and engaging responses to the wide range of excellent questions coming from the audience. I especially liked his response to a question regarding social change, and how our understanding of lineage should summon us, in our social policies regarding the environment, to an enhanced sense of our responsibility to future generations. I was also intrigued by the question regarding subjectivity, and Professor Dupré’s suggestion that there may be far more subjectivity in the natural world than we have been prepared to acknowledge.

  2. John Dupré says:

    Dear Victoria and Zahra,

    Thanks for your very clear and accurate summary and helpful comments. I have nothing immediately to add except just to note that the issues about sex, gender and transgender will get some attention in my fifth lecture on Tuesday. These are indeed difficult and enormously contentious issues, but I do hope to give some encouragement to the idea that the “complex, overlapping gradients” that Zahra describes and that process philosophy helps us to characterise more clearly, will provide some illumination.

    And thanks again, Victoria, for your series of lucid summaries and for organising these excellent commentaries.

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