Illness – An Under-Rated Biological Phenomenon

ABSTRACT

As of May 2007, the Society for the Study of Human Biology enters its fiftieth year. The Society's first half century has coincided with substantial technological advance that now allows greater access to molecular and genetic information. Despite this, the fundamental focus of human biology on understanding the human species within an evolutionary context remains intact. However, with the relatively recent advent of Evolutionary (or Darwinian) Medicine, the potential scope of human biology has been extended to include the study and reinterpretation of much of what has previously been confined to the medical sphere.

While greater medical attention has been paid to the more physically discernable phenomena, such as pathophysiological lesions, the biological significance of illness, as an unpleasant, subjective experience has received only partial scientific attention.

It will be argued, however, that the subjective experience we call illness has an important biological role that can be understood within an evolutionary context. Furthermore, of the core biomedical concepts - health, disease and illness – illness (and related experiences) is of paramount biological significance. While illness's subjective experiential nature tends to preclude it from scientific study, it will be argued that, precisely because of its subjectivity, the experience of illness has a direct bearing upon the success and viability of the individual as a biological entity in respect of the imperatives of survival and reproduction.

As of this month, this Society enters its fiftieth year and, as colleagues on the committee plan next year's anniversary celebrations, there will inevitably be due consideration of what has been achieved over the last half-century. That being the case, I would like to consider a way in which human biology might come to contribute in the future.

The aims of this Society are clear from the following statement to be found on its website:

The Society for the Study of Human Biology (SSHB) is a learned society whose objectives are the general advancement and promotion of research in the biology of human populations in all its branches, including human variability and genetics, human adaptability and ecology, and human evolution.

And, as far as I am aware, these aims are unlikely to change substantively.

In a nutshell, we seek, as a learned society, to understand the human species in both proximate and evolutionary contexts – and not only that – we are also willing to embrace interdisciplinary study in a way that other learned societies are not.

That said, in studying humankind we are studying something which defies complete comprehension. Therefore, we need always to be open to new ways of understanding or looking at our species and must continually be reviewing the conceptual bases we adopt.

At our annual symposium, held at York last December, we considered the question of 'Medicine and Evolution'. In so doing, that symposium explored topics exposed by the relatively new field of evolutionary medicine – which as a dedicated discipline dates from the work of George Williams and Randolph Nesse first published in the early 1990s¹.

Although initially envisaged as a discipline that brings the insights of evolutionary biology to medicine, it is true to say that, so far, evolutionary medicine has experienced greater acceptance and success within departments of anthropology (and the like) than in schools of medicine.

However, there is a potential problem for all concerned in how evolutionary medicine expresses itself. So far, it has adopted an inherently uncritical use of certain core medical terms. Terms such as illness, disease and health are used in a predominantly medical rather than scientific sense. Medically, these words have a long and complex pedigree originating from and still belonging to ordinary language – that is, to everyday speech – where they are used with various nuances and imprecisions. (For example, one finds the word 'disease' applied to whole organisms, to organs or parts thereof and to constituent tissues and cells. Sometimes, the word 'disease' is even used as if referring to an entity with its own independent existence.)

Furthermore, what is frequently overlooked is that these concepts are value-laden and are not, to quote Clouser, Culver and Bert², 'empirically, operationally, or contextually defined', at least not in the way that they note the terms 'cell, molecule, gene, [and] neuron' to be defined. Quite, literally, the terms illness, disease and health have not been derived or arrived at scientifically. This makes for difficulties and ambiguities when using terms that we think we know and understand intimately.

For example, not infrequently one finds the words 'disease' and 'pathology' being used synonymously. At the same time, one often finds the words 'disease' and 'illness' being used synonymously. However, there is no sense in which 'illness' and 'pathology' can be said to be synonymous as would necessarily follow from the above.

Importantly, if the objects of medicine are to be exposed to anthropological study, the scientific rigour must be applied to those objects.

In the philosophy of medicine, the concepts of disease and health continue to be hard to define. In an organism for which there is no Platonic (or genetic) ideal, it is unclear where one ends and the other begins. However, illness has proved to be less problematic and it is generally agreed that illness is a subjective experience.

The following, from Marshall Marinker³, is typical:

'Illness … is a feeling, an experience of unhealth which is entirely personal, interior to the person of the patient.'

In short, it is an experience of one's being somehow diminished in an adverse way. Indeed, 'illness' is a more easily definable concept precisely because of its subjectivity. We experience – or perhaps that should be, create – its reality. If a doctor were to tell us that we had 'such-and-such disease', most of us would have to take this on trust – remembering, of course, that sometimes such diagnoses can be quite wrong – but if we feel ill, we feel ill and we know it irrespective of what the doctor's opinion or the physical basis may be.

However, within the medical and scientific contexts, any significance or role that illness as a subjective phenomenon might have tends to get subjugated in preference to more objectively observable phenomena such as anatomical or physiological lesions.

In 1943, the medically trained French philosopher Georges Canguilhem⁴ posed an important problem that continues to be relevant to this day. Take a man, he suggested, who complaints of no ailments and whose life is suddenly cut short by his being murdered or his dying in a car crash. For various French legal reasons, an autopsy is performed and the dead man is found to have a serious cancerous tumour – in Canguilhem's example, of the kidney. What then do we make of the man – did he have a disease or didn't he? As I intimated earlier, answering this question is not, in fact, as simple as it first appears.

Medically, there is particular emphasis on lesions irrespective of whether they give rise to symptoms at an experiential level – one such was certainly present in the dead man. Frequently these days, medical screening brings to light asymptomatic lesions of the sort the dead man had. Individuals with these lesions are then frequently labelled 'diseased' without the need for the traditional step of having first experienced illness. As a result, a separation between one's experience of oneself and the physical structures and processes within one's body is affected.

A less frequently explored dimension to Canguilhem's problem is revealed in asking whether the dead man's life was, in terms of its biological outworking, impeded in any way. The answer to that question is quite straightforward: there was no such impedance.

From a biological point of view, the important thing is how successfully one is able to attempt two fundamental sets of biological activities: the set of activities associated with survival and the set associated with reproduction. To perform these activities, one must be physically capable of performing them and one must also be experientially capable of performing them. By this, I mean that the individual must feel capable or well enough to perform these activities.

As in Canguilhem's problem, one can feel well while having potentially life-threatening lesions but so long as that man did feel well and the lesion did not have any markedly adverse effects, he was able to perform all the activities necessary for keeping himself alive and he was also able to perform those activities associated with reproduction unimpeded.

Thus, I want to suggest that this experiential dimension to being human deserves greater consideration because it may be contributing more to shaping our species than we usually credit. The experience to which I wish to draw particular attention is illness. Although it is subjective in nature, it is still very much a biological phenomenon – and one whose role, I believe, is somewhat under-rated. That this is the case is perhaps due, at least in part, to our being led by medicine's focus on lesions.

It appears that how one feels is important for survival. What is more, this is not just confined to human beings. To take an example used by Randolph Nesse in his and Williams' book 'Evolution and Healing'⁵, Matthew Kluger has shown how in certain animals a sense of self-awareness seemingly akin to our sense of illness can have a survival benefit. Experimentally infected with aeromonas hydrophila, Kluger found that fish actively sought out warmer parts of their tanks and lizards warmer places in which to bask. In so doing, they were able to raise their body temperatures artificially and to combat their infections more successfully than those kept confined to cooler surroundings.

Understandably, one finds the scientific focus in such experiments to be on the mechanisms involved – in this case fever, or fever-like, mechanisms – rather than on what it is like to be an infected fish or lizard. However, what I hope I have pointed to here is the idea that subjective self-awareness as well as physical status is important in understanding both ourselves and other animals more fully since these feelings impinge directly on how life can be led and the physical consequences that follow on from this.

I am not entirely sure how best to include the subjective in a scientific enterprise that is normally based upon objective phenomena – I am referring here to what are, in effect, 'quality of life' issues – but there is already a place for subjective phenomena in the otherwise material science that is biology even if it is not overtly portrayed as such.

Consider, for example, the whole notion of mate choice sexual selection. This presupposes that there is something about one animal that is attractive (or otherwise) to another. Regardless of what chemical triggers may get pulled and what hormones predispose an animal to behave in one way or another, this works at the entirely subjective level of how animals perceive each other. As a result, very real physical ends often associated with perpetuating certain advantageous genes and shaping the future evolution of a species are achieved.

It would appear that there is an important subjective element to being a biological entity – or at least an animal – and, furthermore, that this subjectivity may be part of an indirect process of achieving certain biological ends. This may be summarized in a phrase borrowed from Helena Cronin⁶:

'Fruit', she notes, 'tastes sweet, not nutritious'.

That is, we derive nutrition secondarily from our subjective enjoyment of eating certain things. Conversely, avoiding or remedying what we find not to be enjoyable may also be to our advantage.

There are two closely-related subjective phenomena which impinge directly upon our 'quality of life' and without which we could not survive. These are hunger and thirst. Hunger and thirst are subjective experiential ways by which an organism ensures an intake of energy and water. Without these experiences, individual survival would be most precarious.

To these, other experiences may be added – experiences of tiredness, pain, heat and cold immediately spring to mind. The one I have chosen to highlight is the sense of illness – or, at least, a sense of one's overall state interpreted as well-being or otherwise. Just as an organism needs a spur to take in energy and water, so too does it need a spur to respond best to its immediate surroundings. This may involve choosing between going out to obtain food or retiring to bed and wrapping up warmly. Without a sense of how the organism is perceived by itself – however rudimentary that sense may be (and we have seen that even fish and lizards seem to have this) – how can an organism relate successfully to its surroundings? And, without consideration of this, how successfully can we understand that organism in context?

Thus, if we are to understand the human species more fully within its proximate and evolutionary contexts – which was the nutshell encapsulation of human biology with which I began – I suggest that one possibility for the future might be to allow a greater consideration of the role of subjective phenomena in our study of the biological effectiveness of human beings. Although it is impossible to know what is being experienced by another individual, it is not impossible to consider what the effects of different subjective phenomena are likely to be on an individual's life in terms of its biological outworking. It is not enough to restrict ourselves to the physical alone; the interplay of the physical and the experiential, I suggest, warrants greater combined consideration.

NOTES

¹ Williams, G., & Nesse, R. (1991). The dawn of Darwinian medicine. The Quarterly Review of Biology, 66, 1-22.

² Clouser, K., Culver, C., & Gert, B. (1997). Malady. In J. Humber & R. Almeder (Eds.), What is Disease? (pp. 175-217). Totowa, NJ: Humana Press. (p175)

³ Marinker, M. (1975). Why make people patients? Journal of Medical Ethics, 1, 81-84.

⁴ Canguilhem, G. (1989). The Normal and the Pathological. New York: Zone Books. (p92)

⁵ Nesse, R., & Williams, G. (1995). Evolution and Healing - The new science of Darwinian medicine. London: Weidenfeld and Nicolson. See also: Kluger, M. (1978). The evolution and adaptive value of fever. American Scientist, 66, 38-43.

⁶ Cronin, H. (1991). The Ant and the Peacock. Cambridge: Cambridge University Press. (p189)

Acknowledgements:

I would like to thank the trustees and fellows of the Konrad Lorenz Institute, Altenberg, Austria, where, as a Visiting Fellow, I was able to develop the ideas expressed here. I would also like to thank Annette Lewis for her help in the preparation of this transcript.