DARWIN AND DISABILITY HARDLY a week goes by these days without the media reporting some new and astonishing medical advance. In the last two decades transplant surgery and in vitro fertilisation have become everyday occurrences, but they represent remarkable scientific and technological achievements. Understanding how things work makes possible their manipulation. The rising star in the medical firmament is molecular medicine and the manipulation of the genome. We seem close to understanding at the molecular level why some developmental processes go wrong, and in some cases we should soon be able to correct these and prevent certain genetic diseases. These advances have come from an approach which analyses component processes and seeks to identify antecedent causes. Medical science and consequently medical education have stressed physics and chemistry and now molecular biology, with the result that the search for proximate causes has led to remarkable advances. With regard to certain kinds of problem, the reductive analysis has proved to be so powerful that it has become synonymous with science. However, explanations of this kind are not the only sort of scientific explanation; different kinds of questions require different approaches.

To my knowledge, Charles Darwin never wrote about disability, but the conceptual scheme he invented for biology offers a useful framework in which to consider some aspects of disability. A central idea in Darwin's theory is the notion of adaptation. Adaptation can be a pretty slippery concept, but it is vital to modern biology. It is the process by which a living organism-plant or parasite, animal or human-becomes fitted to its environment, and a central task of evolutionary biology is the study of the match between organisms and their environments. This match or adaptation relates to all aspects of an organism's biology: its anatomy, physiology, behaviour, diet and even disease.

The behaviour of animals, and particularly the adaptive significance of behaviour, has been the subject of a good deal of fascinating research by ethologists and ecologists over the past 30 years. Many will have seen the remarkable and sometimes exquisite fit of an animal to its environment in natural history films made for television. Rarely, however, has the behaviour of sick animals been considered. Presumably this is because the altered behaviour that animals show when they are sick is assumed to be a result of debilitation from the disease process and certainly not a highly organised behavioural strategy that aids survival and adjustment.

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However, there is a behavioural mode of response to illness, which is an important aspect of adapting to the threat of disease. With a primary focus on animals, and using examples drawn largely from infectious diseases, Hart’ argues that behaviour associated with illness can be seen as representing an all-out effort to deal with invading pathogens. So, coupled with physiological variables, behavioural changes such as anorexia, depression and a reduction of activity are protective adaptations. Williams and Nesse’ have gone further in identifying and analysing behavioural adaptations which serve to protect the individual against disease and damage. Darwinian Medicine, the vivid name they have given to this approach, has widc-ranging implications for models of disease and models of treatment. Like the powerful molecular analysis, the evolutionary model offers a way of thinking about phenomena; although quite different, the two are complementary.

What implications does all of this have for disabled people? Like the rest of us, they have to adapt to their environment, and they have to do so in the face of constraints imposed by their impairments. Some of these adaptations are species-typical and others idiosyncratic. However, it is important that not all changes associated with pathology and disability should be seen as being negative. Some are positive in as much as they represent an attempt to adjust to and cope with environmental demands. An appreciation of the needs of children should help us to understand the functional purposes of what may seem to be no more than disturbing and distressing maladaptive behaviour.

In general terms, we know the needs of children well enough. They need love and security, new experiences, praise and recognition, and they need responsibility and independence. The extent of these needs, their timing and how they are best met, like everything else, varies between individuals. As they develop, children strive to fulfil these needs and in so doing may show behaviours that are both tiresome and maladaptive: consider, for example, the storm and stress of adolescence. The adaptationist paradigm, with its links to more distal explanations, will lead us to seek an understanding for what may seem to be no more than aberrant and maladaptive effects associated with impairment. Of course, some of these effects may be exactly that, but not all of them; and the challenge is to understand and distinguish the functional from the maladaptive. The task of parents and professionals is to understand and support the individual’s development with appropriate interventions. We are not looking for a royal road, for such does not exist-rather, like evolution itself, we are seeking to balance many factors and therefore require a bundle of compromises.

KEVIN CONNOLLY

References 1 . Hart. B. L . (1988) ‘Biological basis of the behavior of sick animals.’ Neuroscience ond Biobehoriorol

2. Williams, G . C.. Nesse. R . M . (1991) ‘The dawn of Darwinian Medicine.’ Quorierly Review o/Biology, 66, Reseurch. 12, 123-137.

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