THIS work is based on human evolution, and stemming from it the perfect adaptation of all species to their natural environment. It is to be recalled that it was this adaptation, universal in extent and profound in degree, that excited the imagination of Darwin from an early date, and it was actually on his explanation for it -- the struggle for existence, with survival of the fittest -- that his theory of evolution was primarily based. Various explanations had been offered in the past for this adaptation, which had excited the imagination of others long before Darwin, but none so logically linked the adaptation with the time factor as his did. This latter factor is likewise of great importance to the present work, where the necessity will be stressed of an adequate period of time for adaptation to take place in a species to any unnatural (i.e., new) feature in the environment, so that any danger in the feature should be assessed by how long it has been there.
It is fortunate that though there may still be differences of opinion over exactly how adaptation in species takes place, there are none over the fact that it does take place, for it is only with the latter fact that we are concerned here.
The adaptation to their environment which is constantly taking place in all species, and which at times has attained stages bordering on the miraculous, will be referred to in these pages as the 'Law of Adaptation', an expression that will be found to confer many advantages.
Hereditary Defects
(commonly, but less accurately (W. W. Park [1]), known as congenital malformations).
The law of adaptation is not absolute. Nature -- that is to say, a 3000-million-year span of evolution -- has not led to completely perfect adaptation in an organism to its natural environment, and evolution is still taking place. Hereditary defects, therefore, do occur. Normally the struggle for existence, i.e., the evolutionary process, keeps these failures very rare indeed. It is a matter of common observation that amongst wild creatures commonly consumed as human food, such as herrings, rabbits, or wood-pigeons, any hereditary defect ('congenital malformation') is a very great rarity. In Man, however, under civilized conditions, these defects have been allowed to become more prominent. Even under these conditions, however, the struggle for existence has prevented the rate of any hereditary defect exceeding 5 per 1000 live births, the highest rates being the following: [2,3]
|
Rate per 1000 Live Births
|
|
| Spina bifida, meningocele |
2.0
|
| Congenital malformations of the heart |
2.8
|
| Cleft palate, hare-lip |
1.5
|
| Pyloric stenosis (not certainly a true congenital malformation) |
3.3
|
| Club-foot |
4.2
|
| Congenital idiocy (including mongolism) |
2.1
|
Most other hereditary defects show much lower figures than these.
It follows from the above that before postulating an exception to the law of adaptation and attributing an ailment to a hereditary defect, the frequency of occurrence, or incidence, of the ailment should be considered. If the incidence is many times as great as that of any known hereditary defect, then, quite apart from other considerations, such a cause for the ailment becomes extraordinarily improbable. For example, in the case of some of the conditions to be studied here, such as varicose veins and peptic ulcer, the incidence is over twenty times as great, which makes hereditary defects as the cause of them correspondingly untenable. This approach by incidence-figures is thus of great value in deciding whether a disease is due to a hereditary defect, or to a new factor in the environment to which no adaptation is yet possible -- in short, to use a commonplace expression redeemed by its clarity, in deciding whether the body is built wrongly or is being used wrongly.
And this distinction is itself of great value in deciding the all-important question of treatment. For if the disease is due to hereditary defect -- i.e., if the body is built wrongly -- the only treatment possible will be either operative repair or some form of replacement therapy; whereas if the disease is due to a new factor in the environment -- i.e., if the body is being used wrongly -- the treatment is at once directed to the removal of the cause. The two types of treatment are utterly different.
Personal Build or Personal Make-up
Another subject of great importance that falls for discussion now is personal build or make-up. These terms are used here to cover the healthy personal variations that occur in any part of the body, including even the smallest structures. Because of the inclusion of even the smallest structures, 'personal make-up' will normally be the term used. (The author prefers these terms to others like 'phenotype', 'constitution', etc., which nowadays are likely also to cover environmental influences, [4] which is exactly what he does not intend here.)
The reason why this subject is so important is that a person's healthy make-up may interact strongly with a new environmental factor, and any resulting disease will then require very careful differentiation from a hereditary defect, since, though healthy make-up and defect are poles apart, they are equally hereditary. This is best made clear by some examples. Consider, first, the infantry assaults against enemy entrenchments in the First World War of 1914-18. In that war it was found, as would be expected, that during these assaults tall men were shot down by machine gunners considerably more often than short men were. Yet no one looking at a tall man killed in this way would have considered the death due to a hereditary defect in the structure of his body, since in natural circumstances the tallness might have been an advantage, not a disadvantage. No: the basic cause of death clearly lay in the new environmental factor of fast-travelling bullets, to which no adaptation could yet exist and to which this man's personal build made him especially vulnerable.
Consider, again, the case of hallux valgus. In this condition a hundred pairs of feet can go into shoes that are too pointed, and yet only ten of them, say, will develop the hallux valgus deformity. These feet have no structural defect! Far from it: unconfined by shoes they might, in fact, be particularly efficient in certain natural circumstances, such as on long marches or during jumping from one piece of rocky ground to another. But the personal make-up of these feet, though perhaps particularly helpful in the foregoing circumstances, happens also to make them particularly vulnerable to the new environmental factor of pointed shoes -- so new a factor that even today only a small fraction of humanity goes about in shoes at all, let alone in pointed ones. And it is this new factor in the environment, to which no adaptation can yet exist, and to which the make-up of these feet renders them especially vulnerable, that is clearly the basic cause of hallux valgus.
These considerations show the enormous distinction that exists between a disease due to a hereditary defect in the body and one due to an unnatural, that is to say new, factor in the environment to which a person's build or make-up renders him especially vulnerable. The distinction is not only a big one -- it is also a crucial one. For once again it constitutes the difference between the body being built wrongly and being used wrongly, with its vital bearing on the type of treatment to be pursued. Thus, in the case of hallux valgus above, one's attention is directed primarily to the shoes, not the feet.
It will be noted that terms like 'susceptibility' to a disease do not properly distinguish between make-up and defect, as set out above, and will therefore particularly be avoided in this work.
Heredity
It follows from what has been written that the presence of hereditary features in a disease may, during a search for the cause of the disease, become a snare and a delusion, owing to make-up being just as hereditary as defect. And if make-up is what is involved, hereditary features in this are utterly unimportant. For example, what does it matter, in the case of the tall man mentioned above, if his father was also tall and was killed in a similar manner in the Boer War? Or if the person with hallux valgus had a parent with a similar type of foot, which, confined in pointed shoes, also developed hallux valgus ? In such cases discussion of hereditary features in personal make-up not only becomes waste of time, but also may act as a red herring drawn across the trail. For it may distract the attention from the only thing that matters -- the removal of the cause, in the shape of the new environmental factor. This distraction of the attention at the present time is seen only too clearly in the diseases to be studied here.
In the differentiation between personal make-up and hereditary defect in the causation of a disease, one is guided by the incidence-figures of the disease, the date of onset, and the presence or absence of certain clinical characteristics, based on developmental details (e.g., the fusion of embryonic planes, etc.). There is seldom any difficulty, but in a doubtful case racial studies may be conclusive, as in those undertaken here.
Such are the evolutionary considerations on which this work is based, and their value will be seen throughout the work.
With regard to the term 'Nature', as used above, it may be added that there is nothing unscientific, and much that is convenient, in this term, provided it is realized that it does no more than personify the total span of evolutionary adaptation on this planet. So compact an expression will therefore be made use of from time to time and much space thereby saved.
References
1. Park, W. W. (1964), Lancet, 2, 579.
2. Grundy, F., and Lewis-Faning, E. (1957), Morbidity and Mortality in the First Year of Life. A Field Enquiry in Fifteen Areas of England and Wales. London: Eugenics Society.
3. Carter, C. O., and McKeown, T. (1961), personal communication.
4. Brock, J. F. (1972), Lancet, 1, 701.
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