CHAPTER XIII. Danger to the Race

Danger to the Race

Radiation may hurt the individual. It may also be harmful for our children and hurt the race. We have seen that the danger from the radiation due to testing is small compared to many risks which we habitually take and almost always ignore, which in fact we have to ignore to continue to live in this civilized world. In addition we are not even quite sure that the danger to the individual is real.

There can be little doubt, however, that radiation does produce some harmful changes in our children. What seems even more frightening, is that these changes may not show up in our children but only in their children or further progeny. A danger which may lie hidden for generations might seem more terrifying, especially as it has often been repeated that all such radiation effects are harmful.

We transmit our properties to coming generations in a most curious and concentrated fashion. From the mother and the father a child inherits a number of chromosomes, twenty-four from each. These are structures along which the actual carriers of the properties—the genes—are strung up.

We are beginning to understand something about the nature of the genes. They seem to be very big spiral molecules. They carry the master plan of our body and even of our character in a strange chemical code.

The laws of heredity are complicated because of the fact that the same property is influenced by a gene from each parent. Frequently these two genes dictate different behavior and then the result is a compromise, sometimes evenhanded, sometimes unbalanced. But of the two genes only one will find its way to the child of the next generation. The compromise is temporary and original properties may emerge again. Which one of any pair of chromosomes (or of the two assemblies of genes) carries on is a matter of chance. In the world of the cells as in the world of atoms it is chance that determines the future—not fate.

Of all these facts we need be particularly interested in one. The units of inheritance are rather constant but not quite immutable. There is a small possibility that any gene may suffer a mutation. That is, it may turn into a new chemical, carrying a new code and new properties.

A gene is an extremely finely and precisely constituted object. It must be so in order to carry all the racial past in so little material. A mutation due to chance will spoil this order in almost every instance. The great majority of mutations are detrimental. Many are lethal.

It is an incredible fact that these random mutations, almost always harmful and never proceeding according to any plan, should have been responsible in the very long run for all the many beautiful and perfect living creatures that nature has produced (and this includes the human race). The thread leading from single cells to cell colonies, worms, fishes, vertebrates, mammals and human beings does certainly not seem to be the work of chance. Much less does it seem to be the work of a gamble taking one chance of a small improvement against a thousand chances of deformity or death. Nevertheless it is such a terrible game of chance which has produced both the human body and in some manner also the human spirit.

Big numbers are strange things and when each member of a huge assembly must be given individual attention then the numbers are even harder to appreciate. Billions of contemporary lives in billions of distinct generations have led to the incredible outcome: the harmony of life produced by gambling.

Radiation is surely disruptive. It does cause mutations. Since the genes appear to be single molecules, a single process of ionization or excitation is likely to result in a change. As has been said before there is doubt whether or not cancer and leukemia can be caused by exceedingly little radiation. There is little doubt, however, that mutations can be caused by any small amount of radiation. The less radiation the less the chance. But the chance will always be there.

A very great increase in the natural rate of mutations could indeed have terrifying effects. We can be quite certain, however, that radiation from atomic tests will increase the chance of mutations by only a very small amount.

The argument is essentially the same as the one concerning the danger to the individual. The tests are responsible for 0.001 or 0.002 roentgens per year to the human reproductive cells. This is equivalent to approximately 0.05 roentgen per generation. Most of this radiation is due to gamma rays from Cs¹³⁷ which has been deposited on the ground or absorbed in the body. The number of mutations caused by this radiation is to be compared with the number of natural mutations.

Some of the natural mutations are caused by heat and chemicals. Some are due to background radiation, to cosmic rays or to gamma and beta rays emitted by natural radioactive substances in or near our bodies. Our best estimate is that 10 per cent of the natural mutations are due to the background radiation.

Over a period of one generation the background radiation dosage to the human reproductive cells is approximately five roentgens. Assuming a simple proportionality between dosage and the number of mutations, it follows that fifty roentgens would be required to induce a number of mutations equal to the total number of natural mutations (from background radiation and all other causes). That is, fifty roentgens is a “doubling dose.”

The atomic tests are therefore increasing the number of mutations by about 0.05 ÷ 50, which is 0.1 per cent. This kind of increase in the rate of mutations would certainly not seem to be a serious reason for worry.

Actually the number of mutations from the tests is very small even compared to geographical and altitude variations in the natural radioactivity. The Inca empire existed for many generations in the high country of Peru. The people of Tibet have been exposed for generation after generation to the greater cosmic ray intensity which bombards them through a thinner layer of atmosphere. These people have been exposed to much greater additional radiation than anything which is caused by atomic tests. Yet genetic differences have not been noticed in the human race or for that matter in any other living species in Peru or Tibet. We are certainly talking here about questions which may strike hard on some individuals but which from the point of view of the community or race are not serious.

It has been often repeated that all mutations due to radiation are harmful. There is every reason to believe that mutations due to radiation are not different in kind from other mutations. Should we then seriously believe that all mutations are harmful? That most of them are is admitted. If all of them were indeed always harmful, we must deny the simplest facts of evolution.

There will be some who maintain that the human race is not capable of improvement. Such an argument is irrefutable. It is also unreasonable. What cannot be further improved is perfect, and not many people will maintain that our species can claim perfection.

Another and much more plausible argument has been advanced: In the wild state living species do perfect themselves by means of natural selection. Human society by caring for the imperfect and defective individual has eliminated natural selection. Therefore further mutations will not improve mankind.

It is very hard to discuss this question for the simple reason that the argument involves the interaction of two processes extremely different in magnitude and in fact different in kind. On the one hand it concerns itself with evolution which proceeds in the slow deliberate way of a glacier. On the other hand it focuses attention upon the process of human civilization with its technical and social changes which has gained momentum like an avalanche. The momentum is still there and it is still increasing and where we shall land we do not know. To consider the motion of the glacier while being carried along by the avalanche puts things completely out of proportion. Long before the present rates of mutation could have any effect upon the human species we shall live in a very different world and we shall have started to influence our own behavior including those of selection, natural or otherwise, in ways which today we cannot foresee.

If we discuss the question how civilization will influence natural selection, we shall not do it with the hope of arriving at a firm answer. We shall do it rather in order to illustrate how doubtful all the arguments are which concern the interplay of two processes which cannot be measured in the same scale.

It is true that we can and do preserve the lives of children who, because of inherited weaknesses, would perish under natural conditions. It is true too that we do this for reasons and for feelings concerning the individual and we do it without regard to the consequences to the race. However, under our present condition of civilization a disease which can be corrected by administering chemicals or using the surgeon’s knife is no longer effectively a disease. In our present condition such a life can be as valuable to society and to the race as a life which does not have these superficial shortcomings. That we can and do preserve more life in this manner only emphasizes that under present conditions biological differences which used to be important no longer matter.

On the other hand, in social living many properties which used to be indifferent for a wild being have become of great significance. Ability to communicate and to get along with our fellows is not the only one, but is perhaps the most obvious one of such properties. The struggle for existence has become more gentle, and the chance of any individual to live on in his children is governed by new ways of behavior. Nevertheless the difference between the individual adapted to civilized living and the one who is not adapted is of great importance and will become of greater importance. It is likely that civilization will not eliminate evolution of the race. Rather it will direct it into new paths.

But the greatest change might be expected from an entirely different direction. We are going to understand in real detail the intricacies of human inheritance. Then we shall be faced with problems and shall find possibilities of an entirely new and different kind. The interest of a person in his children is not a superficial one. It is one of the most strong and lasting forces in biology, sociology and history. A clear understanding of the details of inheritance may bring about some grave difficulties because a new situation is never fitted easily into existing patterns of living. In the end more understanding may bring about improvements of a kind beside which all the worthwhile things that have been so far accomplished, might look unimportant.

The real importance of radioactivity for heredity does not lie in the fact that we may speed up the glacier by one inch in a millennium. The real importance of nuclear radiation is rather that it is helping us to understand the strange processes of life and the curious substances which connect one generation to the next.