use of genetic engineering. The debate on human genetic engineering should become like the debate on nuclear power: one in which large possible benefits have to be weighed against big problems and the risk of great disasters. The discussion has not reached this point, partly because the techniques have not yet been developed. But it is also partly because of the blurred vision which fuses together many separate risks and doubts into a fuzzy‐outlined opposition in principle.
Avoiding the Debate about Genes and the Environment
In discussing the question of genetic engineering, there is everything to be said for not muddling the issue up with the debate over the relative importance of genes and environment in the development of such characteristics as intelligence. One reason for avoiding that debate is that it arouses even stronger passions than genetic engineering, and so is filled with as much acrimony as argument. But, apart from this fastidiousness, there are other reasons.
The nature–nurture dispute is generally seen as an argument about the relative weight the two factors have in causing differences within the human species: ‘IQ is 80 per cent hereditary and 20 per cent environmental’ versus ‘IQ is 80 per cent environmental and 20 per cent hereditary’. No doubt there is some approximate truth of this type to be found if we consider variations within a given population at a particular time. But it is highly unlikely that there is any such statement which is simply true of human nature regardless of context. To take the extreme case, if we could iron out all environmental differences, any residual variations would be 100 per cent genetic. It is only if we make the highly artificial assumption that different groups at different times all have an identical spread of relevant environmental differences that we can expect to find statements of this kind applying to human nature in general. To say this is not to argue that studies on the question should not be conducted, or are bound to fail. It may well be possible, and useful, to find out the relative weights of the two kinds of factor for a given characteristic among a certain group at a particular time. The point is that any such conclusions lose relevance, not only when environmental differences are stretched out or compressed, but also when genetic differences are. And this last case is what we are considering.
We can avoid this dispute because of its irrelevance. Suppose the genetic engineering proposal were to try to make people less aggressive. On a superficial view, the proposal might be shown to be unrealistic if there were evidence to show that variation in aggressiveness is hardly genetic at all: that it is 95 per cent environmental. (Let us grant, most implausibly, that such a figure turned out to be true for the whole of humanity, regardless of social context.) But all this would show is that, within our species, the distribution of genes relevant to aggression is very uniform. It would show nothing about the likely effects on aggression if we use genetic engineering to give people a different set of genes from those they now have.
In other words, to take genetic engineering seriously, we need take no stand on the relative importance or unimportance of genetic factors in the explanation of the present range of individual differences found in people. We need only the minimal assumption that different genes could give us different characteristics. To deny that assumption you need to be the sort of person who thinks it is only living in kennels which makes dogs different from cats.
Methods of Changing the Genetic Composition of Future Generations
There are essentially three ways of altering the genetic composition of future generations. The first is by environmental changes. Discoveries in medicine, the institution of a National Health Service, schemes for poverty relief, agricultural changes, or alterations in the tax position of large families, all alter the selective pressures on genes.1 It is hard to think of any social change which does not make some difference to who survives or who is born.
The second method is to use eugenic policies aimed at altering breeding patterns or patterns of survival of people with different genes. Eugenic methods are ‘environmental’ too: the difference is only that the genetic impact is intended. Possible strategies range from various kinds of compulsion (to have more children, fewer children, or no children, or even compulsion over the choice of sexual partner) to the completely voluntary (our present genetic counselling practice of giving prospective parents information about probabilities of their children having various abnormalities).
The third method is genetic engineering: using enzymes to add to or subtract from a stretch of DNA.
Most people are unworried by the fact that a side‐effect of an environmental change is to alter the gene pool, at least where the alteration is not for the worse. And even in cases where environmental factors increase the proportion of undesirable genes in the pool, we often accept this. Few people oppose the National Health Service, although setting it up meant that some people with genetic defects, who would have died, have had treatment enabling them to survive and reproduce. On the whole, we accept without qualms that much of what we do has genetic impact. Controversy starts when we think of aiming deliberately at genetic changes, by eugenics or genetic engineering. I want to make some brief remarks about eugenic policies, before suggesting that policies of deliberate intervention are best considered in the context of genetic engineering.
Scepticism has been expressed about whether eugenic policies have any practical chance of success. Medawar has pointed out the importance of genetic polymorphism: the persistence of genetically different types in a population.2 (Our different blood groups are a familiar example.) For many characteristics, people get a different gene from each parent. So children do not simply repeat parental characteristics. Any simple picture of producing an improved type of person, and then letting the improvement be passed on unchanged, collapses.
But, although polymorphism is a problem for this crudely utopian form of eugenics, it does not show that more modest schemes of improvement must fail. Suppose the best individuals for some quality (say, colour vision) are heterozygous, so that they inherit a gene A from one parent, and a gene B from the other. These ABs will have AAs and BBs among their children, who will be less good than they are. But AAs and BBs may still be better than ACs or ADs, and perhaps much better than CCs or CDs. If this were so, overall improvement could still be brought about by encouraging people whose genes included an A or a B to have more children than those who had only Cs or Ds. The point of taking a quality like colour vision is that it may be genetically fairly simple. Qualities like kindness or intelligence are more likely to depend on the interaction of many genes, but a similar point can be made at a higher level of complexity.
Polymorphism raises a doubt about whether the offspring of the three ‘exceptionally intelligent women’ fertilized by Dr Shockley or other Nobel prize‐winners will have the same IQ as the parents, even apart from environmental variation. But it does not show the inevitable failure of any large‐scale attempts to alter human characteristics by varying the relative numbers of children different kinds of people have. Yet any attempt, say, to raise the level of intelligence, would be a very slow affair, taking many generations to make much of an impact. This is one reason for preferring to discuss genetic engineering. For the genetic engineering of human improvements, if it becomes possible, will have an immediate effect, so we will not be guessing which qualities will be desirable dozens of generations later.
There is the view that the genetic‐engineering techniques required will not become a practical possibility. Sir Macfarlane Burnet, writing in 1971 about using genetic engineering to cure disorders in people already born, dismissed the possibility of using a virus to carry a new gene to replace a faulty one in cells throughout the body: ‘I should be willing to state in any company that the chance of doing this will remain infinitely small to the last syllable of recorded time.’3 Unless engineering at the stage of sperm cell and egg is easier, this seems a confident dismissal of the topic to be discussed here.
