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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. More recent work casts doubt on this confidence.⁴ So, having mentioned this scepticism, I shall disregard it. We will assume that genetic engineering of people may become possible, and that it is worth discussing. (Sir Macfarlane Burnet’s view has not yet been falsified as totally as Rutherford’s view about atomic energy. But I hope that the last syllable of recorded time is still some way off.)

The main reason for casting the discussion in terms of genetic engineering rather than eugenics is not a practical one. Many eugenic policies are open to fairly straightforward moral objections, which hide the deeper theoretical issues. Such policies as compulsory sterilization, compulsory abortion, compelling people to pair off in certain ways, or compelling people to have more or fewer children than they would otherwise have, are all open to objection on grounds of overriding people’s autonomy. Some are open to objection on grounds of damage to the institution of the family. And the use of discriminatory tax‐ and child‐benefit policies is an intolerable step towards a society of different genetic castes.

Genetic engineering need not involve overriding anyone’s autonomy. It need not be forced on parents against their wishes, and the future person being engineered has no views to be overridden. (The view that despite this, it is still objectionable to have one’s genetic characteristics decided by others, will be considered later.) Genetic engineering will not damage the family in the obvious ways that compulsory eugenic policies would. Nor need it be encouraged by incentives which create inequalities. Because it avoids these highly visible moral objections, genetic engineering allows us to focus more clearly on other values that are involved.

(To avoid a possible misunderstanding, one point should be added before leaving the topic of eugenics. Saying that some eugenic policies are open to obvious moral objections does not commit me to disapproval of all eugenic policies. In particular, I do not want to be taken to be opposing two kinds of policy. One is genetic counselling: warning people of risks in having children, and perhaps advising them against having them. The other is the introduction of screening‐programmes to detect foetal abnormalities, followed by giving the mother the option of abortion where serious defects emerge.)

Let us now turn to the question of what, if anything, we should do in the field of human genetic engineering.