Читать книгу Bioethics - Группа авторов - Страница 111

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.