JOHN HABGOOD
Recent claims to have identified a gene for tallness invited the question: What next? Are we to expect a constant stream of announcements as one human characteristic after another is traced back to its genetic origins, and what we think of as our humanity is revealed in all its starkness as complex chemistry? It is obvious that the enormous resources now being put into genetic research will tell us a lot more about ourselves. It is also inherent in the nature of science not to set limits on what might be discovered. But are there limits to what genetics can explain?
Genetic systems are often mistakenly described as blueprints. The essence of a blueprint is that there is a simple one-to-one relationship between what is on the plan and what is constructed from it. The discovery of genes for tallness, or eye colour, or whatever, tends to reinforce the blueprint image, but the reality is actually much less straightforward. Genes act more like bundles of instructions, setting in motion and controlling a process whose end result will depend in part on what else is happening. The fact that many of these instructions are closely linked with each other makes it extremely difficult to foretell what the result of changing any one of them is likely to be.
In more precise terms, genes manufacture proteins and enzymes, which in turn react with other proteins and enzymes to build cells, organs and bodies. Other factors enter into this process, notably the geometrical properties of the proteins themselves, the supply of raw materials, and the environment in which it all takes place. In a tightly controlled environment, such as the uterus, and with suitable nutrition, the results are fairly predictable. But once an infant leaves the uterus, the number and variety of other influences impinging on it are huge, and all are likely to play their part in shaping the kind of person that infant will become. If genes were blueprints, fantasies about producing an identical clone of oneself would not be absurd. But because they are instructions within a process which does not depend wholly on the genes themselves, the making of identical copies is not a practical possibility. Identical twins who have shared the same environment both inside and outside the womb provide the closest approach to ideal clones, but even they frequently differ in the kind of people they are, and make deliberate choices about how far they are going to emphasise their likeness.
The main interest in human genetic manipulation centres at present on the possibility of correcting defects in individual genes known to be responsible for two thousand or so serious hereditary diseases. To be lastingly effective, the corrections would have to be made at the early embryonic stage, and there are major ethical worries about permitting this degree of interference in somebody's life when there can be no certainty about what further consequences it might have.
Single defects in single genes, however, are child's play compared with the uncertainties likely to be encountered when more than one gene is involved, and when complex human characteristics are the target. Claims have been made about genes for aspects of social behaviour, such as aggressiveness, alcoholism, or homosexuality. But even if a genetic link is established, the effects are likely to amount to no more than a propensity to behave in certain ways, given the enormous number of other factors influencing what people do. Moreover even if such propensities were found to be dependent on single genes, there are far too many steps, both biological and social, between a gene and a form of conduct to justify any claim that one completely determines the other.
Genetic determinism makes no sense in creatures as complex, as open to our environment, and as dependent on social interaction as human beings have always known themselves to be. But scientific talk about genes for this or that can be very seductive. Unless its limitations are made clear, its tendency in the long run is to undermine moral responsibility and our sense of independent personhood. As genetic knowledge expands, and as medical techniques proliferate for manipulating or replacing some of our most vital bodily functions, the question: What is a person? becomes more urgent. We need ways of understanding ourselves more comprehensively, bridging the gulfs between different academic disciplines. We need to relate the scientific story to the story of inner experience and human culture, and to acknowledge the power of language in enabling us to explore and invent other realms of being.
My conviction that this is an urgent task has been my excuse for spending a year of my retirement in writing a book which tries to link such themes with a believable theology. Our genes set the scene for what we are. They are the basis of the given reality of our bodily nature, with all its potentialities and constraints. As human beings we are unique in the degree to which these different capacities can be used in different ways. What we do with them depends to a large extent on the relationships, physical, personal, and ultimately transcendental, within which our lives develop. But from the very start our capacity for reflection, for standing back from our immediate situation, gives us the power of choice. The more we accept responsibility for what we are, the greater our freedom. To blame our genes when things go wrong is to diminish ourselves.
John Habgood is a former physiologist. Ordained into the Church of England; Bishop of Durham and then for 12 years Archbishop of York. He is a former President of the Forum.
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