Knowledge doesn’t always mean power

Everyone knows that scientific advance has the capacity to do harm as well as good. Screening for cancer, for example, may detect the disease early and thus save life; but this has to be balanced against the unnecessary worry caused to those – who may be many more – who test positive but do not have the disease.

Will knowing our own genetic predisposition to disease do us more harm than good? My gut feeling is that it will.

First, most diseases are not straightforwardly genetic. To have a certain gene or combination of genes does not mean that one is certain to get a disease. Genetic differences play an important, but not an all-important part in the pattern of diseases from which we suffer.

Thus, having a certain genetic constitution may tell us that we are four times as likely to get disease X as the next man, or that we have a 17.5 per cent chance of developing disease Y after the age of 55. But what are we to do with this information, apart from worry about it?

It is difficult to keep in mind that what matters to us is not our relative chance of contracting a disease, but our absolute chance of contracting it. Why should I worry if my possession of a certain gene pattern makes me ten times more likely than my neighbour to contract a particular disease, if his chance is only one in ten million? On the other hand, if the possession of a certain gene pattern renders me susceptible to a disease whose environmental determinants are known, then I can take avoiding action if the risk is sufficiently big and the disease sufficiently severe to make it worthwhile.

Moreover, if we do not gather the information, how will we ever understand the interaction between genetic endowment and environmental factors in the causation of disease?

What about the question of whether life insurance companies should have access to our genetic code and alter our premiums accordingly? In principle, there is no objection, since they already do something similar when they ask us about the health of our relatives.

Nevertheless, there is something very Brave New Worldish about the whole idea. By the way, what exactly is wrong with the Brave New World? We all feel very strongly that it is wrong, but not many of us are able to put our fingers on precisely why.