The announcement of the partial completion of the Human Genome Project was accompanied by expansive claims about the impact that this remarkable achievement will have on medical practice in the near future. The media and even some of the scientific community suggested that, within the next 20 years, many of our major killers, at least those of the rich countries, will disappear. What remains of day-to-day clinical practice will be individualized, based on a knowledge of a patient's particular genetic make-up, and survival beyond 100 years will be commonplace. Indeed, the hyperbole continues unabated; as I write a British newspaper announces that, based on the results of manipulating genes in small animals, future generations of humans can look forward to lifespans of 200 years.

This news comes as something of a surprise to the majority of practicing doctors. The older generation had been brought up on the belief that most diseases are environmental in origin and that those that are not, vascular disease and cancer for example, can be lumped together as “degenerative”, that is the natural consequence of increasing age. More recent generations, who know something about the interactions between the environment and vascular pathology and are aware that cancer is the result of the acquisition of mutations of oncogenes, still believe that environmental risk factors are the major cause of illness; if we run six miles before breakfast, do not smoke, imbibe only homeopathic doses of alcohol, and survive on the same diets as our hunter-gatherer forebears, we will grow old gracefully and live to a ripe old age.