Monkeys and slippery slopes

A team of American scientists has presented us with the world's first genetically engineered/modified (GM) monkey. Whilst there was some discussion in the media about the scientific implications of this development, many commentators preferred to dwell on the possibility that 'GM' monkeys will lead to 'GM' humans.

The use of the term GM here is clearly done for a purpose. Genetically modified crops and foodstuffs are so unpopular these days that mere mention of GM is enough to turn many people off. But more than that, referring to the new monkey as GM suggests that we've travelled a long way down the mythical slippery slope. First GM tomatoes, then GM mice, then GM monkeys. What's next? GM humans, of course. But is it?

Perhaps germ -line gene therapy (or genetic modification) in primates does represent one step towards germ-line gene therapy in humans. But only in one sense: technologically. Those who are quick to warn about slippery slopes always concentrate on just one aspect of what is really a complex set of reasons for the development of new medical techniques. Getting over technical hurdles is not enough.

In research, there are financial and practical considerations. Breeding monkeys for research is expensive and time-consuming. In medicine, technologies develop not just because there are researchers willing and able to do the work, but because there is an identifiable set of patients who would benefit from a new technique. Finally, for a new medical technique to really take off and have a noticeable effect upon society, it requires doctors and their patients to be sufficiently convinced of its effectiveness and safety, compared with existing tests or treatments. And all this assumes that politicians haven't stepped in to have their say. As it happens, British politicians have already ruled against germ-line gene therapy in humans.

But despite any legal constraints, do we really need genetically modified humans? Offering parents the opportunity to engineer an hereditary disease out of their family for ever seems like a good thing. Or perhaps sometime in the future we might even be able to alter human embryos to ensure immunity to HIV (human immunodeficiency virus).

But if we consider the limited success with the genetic modification of primates, the cost of the research and the unpredictable knock-on effects of inserting genes into human embryos, 'GM' humans look like a very remote possibility. And if we compare it to existing methods of testing human embryos in vitro or human fetuses in vivo for genetic conditions, genetic modification of human embryos also looks unattractive from the point of view of the patient.