Published on:

Arguments against reproductive technologies appeal to a false analogy

My Times column tackles the misleading metaphor of the slippery slope:


Who first thought up the metaphor of the slippery slope? It’s a persistent meme, invoked in many a debate about ethics, not least over the assisted dying bill for which I expect to vote in the House of Lords on Friday. But in practice, ethical slopes are not slippery; if anything they are sometimes too sticky.

It is in genetics and reproduction that the slippery slope argument gets used most relentlessly. The latest science to suffer from the slippery-slope metaphor is mitochondrial replacement therapy (MRT), a substantially British innovation, which promises to cure human mitochondrial diseases by replacing the mother’s cell batteries with those from a donor. It will be up to regulators to decide if the technique is safe, but first it is up to parliament to decide if it is ethically acceptable.

The only real objection to this intervention to allow certain people to have their own children without horrible diseases is that it is, in the words of one critic, “a slippery slope to human germline modification”. Change the 0.002 per cent of genes that are in the mitochondrion and what’s to stop somebody one day changing the 99.998 per cent of genes in the nucleus of the egg?

Here’s a perennial opponent of genetics, David King, of Human Genetics Alert, on MRT: “Once we’ve crossed this crucial ethical line, which says that we shouldn’t create babies that have been genetically altered, it becomes very difficult to then stop when the next step is wanted and then the next step after that and we will eventually get to this future that everyone wants to avoid of designer babies.”

But why would it be very difficult to stop? If MRT is legalised, it would still be illegal to use it for any purpose other than prevention of mitochondrial genetic disease.

A real slippery slope is a muddy hillside where one small, apparently safe, step can lead to a slide to the bottom on your backside. This is because, the physicists tell me, the static co-efficient of friction is greater than the kinetic co-efficient of friction, so it takes more force to start a bottom sliding than to keep it going.

Look around current debates and it seems we stand atop veritable mountain ranges of slippery slopes. Assisted dying will lead to widespread euthanasia. Gay marriage will lead to approved bestiality. Artificial life will lead to biological warfare. But metaphors can mislead. There is no equivalent in the world of politics to that change in the co-efficient of friction that happens on muddy hillsides. It is easy to stop half way down a moral slope; it’s hard not to. Each step meets fierce opposition however well the previous step went.

When we do carry on down an ethical slope, progressively changing the moral code, it’s not because it is slippery and we wish we could stop, but because we have collectively decided we want to go further at each stage. The Great Reform Bill was a step on the road to universal adult suffrage, as many conservatives at the time feared it would be, but it was hardly a slippery slope, more of a lengthy struggle. The legalisation of homosexuality was indeed a step on the road to gay marriage, as many religious people feared at the time, but only because society chose to take each subsequent step.

Over 40 years we have repeatedly been promised that bad things will come of interfering in reproduction, but so far the good has vastly outweighed the bad. The invention of in-vitro fertilisation in the 1970s was much feared by many people as the precursor to eugenics — people would use the technology to have superior babies by using the sperm of celebrities. Wrong: the demand for high-performance donor fathers is all but non-existent; the technology is used almost entirely to help people have their own babies, to cure the cruel disease of infertility.

Then in the 1980s research on embryos was going to lead inexorably to the cheapening of life. It did the opposite, leading to the development of techniques such as pre-implantation genetic diagnosis (PGD), in which inherited diseases could be avoided, reducing misery for thousands. But then PGD was going to lead to eugenics for the rich, who would pick the best genes for their babies. Not so. There is very little interest in using PGD to “improve” normal genomes rather than avoid faulty ones.

In the 1990s, there was one technology that overreached. Gene therapy — the attempt to replace a faulty gene in a particular tissue using a virus to deliver a new version — did make an early mistake, contributing to the deaths of some patients. But now the technique is safely doing good on a growing scale.

Earlier this year, it was announced that six people with a previously incurable form of blindness had improved their sight after gene therapy. This follows successful gene-therapy trials on children with various life-threatening inherited conditions.

After so many decades of seeing genetics and reproductive technologies prove more beneficial and less open to abuse than expected, you might think an intervention such as MRT had earned the benefit of the doubt. Indeed, you might think that the conservative side of this debate would have seen enough to change its mind and recognise that the alleviation of suffering should take priority over the pious recitation of moral platitudes and appeals to faulty metaphors about muddy hillsides.

You might even, in a sense, think that the slope should be a bit more slippery. If each step proves more beneficial and less harmful to humanity than expected, then the next step should be taken faster. But this is not the way such debates work. The track record of previous innovations in medicine is ignored when we decide each new possibility. The slope is sticky, not slippery.

It staggers me that the resistance to new techniques of genetic and reproductive medicine comes mainly from the right, and the religious right at that. Where, pray, in the Bible or Koran does it say that it is better that a child — or an old person — should suffer than that the sanctity of natural genomes and natural ailments be interfered with? And all just in case some vague and implausible crime be facilitated in the distant future. Slippery slopes are red herrings.

By Matt Ridley | Tagged:  rational-optimist  the-times