It is impossible to understand the appeal of eugenics without realising that it held both utopian and dystopian elements. This is particularly important, because the return of eugenics also involves both. And eugenics really has returned, including under its old name. What may be called the neo-eugenic revival sometimes takes an explicitly racist, white-supremacist form. It talks about birthrates, IQ levels and the impending “civilisational collapse” of the west. It focuses on what it sees as distinct, unequal racial groups. It harkens back to classical eugenic dystopias, such as the influential American writer Madison Grant’s The Passing of the Great Race, published in 1916, an inspiration for Tom Buchanan’s racist rants in The Great Gatsby.

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As it turned out, medical genetics really did produce an effective treatment for spinal muscular atrophy. About a decade ago, a drug called nusinersen was being developed. Some studies suggest that if it is administered early enough, it can wholly counteract the symptoms of the condition, while arresting its progression in adults. But medical genetics also proved that I didn’t have SMA after all. The original diagnosis was made on the basis of muscle biopsies and clinical guesswork. When a test for the genetic markers for SMA became available, mine came back negative. Instead, I was shown to have an even rarer condition – rarer, and less likely to attract research funding. I am tempted to quote Franz Kafka, who once remarked that there is infinite hope in the universe, only not for us.

But, in truth, that isn’t quite apt. Losing both the original diagnosis and the possibility of a treatment felt like a wave of sorrow, tinged with relief. Strange as it may seem, it also gave me a greater sense of freedom, that my life was really my own.

Don’t get me wrong. If there was an actual cure for my condition, I would take it. But there won’t be one, at least not for me. Too much time has passed; too much of my life is behind me. It is my life as it unfolded, and I try my best not to compare it to lives I didn’t live.

It is easier to think this way in your forties than in your teens. In the company of my nondisabled friends, I see plenty of injuries, illnesses and vaguely defined aches. We all have the markings of life. It’s not exactly that my disability ceases to matter as I grow older. In one way, it’s quite the opposite, as I feel the physical impact of the world on my muscles and joints. But I do feel a sense of convergence with my kith and my kin about the tenuousness and frailty of it all, about the need to take care of each other, as we hurtle towards what is coming.

Call it a kind of realism. Those of us who have kids know another side of it. If you plan to have a particular kind of child, you are setting yourself up for failure. Every parent I know has had to abandon their notions of what they thought their children would be for the reality of their particular children. I don’t think any one of them subscribed to the idea of an ideal baby. I hope they didn’t. Such an ideal is a terrible thing for parents as well as children to live up to.

This is the most corrosive effect of liberal neo-eugenics: in positing that an individual ideal of embodiment is something that can be specified, quantified and realised, it creates a framework for torturing both our children and ourselves. Why are we not this perfect thing? Why are we not fitter, happier, more productive? I’m not particularly sentimental about the value of disability in any particular case, but I think it is crucial to acknowledge disability as part of human variation. In treating ever more traits and qualities as things to be measured, ranked and diagnosed, we are doing the opposite – turning variation itself into something like disability.