In 2013, the surgeon Sergio Canavero published his recommendations for a novel surgical procedure in the journal Surgical Neurology International. The paper read like Swift’s Modest Proposal: Canavero was suggesting a protocol for transplanting the head of one human patient to the body of a second, brain-dead person. Its working title was ‘Head Anastomosis Venture’, or HEAVEN for short.

Despite the black humour of his acronym, Canavero was serious. Last year, his modest proposal made headlines when he announced his intention to carry out HEAVEN on a willing human volunteer by 2017. Predictably, every newspaper from The Guardian to The Daily Mail reacted with either frenzied disgust or a bevy of disturbing jokes. But why should we have such strong reactions to an experimental surgery? And is Canavero’s bizarre proposal even feasible, or just the province of crackpot surgeons in science fiction?

Head transplantation has actually been in the neuroscience literature for most of the 20th century – even if its story seems more like a tale from science’s lunatic fringe. These experiments make confronting reading: a Russian surgeon, Vladimir Demikhov, worked on dogs and was credited with the first successful head transplant during the 1950s. (Lest we write him off as a modern-day Frankenstein, Demikhov was also one of the early pioneers of heart and lung transplants.) Later, in 1970, the American neurosurgeon Robert J. White made more headlines when he performed the first ever head transplant in a rhesus monkey. The transplanted head regained consciousness after the operation, but the resulting head-body chimera died a few days later.

The media and ethical furore over White’s experiment died down over the next few decades. Now, though, it’s being resurrected. A team in China, for instance, has performed hundreds of head transplants on mice. And then there’s Canavero, whose human guinea pig is Valery Spiridonov, a man suffering from a rare muscle-wasting disease. At least one neurologist has already suggested that Spiridonov’s fate if the operation goes ahead will be a form of insanity worse than death. (This does at least make clinical sense, given that post-traumatic stress disorder can affect patients after any transplant surgery, let alone one like this where the sheer physiological and psychological trauma is unimaginable.) In all the news reports, though, there is still an overwhelming ‘yuck’ factor that hasn’t changed since the 1970s. Why?

For one, the idea of a head transplant strikes deeply at our sense of self – or rather, reveals just how uncertain of self-hood we really are. In English, we use the phrase ‘my body’, which implies (grammatically at least) that ‘body’ is somehow different from ‘me’. We might imagine being the same person after removing a finger, or even a limb, but how much can we really lop off before this breaks down? Then, of course, descriptions of ‘self’ are notoriously confused anyway: there’s self-as-brain only, self-as-brain plus rest of body, or self as something ill-defined separate from both brain and body. Since we don’t have comprehensive proof of which one is right – despite vehement religious or scientific protests to the contrary – it’s no wonder that head-body transplants trigger existential panic.

Then, of course, there’s the problem of selecting the body donor and the recipient, which takes transplant ethics to a whole new level. Using a brain-dead donor might not sound so bad, but what about the effect on the donor’s relatives? Organ donation at least leaves most of the body intact, but here the family would lose the entire body. We could frame this as a special case of donating one’s body to science; realistically, though, the idea of a relative’s decapitated body effectively walking around with someone else’s head on it would be too much to bear.

Finding a suitable recipient is where things get really murky. Canavero’s ideal situation is to rescue a ‘working mind’ in a body afflicted by paralysis or degenerative disease, like Spiridonov’s condition (invariably fatal). But if we don’t understand what a working mind is to begin with, how do we know whose mind should be deemed worthy of the procedure? At this rate, if head transplants really do become part of our surgical repertoire, this writer would far prefer us to start growing the bodies in vats. At least the ethics might be easier to swallow.