Recently, the media has been abuzz with news that Sergio Canavero of Italy and his colleague Xiaoping Ren of China plan to transplant a human head from a living person onto a donor cadaver. The two surgeons — who portray themselves as pioneers defying a stodgy medical establishment but are considered reckless renegades by many peers — say the head donor will be someone with a degenerative disease, whose body is wasting away while his or her mind remains active.

The body donor, meanwhile, will likely be a someone who died of severe head trauma but whose body was left unscathed. The researchers claim to have been perfecting the technique on mice, a dog, a monkey, and, recently, a human cadaver. Originally, they predicted a fall 2017 transplant but now just say it is “imminent.”

Canavero has moved the intended surgery to China because no American or European institute would permit such an operation. “Western bioethicists needed to stop patronizing the world,” he told the South China Morning Post. In contrast, he suggested, “Chinese President Xi Jinping wants to restore China to greatness” by providing a home for such cutting-edge work.

The announcement has been met with significant skepticism, to put it mildly. The implausible claims and radical proposed operation deserves “not headlines but only contempt and condemnation,” wrote Arthur L. Caplan, head of the division of medical ethics at the New York University School of Medicine, in the Chicago Tribune in December.

Critics cite the lack of adequate preliminary and animal studies, the absence of published literature on the techniques and their outcomes, the unexplored ethical problems, and the circus-like atmosphere encouraged by Canavero. Many are also understandably worried about the source of the cadaver — China has a troubling history of using executed prisoners as their body supply for transplants.

Some bioethicists argue we should simply ignore this subject, lest we contribute to the circus. A few made precisely that point in a recent special issue of the American Journal of Bioethics Neuroscience, which I edit, devoted to head transplants. One writer argued for dropping the discussion, henceforth, in favor of “discourse that actually affects people’s lives not just fuels ghoulish fantasies.”

But I disagree that bioethicists should ignore head transplants. Perhaps Canavero and Ren will not succeed in attempting a live head transplant this time around, yet they will undoubtedly not be the last to try, which makes it important to consider the ethical implications of such an attempt.

It is undeniable that the joining of a new head and body raises intriguing questions of personal identity, legal and social definitions of selfhood, and questions about the limits of science and medicine.

Canavero and Ren present head-body transplants as a natural next step in the story of transplant success. And indeed, the arc of that story has been remarkable: People have now been living for years with donated hearts, lungs, livers, kidneys, and other internal organs.

2017 marked the anniversary of the oldest living kidney transplant, given from a father to his daughter; both are alive and healthy 50 years later. More recently, we have seen successfully transplanted hands, arms, legs, and faces. The first fully successful penis transplantation occurred in 2014, as did the first live birth from a woman with a transplanted uterus.

But while face or penis transplants are difficult (many still fail), a head-body transplant presents a whole new world of complexity.

Basic scientific concerns

Canavero and Ren have published experiments with transplanting mouse heads onto rat bodies. The test animals experienced high failure rates: In one study, of 60 rats in the initial sample, only 14 mice seemed to have survived longer than 36 hours. The surgeons also claim to have successfully tested the transplant technique, by re-fusing severed spinal cords in a dog and a monkey, but they have published scant reliable evidence of those experiments or sufficient data about the outcomes.

Canavero and Ren have claimed in news reports that the dog and monkey regained movement, but there are no peer-reviewed articles and no indications they regained self-consciousness or could feel sensation. Some gruesome still pictures of a monkey with sutures around his neck have been circulated, but that is not reliable evidence.

This is not how science ought to proceed. Peer review and animal studies are there to protect patients and to double-check reported outcomes and safety. The two surgeons —who call their project HEAVEN (an acronym for “head anastomosis venture”) — have not come close to offering evidence that head transplants are safe or effective.

The key obstacle to a head transplant is the restoration of connections in the spinal cord. We all know the devastating results of broken backs and crushed spines. In a head transplant, the spinal cord is intentionally severed, and the astonishing advance claimed by Canavero and his colleagues — but, again, not proved — is that they can restore that function to a large degree. They claim to be able to do this through a two-part method: First, they make a very sharp cut that minimizes damage of the cord, and second, they use “fusogens,” chemicals that accelerate the process of re-fusing severed neurons.

However, even Canavero admits that when they reattach the spinal cord, as little as 10 to 15 percent of the nerves are actually restored. Canavero insists that his animals regain some movement. But even if that’s true, the spinal cord is also the conduit for sensation, proprioception (knowing where we are relative to the space around us), pain, etc. He has published no evidence that these sensations are restored.

Who would the person that emerges from such a surgery really be?

Some say the odds of success are so low that an attempt at a head transplant would amount to murder. But even if it were feasible, even if we could put a head and a body together and have a living human being at the end, it is only the beginning of the ethical questions about the procedure and the hybrid life created.

If we transplanted your head onto my body, who would that resulting creature be? In the West, we tend to think that what is most essentially you — your thoughts, memories, emotions — reside entirely in your brain. Since the resulting hybrid has your brain, we take for granted that this person will be “you.”

But there are many reasons to worry that such a conclusion is premature.

First, our brains are constantly monitoring, responding to, and adapting to our bodies. An entirely new body would cause the brain to engage in a massive reorientation to all its new inputs, which could, over time, alter the fundamental nature and connective pathways of the brain (what scientists call the “connectome”).

Your brain would not be the same brain as it was when it was still attached to your body. We don’t know exactly how that would change you, your sense of self, your memories, your connection to the world — only that it will.

Second, neither scientists nor philosophers have a firm idea of how the body contributes to our essential sense of self. But it may play quite a large role. We are embodied beings, as the currently fashionable phrase in intellectual circles goes, meaning we experience the world through bodily inputs and reactions, not just through our heads.

The second-largest nervous cluster in our bodies, after the brain, is the bundle in our gut (technically called the enteric nervous system, or ENS). The ENS has often been described as a “second brain,” and it is so extensive that it can operate independently of our brain; that is, it can make its own “decisions” without input from the brain. In fact, the ENS uses the same neurotransmitters as the brain.

You may have heard of serotonin, which may play a role in regulating our moods. Well, about 95 percent of the body’s serotonin is in the gut, not the brain! We know the ENS has a strong influence over our emotional states, but we don’t understand its full role in determining who we are, how we feel, and how we behave.

What’s more, there’s been an explosion recently in human research on the microbiome, the large mix of bacterial life that lives within us; it turns out we have more microorganisms in our bodies than human cells. More than 500 species of bacteria live in the gut, and their exact makeup is different in every person.

Research is increasingly demonstrating that our microbiome influences things like our stress levels, fear, even psychiatric symptoms. Researchers are now experimenting with therapies for depression through altering the microbiome in the gut — meaning we might be able to treat depression by bypassing the brain altogether.

We do not know how far the microbiome’s influence on our behavior goes. In one study, however, scientists took two sets of mice — one set timid, the other adventurous. They then took the gut microbes from each set and transplanted them into another set of mice (whose microbiomes had been removed). Astonishingly, the recipient mice took on the personality traits of the mice whose microbiomes they received. The prominence of the gut microbiome and the ENS gives scientific backing to the notion of having a “gut feeling.”

Nor do we fully understand the extent of the role of the ENS or microbiome in what makes us who we are. It may turn out that the head-body transplant may end up with as much of the personality of the body donor as the head donor.

Also, remember that even though our new hybrid has your head, if it has my body, it would have my fingerprints, most of my diseases, my old injuries, and probably my gestures and ways of moving in the world. Any children fathered by our hybrid creature would be genetically mine; my parents would be the genetic forebears.

Questions involving the proper allocation of resources

There are other reasons to be worried about head transplants. In the United States, we are suffering from a severe shortage of donated organs. The average wait time for transplant for a kidney is five years, a liver is 11 months, a pancreas is two years. One cadaver can donate two kidneys, as well as a heart, a liver, a pancreas, and perhaps other organs. To use it instead for a single head transplant with a slim chance of success is unethical.

Canavero estimates the cost of the first head transplant at $100 million. How much good could be done with such funds, dedicated to treatments and transplants that we know are effective?

When and if it becomes possible to reattach a severed spinal cord, surely that revolutionary advance should be targeted first on the many thousands of people who suffer from paralysis as a result of a cord severed or damaged by injury.

There are also unresolved legal questions. Who is the hybrid person, legally speaking? Is it legally the “head” or the “body” — that is, is it me or you? The body is more than 80 percent of our mass, so by that measure, it is majority me, and it is possible its handwriting looks more like the body donor’s than the head donor. And who are legally its children, or its spouse?

If, as seems likely, the surgery results in someone who is paralyzed or otherwise severely impaired, who will assume the cost and responsibility of their long-term care? (Whose insurance pays, the body’s or the head’s?)

Critics claim that Canavero’s agenda is more about self-promotion than surgical innovation, and that head transplants will not happen soon. They may be right.

But there is nothing preventing a head transplant in theory at some time in the future. And if that’s true, there is some reason to think about these issues — wait for it — ahead of time.

Paul Root Wolpe is the Asa Griggs Candler professor of bioethics, director of the center for ethics, and a professor in the departments of medicine, pediatrics, psychiatry, and sociology at Emory University. He is also editor and chief of the American Journal of Bioethics Neuroscience. Find him on Twitter @parowol.

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