Human beings have always dreamed of immortality, and with the development of science and technology, organ transplants such as heart and liver are no longer a fantasy.

Scientists have turned their attention to another part of the human body - the head. Why can we replace the kidneys and lungs, but not the brain?

If a person's head could be transplanted into another person, it would be a "boon" for patients with quadriplegia, muscular dystrophy, organ failure, etc.

This sensational project is called "head transplantation", also known as "head transplantation".

In China's ancient books "So Shen Ji" "Liao Zhai Zhi Yi" has described a number of "head renewal" of the bizarre bridge, such a mind-boggling operation, can really become a reality?

In fact, there have been many crazy attempts at "head replacement surgery", so how far has this head replacement technology progressed to date?

History of "head transplantation" research

Head replacement surgery dates back to the early 1900s, and for nearly a century, experiments have been conducted on dogs, rats, monkeys and other animals.

According to the information, the first person in the world to experiment on animals was the American doctor Charles Claude Guth. On May 12, 1908, Guth led a research team to transplant a dog's head next to another dog's neck and connect blood vessels, creating the world's first two-headed dog.

Although Gus's operation was not strictly a head transplant, it is considered the beginning of head transplantation, and the strange two-headed dog survived for only 20 minutes.

In the 1950s, Soviet scientist Vladimir Demikhov successfully created another two-headed dog by attempting to transplant the head of a one-month-old puppy onto the neck of an adult German shepherd.

In his book, "Experimental Transplantation of Vital Organs," Demikhov said that they transplanted the heads of a total of 20 puppies onto the heads of adult dogs, with an average survival time of 2-6 days and a maximum of 29 days, and that all of these two-headed dogs eventually died due to an immune rejection reaction.

On March 14, 1970, American neurosurgeon Robert White successfully transplanted the head of a live macaque into another headless macaque. However, after eight days, the head of this monkey resisted its bodily functions, causing the monkey to end up paralyzed and not survive.

White's surgery to transplant the heads of monkeys was the world's first head transplantation performed on animals in the strictest sense. He and his team later performed more than 20 trials of head transplants with monkeys and dogs, all of which died because they were unable to reconnect the dense nerve fibers.

White has always wanted to experiment with head replacement on people, and he believes that it is much easier to replace a human head than a monkey's, because the blood vessels and other tissues would be much larger in a human than in a monkey. However, White ultimately failed to realize his idea and died on September 16, 2010, at the age of 84.

In 2013, Chinese medical expert Professor Ren Xiaoping and his team conducted the first experiments on rats with brain transplants, and rats successfully transplanted with brand new brains began to breathe and resume their heartbeats after the surgery.

Ren Xiaoping's success in giving mice brain transplants has given hope to some people who fantasize about giving humans "head replacements.

In 2013, Italian neuroscientist Sérgio Canavero proposed the idea of a human "head transplant" and publicly announced his intention to perform a human head transplant, a crazy move that has been called "Frankenstein".

Russian computer engineer Valery Donov is a "strong man" who grew up with congenital muscular dystrophy and volunteered for head replacement surgery, which Canavero plans to schedule for him in 2017.

In the first half of 2017, however, Donov suddenly changed his mind; having married a beautiful wife and had a child, Donov, who had a family, refused to have a head transplant and planned to take traditional treatments to improve his condition.

But Canavero isn't worried, saying there will be other volunteers willing to undergo the procedure in the future.

Both Ren Xiaoping and Canavero are active promoters of "head transplantation," and they agreed to collaborate on the world's first human "head transplant" in late 2017, which was a sensation.

World's first posthumous "head transplant"

On November 17, 2017, Canavero announced that under the direction of Professor Ren Xiaoping of Harbin Medical University in China, they completed the world's first human head transplant, which took 18 hours and cost $70 million.

It is worth mentioning that this "head swap" is not a real exchange of two living heads, but on two human remains used for scientific experiments.

Professor Ren said that the whole process is very complicated, and this is the first time that modern human medicine has presented the whole surgical procedure and design of "head transplantation", and called the operation "allograft head and body reconstruction".

Canavero claims that this "head transplant" is "the final preparation before a living human head transplant".

The next goal for Canavero and his team is to perform head transplants on brain-dead patients (a.k.a. vegetatives), eventually leading to a living human head transplant.

Canavero revealed that if the surgery is successful, patients can learn to walk, adapt to their new bodies and even speak in their original voices within a year, a procedure that will probably cost tens of millions of dollars.

Prior to performing human head replacement surgery on human remains, in 2016, Ren's team successfully performed head replacement surgery on monkeys, which were euthanized 20 hours later.

So can human "head transplantation", a technology that could cause a medical revolution, really become a living reality?

Head replacement surgery, is it really reliable?

Seeing this, some may wonder how the head replacement surgery, as scientists call it, is actually performed.

In a paper published in Neurosurgery International, Canavero describes the steps of a "head transplant" in detail.

First, the donor and the recipient must be in the same operating room, and the procedure needs to be performed at about 12°C to 15°C to slow down the rate of cell death.

Second, the neck of the recipient and donor must be severed at the same time, with the large blood vessels connected to the artificial vessels, followed by severing the cervical spine.

Third, the patient's head is quickly transplanted into the donor's neck and the spinal cord is joined together using a medical "glue" that sews the muscles and blood vessels of the two together.

Fourth, the nerves within the cervical spine are also stimulated with weak electrical currents for 4 weeks while the patient is healing to strengthen the connection between the head and the body.

Canavero noted that the operation had to be performed with an extremely sharp knife to cut the head crisply, and that the entire process of cutting and suturing needed to be completed within an hour. Once successful, the recipient's heart can beat again within minutes.

So, human living head replacement surgery, can it really be achieved?

First, this technology is still very far from real success, and there are three main difficulties that cannot be broken through: first, complete regeneration of the central nervous system; second, immune rejection; and third, ischemia-reperfusion injury.

Each of these is a medical challenge that is currently unsolvable, and the American Association of Neurological Surgeons Batjer says that the consequences of surgery are even "worse than death" and hopes that people will not accept them.

Secondly, head transplantation surgery from animals to humans, like cloning technology from animals to humans, has suffered a lot of moral and ethical criticism, the voice of opposition, some people call it a "barbaric" technology.

Leaving aside the technical difficulties, the "assembler" that came out of nowhere, in the end, is "who"? What kind of identity should it take to live in society? Does the personality depend on the brain, or the body of the person being exchanged? ......