The world's first attempted head transplant on a monkey dates back to 1970, when American neurosurgeon Robert J. White transplanted the head of one monkey to the body of another. The monkey died after several days due to immunorejection.

The most recent planned head transplant was announced by Italian physician Sergio Canavero, who said he will transplant a human head to a new body in 2017. He has identified a 30-year-old Russian man who suffers from a rare genetic disorder as the first patient, according to CNN.

However, skepticism remains on the feasibility of head transplants and Ren's team has faced criticism on its violation of animal rights, as well potential moral and ethical problems.

Jiang Jinsong, associate professor with the Institute of Science, Technology and Society of Tsinghua University, said such costly operations might never be within the realm of possibility.

He also criticized using animals in medical experiments. "[The project] needs countless head transplants on animals. The cost is relatively low, but it's unnecessary and cruel."

Many animal protection volunteers feel the same.

"Humans don't have the right to kill animals for the purpose of saving humans themselves," one user commented on Sina Weibo.

Wang Yifang, a medical ethics expert with Institute of Medical Humanities at Peking University, welcomes possible breakthroughs in medical science brought by a successful head transplant on animals. But when it comes to human head transplants, he believes there are stricter ethical evaluations that need to take place.

"It's very complicated. You have your own head but another's body, so who are you and who is your family?" he asked.

"We don't know what will happen. But the fact humans 'can' do the surgical procedure in the future does not mean they 'should' do it," he said.