Scientists say they have created the world’s first human-monkey hybrid in a laboratory in China.
The researchers, who want to use animals to create organs for human life-saving transplants, say creating the hybrid was an important step.
And they pledged to continue their experiments using primates.
The team revealed that they had injected human stem cells capable of creating any type of tissue into a monkey embryo.
The experiment was stopped before the embryo was old enough to be born.
But the scientists – who were Spanish but held the trial in China to get round a ban on such procedures at home – said a human-monkey hybrid could have potentially been born.
The embryo had first been genetically modified to deactivate genes that control organ growth.
Ethical concerns were raised over the trial, partly over fears that human stem cells could migrate to the brain.
Angel Raya, of the Barcelona Regenerative Medicine Centre, said experiments on organisms with cells from two species faced “ethical barriers”..
He told El Pais: “What happens if the stem cells escape and form human neurons in the brain of the animal? Would it have consciousness? And what happens if these stem cells turn into sperm cells?”
But Estrella Nunez, of Murcia Catholic University (UCAM) and the project collaborator, said mechanisms were put in place so that if human cells did migrate to the brain, they would self-destruct.
“The results are very promising,” Ms Nunez said.
The research, which was financed largely by the university, was costly. “If we combine the human/pig, human/rat and human/monkey research, it is many hundreds of thousands of euros,” she said.
Dr Raya said scientists have traditionally set a “red line” at 14 days’ gestation, which is not long enough for the embryo to develop a human central nervous system. All chimera embryos are destroyed before that time.
Juan Carlos Izpisua, who created the world’s first human-pig hybrid in 2017 and led the latest experiment, said: “We are now trying not only to move forward and continue experimenting with human cells and rodent and pig cells, but also with non-human primates. Our country is a pioneer and a world leader in these investigations.”. .