The experiment, which was conducted at the Kunming Institute of Zoology and the Chinese Academy of Sciences with the help of US researchers at the University of North Carolina, involves inserting a human version of Microcephalin (MCPH1), a gene that is believed to play a role in the development of human brains, into the brains of 11 rhesus monkeys, according to AFP.
The "transgenic" monkeys also appeared to have better short-term memory.
A new study reveals the details of the experiment conducted by bioscientists from the Kunming Institute of Zoology in China, which added a human gene responsible for brain growth to the genome of monkeys.
Su's research is said to be probing the Darwinian selection and the development of the brain.
Despite Bing defending the experiment, some scientists aren't on board with it. Barbara J. King, author of How Animals Grieve and an emerita professor of anthropology at the College of William and Mary, told Vox via email that Su's experiment was "an ethical nightmare".
A Chinese researcher who sparked improved cognitive function in monkeys by implanting human genes into their brains has defended his experiment, which has divided the scientific community and caused some researchers at the University of Colorado to question the risks.More news: Ex-Trump staffer says Twitter account 'liberated' from White House control
The Chinese scientists had been badly criticized by a number of USA scientists who called the experiments reckless and questioned the ethics of genetically modifying primates.
In January, Chinese scientists unveiled five macaques cloned from a single animal that was genetically engineered to have a sleep disorder, which all developed signs of mental problems including depression, anxiety and behaviours linked to schizophrenia. "In this vile study, female monkeys were cut open and artificially fertilized - and many pregnancies failed", said PETA UK's Anna Van Der Zalm.
"When infants survived, some were removed from their mothers shortly after birth, devastating those loving mothers". Chinese authorities took a dim view of the experiment, branding it "illegal" and ordering an investigation.
The Chinese said the MCPH1 gene is one of the strongest candidates for human brain evolution.
We know that our distant ancestors' brains outgrew similar species in terms of size and power.
As part of the process to discover the similarities and differences between monkeys, Su introduced monkey embryos with a virus carrying the human version of microcephalin.More news: Shenmue III has finally arrived after almost two decades of waiting
Their brains may not be bigger than normal, but monkeys created with human brain genes are exhibiting cognitive changes that suggest they might be smarter - and the experiments have ethicists shuddering.
But the experiments have unsurprisingly sparked controversy.
"You just go to the Planet of the Apes immediately in the popular imagination", University of Colorado bioethicist, Jacqueline Glover says. Where would they live and what would they do? "Do not create a being that can't have a meaningful life in any context".
"Monkeys are highly sentient individuals, capable of experiencing suffering and distress".
Looks like Caesar might as well become a reality because scientists are already testing ethical boundaries. "They will also be questioning whether there are any limits on what someone, somewhere will be prepared to do to animals in the name of science".More news: Lawyer to address Pugh's fraud charges in court