Chinese scientists have put genes of human brains into transgenic rhesus monkeys to make them smarter.

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.

Gene-Editing Technique

Using gene-editing techniques, the researchers added a human gene called microcephalin or MCPH1 to the genome of several rhesus monkeys to learn more about human brain development and brain evolution.

MCPH1, which is expressed during the fetal stage of the human brain's development, has been linked to brain size. Babies with damaged microcephalin are said to be born with tiny heads.

"This was the first attempt to understand the evolution of human cognition using a transgenic monkey model," said Bing Su, a geneticist at Kunming Institute of Zoology.

To mesh the human gene into the monkey genomes, the scientists injected viruses carrying the MCPH1 gene into monkey embryos and then allowed the monkeys to develop naturally. Each monkeys have between two to nine copies of the human gene in their bodies.

Eleven monkeys with the edited genome were born, but only five survived. Those that survived had their brains measured in MRI machines and were studied to see what impact the human gene had on their development and abilities.

Although the monkeys did not develop a larger-than-usual brain size, they appeared to be better than average in memory tests and processing abilities. The gene-hacked monkeys showed better reaction times and enhanced short-term memories compared to their unaltered peers.

A Controversial Experiment

Su's research is said to be probing the Darwinian selection and the development of the brain. Other scientists questioned and rasied animal rights concerns about his works involving modified primates.

Other scientists regarded Su's latest experiment as reckless, as they questioned the ethics of genetically modifying primates.

"The use of transgenic monkeys to study human genes linked to brain evolution is a very risky road to take," according to James Sikela of the University of Colorado.

Animal rights group PETA also did not favor the experiment, saying that genetic engineering is absolutely unethical and only increases animal suffering.

"Macaque monkeys are highly intelligent fellow primates who form intricate social relationships, experience every emotion humans do and can suffer just as much as we can. In this vile study, female monkeys were cut open and artificially fertilized — and many pregnancies failed," said PETA UK's Anna Van Der Zalm.

Experiments using primates is difficult to conduct in the Europe and the United States, but in China, scientists are using the latest DNA editing tools on the animals.

The study is published in the Beijing-based National Science Review.

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