Anti-vivisectionists have lambasted the "cruel" and "flawed" creation of the world's first ever autistic monkeys.
Scientists in China have genetically engineered eight macaques to carry a gene linked to autism in humans.
According to science journal, Nature, researchers said that the animals have begun to show signs of the disorder, including running "obsessively in circles", ignoring their peers and grunting anxiously when stared at.
Up until now, research into autism has predominantly used mice and rats.
Lead scientist Dr Zilong Qiu, from the Institute of Neuroscience at the Chinese Academy of Sciences, told a press conference: “The mouse model is not close enough. There's no choice. We have to go to a non-human primate species.”
He added: “We think this non-human primate is absolutely required in the long run for the development of therapies and drugs for human psychiatric and neurological diseases,” the Press Association reports.
But the study has been criticised by anti-vivisection campaign group, Cruelty Free International, who said not only is the research likely to fail but it also causes immense suffering to the macaques.
Dr Katy Taylor, Director of Science at Cruelty Free International, said: “Autism is a complex disorder and the genetic causes are far from clear.
“Attempts to improve the utility of using monkeys to model human diseases is in our view flawed and unlikely to succeed.
“Whilst you may be able to alter one or two genes, you cannot overcome the massive differences between us and other non-human primates in other areas including gene expression. It is also cruel; several monkeys in this recent work became very ill and were killed.
“Instead of developing techniques that may lead to a rise in the use of monkeys in research, scientists should be focusing their efforts on the development of more human-relevant approaches.”
The team of researchers gave the MECP2 gene - thought to be linked to autism in humans - to dozens of monkey eggs, which were fertilised using IVF.
The animals were born to surrogate females and they were studied as they grew up.