Monkeys with an inserted human gene involved in brain development performed better on cognitive tasks, a new study has found.
The monkeys had heightened scores in short-term memory tasks and their brains also took longer to develop, compared with monkeys who were not given the gene, known as MCPH1.
'This was the first attempt to understand the evolution of human cognition using a transgenic monkey model,' Professor Bing Su, from the Kunming Institute of Zoology in south-west China, who was involved in the research, told the MIT Technology Review. Evolutionary changes in the brain size and cognitive ability of humans set them apart from other non-human primates. Existing research suggests that this may be due to genetic differences.
The researchers injected the viral vector containing the human MCPH1 gene into monkey embryos. These embryos were then transferred into surrogate monkeys who gave birth to baby monkeys with the human MCPH1 gene integrated into their genomes. Eleven monkeys with the additional gene were created, five of which survived long enough to take the cognitive tests.
The researchers used magnetic resonance imaging to investigate the brain structure and development of the monkeys. According to the results, published in the journal National Science Review, monkeys harbouring the human MCPH1 gene did not have enlarged brains. But they did exhibit a delay in brain development, similar to the slowed development seen in humans.
The monkeys also had to perform a task assessing short-term memory, in which they had to remember the colour and shape of images presented to them on a screen. Researchers reported that monkeys with the human MCPH1 gene performed better on this task compared with the control monkeys.
They concluded that the brain developmental delay observed in monkeys with the human MCPH1 gene may have led to an enhancement of short-term memory in these monkeys.
Professor Su told CNN: 'In the long run, such basic research will also provide valuable information for the analysis of the aetiology and treatment of human brain diseases (such as autism) caused by abnormal brain development.'
This study has raised ethical issues within the scientific community, concerning the use of primates in research. 'You just go to the Planet of the Apes immediately in the popular imagination,' Professor Jacqueline Glover, from the University of Colorado, told the MIT Technology Review. 'To humanise them is to cause harm. Where would they live and what would they do? Do not create a being that can't have a meaningful life in any context.'
In an email to the MIT Technology Review, Professor Su expressed his opinion that ethical concerns are alleviated because monkeys and humans shared a common ancestor 25 million years ago. He said: 'Although their genome is close to ours, there are also tens of millions of differences.' He also did not think the monkeys will become anything more than monkeys – something that would be 'impossible by introducing only a few human genes'.