Aiming to learn more about human unique traits, scientists inserted a few human genes into some rhesus monkeys. The study we’re looking at today studied brain size and cognitive skills and the genetic mechanisms through which they’re generated and grown. The study generated 11 transgenic rhesus monkeys carrying human copies of MCPH1, “an important gene for brain development and brain evolution.” What could go wrong?
Scientists want to know more about why the human brain is so far advanced beyond our closest genetic relatives. They want to know why and how brain size and cognitive skills became so far advanced beyond other creatures with common ancestors. As such, they’re taking parts of one, putting them into another.
They tested the monkeys that survived the process. Test showed these “transgenic” monkeys had better short-term memory and shorter reaction time compared to the wild type controls in the “delayed matching to sample” task at hand.
In the surviving monkeys they also found an altered pattern of neural cell differentiation. They found developmental delay (neoteny) in these monkeys similar to that of humans. Neoteny is the delaying of psychological or somatic development, in the brain in this case, of an animal.
Humans exhibit neoteny in a number of ways – like retaining a relatively thin skull into adulthood, and retaining a large brain that continues to be able to learn new skills throughout life. This study showed brain-based neoteny in these modified monkeys. That could end up leading scientists to find out how to modify genes for humans in the future – for now the big news is the ethically questionable nature of the study itself.
We don’t test stuff like this on humans because it’s unthinkable. But if we start to create monkeys that become more capable of understanding the situation inside which they’re trapped – if they become more human – at what point does this stop being ethically questionable and start being unacceptable?
For more information on the study, head to “Transgenic rhesus monkeys carrying the human MCPH1 gene copies show human-like neoteny of brain development” with code DOI:10.1093/nsr/nwz043 in the National Science Review (NSR). National Science Review, nwz043, authored by Lei Shi, Xin Luo, Jin Jiang, Yongchang Chen, Cirong Liu, Ting Hu, Min Li, Qiang Lin, Yanjiao Li, Jun Huang, et. al. published 27 March 2019.