A team of Scottish researchers say that they have made a breakthrough discovery, locating the moment in evolutionary history when intelligence and the ability to reason first appeared in our earliest ancestors. They also say that the root cause of many brain disorders can also be traced back to the same genetic events.
According to Seth Grant, the lead researcher on the study and a professor of molecular neuroscience at University of Edinburgh: “One of the greatest scientific problems is to explain how intelligence and complex behaviours arose during evolution.”
Grant and his colleagues say this happened around 500 million years ago as a result of a sudden increase in the number of brain genes possessed by our early invertebrate ancestors. The researchers say that these simple ocean-dwelling animals experienced a ‘genetic accident’ that resulted in an unintended multiplication in the number of brain genes that they possessed. In the millions of years that followed, these extra intelligence genes provided survival benefits to the animals that inherited them and gave rise to increasingly sophisticated behaviors. In humans, these abilities reached their peak with our unique abilities to analyze situations, understand abstract concepts and learn complicated skills.
The study results, which have been published as two papers in the journal Nature Neuroscience, also point to a direct link between the evolution of complex behavior and the origins of a number of brain disorders. The scientists say that the same genes that gave us our enhanced cognitive abilities are also to blame for a variety of common brain diseases.
“This ground breaking work has implications for how we understand the emergence of psychiatric disorders and will offer new avenues for the development of new treatments,” said John Williams, head of Neuroscience and Mental Health at the Wellcome Trust and a sponsor of the study.
The research team examined and compared the mental abilities of mice and humans through the use of tasks that involved the identification of objects on touch-screen computers. The results of these tests were then combined with detailed genetic information from a variety of animal species. In this way, the scientists were able to determine when different types of animal behavior evolved.
Their results indicated that higher-level cognitive functions in both humans and mice are actually controlled by the same genes. They also observed that when these genes were damaged through mutation, they tended to damage the sophisticated mental functions in both species.
“Our work shows that the price of higher intelligence and more complex behaviours is more mental illness,” concluded Grant.
The same research team previously demonstrated that over 100 childhood and adult brain diseases are caused by genetic mutations.
“We can now apply genetics and behavioural testing to help patients with these diseases,” said Professor Tim Bussey, a neuroscientist at Cambridge University who was also involved in the study.