Genes that are responsible for the development of mental illness are the same as those that helped to improve our intelligence.
Scientists have discovered for the first time how intelligence in humans and other mammals has evolved and found a direct link between the development of the evolution of behaviour and the origins of 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, one of the study funders.
Two papers published in Nature Neuroscience shows that about 500 million years ago, a simple invertebrate sea animal underwent a “genetic accident”, which resulted in extra copies of brain genes being made.
Its descendants went on to benefit from these extra genes, leading to behaviourally sophisticated vertebrates – including humans.
Researchers studied the mental abilities of mice and humans, using comparative tasks that involved identifying objects on touch-screen computers, and combined the results of the tests with information from the genetic codes of various species to work out when different behaviours evolved.
The study not only demonstrated that higher mental functions in humans and mice were controlled by the same genes, but also when these genes were mutated or damaged, reducing the ability to carry out higher mental functions.
Researcher Professor Seth Grant, of the University of Edinburgh, Scotland, said: “Our work shows that the price of higher intelligence and more complex behaviours is more mental illness.”
Nature Neuroscience 2 December 2012
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