Scientists have discovered that our ability to think and reason is the result of a genetic accident that occurred 500 million years ago.
A new study suggests that human intelligence is the result of the accidental replication of brain genes that took place in one of our evolutionary ancestors. The descendants of this a simple invertebrate animal, living in the sea 500 million years ago, benefitted from the additional genes and through evolution this led to intelligent vertebrates, including humans.
Professor Seth Grant, of the University of Edinburgh, who led the research, said: "One of the greatest scientific problems is to explain how intelligence and complex behaviours arose during evolution."
The research team studied the mental abilities of mice and humans, using comparative tasks that involved identifying objects on touch-screen computers. They then combined the results of these tests with information from the genetic codes of various species to work out at what point different behaviour evolved and discovered that higher mental functions in humans and mice were controlled by the same genes.
The research, published in two papers in Nature Neuroscience, also shows a direct link between the evolution of behaviour and the origins of brain diseases. Scientists believe that this suggests that the same genes that improved our mental capacity are also responsible for a number of brain disorders.
"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.
"Our work shows that the price of higher intelligence and more complex behaviours is more mental illness," added Professor Grant.
The researchers had previously shown that more than 100 childhood and adult brain diseases are caused by gene mutations.
