SCIENTISTS have discovered how and when humans and other mammals evolved over time to have intelligence.
Researchers from Edinburgh University have identified the moment in history when the genes that enabled us to think and reason emerged.
They have found the exact point, 500 million years ago, which provided mammals with the ability to learn complex skills, including being able to analyse situations and have flexibility in thinking.
The research concluded that as mammals gained greater intelligence and mental capacity they were more susceptible to suffering from brain disorders, including mental health issues such as stress, depression and anxiety.
Study leader Professor Seth Grant, head of the university’s molecular neuroscience department, said: “One of the greatest scientific problems is to explain how intelligence and complex behaviours arose during evolution.
“Our work shows that the price of higher intelligence and more complex behaviours is more mental illness.”
The research, which appears in the journal Nature Neuroscience, shows that intelligence in humans developed as the result of an increase in the number of brain genes in our evolutionary ancestors.
The researchers believe a simple invertebrate animal living in the sea about 500 million years ago experienced a “genetic accident”, which resulted in extra copies of these genes being made. This animal’s descendants benefited from these extra genes, leading to behaviourally sophisticated vertebrates – including humans.