Scientists have discovered for the first time how humans - and other mammals - have evolved to have intelligence.
Researchers have identified the moment in history when the genes that enabled us to think and reason evolved.
This point 500 million years ago provided our ability to learn complex skills, analyse situations and have flexibility in the way in which we think.
One of the greatest scientific problems is to explain how intelligence and complex behaviours arose during evolution.
The research also shows a direct link between the evolution of behaviour and the origins of brain diseases.
Scientists believe that the same genes that improved our mental capacity are also responsible for a number of brain disorders.
The study shows that intelligence in humans developed as the result of an increase in the number of brain genes in our evolutionary ancestors.
The researchers suggest that a simple invertebrate animal living in the sea 500 million years ago experienced a ‘genetic accident’ ( via ed.ac.uk ).