Researchers, at the Univ. of Edinburgh, 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, analyze situations and have flexibility in the way in which we think.

"One of the greatest scientific problems is to explain how intelligence and complex behaviors arose during evolution," says Seth Grant, professor of Molecular Neuroscience, Univ. of Edinburgh

Origins of intelligence linked to brain disease

The research also shows a direct link between the evolution of behavior 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. “Our work shows that the price of higher intelligence and more complex behaviors is more mental illness,” says Grant.

Their study is detailed in two papers in Nature Neuroscience.

Evolutionary ancestors

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.”

This resulted in extra copies of these genes being made. This animal’s descendants benefited from these extra genes, leading to behaviorally sophisticated vertebrates – including humans.

Important genes

The research team studied the mental abilities of mice and humans, using comparative tasks that involved identifying objects on touch-screen computers.

Researchers then combined results of these behavioral tests with information from the genetic codes of various species to work out when different behaviors evolved.

They found that higher mental functions in humans and mice were controlled by the same genes.

The study also showed that when these genes were mutated or damaged, they impaired higher mental functions.

The researchers had previously shown that more than 100 childhood and adult brain diseases are caused by gene mutations.

The study was funded by the Wellcome Trust, the Medical Research Council and European Union.