SCOTTISH scientists have discovered that intelligence is linked to genes in the largest study of its kind ever undertaken.

Researchers compared variations in the DNA of more than 240,000 people from around the world, and found more than 500 genes they linked to intelligence – ten times more than was previously thought.

However, their discovery raises the moral issue of gene manipulation leading to “designer babies” in the future, where the rich are able to pay for gene manipulation to make their offspring smarter.

Campaigners in the past have also voiced fears that the ability to select embryos based on their “intelligence genes” through genetic engineering could lead to a loss of diversity.

The genes also seemed to influence other biological processes, with some associated with living longer and better health.

Those that contributed to problem-solving powers boosted the process by which neurons carry signals from one place to another in the brain.

Principal investigator Professor Ian Deary, of the Centre for Cognitive Ageing and Cognitive Epidemiology at Edinburgh University, said: “We know environments and genes both contribute to the differences we observe in people’s intelligence.

“This study adds to what we know about which genes influence intelligence – and suggests health and intelligence are related in part because some of the same genes influence them.”

His team pinpointed 538 genes that play a role in intellectual ability – and 187 regions in the human genome connected to thinking skills.The findings, published in Molecular Psychiatry, shed fresh light on the biological building blocks of people’s differences in intelligence.

They enabled Mr Deary and colleagues at Southampton University and Harvard University in Boston to predict seven per cent of differences in IQ between an independent group of individuals – by their DNA alone.

Study leader Dr David Hill, also from the Centre for Cognitive Ageing and Cognitive Epidemiology, said: “Our study identified a large number of genes linked to intelligence.

“Importantly we were also able to identify some of the biological processes that genetic variation appears to influence to produce such differences in intelligence – and we were also able to predict intelligence in another group using only their DNA.”

The researchers used data from the UK Biobank – a major genetic study into the role of nature and nurture in health and disease. This enabled them to compare DNA with IQ scores based on verbal and numerical tests.

Earlier this year it was reported 52 genes linked to intelligence had been uncovered following a similar study of over 78,000 individuals.

The genes were said to bring a host of other benefits, with those who had them less likely to suffer from Alzheimer’s disease, depression, schizophrenia and obesity.

Dr Hill said intelligence accounts for around 40 per cent of the variation between individuals in scores on diverse cognitive tests.

Lower levels in childhood are associated with earlier death over the next several decades.

He said: “Intelligence is a heritable trait with twin and family-based estimates of heritability indicating between 50-80 per cent of differences in intelligence can be explained by genetic factors.

“People with a higher level of cognitive function have been observed to have better physical and mental health, and to have longer lives.

“First, we found 187 independent associations for intelligence and highlighted the role of 538 genes being involved – a substantial advance.” He added: “We used our data to predict almost seven per cent of the variation in intelligence in one of three independent samples.

“Previous estimates of prediction have been around five per cent.”

Last year scientists were able to successfully edit the genes of a human embryo for the first time in the US using a technique known as CRISPr.

This led to faith groups warning genetic engineering could lead others to question people with disabilities right to exist.


ANALYSIS: Genetic link to IQ will lead scientists into very tricky moral dilemmas

By Dr Calum MacKellar, Director of Research, Scottish Council on Human Bioethics in Edinburgh

RESEARCH demonstrating that more than 500 genes are linked to intellectual ability is certain to raise significant ethical concerns.

The science journalist Jerome Burne even indicated, in 1998, that “anything to do with intelligence is deep water; combine it with genetics and it becomes positively shark-infested”. The extreme sensitivity in this field is best represented by the manner in which the media and subsequent public discussions have dismissed, in the past, claims suggesting that variations in people’s Intelligence Quotient (IQ) are based on their genes.

This happened, in part, because of a fear of a return to a new eugenics which would promote selection strategies based on the genetic quality of children.

For example, concerns exist that as soon as genes for intelligence are determined, people will begin asking for genetic tests so that they may select their children to give them the best possible chance of eventually going to a top university. Continuing comments making reference to a person’s lack of intellectual facilities as “mild mental impairment” has also been seen as being dangerous.

Some senior scientists, for example, have already spoken approvingly of low IQ levels as “mild mental handicap” which could easily be compared with labels such as “moderate learning difficulties” or “moderate sub-normality” used in past education legislation.

But the sensitivity of the debates relating to the association of genetics and intelligence may reflect an even deeper challenge.

This is because it could enable each and every human being to question their own worth and value in society.

In this respect, it has already been suggested that the more intelligent a person is seen to be, the more of a “human person”’ he or she becomes!

Thus, a real fear exists in many human beings that they may not be as intellectually capable as others and may, therefore, be considered as less valuable to society or even less of a person than others. This means that a real and open ethical discussion in society has become necessary to follow future trends in the relationship between genetics and intelligence.

At the same time, the possible consequences of such results will need to be carefully scrutinised to determine possible risks of discrimination.

Dr Calum MacKellar is Director of Research, Scottish Council on Human Bioethics in Edinburgh.