- 2. They suggest, a range of genes may affect intelligence cumulatively ... Up to 40 per cent of a child's intelligence is passed down from the parents, according to a new study.
The finding from the largest ever genetic study of childhood intelligence adds yet more fuel to the debate over whether intelligence is a product of nature or nurture.
Using genetic data and IQ scores of thousands of children from four countries, researchers from the University of Queensland found attempted to separate out the environmental effects.
They found that between 20 and 40 per cent of the variation in childhood IQ is due to genetic factors, less than the 40 to 50 per cent suggested by previous research.
Dr. Beben Benyamin, from the University of Queensland, told ABC: 'This estimate from DNA information is lower than family studies, but it is consistent with the conclusion childhood intelligence is heritable.'
Dr. Benyamin and his colleagues analyzed DNA samples from 18,000 children aged six to 18 from Australia, the Netherlands, the UK and the U.S, along with their IQ scores.
They looked for any correlations between patterns of differences in the youngsters' DNA with patterns of differences in their IQ.
Findings showed that a gene known as FNBP1L was significantly linked to childhood intelligence. The same gene had previously been shown to be the most significant gene in predicting adult intelligence.
Usually when looking at how genetic factors influence individual traits scientists prefer to look for gene variants known as single-nucleotide polymorphisms (SNPs), as these give more precise genetic information, ABC reported.
However, Professor Benyamin said, the study did not find any single SNP gene variant that could strongly predict childhood intelligence.
'But when we looked at the combined effect of all SNPs we can estimate the contribution of genetics to be about 20 to 40 per cent of the difference in IQ,' he said.
That means it could be many genes that contribute to intelligence in children, with each having a small, but cumulative effect, the study suggests.
Understanding the factors influencing intelligence is important since IQ is a good predictor for lifespan, educational achievement and adult income, said Professor Benyamin.
The findings may also help researchers to better understand intellectual disability, he added.