If you struggle with sums or can’t finish a crossword, who should you curse – your teachers or your parents?
Well according to the latest evidence, you really should blame both.
Researchers have found that up to half of our intelligence (or lack of it) is inherited.
They examined the blood of more than 3,500 people from England and Scotland for half a million genetic markers – tiny changes in their DNA.
Analysis of these results and those of intelligence tests completed by the study’s participants revealed that 40 per cent of the differences in ‘crystallised-type intelligence’, the ability to acquire knowledge and skills over the years, were in the genes.
So-called fluid-type intelligence, the ability to reason and think abstractly under pressure, was governed by genetics to an even greater extent. Some 51 per cent of a person’s ability to ‘think outside the box’ is down to DNA, the journal Molecular Psychiatry reports.
The research, made possible by a new type of genetic analysis pioneered by Peter Visscher of the Queensland Institute of Medical Research in Australia, points to numerous genes being involved.
Struggling? It's not your fault! The brain is governed by genes
Lead researcher Professor Ian Deary, of the University of Edinburgh, said: ‘Individual differences in intelligence are strongly associated with many important life outcomes, including educational and occupational attainments, income, health and lifespan.’
However, he added that the study’s results ‘unequivocally confirm that a substantial proportion of individual differences in human intelligence is due to genetic variation’. He hopes to unlock the secrets of those whose brains age well, with a view to helping others stay sharp as they get older.
‘If we can find specific genetic contributions to people’s experience of cognitive ageing, this can suggest the mechanisms by which people differ,’ he said. ‘We are studying genetics to find out how things work.’
Professor Deary added that those dealt a poor hereditary hand should not act as if their fate is sealed, as it is possible for people to overcome their intellectual inheritance.
The research may explain why humans have advanced so much further than chimpanzees, despite their genetic similarity. Simon Underdown, an anthropologist from Oxford Brookes University, said: ‘The devil is clearly in the detail. It is not necessarily that we share the same genes – it is how they interact with other genes that controls intelligence.
‘Human intelligence is a stunning product of our evolution and this brilliantly demonstrates that the genetic basis for our intelligence is not the result of a simple mutation in a single gene.
‘It moves away from the old-fashioned idea that there may be a gene or a couple of genes for intelligence. It looks as if there are lots and lots of genes across the chromosomes.’
-Dailymail
Intelligence tests highlight importance of genetic differences
DNA study links variations in intelligence to large numbers of genes, each with a small effect on individual brainpower
Genetic differences between people account for up to half of the variation in intelligence, according to a study of more than 3,000 individuals.
Intelligence is known to run in families, but no single genes have yet been identified that can be reliably linked to mental ability. Instead, researchers think, many hundreds or thousands of genes could be involved, each with a small influence on a person's overall intelligence.
"It has been getting clearer and clearer that any genetic contribution to traits on which people differ – like height and weight – comes about from large numbers of gene differences, each with very small effects," said Prof Ian Deary of the University of Edinburgh, who led the research on intelligence. "We thought that was one possibility for cognitive ability differences, and our results are compatible with that."
To test his idea, researchers looked at more than half a million locations in the genetic code of 3,511 unrelated adults. Each of these sites is where people are known to have single-letter variations in their DNA, called single nucleotide polymorphisms (SNPs). These variations were correlated with the individuals' performance in two types of psychometric tests that are established in assessing intelligence: one test measuring recalled knowledge (via vocabulary) and the second measuring problem-solving skills.
They found that 40% of the variation in knowledge (called "crystallised intelligence" by the researchers) and 51% of the variation in problem-solving skills ("fluid-type intelligence") between individuals could be accounted for by the differences in DNA. The results are published on Tuesday in the journal Molecular Psychiatry.
Previous work on the environmental and genetic contributions to cognitive ability has been based on comparing intelligence in identical and non-identical twins, or studying it in people who were adopted. In the study led by Deary, the conclusions were gleaned from direct testing of people's DNA. "It is the first to show biologically and unequivocally that human intelligence is highly polygenic [involving lots of genes] and that purely genetic (SNP) information can be used to predict intelligence," Deary wrote in the journal paper.
Though the researchers now know the proportion of the variation in intelligence that is likely to be a result of genes, they do not know which genes are likely to be most important in determining intelligence. "If they can be found, and if we want to follow them up, to find out some of the mechanisms that underlie successful thinking, our best guess at present is that the number is huge. It could be many thousands," said Deary. "That could be a limitation to progress using this type of research."
Dr Simon Underdown, senior lecturer in biological anthropology at Oxford Brookes University, said human intelligence was a "stunning product of our evolution". He continued: "This paper brilliantly demonstrates that the genetic basis for our intelligence is not the result of a simple mutation in a single gene. Rather, the diverse range of genes that appear to influence our ability to think must have been actively selected for over hundreds of thousands of years. That we display such genetically influenced variation in intelligence across our species further hints at how important cultural, as well as biological, evolution has been to the human story."
-Gaurdian
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