The first DNA analysis of people with extremely high intelligence living in the United States revealed small but significant genetic differences between them and the rest of the country's citizens.
The research work, carried out by specialists from King's College London, was based on data on the genetics of 1400 individuals with high intelligence, identified through the Duke University Talent Identification program. These people have IQs of 170 and above, which is significantly higher than the Nobel laureates, whose average IQ is 145.
Genetic studies of the basis of intelligence show that about half of the differences between people can be explained by genetic factors. Scientists studied more than three thousand ordinary US citizens with average intelligence to find genes responsible for inheriting high IQ.
The researchers focused on single nucleotide polymorphisms (SNPs), which differ in the DNA of individuals (among the order of three billion base pairs).
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Each SNP is a difference in a pair of nucleotides, and these SNPs often determine inherited differences between people, including intellectual ones. This is the first time this study has focused on rare, functional polymorphisms, while previous work has only looked at generic SNPs that can cause differences in the creation of proteins (formed from the genetic code).
The researchers found no fundamental differences in protein SNPs. Nevertheless, the difference between people with high intelligence was found, and it consisted in a large number of rare functional alleles.
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"Rare functional alleles do not have much impact on their own, but when there are many, the impact becomes significant," said study author Professor Robert Plomin.
Our research has shown that there are no genes for genius. However, in order to have super-high intelligence, it is necessary to have a large number of positive alleles and a small number of alleles that affect negatively."
Professor Plomin added that functional SNPs explain about 17% of the differences between people in intelligence. Also, the IQ of a person is influenced by the environment and other conditions that contribute to the development of natural abilities, in particular, access to literature and higher education.
A scientific article by Professor Plomin was published in the Molecular Psychiatry.