Prior to the era of cheap DNA sequencing, scientists studied identical and dizygotic twins to find out if genetics helped people finish school.
They found that the siblings who had the same genes had a similar track record at school who did not. These proposed genes might play a role, but there were too many other variables that need to be known for sure. What the researchers needed was a very large, homogeneous sample.
This week, one of the largest genetic studies of all time was published in the journal Nature Genetics, based on the analysis of genetic sequencing of more than 1.1 million people.
An International team of scientists identified 1,271 genetic variants related to how much training someone can complete.
The average human genome has millions of variants. Some variants occur in genes, but most occur in DNA sequences outside of genes.
Researchers found a weak statistical correlation between people with certain variants and individuals who stayed longer in school.
How weak? When compared to groups of people with or without a specific variation, their average school time was only different by days.
According to Daniel Benjamin, co-author and associate professor for the Center for Economic and Social Research at the University of Southern California, the genes with the highest impact predicted an average of only three weeks of schooling. 19659002] So a single gene alone has no great effect. But where it gets interesting is the combined effect of many genes.
& # 39; Genetic score & # 39; could be as important as household income
After identifying the genes associated with literacy, Drs. Benjamin and his colleagues, how to "score" the unique combination of genes for educational success.
The more variations associated with staying at school, the higher the score of an individual.
Researchers found a much stronger correlation between this "polygenic score" and a person's education.
It ranked 4,775 people in five groups and found 12 percent in the lowest fifth college finished (the people were all Americans). 57 percent have graduated from the top fifth. There was a similar trend in how many people in each group had to repeat a grade.
Overall, the "polygenic score" made a difference of 11-13 percent in educational level.
"The combined effects of many genetic variants … can predict the length of a person's formal education as well as demographic factors," Dr. Benjamin.
Demographic factors that predict educational outcomes include things like household income or the educational level of a mother. 19659002] Dr. med. Benjamin emphasized that it is "completely misleading" to say that researchers have found "genes for education" that determine individual performance.
Gene variants can not predict how well a person will fare at school. A low polygenetic score does not mean that someone does not achieve a high level of education, researchers say.
Why do these genes have this effect?
Many of the genes associated with educational attainment are important in all stages of brain development, according to Professor Peter Visscher, co-author of the study by the Queensland Brain Institute of the UQ and the Institute for Molecular Bioscience
all speculation. One theory is that the genes help neurons to connect and share information between different regions.
Another theory is that genes influence the behavior of parents (who share a similar genetic profile) and their children's environment to influence school time.
The latest study was based on hundreds of thousands of people genetic profiles of the commercial genome sequencing company 23andMe and other databases.
Dr. Benjamin said there are many other genetic variants associated with education that have not yet been identified.
"We will need even larger samples to identify them," he said.