In the largest genetic study ever published in a scientific journal, an international team of scientists identified more than a thousand variations in human genes on Monday, affecting how long people stay in school.
The level of education has aroused great interest among researchers in recent years as it is linked to many other aspects of people's lives, including their income as adults, overall health and even lifespan.
The newly discovered gene variants account for only a fraction of the differences in education observed between groups of humans. Environmental influences, which may include family wealth or parenting, play a greater role together.
With a better understanding of the influences of genes, scientists believe that they can better measure when they try to improve a child's learning environment.
The new study, published in the journal Nature Genetics, notes that many of the genetic variations associated with educational attainment play a role in the communication of neurons in the brain.
A noteworthy number is involved in the forwarding of signals from neurons and in neighboring ones through connections, called synapses.
The results are based on the genetic sequencing of more than 1.1 million people. But the topics were all white people of European descent. To maximize the likelihood of discovering genetic compounds, scientists needed a very large, homogeneous sample.
When the team tried to use these genetic variants to explain differences in schooling in African Americans, the predictions failed.
[ Like the Science Times page on Facebook. | Sign up for Science Times Newsletter. ]
The researchers also found that genes do not have a unified effect: the influences of genes varied from country to country. The researchers could not determine the cause of these differences.
But if educators in one country emphasize, for example, memory for solving problems in mathematics education, then some of the gene variants could bring more benefit to some students than others, the scientists speculated.
A truly global understanding of these genetic influences would require similar sized studies from people of other backgrounds, the researchers said.
The data can not be used to predict the educational attainment of a particular schoolchild. The researchers warned that the genetic patterns are only seen in large groups; In each child, genetics plays only a minor role for the duration of their schooling.
"It does not really make sense for individuals," says Aysu Okbay, a geneticist at Vrije University in Amsterdam and co-author of the new study.
The first insights into the genetic influences on education came in the 1970s. In the days before cheap DNA sequencing, researchers have studied families.
Identical twins sharing the same set of genes tended to have similar success at school as twins, researchers found. Later studies comparing siblings with half-siblings, or siblings enrolled in different families, also confirmed a modest genetic influence.
In the early 2000s, a few social scientists tried to confirm links between certain genes and education, but their efforts largely failed. One of the main reasons was the small size of their studies.
In 2011, Daniel J. Benjamin, a behavioral economist at the University of Southern California, and his colleagues launched a large-scale expedition into human DNA. They founded the Social Science Genetic Association Consortium to gather information about thousands of topics.
The researchers have put their educational research into medical research. For example, when people volunteer for a genetic study on blood pressure, they often fill in questionnaires about different aspects of their lives. One of the most common questions is how much education they had.
Until 2016, Dr. Benjamin and his colleagues studied nearly 300,000 people and linked 71 gene variants with education. But then, two important developments in DNA testing have helped the team significantly expand their research.
Recently, a genetic database called UK Biobank was launched in the UK. Approximately 442,183 of these genetic profiles were added to the study by the consortium. And after 23andMe scientists began sharing information about customers who volunteered to participate in scientific research, the team comprised 365,538 of these profiles.
Dr. Benjamin and his colleagues studied the DNA of these people and found a number of genetic variations that were uncommonly common in people who had completed much at school and others who were more likely to appear in people who graduated earlier.
Often scientists could not exclude chance as an explanation. But 1,271 of these variants were so closely linked with school education that they could not be dismissed.
Nevertheless, the relationship between gene variant and formation was very weak. When the researchers compared groups of people with or without a specific variant, their average schooling was only different by days.
The researchers scanned the DNA surrounding these influential variants and found a fascinating pattern.
"Not only are they randomly scattered in the genome," said James J. Lee, behavioral geneticist at the University of Minnesota and co-author of the new study.
The variants are linked to genes that are active in the brain and help neurons to form compounds. One key to graduating may not be how quickly information is collected but how quickly it can be shared between different regions.
"Maybe it's not about how fast a signal can rip along a cable," Dr. Lee. "It's about the complexity of the connections between point A and B."
But the genetic links point to another, perhaps even stranger possibility: some variants related to education work not in the brains of students, but in the human variants of – their parents.
By somehow influencing parents' behavior, these variants can change the environment in which children grow up, which supports or influences schooling.
Dr. Benjamin and his colleagues based their findings on how to calculate a genetic "score" for educational success. The more variations associated with staying longer in school, the higher the score of a person.
The researchers calculated a score for a group of 4,775 Americans, who classified them into five groups. The researchers found that 12 percent of people finished college in the bottom fifth. Among the top fives, 57 percent finished college.
A similar result emerged when the scientists examined how many people in each group had to repeat a grade. In the bottom fifth, 29 percent had in the top fifth, only 8 percent.
But as Dr. Benjamin and his colleagues calculated the points for African Americans, she could not predict how good the different groups in the school were. One possible reason for this is that genetic markers do not provide reliable clues as to how genes affect properties in different populations.
Dr. Benjamin and his colleagues hope to expand their study to 2 million people or more, and expect them to find thousands more genes related to education.
He and other researchers plan to conduct other behavioral studies based on gene profiles of one million people or more.
In fact, the latest study is just the latest in what promises to be a flurry of large genetic studies. The study of 1.3 million-person insomnia, for example, was published earlier this year on an open-access Web site. A number of similar studies, each involving over one million people, are moving towards publication.
"It's going to happen very quickly," Dr. Benjamin.