Genetic factors may exert a tiny influence on how much schooling a person ends up with, a new study suggests.
But the main lesson of the research, experts say, should be that attributing cultural and socioeconomic traits to genes is a dicey enterprise.
“If there is a policy implication, it’s that there’s even more reason to be skeptical of genetic determinism,” says sociologist Jeremy Freese of Northwestern University in Evanston, Ill.
Published May 30 in Science by a group of more than 200 researchers, the study does mark the first time genetic factors have been reproducibly associated with a social trait, says Richard Ebstein, a behavioral geneticist at the National University of Singapore. “It announces to social scientists that some things they’ve been studying that make a difference to health and life success do have a base in genetics.”
But even if it does survive further inspection — and many similar links between genes and social characteristics have not — the study accounts for no more than 2 percent of whatever it is that makes one person continue school while someone in similar circumstances chooses to move on to something else.
Previous studies comparing twins and family members have suggested that not-yet-identified genetic factors can explain 40 percent of people’s educational attainment; factors such as social groups, economic status and access to education would explain the other 60 percent. That percentage attributed to genetics is similar to the heritability of physical and medical characteristics such as weight and risk of heart disease.That makes a hunt for the genetic factors underlying educational attainment an attractive prospect.
Researchers from the Social Science Genetic Association Consortium set up an experiment that searched 2 million variable locations known as SNPs in the DNA of 101,069 people for variants that appeared to be linked to educational attainment. They found only one that was associated with years of education. Two more SNPs were associated with whether a person had finished college. The researchers then replicated the findings by doing the same sort of analysis on another 25,490 people’s DNA and finding that the same SNPs popped up.
Considering the apparent effect of all 2 million SNPs, the analysis can account for only about 2 percent of the difference between those with the highest and lowest levels of education. The single SNP with the strongest effect explains just 0.022 percent of the variation in educational attainment in the people sampled. The SNP most strongly associated with finishing college gives people about a 1.8 percentage point difference in the odds of completing a degree.
It’s common for genetic variants to have only weak influences on whether someone will develop a particular trait: Variants associated with height, for instance, exert about a 0.4 percent influence. But even scientists used to tiny effects have expressed disappointment at the small contribution of these variants. “It’s not even like a cup half full,” says Robert Plomin, a behavioral geneticist at Kings College London. “It’s a cup that is less than 1 percent full.”
Critics of the study don’t quibble with the way it was done. Their concern — one the authors share — is that there is no gene “for” going to college. The scientists used educational attainment because data on it are available for large numbers of people. But it is a proxy for something else — perhaps differences in the way peoples’ brains work or in personality traits like perseverance that could help people get through school. That means it is impossible to know what the researchers are really measuring.
The researchers caution that they have not identified specific genes, but merely found variants implicating some regions of the genome in educational attainment. Even if they had pinpointed a particular gene, “it doesn’t tell you the mechanism by which the gene is having a relationship with education,” says study coauthor Daniel Benjamin, an economist at Cornell University.
At best, the study may set an upper limit of effects scientists can expect to find in genetic studies of social traits, says Anna Need, a neuropsychiatric geneticist at Imperial College London. If a study of so many people can find only marginal genetic associations, smaller studies claiming to have uncovered genes strongly linked to political views or other social values are probably nonsense, she says. She fears that people will interpret the study to mean that genes determine education levels.
It is a fear shared by Duke University geneticist David Goldstein. “This tiny, tiny, tiny signal is completely pointless and will be misinterpreted,” he says. “Now we’re beating the poor methodology to a point that it will confess to pretty darn near anything.”
The study barely clears a widely accepted statistical hurdle for ruling out apparent associations that actually occur by chance. Some studies that skim that hurdle turn out not to be true when later repeated, especially when the trait is not clearly genetic. “This is literally right on the border,” Goldstein says, and “has a real good chance of being wrong.”
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Editor’s note: This story was updated on June 3, 2013, to correct and clarify comments from David Goldstein.