Why we should study the relationship between genes and school performance
Much of the research in human genetics is done with some medical goal in mind, often to better understand the biology of a disease in order to get closer to better drug treatments. With this in mind, genetics research into social traits like educational attainment may sound questionable. Most people don’t like to think about messing around with the biology underlying such traits, and rightly so. It was not long ago that we experienced what a different public opinion about such biological interventions can lead to. Driven by the knowledge that these traits were heritable, widely accepted eugenics policies were implemented that tried to interfere in the genetic make-up of the population by restricting the ability to procreate for groups of people that were deemed not genetically fit. This has made the general public increasingly thoughtful and aware of the potential to misuse of this kind of research, with hopefully a healthy level of anxiety that should keep us on our toes. I would not hope however that we let our fears stifle this type of research altogether; there are a number of ways in which good research on the relationship between genes and school performance can benefit us on a societal level, on an individual level, and even on a medical level. Before I summarize these potential benefits, I will give a short overview of the history and the current state of this research and its expected directions for the future.
Findings So Far
The relationship between educational attainment and genes is complicated, and we are still at the beginning of trying to disentangling this. The fact that genes play a role in educational outcomes has been established decades ago with twin studies, whereby identical twins, who share 100% of their DNA, were compared to fraternal twins, who share as much DNA as a normal pair of siblings. Like all behavioral traits that were studied in twins, identical twins were more likely to have similar educational levels than fraternal twins, which is a strong indication that the trait is heritable. The heritability of educational attainment has been estimated to be ~40%. More recently, we have been able to pin-point specific locations in the genome that are responsible for these heritability estimates. The effects of individual genetic variants are very small, so very large sample sizes are required to reach sufficient statistical power to identify these tiny effects. The first three common genetic variants associated with education were detected in a 2013 study where DNA was measured for 126,000 individuals. Larger studies followed soon thereafter, with the most recent study from 2018 consisting of 1.1 million individuals, which identified 1,271 genetic variants to be significantly associated with school performance. This number will certainly increase as these studies grow. In this latest study, all these small effects in aggregate explain about 10% of the individual differences in educational attainment.
Thanks to more ingenious study designs, we are now starting to find out that not all of these genetic effects come from the DNA of the individuals themselves. You inherited all the genes that you carry from your parents. If your genes increase your chances for a higher educational attainment, your parents will likely be higher educated as well. If your parents have a higher education, they will be more likely to have a better job and therefore have better resources to provide you with an environment that makes it more likely for you to succeed as well. We are now able to show, using molecular DNA measures, that the association between your genes and educational attainment can in part be explained by these indirect genetic effects that travel from your parents trough your rearing environment. This means that these genetic effects are about half as predictive of school outcomes in adopted children than in children that grew up with their biological parents. A similar effect is visible on a regional level as well. We showed recently in a study of 450,000 people from all over Great Britain that people with similar genetic propensities for educational attainment cluster together geographically, and that the geographic patterns of these genes strongly resemble regional differences in socio-economic status. The environmental living circumstances also differ greatly between these regions, resulting in regional differences in physical and mental health problems, which in turn has its impact on regional differences in educational attainment as well. Part of the associations between genes and educational attainment are due to these regional differences in environmental living circumstances, making these genes less predictive for educational attainment within regions than across the country.
Future Directions
We are just starting to disentangle what these associations between our genes and school performance mean, and we still have a long way to go. There are a number of directions in which this research will continue. Firstly, we will continue to increase the sample sizes, so we can produce better estimates of the genetic effects and identify more associated genetic variants. These larger studies will have to be conducted within families and within regions as well in order to control for the environmental influences that artificially inflate the estimated genetic effects, while also learning more about the indirect genetic effects of the genes carried by the people around us. Secondly, we will have to tease out through which lower-level traits these genetic variants express themselves. Genes do not directly influence educational attainment, instead they influence biological processes that are associated with a wide range of lower level outcomes that together have an influence on your school performance. These lower-level outcomes include things like intelligence and personality, but also outcomes related to physical and mental health. Finally, once we have teased out through which traits the genetic effects travel, it will perhaps become more feasible to start learning more about all the layers of complex biological processes in between these traits and our DNA sequence.
Why should we continue this research?
Everyone has their own inner motivations that drive them to pursue certain questions. For me, the pursuit of knowledge for the sake of knowledge is a major driver in itself; a drive to better understand us, the world, and our place in it. There are many directions one can go in pursuing this, and at this stage of my life I happen to be pre-occupied with the relationship between our genetic make-up and complex behavioral traits. A curiosity for how the world works will not be enough for many to justify these research endeavors, so here are some ways in which our understanding of the relationship between our genes and school performance may benefit our society and public health.
Firstly, genetics can be used as a control variable to determine whether an environmental intervention works. If you want to know if a certain change in the curriculum or in a social policy leads to better student performance, you need to control for the genetic differences between the students.
Second, insights into genetic or biological factors may help identify channels through which interventions may lead to an improved performance. Understanding the genetic and biological mechanisms underlying a complex behavioral outcome may reveal pathways that are sensitive for non-genetic interventions such as specific diets or training. A good example of a less complex trait where this has happened is phenylketonuria (PKU), an inherited amino acid metabolism disorder. PKU prevents your body from processing part of a protein called phenylalanine (Phe). When Phe levels get too high, it causes brain damage which can lead to severe intellectual disability. If you find out in time that a person has inherited this disorder, a diet of low-protein foods can prevent these detrimental symptoms and result in a healthy development.
Third, there are a number of diseases that share a substantial amount of genetic influences with educational attainment. Many genes that are associated with a lower educational attainment increase the likelihood of developing dementia, while many genes associated with a higher educational attainment are associated with a higher risk for bipolar disorder or autism. So why not study the genetics of bipolar or dementia directly? Well, we are, but given the small effects of individual genetic variants, the size of your study sample is a crucial factor in determining how many signals you can pick up. It is much easier to collect huge sample sizes for educational attainment than it is for psychiatric disorders. Collecting large amounts of cases and properly diagnosing them requires a lot of time and effort. The measurement of educational attainment is very easy in comparison, you need to ask only one question of your participants, namely “What is your highest degree?”. That is why we the largest genetic study to date on educational attainment includes more than a million participants, while for autism, bipolar disorder, or Alzheimer’s disease we are still stuck at around 60 to 70 thousand subjects.
And finally, on a larger scale, genetics could help raise awareness about the difficulty that substantial parts of the population have with climbing the socio-economic ladder in an increasingly complex society. Policy makers often overlook the role of genetics in the rapidly growing social inequalities. When we disregard genetics, we end up in a society where everyone is expected to have the capability to perform well in school and on the job market, and whoever does not is likely to be regarded as not having worked hard enough. Accepting that both genetics and environmental influences have a role in people’s failures and achievements might bring us a little bit closer to building a more fair society.
