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For decades, researchers have linked a person’s social mobility to their education. The more educated you are the more likely you are to be upwardly socially mobile. And if your parents attended university, you are more likely to do so too.
This link between the education level of parents and their children has been considered to be caused purely by the environment in which children were brought up. But as our new study shows, genes – passed down from parents to their children – do play a role. In fact, we found that genes explained half of differences in whether offspring are socially mobile or not.
We tested for genetic influence on social mobility in more than 6,000 families from the Twins Early Development Study, which is funded by the Medical Research Council. As the picture below shows, we measured genetic influence on four categories of social mobility: stably educated, stably uneducated, upwardly mobile and downwardly mobile.
The four social mobility groups. King's College London
We used two methods to test for genetic influence on social mobility: one measured the contribution of genetic factors by studying large samples of twins, while the other tested for actual DNA differences between unrelated people within the study.
In the first method – the standard twin design test – we compared rates of social mobility between identical twins who share 100% of their genetic material, and non-identical fraternal twins, who share 50% of the genes that differ between people. If identical twins are more similar than non-identical twins on social mobility this indicates genetics is playing a role.
For example, we found that if one twin in an identical pair is upwardly mobile, the likelihood that their twin was also upwardly mobile was greater than if they were non-identical twins.
Overall, we found that almost 50% of differences in whether families were socially mobile or not are due to their genes. This means that across the population, inherited DNA differences contribute substantially to how socially mobile people in the UK are. This statistic cannot, however, be applied to an individual – so this does not mean that whether any given child is socially mobile or not is 50% due to their genes. This is because estimates from twin studies tell us about differences between individuals in a particular population at a particular time.
The second method we used was called “polygenic scoring”. To create a polygenic score we inspected the genome of 5,825 unrelated members of our study sample (one randomly selected twin from a pair). We looked at thousands of genetic variants that have previously been linked to educational attainment and added up the number of education-associated bits of DNA that each person has to create what we call a polygenic score.