03 August 2015
Professor of Genetics, School of Biosciences, University of Kent, CanterburyAppeared in BioNews 813
My mother was a dinner lady and my father worked in a market. Even the most talented geneticist would be hard pressed to find a genetic predisposition for academic success in my family. In a recent edition of Scientific Reports, however, Rimfeld et al present a study indicating a heritable component for success in GCSE exams (BioNews 812).
The authors followed a well-trodden path – study identical twins and ask whether the thing you are measuring is more closely correlated than in their non-identical counterparts. Fraternal twins are no more genetically related than 'regular' siblings. They nonetheless share everything else: a uterine environment, an upbringing and a point in history. Identical twins have all of that plus 100 percent of their genome sequence. In population genetics this is about as close as one gets to a controlled experiment.
I like this study; it 'does exactly what it says on the tin' and makes no pretensions otherwise. The Kings College London group, led by Professor Robert Plomin, is well respected and has made a comprehensive examination of a large population. Their conclusions ('performance differences for all subjects are highly heritable' … 'many of the same genes affect different subjects, independent of intelligence') are largely supported by the findings and by previous studies, which found similar effects for English, maths and science. The main selling point of this paper, however, is that it observed the effect across the whole range of GCSEs, and they have gone to the effort of applying two fundamentally different types of analysis support their findings.
The danger, however, lies in how the results could be misinterpreted. The cry 'Ah, this means that our kids' GCSE grades are predetermined' is bound to rear its ugly head, and we must be cautious not to let such misconceptions influence social policy by those with their own political agendas. Academic success is grounded in a degree of intelligence (the authors discuss this) but also involves a lot of hard work – the students who apply themselves are the ones who will rise to the top.
A very well-known statistical geneticist once said, 'I think twin studies are best left to twins.' He clearly wasn't a fan. Indeed, being one of the first ways in which genetic studies were performed, twin studies can often be considered a bit old hat. This is a little unfair. Twin studies certainly have their place, but ultimately we want to know about heritable components within pedigrees of (on average) distantly related individuals. Twin studies just help us narrow down where to look.
Also, I should sound a note of caution about what '50 percent heritable' (their headline conclusion) actually means. The truth is, no one really knows (or at least no one can agree). It's easy to jump to the conclusion that it means that 'half the time exam success is in your genes'. Nothing could be further from the truth. Some specialists in this area do not even get very excited about a value of 50 percent, and only describe values of more than 75 percent as 'highly heritable'. (This is a very complex subject but a really good article on the issue can be found here).
It really should really come as no surprise that identical twins are more similar than their fraternal counterparts – just look at them, see how they behave and you'll get the idea. Equally, it should it should come as no surprise that learning and behavioural traits have a genetic component. Put an orphan fox terrier with a litter of border collies and it will not likely grow up to be the world's best sheep dog. It might, nonetheless, be very good at getting rats out of holes, despite its upbringing.
We therefore need to put this excellent research in its proper context. It is the first step in trying to understand how the genes that may influence our learning processes interact with their environment, and how we might ultimately put this to good effect for the benefit of our children. As the authors correctly say, 'Understanding the specific and genetic and unique environmental factors influencing individual differences in educational achievement … could help educationalists develop effective personalised learning programs so that every child could reach their maximum potential.'
I count myself very lucky that, despite my genetic background, I managed to end up in a senior academic position. To be fair to my parents, my slightly Pythonesque opening to this opinion piece was a little mischievous. My dad was a talented electrician and is a whiz at pub quizzes. My mum ran a busy school kitchen and delivered a nutritionally balanced meal on a meagre budget on the stroke of 12.30 every weekday for about seven years. I'd like to think that I consistently employ heritable traits when running a busy lab in a highly technical and knowledge-based environment.
Where I benefitted (and my parents didn't) was through the expansion in the universities that occurred in the mid-to-late 1960s and through a family that pushed me hard to study. Herein lies the point – times change. Our experiences, our achievements, the expression of our genes; all are shaped by the environment in which we find ourselves. Genetics is the study of inheritance, not pre-determinism.
So, I would like to offer my congratulations to Professor Plomin's group on a nice study in a highly socially relevant area. It was well written, clear and robust. But let's not get carried away with our interpretations. My message to students is this: apply yourself and work hard. And if you come to me with this research paper in hand, telling me that your low mark is 'because of your genetics', then I won't be listening.