I’m no geneticist, but I was interested to see the recent comments on the heritability of academic performance. I thought it demonstrated the sorry lack of understanding of these things in the media and general public (including me), and I was disappointed in the quality of the debate.

A government advisor, Dominic Cummings, wrote a report in the course of which he stated that “70% of cognitive capacity is genetic, beside which the quality of teaching pales into insignificance”. This got a lot of comment, e.e.g from Polly Toynbee in the Guardian. Toynbee does make clear that she doesn’t understand genetics, and seeks advice from genetics Prof Steve Jones. I eagerly heard a discussion of this on the BBC Radio 4 programme “Inside Science” between Profs Jones and Plomin, hoping they would give a clear explanation of what exactly heritability is which would help people like me.

For example, Toynbee says at one point, “Wealth is considerably more heritable than genes”. This is obvious true in an everyday interpretation of the word – you can will your millions to your children, but you can’t guarantee they’ll inherit your striking red hair. But in the scientific definition of the word, nothing is more heritable than genes. I felt this demonstrated the confusion, and this is where we really needed a nice BBC science programme to go into these issues.

Despite the august guests, I felt they didn’t really rise to the occasion. I’m no expert, but I find it helpful to realise that when we talk about heritability, we’re not talking about a fixed quantity, like the mass of the electron. It depends on the context. It may be 70% in Britain now, but it might have been 20% in the past and 90% in Finland. If you just consider one school where the kids come from similar backgrounds, the heritability may be close to 100% – there are bright kids and dimmer kids even within the same family, and it’s just how they are. But if you look between schools, comparing privileged vs deprived kids, you might find the variation between kids in each group is swamped by the large difference between the groups, indicating almost no heritability and an overwhelming effect of the environment.

The closest the discussion got to this was a throw-away comment by Steve Jones: “If everyone stopped smoking, lung cancer would be a genetic disease”. I thought this was an important point which should have been pursued: if we could arrange things so that every child could get the best possible education to enable them to achieve their potential, academic performance would be 100% genetic.

Finally,as far as I remember, no one stated that heritability has nothing to say about the importance of teaching quality, class size, resources and so on. If we find academic performance is 100% genetic, that indicates variation in these factors is not affecting results: children are receiving the same opportunities. But they may not be receiving the best opportunities.

As I said above, I’m not a geneticist, so I’d welcome any correction if I’ve got the wrong end of the stick anywhere in the above…