There’s not a huge debate about the heritability of IQ, but a huge amount of debate about how much intelligence can be tied to genes and how much to the environment. Alas, the science of this looks to be facing a very steep struggle to get anywhere – largely because so many genes may play a role and you need vast studies of human DNA to isolate or discover any of them. A new study of more than 126,000 people has made some incremental progress. Money quote from the authors:
Previously, using a genome-wide study in a sample of 18,000 individuals, we could not identify a single genetic variant associated with cognitive performance. Using the new proxy strategy, though, we identified three genetic variants associated with cognitive performance. As expected from the calculation, the effects of these variants on cognitive performance are tiny. A copy of each variant accounts for only 0.3 points on a standard IQ test (with a mean of 100 and standard deviation of 15). A person who inherits all six copies (note: one genetic variant has two copies) of increasing variants differs by 1.8 points compared to individual who inherits none. That’s a small difference.
What to make of this with respect to our cultural and political debate about genes and intelligence? For me, some relief that the area is so complex, and varied, and hard to decipher that we may have more time ahead before these things become more knowable, and thereby may avoid any of the worst social implications for longer than some of us feared. Also: we’re bound to come up with surprises that take us in different directions. So, in this study, they found that
a combination of genetic effect calculated from 60 education attainment-associated variants is correlated with memory and absence of dementia in an independent sample of almost 9,000 individuals. While it is premature to suggest the biological function of the genes identified, our additional analysis suggests that the genes are related to synaptic plasticity – the main mechanism in the brain for learning and memory.
The Dish 