Apologies for not posting anything recently. I have something in the works at BigThink and a few more in the pipeline but it has been hard finding the time to blog recently. I hope to be back to it in a couple of weeks.
What if we’ve been thinking about the genetics of intelligence from completely the wrong angle? Intelligence (as indexed by IQ or the general intelligence factor “ g ”) is clearly highly heritable in humans – people who are more genetically similar are also more similar in this factor. (Genetic variance has been estimated as explaining ~75% of variance in g , depending on age and other factors). There must therefore be genetic variants in the population that affect intelligence – so far, so good. But the search for such variants has, at its heart, an implicit assumption: that these variants affect intelligence in a fairly specific way – that they will occur in genes “for intelligence”. An implication of that phrase is that mutations in those genes were positively selected for at some stage in humanity’s descent from our common ancestor with apes, on the basis of conferring increased intelligence . This seems a fairly reasonable leap to make – such genes must exist and,
Mental illness is surprisingly common. About 10% of the population is affected by it at any one time and up to 25% suffer some kind of mental illness over their lifetime. This has led some people (many people in fact) to surmise that it must exist for a reason – in particular that it must be associated with some kind of evolutionary advantage. Indeed, this is a popular and persistent idea both in scientific circles and in the general public. (See the recent article “ Depression’s Upside ” from the New York Times Magazine, for example). Such theories come in two main varieties – the first, that mental illness confers some specific advantage to those afflicted; and second, that the mutations which cause mental illness in one person’s genetic background may confer an advantage when they are in a different genetic background (balancing selection). Both of these suffer from some misconceptions about how evolution by natural selection works. The intuitive appeal of the “surv
Did I miss a memo? Has eugenics somehow become respectable again? Source There has been a lot of talk lately, in the blogosphere at least ( 1 , 2 , 3 , 4 , 5 ), about the idea of using molecular genetics to predict and select for higher intelligence in humans (through pre-implantation screening of embryos, for example). The prevailing view among many discussing this idea seems to be that if we can do it, we obviously should do it. The casualness with which this conclusion is reached is astonishing to me, given the history of humanity’s efforts in this area. To many commentators, it seems to be a given that having more intelligent people, across the population, is not only obviously a good thing, but one that supersedes any other considerations. Selecting for increased intelligence doesn’t sound so bad, when you phrase it like that, until you realise that it actually involves the converse – selecting against individuals with lower predicted intelligence. I am not ascribin