Om ärftlighet, intelligens och policy

Jag har svarat i ett kommentarsfält i ämnet, men tänkte att kommentarerna är en egen blogg-post i sig som kan vara bra att behålla som referens.

"Although individual differences in cognitive ability are primarily due to genes, one cannot from this infer an intergenerational transmission. To inherit genes is not synonymous with inheriting traits, when the trait is dependent on a large number of interacting gene functions. (Certain combinations of alleles can be very favourable, while the very same gene variant that promotes cognitive ability in one individual can be detrimental in another genetic environment that can arise during meiosis) The intergenerational transmission of IQ, which is implied in your reasoning, has (still) not been sufficiently studied.

Why is it of such crucial importance for policy if intelligence is transmitted between the generations as genetic elements or as social inheritance? (Because no-one is disputing that cognitive ability is transferred from parents to children).
If parental intelligence is genetically transmitted to the offspring, it would make sense to have a policy where intelligent parents of high socioeconomic status could promote the education of their (genetically favourably predisposed) children – presuming that the whole society would benefit more from seeing the gifted reaching their full potential rather than the less gifted (actually a far-fetched assumption).
On the other hand, if the combinations of common alleles (gene variants) that would predispose for exceptional cognitive abilities arose more randomly distributed in the population, if parental behaviour from the moment of conception until 2 or 5 or 10 years of age determined how the genetic potential could be played out, then optimal policy would be completely different. In the latter case, it would be wise policy to have extensive maternal care programmes, parental support programmes, and freely available, high quality day-care for small children, in order to catch the potential. In this case, no special attention would have to be given to children in privileged environments where they are already likely to find the stimulation to reach their potential.
So, when we are talking of heritability of intelligence and the effect on policy, we cannot mix these two scenarios up.
I can see a lot of wishful thinking amongst neo-liberal economist, and a lot of shoehorning in order to have reality fit the first scenario. But, there is no evidence for it. Rather the opposite.

On top of this, epigenetic might be a complicating factor where people of low socioeconomic status might transfer unfavourable DNA modifications to their children. These modifications can be reversed with enhanced socioeconomic and/or psychosocial conditions (the specifics are really unclear here). If we want to promote an intelligent society, policy should therefore be to promote the socioeconomic status of affected groups. In many societies, the opposite is rather seen, when the already dispossessed take the hardest blow of the economic downturn. How will their stress response affect the cognitive ability of their children?