Luke Ford

WP: “People who have less ability and marry people with less ability have children who, on balance, on average, have less ability,” he said. Thompson noted that there is a genetic component to intelligence that Noble and Sowell failed to consider.

“It makes my jaw drop that we’ve known for years intelligence is inheritable and scientists are beginning to track down exactly how it happens,” Thompson said. “The well-known genetic hypothesis has not even had a chance to enter the door in this discussion.”

Charles Murray, a conservative political scientist who argues there is a relationship between intelligence and economic class in his book “The Bell Curve,” said genetics cannot be ignored.

“It is confidently known that brain size is correlated with IQ, IQ measured in childhood is correlated with income as an adult, and parental IQ is correlated with children’s IQ,” Murray wrote in an e-mail. “I would be astonished if children’s brain size were NOT correlated with parental income. How could it be otherwise?”

STEVE SAILER COMMENTS: I’ve observed that your hat size correlates pretty closely with whether you believe brain size correlates with intelligence. I wear a 7 and 5/8ths hat, which is Extra Large, so the notion that brain size and intelligence are correlated always seemed pretty plausible to me.

My guess would be that head size is a tradeoff with running speed, via the mechanism of your mother’s pelvis width. The fastest runners tend to have very narrow hip bones, but that makes birthing babies with big heads dicier. I’ve always been an extremely slow runner, while the Kenyan Olympic champion runners looks to me like they have remarkably narrow heads.

COMMENTS TO STEVE SAILER:

* Have you noticed that WaPo has for some reason become one of the top smugglers of Steveosphere ideas into the mainstream? Obviously they played a laudatory role in the the UVA thing, but that wasn’t the first or the last time…

* Steve, have a look at the original Nature Neuroscience study that this is all based on. In order to obtain the result that got all the publicity the researchers had to correct for racial differences in brain size. The single largest effect (larger than the poverty result), and the most statistically significant, is the association of cortical surface area with African ancestry.

.25 increase in African ancestry is roughly equivalent to reduction in income by $77k (from mean of ~$100k), in terms of effect on brain surface area. (See Table 1.)

Strange that all the people who wrote or blogged about this article failed to notice this. It stands out like a flashing red light in the paper, if you read with comprehension.

* There’s a formula for correlating brain size with body size that is relatively valid across species: e.g., whales have really big brains in an absolute sense, but not relative to the body size of humans. A lot of the brain volume appears to be devoted to monitoring the body: Ouch that hurts. Of course it helps that whales can support a lot of mass because they are in the water.

Some birds, such as parrots and crows, are amazingly smart for their tiny bird brains.

* There is a factor that has sound evidence for affecting the mental abilities of infants that will carry through their lives, more breast feeding, but there is no practical way for the government to take on that responsibility so there is little interest among the wonks.

But, like most things in life, intelligence is “determined” (eek!) by multiple factors, and more breast feeding is not going to erase the differences. It has the added disadvantage of requiring personal responsibility.

* STUDY: Does gestation vary by ethnic group? A London-based study of over 122 000 pregnancies with spontaneous onset of labour
[…]
Results The median gestational age at delivery was 39 weeks in Blacks and Asians and 40 weeks in white Europeans. Black women with normal body mass index (BMI) (18.5–24.9 kg/m2) had increased odds of preterm delivery (odds ratio [OR] = 1.33, 95% CI: 1.15, 1.56, adjusted for deprivation and BMI) compared with white Europeans. The OR of preterm delivery was also increased in Asians compared with white Europeans (OR = 1.45, 95% CI: 1.33, 1.56, adjusted for single unsupported status and smoking). Meconium stained amniotic fluid, which is a sign of fetal maturity, was statistically significantly more frequent in preterm Black and Asian infants and term Black infants compared with white European infants. [Meconium is the first BM. –UR]
[…]
One hypothesis for shorter average gestational length amongst black infants is that earlier maturation of the feto-placental unit relates to the maternal pelvic size. A smaller pelvis benefits the mother in evolutionary terms in relation to posture and stability when running. However, a smaller pelvis is also associated with a higher incidence of both obstructed labour and maternal mortality. Indeed, Africans have been observed to have amongst the highest emergency caesarean section rates. In fetal terms it is advantageous for the fetus to have a large head because of the improved brain growth. Thus, this creates conflict in the maternal/fetal relationship. It therefore would be in the interest of the fetus to mature faster and deliver earlier to avoid the complications described.

* There’s actually a study that tests exactly this premise. It examines Swedish lottery winners. Conclusion: the effect of large amounts of money on infant health, drug consumption, scholastic performance and cognitive and non-cognitive skills is exactly zero.