Heritability estimtes for intelligence quotient (IQ) range from 0.50 to 0.80. This makes IQ a suitable target for attempts to identify the specific genes involved.” Chorney et al, Role of the cholinergic muscarinic 2 receptor (CHRM@) gene in cognition. Molecular Psychiatry (2003) 8. 10-13.

“A substantial body of literature from twin, family and adoption studies documents significant genetic effects on human intelligence. Heritability estimates range from 40 to 80% and meta-analyses suggest an overall heritability of around 50%” Dick et al, (2006) “Association of CHRM2 with IQ: Converging Evidence for Genes Influencing Intelligence.” Behavioral Genetics.

“Multivariate genetic analyses indicate that general intelligence is highly heritable, and that the overlap in the cognitive processes is twice as great as the overall phenotypic overlap, with genetic correlations averaging around .80.”
Plomin et al (2004) “A functional polymorphism in the succinate-semialdehyde dehydrogenase genes is associated with cognitive ability,” Molecular Psychology 9, 582-586.

In terms of the Ashkenazi paper:

Here is a comment from one of the authors, Greg Cochran regarding that paper:

“Suppose that there are N balls in an urn, of which m are red. The hypergeometric distribution describes the probability that exactly k balls are red in a sample of p distinct balls drawn from that urn.

There are about 20 surprisingly common genetic diseases among the Ashkenazi Jews, of which 4 affect sphingolipid metabolism (and, incidentally, promote the growth of neural connections). We now know, to a pretty good approximation, how many human genes there are, and how many of those genes affect sphingolipid metabolism. Using a strategy that is an extended version of the simple hypergeometric model (also applying Bonferroni corrections for multiple comparisons, among other complications) you can get an estimate of the probability of such a cluster of mutations occurring by chance. It’s something less than 1 in 100,000. To do this, we used the Gene Ontology database (GO-EBI,EMBL-EBI, 2003), an established tool used to assess the statistical significance of human gene clusters obtained by high-throughput methods such as microarrays.

Rudyard Kipling wrote the Just-So Stories, which explain how the leopard got his spots and so on. He was not ion fact responsible for our current understanding of the hypergeometric distribution: that was a joke.

In my opinion, a careful look at the psychometric data, medieval history, and the biochemical effects of the sphingolipid mutations, combined with Gene Ontology calculations of cluster likelihood, combined with millions of simulations of the population genetics of a surprisingly frequency recessive lethal like Tay-Sachs ultimately produces something more than a Just-So Story.

Posted by: gcochran at Jan 22, 2009 3:29:54 PM”

http://www.marginalrevolution.com/marginalrevolution/2009/01/the-10000-year-explosion/comments/page/2/#comment

Also, there is a series of interviews at 2Blowhards with Cochran:

“2B: Is part of what enables us to think of culture affecting evolution the fact that we now know that evolution is proceeding rapidly?

GC: Yes. And because different cultures result in different selective pressures, sometimes quite strong ones….

2B: How controversial would the thesis that culture influences evolution be among the general run of scientists? What kinds of scientists would try to take issue with you? On what grounds?

GC: On some points I think I’d get very little argument — lactase persistence for example. On anything that influences personality or cognition, I think they’d hate it, but that kind of evolutionary change is bound to happen. The social world changed and we changed too. There’s genetic evidence for it, and of course lots of evidence of psychometric differences.

2B: The main example you use to illustrate how cultural developments can influence evolution is agriculture. Why was the development of agriculture such a major event where human evolution was concerned?

GC: It increased human density by tens of times, which made a big difference in disease risks. It radically changed diet, and it dramatically furthered hierarchy and social complexity.

2B: You and Henry assert that populations that adopted agriculture were much influenced by the development, and in non-insignificant, deep-in-the-biochemistry sorts of ways. What would your favorite examples of those adaptations be?

GC: Metabolic/diet changes like lactose tolerance, many changes in genes involved with defense against infectious disease, many changes in genes that affect hearing and smell, changes in neurotransmitters and related genes that most likely influence personality, changes in genes involved with the regulation of nerve connections and brain growth.

2B: One implication would seem to be that there are striking differences between populations that developed agriculture long ago and ones that encountered it only recently. Fair?

GC: Yes. Peoples with short histories of agriculture have trouble with alcoholism, diabetes, and generally have a lot of trouble fitting into complex hierarchical societies.

2B: Can you tell us a bit more about all this? And can you explain why should we think of these differences as more significant than, say, hair or eye color?

GC: Eye and hair color are somehow involved with genetic changes that gave advantage — Vitamin D looks to have been important, but I don’t think we know the whole story on that. I tend to think things like vulnerability to diabetes or TB are important because they cripple and kill people: generally I’m against that.”

http://www.2blowhards.com/ archiv…e_1.html#005818

“2B: Are all population groups evolving at the same rate? Is it possible that some population groups are evolving lickety-split, where others are fairly static evolution-wise?

GC: If we’re right about big populations under agriculture changing rapidly, hunter-gatherers must have changed less. It would seem that Chinese probably changed a good deal faster than Australian Aborigines.”

http://www.2blowhards.com/ archiv…e_3.html#005819

But it’s obvious that intelligence can be inherited through genetics. We are smarter than apes because of our genes. In humans, you can see from the youngest age that some kids are naturally better at math/English/music/etc.

Ashkenazi Jewish culture values education very strongly. Obviously that has a huge role in their success. But I also wouldn’t be surprised if, after 5000 years, a slight but discernible effect could be seen in “intelligence” scores.

I shudder to think what the long term implications are for our Britney Spears obsessed culture. Will these trends be our future? http://www.thinkgene.com/genetic-engineering-will-not-save-population-trends/

Do you know any of the literature on these issues, beyond Stephen Jay Gould that is? This is easily one of the _least_ controversial topics in the book.

Von