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Study Links Genetic Diseases to Intelligence
FleaPlus writes "The Economist, Sun-Sentinel, and FuturePundit report on a controversial study by Gregory Cochran and others which proposes a link between certain genetic conditions and above-average intelligence in Ashkenazi Jews. The 40-page study, published in the Journal of Biosocial Science, analyzes data on unusual patterns of genetic disease and relates it to a number of intelligence metrics. Although the intelligence data have traditionally been attributed to cultural factors, Cochran proposes that due to the unusual selection pressures the Ashkenazi faced between 800 and 1600AD certain genes developed which promote intelligence as single copies, but lead to particular diseases when somebody inherits two copies. According to Harvard cognitive scientist Steven Pinker, "It would be hard to overstate how politically incorrect this paper is... [though] it's certainly a thorough and well-argued paper, not one that can easily be dismissed outright.""
It's not a subset of the jewish religion, it is where those jews came from.
in modern usage, ashkenazis come from europe. Sephardic jews come from the near/middle east.
the definitions are a little different though. Ashkenazis are, by definitions, supposed to be jews whos family came from germany or eastern europe. sephardics, oddly enough, are supposed to be descended from families from spain or portugal.
the latter makes a little more sense, though. a lot of iberian jews were expelled during the spanish inquisition. many fled to the near east.
What comes first, finding a teacher or becoming a student?
I'm friends with Cochran. One of his interests is in using this research to find out methods of copying pharmecutically what these genes are doing naturally. (The genetic disease occurs for most of these genes when a person has two copies of the gene. The intelligence advantage comes from just one.) In other words, he wants to create a "smart pill" to raise IQ.
The selection would only apply to people who are heterozygous for Tay-Sachs, i.e. they are carriers of the gene. Infants who are born homozygous, with two copies of the gene, only live a few years. All die by age 5. There is no cure.
So, as you can see, there wouldn't be a whole lot of people crippled with Tay-Sachs running away from the Cossacks....
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Challenging that claim would certainly not be incorrect, but I hardly think that's what judaism claims. There are a lot of religions out there that claim to be chosen by god, and while, yes, it does come across as elitist, it is necessary to realize that it is not in reference to a bloodline or genetics, but a way of life. Similar to most religions, Judaism feels that religion brings them closer to god, and by choosing to follow this religion that they become a part of god's people. This isn't something that is only common to Judaism either.
Yes, it is tracked through the bloodline, but many other religions are also traced this way for the simple fact that people of a certain religion tend to bring up their children to hold their same beliefs. But make no mistake - just because something is passed down through parents does NOT mean that Jewish people claim RACIAL superiority.
For example, I am jewish, but not by blood...converted when I was quite little, actually. But even without that genetic trace, I've never been treated any differently, and I'm able to participate fully in all of the rites that all jewish people are. It's not a genetics/race thing, it's a beliefs thing, and it's common with a large number of religions.
...no two people are not on fire.
Turns out that Pinker was one of the defenders of President Summers' comments concerning gender. From the Harvard Crimson:
Don't believe me? Arthur Jensen, an intelligence researcher who started talking about a genetic component for intelligence back in the 60s, received death threats for his work. Pinker outlines in his most recent book, The Blank Slate: The Modern Denial of Human Nature, how much grief and ostracism other researchers have suffered for any implication that intelligence is not 100% environmental.
I just got a Master's in gifted education, and when I interviewed for a PhD program in Learning Sciences I had at least two different professors tell me (very enthusiastically) "Giftedness! That's so politically incorrect! I love it, we need someone who's brave enough to study that here! You know everyone's going to hate you, don't you?" And that's just for implying that smart people have different educational needs than other people, not even saying that it's innate. My professor in gifted ed here spends a lot of her time defending herself in the media, a lot more time than someone researching, say, reading would have to spend.
If you think this isn't a horrifically politically charged issue, you obviously haven't been anywhere near the field.
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Except that the authors showed mechanisms whereby the genes that cause these diseases could also cause increased intelligence. The sphingolipid cluster has a side effect of promoting axonal growth and branching as well as dendritogenesis. The DNA repair cluster are involved in regulating the proliferation of neurons during fetal development.
The authors also addressed the "bottleneck" theory (a group of people who had genes for these diseases just happened to survive by chance). This is the leading theory today as to why Ashkenazik Jews have such a high prevalence of numerous genetic diseases. In my opinion, they did a very good job of disproving that theory. Bottlenecks lead to severe decreases in genetic variability, and they demonstrate that Ashkenazik Jews are similar in variability to other populations including Europeans in general.
Here is my summary of the paper.
They demonstrate evidence that:
1) Ashkenazik Jews have higher IQ's as a group, but only in the mathematical and verbal subportions of IQ tests. They score lower than average on the visuospatial portions. This difference may be disappearing in recent times.
2) Post-Diaspora Jews were often persecuted and restricted to occupations that the majority (whether Christian or Islam) wouldn't do. In Christian lands, this included lending money for interest, whereas in Islamic areas, this avenue wasn't available, and only the most menial jobs were available to Jews there.
3) A very high percentage (up to 85 percent of adult males) were involved in a very narrow occupation range, mainly that of moneylender or other occupation that involved complex transactions involving money.
4) Those of higher intelligence got richer in these narrow range of occupations.
5) The richer you were the more children survived to adulthood.
6) Ashkenazik Jews were genetically isolated from the surrounding population by self selection.
7) Many of the genetic diseases that are at high incidence among Ashkenazik Jews cluster into only a few "types".
8) Two of these "types" (the sphingolipid storage type and the DNA repair type) are known to have positive effects on neural proliferation and growth.
Thus their conclusion is that these genetic mutations increase intelligence and the situation with Ashkenazik Jews is that the selective pressure towards intelligence was more than enough to outweigh the deleterious effect that these genes have on fitness otherwise. They suggest as a test for their theory, within Ashkenazik populations, heterozygotes for these genes should show increased intelligence relative to those who are not carriers.
It bothers me somewhat that this paper comes out of a Department of Anthropology. When addressing genetics, the quality of researchers in this area can be very widespread. However, I don't see that they have made any errors with respect to the genetics or the neurobiological aspects. It is very common to see in populations that a strong selective pressure at first yields mutations that are negative in some other way, but whose benefit outweighs the negative aspects. Subsequent selection yields compensating mutations (typically in other genes) that temper or eliminate the negative aspects.
In this case, the selection pressure has been removed, Jews are no longer restricted in their choice of profession, so it is likely that the negative aspects of these genes will push back and their incidence among Ashkenazik Jews will diminish, especially if carriers of the most devastating genes (such as Tay-Sachs) choose not to have children at all or fewer of them (such as couples who are both carriers and who have one healthy child deciding not to push the odds with more).
I find it interesting that because of the need for social and verbal ability among financiers, the other sorts of genes related to autism that also often increase intelligence weren't selected for among Ashkenazik Jews.