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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.""
Sometimes, science will be politically incorrect. That does not mean that it should not be pursued.
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No, I think Pinker statement is intended to suggest that because this paper is politically incorrect people will try harder to disprove it, as with numerous other studies linking abilities or disabilities to racial, social or sexual characteristics. If you read his books, it's pretty clear he doesn't have much respect for political correctness, though he does shy away from some of the logical conclusions of his reasoning, IMHO.
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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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From a quick Google (I'm an undergrad genetics major, with two minor subjects left to go), the Journal of Biosocial Science has an impact factor of only 0.449 - generally, people don't read it, and serious research doesn't appear to go into it.
Compared to some other journal impact factors:
NATURE - 27.955
SCIENCE - 23.32
GENOME RESEARCH - 9.863
and
ACTA PSYCHIATRICA SCANDINAVICA - 1.554
(I assume this is a Scandinavian psychiatric journal - hardly *THAT* common)
Btw, impact factors are just a rough guide of the number of citations - they show what journals you'd like your research to go into in order for it to be cited lots - effectively scientific currency. Some good research could go into poor journals...
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but theres no need to use incorrect terms (AKA African-American if you're not from Africa) to please some minority
What I hate is people who use it incorrectly in the other direction. I've heard black people born and living in Africa called "African-American" (by reporters, no less), despite the fact they have never had any sort of residence in the Western Hemisphere.
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.
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Turns out that Pinker was one of the defenders of President Summers' comments concerning gender. From the Harvard Crimson:
Steven Pinker is the LAST person to imply that because something is politically incorrect, it's flat-out wrong. You're right, that quote might sound like it, but I think it's just a bad quote.
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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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You're talking about two seperate things though, intelligence and knowledge. Knowledge is attained through hard work and intelligence applies knowledge for practical reasons. Yes, a greater knowledge base probably includes better techniques of information deployment but reading a book probably isn't going to raise your IQ or improve your Raven scores.
I've met plenty of people who did very well academically but were incapable, or at least at the age I knew them at, were unable to deploy that knowledge in an effective manner. These were the kids who would spend an entire class period attempting to discern the answer that the teacher wanted on the essay. This is not intelligence, this is knowledge regergitation. Intelligence is taking knowledge and synthesizing it for a greater purpose...two completely different things in my mind.
I wouldn't worry much about lawsuits.
On the other hand, if you publish to much "politically incorrect" material, you may find your funding drying up pretty quickly which accomplishes the same thing.
Let's assume that intelligence is controlled by one gene. If that's the case, smaller, isolated groups will likely have higher or lower occurrence of the gene in much the same way that populations can have higher or lower occurrence of sickle-cell anemia or hemophilia. The effect is mitigated in the general population because of a high degree of mixing.
More likely, though, intelligence is controlled by at least a handful, if not a multitude of genes. In this case, even smaller populations will average out.
But this assumes that intelligence is unaffected by other factors. We would have to ignore:
a. that intelligence is hard to define
b. intelligence is hard to measure without bias
c. cultural pressures
d. economic pressures
e. educational differences
f. emotional differences
g.....
h....
It's possible that different groups have differences in intelligence, but for now, it's impossible to cut through all the bullshit.
- In the Middle Ages only intelligent Jews survive
- Conditions improve, but because of few Ashkenazi Jews marrying outside their communities, intelligence genes are retained
- However, this lack of genetic diversity serves not only to maintain intelligence but also to make the population more liable to the various diseases mentioned
Also, the difference between some groups is not just 5 points on the test; I understand that it is closer to 20 points between different ethnic groups in the USA alone.
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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.
Detecting macrostructural brain alterations from the norm does not necessarily imply causality. It is well documented that certain parts of the brain can physically grow in size due to usage even in adulthood - in a fairly famous early MRI study, it was shown that a part of the hippocampus of taxi-cab drivers significantly enlarged after a few months of driving, and shrank again if they stopped driving for several months.
More permanent changes can occur if intense use occurs at a young age. In pianists who begin playing by the age of seven, the corpus callosum (the neural bridge between the two hemispheres) was measured to be an average of 30 percent ( ! ) bigger than controls and those who began training after age 10.
Einstein's brain may very well have been structurally different from the norm, but we cannot say that this is due to genetics, as he may have simply nurtured these areas of the brain from a young age.
With respect to the specific case here, we will do a bit of common sense for ourselves: imagine a gene that has no effect when heterozygous but is lethal when homozygous. Now when that gene is common, there will be a good number of homozygotes to kill off through selection. Great. But now imagine that it is at low frequency, say 1/1,000. Then the homozygotes will be only at a frequency of 1/1,000,000... So roughly 2 copies of the lethal gene will be eliminated each generation in a population of a million, while there are still 998 copies floating around the population. It will take a very long time to completely eliminate the gene from the population. Random effects will speed up the loss in most cases (and to be clear, most of the time the gene won't even get to the low frequency I hypothesized), but at the same time those random effects can keep the gene around much longer than you would expect in a deterministic case.
Finally, I would also like to point out that this is all a very active area of research. The precise effects of different kinds of selection and random drift under different situations (subdivided populations, bottlenecks, population growth, etc) are still only somewhat known. We are learning a lot, but it takes a lot of time/effort. Common sense is rarely very informative. (Hence the big iron over at the Sanger center that was mentioned a few articles back)
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Is there any benefit to having an appendix? Other than your 1 in 700 shot of having acute Appendicitis, which was deadly before modern medicine? Or any advantage of having tonsils, which are prone to infection?
Or what about the genetic predisposition to certain cancers that this study talks about? Could it be that they weren't selected out because a) most people didn't tend to live long enough for the cancer to manifest itself, or b) the cancer manifested itself long after parents passed their prime reproductive age?
The human genome is vast, human populations are large, and there are many forces at work. Saying, "Well, my gut tells me this is true." doesn't really cut it. And, anyway, what was this huge benefit that kept these genes in? 5 IQ points, on average? Whoopdee doo.
Perhaps there just wasn't enough pressure to select these genes out. The chances of two random Ashkenazi Jews having a Tay-Sachs baby are roughly 1 in 3,600. The effect of having a Tay-Sachs baby is the kid dies within a few years. Well, lots of babies die for lots of reasons. The incidence rate for SIDS is in the 2.5 per 1,000 range (but not much is known about SIDS, so it's not diagnosed as easily as T-S.) Even among parents who are both T-S carriers, each of their kids only has a 25% chance of having T-S. So a couple has a kid that dies young. Lots of kids die young (especially a few hundred years ago). That's why you have lots of kids (back then, anyway).
We may never know why these genetic diseases were never selected out. For all we know, there just wasn't enough time and in a thousand years they might be gone.
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Slightly OT but important.....
That's a superficial and flawed reading of the evidence. First of all, behavior genetic studies typically show that the heritability of intelligence is about .50, which means that about 50% of the population variance is attributable to genetic differences. The rest -- the other half -- is environment, mostly nonshared environment (i.e., unique individual experience).
However, what most people do not realize is that heritability quotients depend on the population in which they're derived. Most heritability studies have been on middle- to upper-middle class subjects. It turns out that when you look at poorer populations (see original study here), heritability goes way down, and the importance of environment (including shared environment) increases dramatically.
The upshot is that for a poor kid, the expected return on an investment in the environment is huge. For a well-off kid, it's smaller but still real.
In all fairness to the Jews, what they actually believe is that they are worse than others, and that God specifically challenges them to behave well, and that when they can all do that for a year, then we all get the benefit of god making everything right on earth.
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Actually the paper makes a strong case that they are not inbred. Indeed that is one of the central thesis of the paper. RTFP!