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Natural Genius? Culture & Intelligence


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Natural genius?

Jun 2nd 2005

From The Economist print edition



The high intelligence of Ashkenazi Jews may be a result of their persecuted past

The idea that some ethnic groups may, on average, be more intelligent than others is one of those hypotheses that dare not speak its name. But Gregory Cochran, a noted scientific iconoclast, is prepared to say it anyway. He is that rare bird, a scientist who works independently of any institution. He helped popularise the idea that some diseases not previously thought to have a bacterial cause were actually infections, which ruffled many scientific feathers when it was first suggested. And more controversially still, he has suggested that homosexuality is caused by an infection.

Even he, however, might tremble at the thought of what he is about to do. Together with Jason Hardy and Henry Harpending, of the University of Utah, he is publishing, in a forthcoming edition of the Journal of Biosocial Science, a paper which not only suggests that one group of humanity is more intelligent than the others, but explains the process that has brought this about. The group in question are Ashkenazi Jews. The process is natural selection.

History before science

Ashkenazim generally do well in IQ tests, scoring 12-15 points above the mean value of 100, and have contributed disproportionately to the intellectual and cultural life of the West, as the careers of Freud, Einstein and Mahler, pictured above, affirm. They also suffer more often than most people from a number of nasty genetic diseases, such as Tay-Sachs and breast cancer. These facts, however, have previously been thought unrelated. The former has been put down to social effects, such as a strong tradition of valuing education. The latter was seen as a consequence of genetic isolation. Even now, Ashkenazim tend to marry among themselves. In the past they did so almost exclusively.

Dr Cochran, however, suspects that the intelligence and the diseases are intimately linked. His argument is that the unusual history of the Ashkenazim has subjected them to unique evolutionary pressures that have resulted in this paradoxical state of affairs.

Ashkenazi history begins with the Jewish rebellion against Roman rule in the first century AD. When this was crushed, Jewish refugees fled in all directions. The descendants of those who fled to Europe became known as Ashkenazim.

In the Middle Ages, European Jews were subjected to legal discrimination, one effect of which was to drive them into money-related professions such as banking and tax farming which were often disdained by, or forbidden to, Christians. This, along with the low level of intermarriage with their gentile neighbours (which modern genetic analysis confirms was the case), is Dr Cochran's starting point.

He argues that the professions occupied by European Jews were all ones that put a premium on intelligence. Of course, it is hard to prove that this intelligence premium existed in the Middle Ages, but it is certainly true that it exists in the modern versions of those occupations. Several studies have shown that intelligence, as measured by IQ tests, is highly correlated with income in jobs such as banking.

What can, however, be shown from the historical records is that European Jews at the top of their professions in the Middle Ages raised more children to adulthood than those at the bottom. Of course, that was true of successful gentiles as well. But in the Middle Ages, success in Christian society tended to be violently aristocratic (warfare and land), rather than peacefully meritocratic (banking and trade).

Put these two things together—a correlation of intelligence and success, and a correlation of success and fecundity—and you have circumstances that favour the spread of genes that enhance intelligence. The questions are, do such genes exist, and what are they if they do? Dr Cochran thinks they do exist, and that they are exactly the genes that cause the inherited diseases which afflict Ashkenazi society.

That small, reproductively isolated groups of people are susceptible to genetic disease is well known. Constant mating with even distant relatives reduces genetic diversity, and some disease genes will thus, randomly, become more common. But the very randomness of this process means there should be no discernible pattern about which disease genes increase in frequency. In the case of Ashkenazim, Dr Cochran argues, this is not the case. Most of the dozen or so disease genes that are common in them belong to one of two types: they are involved either in the storage in nerve cells of special fats called sphingolipids, which form part of the insulating outer sheaths that allow nerve cells to transmit electrical signals, or in DNA repair. The former genes cause neurological diseases, such as Tay-Sachs, Gaucher's and Niemann-Pick. The latter cause cancer.

That does not look random. And what is even less random is that in several cases the genes for particular diseases come in different varieties, each the result of an independent original mutation. This really does suggest the mutated genes are being preserved by natural selection. But it does not answer the question of how evolution can favour genetic diseases. However, in certain circumstances, evolution can.

West Africans, and people of West African descent, are susceptible to a disease called sickle-cell anaemia that is virtually unknown elsewhere. The anaemia develops in those whose red blood cells contain a particular type of haemoglobin, the protein that carries oxygen. But the disease occurs only in those who have two copies of the gene for the disease-causing haemoglobin (one copy from each parent). Those who have only one copy have no symptoms. They are, however, protected against malaria, one of the biggest killers in that part of the world. Thus, the theory goes, the pressure to keep the sickle-cell gene in the population because of its malaria-protective effects balances the pressure to drive it out because of its anaemia-causing effects. It therefore persists without becoming ubiquitous.

Dr Cochran argues that something similar happened to the Ashkenazim. Genes that promote intelligence in an individual when present as a single copy create disease when present as a double copy. His thesis is not as strong as the sickle-cell/malaria theory, because he has not proved that any of his disease genes do actually affect intelligence. But the area of operation of some of them suggests that they might.

The sphingolipid-storage diseases, Tay-Sachs, Gaucher's and Niemann-Pick, all involve extra growth and branching of the protuberances that connect nerve cells together. Too much of this (as caused in those with double copies) is clearly pathological. But it may be that those with single copies experience a more limited, but still enhanced, protuberance growth. That would yield better linkage between brain cells, and might thus lead to increased intelligence. Indeed, in the case of Gaucher's disease, the only one of the three in which people routinely live to adulthood, there is evidence that those with full symptoms are more intelligent than the average. An Israeli clinic devoted to treating people with Gaucher's has vastly more engineers, scientists, accountants and lawyers on its books than would be expected by chance.

Why a failure of the DNA-repair system should boost intelligence is unclear—and is, perhaps, the weakest part of the thesis, although evidence is emerging that one of the genes in question is involved in regulating the early growth of the brain. But the thesis also has a strong point: it makes a clear and testable prediction. This is that people with a single copy of the gene for Tay-Sachs, or that for Gaucher's, or that for Niemann-Pick should be more intelligent than average. Dr Cochran and his colleagues predict they will be so by about five IQ points. If that turns out to be the case, it will strengthen the idea that, albeit unwillingly, Ashkenazi Jews have been part of an accidental experiment in eugenics. It has brought them some advantages. But, like the deliberate eugenics experiments of the 20th century, it has also exacted a terrible price.

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Originally posted by GoSkinsGo

Well now, that is interesting. I would love to read the entire study. He's got some really interesting outside the box thinking going on.

It's definitely interesting and certianly controversial. It seems like the journal in which their findings are to appear is reputable as it's published by the Unversity of Cambridge. Here's the capsule about it from their website:


Aims and Scope

Journal of Biosocial Science is a leading interdisciplinary and international journal in the field of biosocial science, the common ground between biology and sociology. It acts as an essential reference guide for all biological and social scientists working in these interdisciplinary areas, including social and biological aspects of reproduction and its control, gerontology, ecology, genetics, applied psychology, sociology, education, criminology, demography, health and epidemiology. Publishing original research papers, short reports, reviews, lectures and book reviews, the journal also includes a Debate section which encourages readers’ comments on specific articles, with subsequent response from the original author. JBS is truly international both in terms of geographical areas covered and its contributors. Its reputation for high quality and outstanding scholarship has made it into one of the leading journals in the area of biosocial science.

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Here's another article from the New York Times:


June 3, 2005

Researchers Say Intelligence and Diseases May Be Linked in Ashkenazic Genes


A team of scientists at the University of Utah has proposed that the unusual pattern of genetic diseases seen among Jews of central or northern European origin, or Ashkenazim, is the result of natural selection for enhanced intellectual ability.

The selective force was the restriction of Ashkenazim in medieval Europe to occupations that required more than usual mental agility, the researchers say in a paper that has been accepted by the Journal of Biosocial Science, published by Cambridge University Press in England.

The hypothesis advanced by the Utah researchers has drawn a mixed reaction among scientists, some of whom dismissed it as extremely implausible, while others said they had made an interesting case, although one liable to raise many hackles.

"It would be hard to overstate how politically incorrect this paper is," said Steven Pinker, a cognitive scientist at Harvard, noting that it argues for an inherited difference in intelligence between groups. Still, he said, "it's certainly a thorough and well-argued paper, not one that can easily be dismissed outright."

"Absolutely anything in human biology that is interesting is going to be controversial," said one of the report's authors, Dr. Henry Harpending, an anthropologist and a member of the National Academy of Sciences.

He and two colleagues at the University of Utah, Gregory Cochran and Jason Hardy, see the pattern of genetic disease among the Ashkenazi Jewish population as reminiscent of blood disorders like sickle cell anemia that occur in populations exposed to malaria, a disease that is only 5,000 years old.

In both cases, the Utah researchers argue, evolution has had to counter a sudden threat by favoring any mutation that protected against it, whatever the side effects. Ashkenazic diseases like Tay-Sachs, they say, are a side effect of genes that promote intelligence.

The explanation that the Ashkenazic disease genes must have some hidden value has long been accepted by other researchers, but no one could find a convincing infectious disease or other threat to which the Ashkenazic genetic ailments might confer protection.

A second suggestion, wrote Dr. Jared Diamond of the University of California, Los Angeles, in a 1994 article, "is selection in Jews for the intelligence putatively required to survive recurrent persecution, and also to make a living by commerce, because Jews were barred from the agricultural jobs available to the non-Jewish population."

The Utah researchers have built on this idea, arguing that for some 900 years Jews in Europe were restricted to managerial occupations, which were intellectually demanding, that those who were more successful also left more offspring, and that there was time in this period for the intelligence of the Ashkenazi population as a whole to become appreciably enhanced.

But the Utah researchers' analysis comes at a time when some geneticists have suggested natural selection is not the reason for the Ashkenazic diseases after all. Two years ago, Dr. Neil Risch, a geneticist now at the University of California, San Francisco, proposed a different genetic mechanism known as a founder effect, which occurs when a population is reduced for a time.

He found that all the Ashkenazic diseases had similar properties, including having arisen within the last 1,100 years. Therefore they had all arisen through the same cause, he argued, which must be founder effects, because it was unlikely that all could be due to natural selection. Last year, Dr. Montgomery Slatkin of the University of California, Berkeley, came to much the same conclusion for different reasons.

The Utah team agrees with Dr. Risch that the diseases all arose in historical times from the same cause but say natural selection is more likely because none of the non-disease Ashkenazic genes they tested showed any sign of a founder effect. They say the clustering of four of the diseases in the same biochemical pathway could only have arisen under the influence of natural selection, and calculate that the odds of a founder effect producing such a cluster are vanishingly low.

The four diseases, all of which are caused by mutations that affect the cell's management of chemicals known as sphingolipids, are Tay-Sachs, Niemann-Pick, Gaucher, and mucolipidosis type IV. A second cluster of diseases affects repair of DNA.

Turning to the possibility that some infection was the cause of the selective effect, the Utah researchers noted that Ashkenazim and Europeans lived together in the same cities and were exposed to the same microbes. If disease were the agent of selection, the Utah team argues, the European population would have developed a similar genetic response.

Ashkenazi Jews occupied a different social niche from their European hosts, and that is where any selective effect must have operated, the Utah researchers say. From A.D. 800, when the Ashkenazi presence in Europe is first recorded, to about 1700, Ashkenazi Jews held a restricted range of occupations, which required considerable intellectual acumen. In France, most were moneylenders by A.D. 1100. Expelled from France in 1394, and from parts of Germany in the 15th century, they moved eastward and were employed by Polish rulers first as moneylenders and then as agents who paid a large tax to a noble and then tried to collect the amount, at a profit, from the peasantry. After 1700, the occupational restrictions on Jews were eased.

As to how the disease mutations might affect intelligence, the Utah researchers cite evidence that the sphingolipid disorders promote the growth and interconnection of brain cells. Mutations in the DNA repair genes, involved in second cluster of Ashkenazic diseases, may also unleash growth of neurons.

In describing what they see as the result of the Ashkenazic mutations, the researchers cite the fact that Ashkenazi Jews make up 3 percent of the American population but won 27 percent of its Nobel prizes, and account for more than half of world chess champions. They say that the reason for this unusual record may be that differences in Ashkenazic and northern European I.Q. are not large at the average, where most people fall, but become more noticeable at the extremes; for people with an I.Q. over 140, the proportion is 4 per 1,000 among northern Europeans but 23 per 1,000 with Ashkenazim.

The Utah researchers describe their proposal as a hypothesis. Unlike many speculations, it makes a testable prediction: that people who carry one of the sphingolipid or other Ashkenazic disease mutations should do better than average on I.Q. tests.

The researchers have identified two reasonably well accepted issues, the puzzling pattern of diseases inherited by the Ashkenazi population and the population's general intellectual achievement. But in trying to draw a link between them they have crossed some fiercely disputed academic territories, including whether I.Q. scores are a true measure of intelligence and the extent to which intelligence can be inherited.

The authors "make pretty much all of the classic mistakes in interpreting heritability," said Dr. Andrew Clark, a population geneticist at Cornell University, and the argument that the sphingolipid gene variants are associated with intelligence, he said, is "far-fetched."

In addition, the genetic issue of natural selection versus founder effects is far from settled. Dr. Risch, whose research supports founder effects, said he was not persuaded by the Utah team's arguments. Dr. David Goldstein, a geneticist at Duke University who was not connected with either Dr. Risch's or the Utah study, was more open on the issue, saying Dr. Risch had made "quite a strong case" that founder effects could be the cause, but had not ruled out the possibility of selection.

Dr. Slatkin, though favoring a founder effect over all, said he agreed with the Utah team that this would not account for the cluster of sphingolipid diseases.

As for the Utah researchers' interpretation of Jewish medieval history, Paul Rose, professor of Jewish studies at Pennsylvania State University, said, "I think that some of their conclusions may be right though they still need a lot of work to be persuasive to historians and others."

Dr. Gregory Cochran, the first author on the Utah team's paper and a physicist who took up biology, said he became interested in the subject upon learning that patients with a particular Ashkenazic disease known as torsion dystonia were told by their physicians that "the positive thing is that this makes you smart."

"When you're in a hurry and have strong selection, you have a lot of genes with bad side effects," he said. The Ashkenazi Jewish population seemed to fit this pattern, he said, since they married only inside the community, making selection possible, and they had an urgent need for greater intelligence. Evolution had therefore selected every possible mutation that worked in this direction, despite their harmful side effects when inherited from both parents. "In a sense, I consider this a very boring paper since it raises no new principles of genetics," Dr. Cochran said.

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The theory I heard years ago was that Ashkenazim had higher average IQs because for centuries the best scholar growing up was elevated to rabbi, supported by the local community, provided a gifted wife, and enocuraged to have as many children as possible. Consequently, the best and brightest produced the most offspring. This is in sharp contrast to modern society, where the average number of children is inversely proportional to the education level of parents.

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Originally posted by Riggo-toni

The theory I heard years ago was that Ashkenazim had higher average IQs because for centuries the best scholar growing up was elevated to rabbi, supported by the local community, provided a gifted wife, and enocuraged to have as many children as possible. Consequently, the best and brightest produced the most offspring. This is in sharp contrast to modern society, where the average number of children is inversely proportional to the education level of parents.

That was my take on the theory. IMHO, intellegence is defined not by IQ tests, but by the brains ability to retain information and use it. It is no coincidence that once humans started to absorb knowledge, they are pretty much even across the board. There may be a few examples, such as listed in the articles, but you can do that within any racial division in homosapians. Was Booker T. Washington and smarter then Edison? How about Hawking, does this mean Brits from Manchester and inherently smarter then Scotts from Glasgow? Hell no, it only means there is a certain subject who has a high intellegence capacity.

We only use a very small portion of our brain at any one time, and there are no real advantages to one race or species over another, all the factors are environmental. For example, relativity was a theory thought to be understood by only the top scientists at the turn of the century, now it is common to find undergraduates and even freshmen who have a good handle on the theory. Does that mean we are smarter then those people, no it doesn't. It only means that we have the ability through modern teaching techniques to better relay the material. String Theory will be the same after a while as well. As a society progresses, the capacity to learn increases, not intelligence in general. . .

Although, I did read a really good theory on how homosapiens won out over Neanderthal man, it was based on empathy and thinking about the "other person". The theory goes that Neanderthal man did not know there was a neighbor right around the corner unless he saw him. The homosapien could deduce that there MAY be a man around the corner, thus thinking in terms of someone else. It's not to good of an example, but it is similar to how it was explained to me.

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Originally posted by chomerics

Although, I did read a really good theory on how homosapiens won out over Neanderthal man, it was based on empathy and thinking about the "other person". The theory goes that Neanderthal man did not know there was a neighbor right around the corner unless he saw him. The homosapien could deduce that there MAY be a man around the corner, thus thinking in terms of someone else. It's not to good of an example, but it is similar to how it was explained to me.

...I think you got the theory mixed up they practiced burial rituals which would obviously contradict that theory.

Intelligence is a tricky thing and who is to say that an ethnic group might be born with a few extra connections between different sides of the brain or whatever.

I think socially we'd like to not believe this b.c. it hurt people's feelings.

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