Jews Have Higher IQs than White People
- From: andrewchungamerican@xxxxxxxxx
- Date: 4 Aug 2005 21:28:51 -0700
http://www.economist.com/science/displaystory.cfm?story_id=4032638
The evolution of intelligence
Natural genius?
Jun 2nd 2005
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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