Intelligence Tests Highlight Importance of Genetic Differences

Alok Jha, Guardian (London), August 9, 2011

Genetic differences between people account for up to half of the variation in intelligence, according to a study of more than 3,000 individuals.

Intelligence is known to run in families, but no single genes have yet been identified that can be reliably linked to mental ability. Instead, researchers think, many hundreds or thousands of genes could be involved, each with a small influence on a person’s overall intelligence.

“It has been getting clearer and clearer that any genetic contribution to traits on which people differ–like height and weight–comes about from large numbers of gene differences, each with very small effects,” said Prof Ian Deary of the University of Edinburgh, who led the research on intelligence. “We thought that was one possibility for cognitive ability differences, and our results are compatible with that.”

To test his idea, researchers looked at more than half a million locations in the genetic code of 3,511 unrelated adults. Each of these sites is where people are known to have single-letter variations in their DNA, called single nucleotide polymorphisms (SNPs). These variations were correlated with the individuals’ performance in two types of psychometric tests that are established in assessing intelligence: one test measuring recalled knowledge (via vocabulary) and the second measuring problem-solving skills.

They found that 40% of the variation in knowledge (called “crystallised intelligence” by the researchers) and 51% of the variation in problem-solving skills (“fluid-type intelligence”) between individuals could be accounted for by the differences in DNA. The results are published on Tuesday in the journal Molecular Psychiatry.

Previous work on the environmental and genetic contributions to cognitive ability has been based on comparing intelligence in identical and non-identical twins, or studying it in people who were adopted. In the study led by Deary, the conclusions were gleaned from direct testing of people’s DNA. “It is the first to show biologically and unequivocally that human intelligence is highly polygenic [involving lots of genes] and that purely genetic (SNP) information can be used to predict intelligence,” Deary wrote in the journal paper.

Though the researchers now know the proportion of the variation in intelligence that is likely to be a result of genes, they do not know which genes are likely to be most important in determining intelligence. “If they can be found, and if we want to follow them up, to find out some of the mechanisms that underlie successful thinking, our best guess at present is that the number is huge. It could be many thousands,” said Deary. “That could be a limitation to progress using this type of research.”

Dr Simon Underdown, senior lecturer in biological anthropology at Oxford Brookes University, said human intelligence was a “stunning product of our evolution”. He continued: “This paper brilliantly demonstrates that the genetic basis for our intelligence is not the result of a simple mutation in a single gene. Rather, the diverse range of genes that appear to influence our ability to think must have been actively selected for over hundreds of thousands of years. That we display such genetically influenced variation in intelligence across our species further hints at how important cultural, as well as biological, evolution has been to the human story.”

[Editor’s Note: Here is a link to the abstract of the study.]

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  • Jupiter7

    The fundamental issue facing Native Born White Americans is rapid race-replacement at the hands of high fertility post-1965 nonwhites. So my question is this:what does this news story have to with the fundamental issue facing Native Born White Americans? Answer:0.

    As far as the scientific merit of study goes, it really isn’t anything that should make true believers in the strict gene-centric story all that happy. If anything it pushes the issue way further from this point of view. Now, the causes of intelligence are much less localized at the gene level and spread out through the genome. This is just another way of saying that researchers no very little about the gene-phenotype(IQ) causal story.

    There already was a huge conceptual gap between genes and phenotype on this particular issue. IQist boldy assert genes..then organic structures for IQ scores. In other words, put a quarter in the slot machine, and out pops a biological structure for IQ scores. This is what you call handwaving to cover massive ignorance about the very big gap between the assertion that genes are fundamental determinants of brain structure for an IQ score on a test.

    The are also very serious statisical problems with the twin adoption studies which is the basis of the claim that intelligence is 50% inherited.

    Here is my point. The IQist true believers are full of massive confidence about the correctness of their postion. But I say they are skating on very thin ice. Yes, genes are important..but we really don’t know precisely how. But more importantly, this issue is completely irrelevant to the race-replacement issue. So go ahead, blather on about this study in a MSM appearance..and wth 100 percent certainty, you will completely sidetrack a discussion about the race-replacement of the Native Born White American Majority with an eyes-glaze-over-mind-numbing discussion about psychometric babble.

    Chek out the most recent issue of “The Sciences” where you can read a fascinating critique of gene-centric determinism by a world renown research biologist.

    The issue is not genetic determinism versus environmental determinism. Both are patently false. There is a way more interesting story emerging in the research.

    Stick with gut-level racial tribalism..this is all you need.

  • Dutchman

    Interesting study, but I think they purposely understated the genetic side of the equation. It should read ‘intelligence is at least 50% inherited’. I myself would think it was more in the region of 60-80%.

    The Guardian commentators are typical of their readership with the exception of one or two. They must lack cognitive ability!

    I read the Guardian’s opinion columns everyday as an exercise in how not to think.

    One amusing thing about these scientific studies is that you don’t actually need a laboratory and a doctorate to figure it our for yourself. Any ancient Greek could have told you that if you mate a bay stallion with a bay mare you get (surprise!) a bay foal.

  • Kingoldby

    ”That we display such genetically influenced variation in intelligence across our species further hints at how important cultural, as well as biological, evolution has been to the human story”

    Exactly WRONG!

    Genetic influences on intelligent prove that it is biology NOT cultural factors that are important.

    And for a follow up he will state that Black is White and that 2 + 2 = 5. Why is it that so many people deliberately misstate clear facts? He just deliberately misrepresented the evidence. Pathetic.

  • B.B.

    All things considered, this is a pretty decent summary of Ian Deary’s paper from a left-wing publication. Meanwhile, the coverage in The Atlantic Wire took the opportunity to repeat the same long-debunked criticisms of IQ tests and the concept of race.

  • Anon

    Despite what the article says, raw cunning appears to be more important than any test-related IQ ability for passing on genes. That’s the only way to explain why unintelligent and parasitic blacks have figured out how to make someone else pay for the raising of their own offspring. Much like how cuckoos lay their eggs in other birds’ nests, blacks with low IQs are very cunning at using the behavior of altruistic whites for their own purposes and to the detriment of whites.

    One good thing about altruism is that it’s useful for the preservation of multiple strains of intelligence–mathematical, musical, mechanical, etc. Societal altruism allows them to flourish and be passed on. It’s not an accident you see a larger variety of high intelligence strains in whites than in any other race. Unfortunately, the sociopathic cunning in blacks mentioned above is one of the types of ‘intelligence’ whites unwittingly preserve.

  • Pete

    This is simply stunning news! Does this mean intelligence is largely hereditary?

    I mean, I know people have been thinking that through simple observation and experience for several thousand years now, but who would have thought these observations would be borne out by actual testing?

    Clearly, we must continue to spend billions analyzing this new information before leaping to any premature conclusions.

  • Jupiter7

    This news of this study appeared first on Steve Sailer’s website and Peter Brimelow’s website vdare.com. And to be honest, when a study such as this one appears on Sailer.com and vdare.com, it is deeply embedded in a policy wonk framework. And the policy wonk debate that Peter Brimelow and Steve Sailer want to have is one where Steve and Peter will be in a symposium with the Cuban Foreigner George Borjas seated across from the Immigration Enthusiasts in a Brookings Institute conference room having a discussion about an immigration policy that selects for a higher quality immigrant..ones with the right IQ score..and this, always means, and leads to keeping the legal Asian immigrant spigot on..despite the very nasty intentions that the Asians in our America harbor towards the Native Born White American Majority. And this framework on immigration can be summed up in one word:moratorium..which means:a temporary time out on immigration..and when labor markets tighten..full speed ahead with Asian legal immigrants..because, for the immigration policy wonks..the Asians are the right kind of immigrants. Well, the Asians are not the right kind of immigrants to allow into our America…they never were..they are actively participating in the deskilling of the Native Born White American Majority..and this is most definitely within the realm of genocide. When you sidetrack a “debate” about race-replacing the Native Born White American Majority with a psychometric discussion about a score on an IQ test..which is in itself a terrible thing to do..you open the door to a policy wonk discussion about low quality nonwhite immigrants versus high quality nonwhite immigrants. Do not play the vdare.com policy wonk game, for it is one minute before midnight demographically for the Native Born White American Majority within the borders of America. The only acceptable policy is 0 legal immigration,0 illegal immigration, and the deportation of the Mexican,Asian,Muslim and African fifth columns that vote at election time to make the Native Born White American Majority an ever dwindling racial minority within the borders of “America”. Full-blown Native Born White American Racial Tribalism is the only game in town.

  • Rara Avis

    Anon @5

    That’s the only way to explain why unintelligent and parasitic blacks have figured out how to make someone else pay for the raising of their own offspring.

    Blacks are not intelligent enough to figure out how to make someone else pay.

    But those who control them and pull their strings to demand such of whites are.

  • Preparation H-Bomb

    Anyone who has been involved with the breeding of animals knows that intelligence is one of the many traits that are in fact genetic; one breeds for appearance, bone structure, health, intelligence, temperament — any number of genetically-passed traits, depending on the species involved. Why is it so surprising that genetically-passed intelligence levels are also part of human breeding and genetics? We are mammals, after all — and the rules of good breeding do NOT pass us by. All these scientists who so eruditely state their opinions, experimental results, and so forth on this subject should really forget all that and go visit a working farm where horses or hunting dogs are bred. It’s pretty basic, pretty simple — and yes, race does come into the issue as a factor. You don’t have to like it. You just have to tell the truth — unless you’re a PC liberal. The Bell Curve rules, people – never forget that!