Genetic Intelligence - Fact or Myth?

[SagGal]

Is this because of my "Age Difference" thread? OMG. I did not say that women are smarter than men. Jees. Maturity does not mean the same as smarts.

[loseyourname]

Bouchard and McGue (1981) conducted a review of family studies on IQ, and found that results obtained from many of the studies were consistent with the polygenetic theory of inheritance because the correlation between family member's scores on intelligence measures roughly corresponded to the proportion of genes shared between those family members.

One of the most well researched genes known to play a role in cognitive ability is the fragile X mental retardation gene FMR1 located on the X chromosome. Fragile X syndrome is characterized by x linked physical characteristics such as macroorchidism (increased testicular volume), long face, large protruding ears, and social eye gaze avoidance (De Vries et. al., 1997). The cognitive phenotype of the fragile X syndrome includes deficits in executive function, decrease in attention and viseo spatial memory, and decreased IQ (Menon et. al., 2000).

The FMR1 gene is associated with a series of trinucleotide repeats (CGG). Normal FMR1 genes are associated with 6 to 54 repeats, but can also expand to a length of 50 to 200 repeats in phenotypically normal individuals (Fu, et. al., 1991). The full mutation of FMR1 can contain as many as 2000 repeats, and individuals with the full mutation almost always show IQ scores in the mentally retarded range (Daniels, et. al., 1998). However, the length of the trinucleotide repeat series in those who do not carry the full mutation was not found to have any significant correlation with intelligence scores in those individuals (Franke et. al., 1999).

Menon et. al. (2000) found that disruption in FMR1 gene expression leads to decreased levels of FMR1 protein (FMRP) levels in the brain. The mutated gene form contains an area within the gene that prevents transcription of the gene leading to a decreased level of FMRP in the brain, which has been linked to abnormal formation of dendritic spines in the cortex which may impede learning and memory (Hinton et. al., 1991).

Additionally, the FMR2 gene, which lies distal to FMR1 along the X chromosome, has been implicated in fragile X syndrome. FMR2 is similar to FMR1 in that it contains a series of trinucleotide repeats (CGG) that result in expression of the fragile X phenotype in mutations containing over 200 repeats. As with FMR1, however, normal variation in the size of the gene is not associated with variation in intellectual performance (Mazzocco and Reiss, 1999).

While fragile X syndrome is the leading cause of inherited familial mental retardation, there are also a number of other genes present on the X chromosome that seem to play a role in intelligence and cognitive ability. For instance, Borjeson Forssman Lehmann syndrome (BFLS) is a syndromal X linked mental retardation involving a gene coding for fibroplast growth factor homologous factor 2 (FGF2) (Baker et al, 1999). Also, Hamel et al (1997) describe a syndrome involving X linked mental retardation, ataxia, loss of vision, and a fatal course in early childhood. This syndrome was linked to a gene (Xq21.33 to q24) that codes for two myelin proteins in the central nervous system. Finally, Nussbaum et al (1997) have linked the oculocerebrorenal syndrome of Lowe (OCRL), a rare X linked disorder characterized by mental retardation, congenital cataracts, and a disorder of the renal system, to a gene on the X chromosome (Xq25 to 26). However, they have not yet uncovered the action of the gene, nor have they uncovered its effects on the body's systems.

Another effort to track down genes that may play a role in intelligence is the IQ quantitative trait loci project, an association study examining gene markers of neurological relevance linked with intelligence (Plomin et al, 1994). Thus far, the study has singled out three markers that seem to have a significant association with IQ; the HLA A (B) allele; CTG B33, a trinucleotide repeat; and EST00083, a marker associated with mitochondrial DNA.

The HLA A (B) allele has been associated, along with the apolipoprotein E (ApoE) gene, with the age of onset of Alzheimer's disease. The e4 allele of the ApoE gene has been shown to be one of the factors considered to increase the risk and decrease the age of onset of Alzheimer's disease in direct proportion to the number of e4 alleles expressed (Owen, Liddell, and McGuffin, 1994). ApoE is present in cerebrospinal fluid and is thought to have a stimulatory effect in promoting structural changes following brain injury and neurodegeneration (Turic et al, 2001). Less is known about the HLA A (B) gene, but studies have associated it with late onset Alzheimer's in ApoE negative subjects (Lehmann et al, 2001). However, no associated between general intelligence scores and HLA A or ApoE genes has been found in the general population (Jacomb et al., 1999; Turic et al., 2001).

Additionally, little is yet known about the other two markers uncovered by the IQ quantitative trait loci project: CTG B33, and the mitochondrial EST00083. Moises et al (1999) examined EST00083, but found no association with high versus average IQ in the general population. Jacomb et al (1999) also examined CTG B33 polymorphisms and found no association with variation in IQ.

[PASAMONSTER]

Saggal it wasn't you

It was Ms. Feminist thang over there.

[loseyourname]

Genius Gene

Scientists in the United States claim to have found a genetic basis for intelligence. In a study of intellectually gifted children, the researchers say they've found differences in their DNA compared to that of average children. Advocates of eugenics - the science of selectively breeding humans for certain traits or behaviours, have welcomed the research. They say it could be used to breed brighter humans. But critics maintain that something as complex as intelligence can't be narrowed down to just a few genes. Corinne Podger, of BBC Science, reports.

The genes and intelligence research is being done at Vanderbilt University in Nashville. Two hundred intellectually gifted children are here for the summer to attend intensive college-level courses. In exams and IQ tests, they score in the top few per-cent for their age. And, as part of a study of 5,000 extremely bright children, samples have been taken of their DNA - and that of their parents - to see if there's anything unusual about it. Dr David Lubinski, Psychology Professor at Vanderbilt, explains:

‘Basically what we’re looking at is different genes and looking at different gene frequencies in high ability children versus typical children. We’re uncovering a few gene frequencies that do appear to be different.’

Listen to Dr David Lubinski explain the purpose of his research programme

In other words, Dr Lubinski says they're finding some genes occurring "more frequently" in bright children compared to their average peers. The discovery's been welcomed by right-wing eugenicists like Charles Murray, who's published books and articles in the US arguing that genetics holds the key to social problems like poverty. Mr Murray believes the Nashville team are close to finding a so-called "genius gene" which could bestow intelligence on anyone who has it. Such a finding, he says, would enable scientists and parents to breed brighter children.

‘What's going to happen in the next 10 or 20 years is we can have eugenics with a smiling face, so we no longer require that the lower classes have fewer babies, we will just have them have better babies as we learn how to do gene therapy. Well, in a sense this isn't so bad - suppose we have a gene therapy that will raise IQ’s by 15 points. I think parents - it’s okay if they have the right to introduce those changes, in their own children.’

Whilst Lubinski and his team have found that particular genes appear to occur more commonly in children who do well at school, he claims that many other genes are crucial to the learning process. Susan Greenfield, Pharmacology Professor at Oxford University, agrees. She says manipulating individual genes won't guarantee smarter babies:

‘What a gene will do is express a protein, and we’re talking here probably about a protein in the brain. Now that could do many things. It would perhaps change the availability of a certain chemical in the brain or the way that chemical worked, and what you could talk about perhaps is a change in arousal levels or something very basic and very widespread in the brain that in turn had an indirect effect on how well people concentrated let’s say, and therefore how well they performed in tests. And that’s very different from talking about a gene for a specific defined trait like intelligence.’

'While a single defective gene can cause disease or dysfunctional behaviour, a single healthy gene isn't a magic key to intelligence or athletic ability'

'We are always better off with good knowledge than we are with ignorance'

Some day, scientists may be able to influence a person's intelligence by manipulating their genes - but even the Vanderbilt University team admit that's decades away. For Lubinski, he says that unproven hopes - or fears shouldn’t govern research in this field:

‘Sometimes it frightens people, because all-powerful scientific findings can be misused. But the position most scientists take and the position I take is that we’re always better off with good knowledge than we are with ignorance.’

Dr Lubinski's work will be published by the US National Institute of Health next year. In the meantime, the prospect that babies may one day be "engineered" to be smarter will continue to be thrilling to some, and deeply unsettling to others.

[SagGal]

Originally posted by PASAMONSTER Saggal it wasn't you

It was Ms. Feminist thang over there.

Oooooh k.

[anileve]

Originally posted by SagGal Is this because of my "Age Difference" thread? OMG. I did not say that women are smarter than men. Jees. Maturity does not mean the same as smarts.

No dear, it was Arvy's lucid post and it took a Man with a Gun to take it to the chauvinist concept, then loser stepped in to make his empty point about the significance of a Y chromosomes.

Once again, I will say this, this is a discussion for arrogant chauvinists who keep ranting on about the superiority of intelligence in male genes. I was simply advocating that it is decided by social factors and cannot be dictated on the bases of a gender. But they keep going at it, trying to prove that men are smarter than women. Well keep on gentlemen, I will scurry out of this thread. This has been taken out of a context and turned into a battle of sexes fit for a late night Friday conversation with darts and a few bitter men.

[Anonymouse]

This thread is not an intellectual thread of discussing a topic cordially, it is an ideological battleground, I see no point to it. It's 'true believer' vs 'true believer'. Now loser, lets focus on the book club.

[loseyourname]

I never claimed men are smarter than women. I am only demonstrating that intelligence is genetically determined and that the vast majority of traits show no sex-linkage. I suggest the rest of you cool off. And yes, let us get back to the book club.

[anileve]

Thank you Moderator Loser, much better *sigh*

[Arvestaked]

Originally posted by anileve So where are the results of so called "tests that men are smarter on the average?" I'd like to see a proof of that, rather than some inflated assumption based on subjectivity and limited personal experience, nothing more than an attempt to fuel the fire and step on people's toes to elevate one's self worth.

Originally posted by anileve I believe you were one of the 3 musketeers that agreed with the idea that "men are generally smarter than women", now contribute or keep smiling.

Originally posted by me because I am tired of this nonsenseThis is the last time I will say this. I never said that men are smarter. I was making a point about social conditioning. I do not believe in superiority between genders in anyway. If anyone from now on still believes that I have these chauvinistic views, you should do yourself and everyone else a favor a kill yourself.