December 11, 2008

Inbreeding depression and IQ

Intelligence doi:10.1016/j.intell.2008.10.007

Inbreeding depression and IQ in a study of 72 countries

Michael A. Woodley

Abstract

In this ecological study, a robust negative correlation of r = − .62 (P less than .01) is reported between national IQs and consanguinity as measured by the log10 transformed percentage of consanguineous marriages for 72 countries. This correlation is reduced in magnitude, when IQ is controlled for GDP per capita (r = − .41, P less than .01); education index (r = − .40, P less than .01); and democracy index (r = − .42, P less than .01). Multiple regression analysis revealed that in the absence of the democracy index; percentage consanguineous marriages, education index and GDP per capita all exhibited stable final standardized β coefficients, however consanguinity had the least impact (β = 0, P greater than .05) whereas GDP per capita had the highest (β = .35, P greater than .01). This result is interpreted in light of cultural feedback theory, whereby it is suggested that consanguinity could subtly influence IQ at larger scales as a result of small IQ handicaps bought about through inbreeding being amplified into much larger differences through their effect on factors that maximize IQ such as access to education and adequate nutrition. Finally, consideration is given to future potential research directions.

Link

10 comments:

Maju said...

however consanguinity had the least impact (β = 0, P greater than .05) whereas GDP per capita had the highest (β = .35, P greater than .01).

This says it all: poverty causes mental damage by limited cultural enviroment and emotional stress, as has been shown recently.

BlaiseVillaume said...

That claim seems contrary to logic. Human activity is directed by mental function which of course is limited by mental ability. Society is essentially the interaction of a particular group of people, and that interaction is fundamentally dependent on the mental limitations of those within the society.

Why should it be surprising to anyone that people with less ability to solve problems and less ability to think creatively would be less successful in competition against better problem solvers?

Plus, your use of the phrase "mental damage" implies a degradation of superior mental condition. You would be better suited to say poverty "retards" or "stunts" mental activity. In which case I'd like to know exactly how that happens

Maju said...

Did you read the news link? It says that, everything else equal, children born in poor families stongly tend to have an ineffective frontal lobe, much as adults who have suffered physical damage in that area.

This is not genetic but enviromental.

Your logic is somewhat valid in its pure abstract terms (though as a persistent loser with high IQ, I know well it's not all up to mere intelligence but largely also dependent on other factors like conformism, discipline or social abilities - or even just the level that money and status takes in your personal scale of values) but, in any case, what I mentioned rather defies that raw logic and strongly suggests that nurture is at least as important, if not more, than genetics in this issue. That poor people markedly tend to suffer intellectually from their enviroment ("poverty culture" or whatever). The frontal lobe appears to be of major importance in human-specific (intelligence) mental behaviour: its enviromental damage cannot have just no consequences.

This may also explain the abnormally low IQs registered by certain controversial studies in many poor countries. And this without even pondering the effects (probably even more severe) of malnutrition in young people.

BlaiseVillaume said...

How did they isolate the variables to make all things equal? Did they take twins at birth and raise one poor and one wealthy? I don't mean to nitpick or be argumentative, but I am skeptical of the article.

I also don't mean to come across as being somebody who exclusively looks at "nature" or individual biology. It seems to me that a person is shaped in the synthesis of an individual's physical and mental being, external human factors, natural law, and natural circumstance.

Maju said...

Well, they mention that it was certainly not dependent on other factors like exposure to drugs or whatever, but guess not all factors can be controlled so easily.

In any case the article reads:

"These kids have no neural damage, no prenatal exposure to drugs and alcohol, no neurological damage," Kishiyama said. "Yet, the prefrontal cortex is not functioning as efficiently as it should be. This difference may manifest itself in problem solving and school performance."

The researchers suspect that stressful environments and cognitive impoverishment are to blame, since in animals, stress and environmental deprivation have been shown to affect the prefrontal cortex.


For me that is pretty much conclusive, at least until further research comes to expand our knowledge. The research was not intended specifically to elucidate if there is a genetic component in intelligence but does imply that there are hidden factors associated with poverty that cause an invpoverished frontal lobe and that a similar phenomenon is known among other animals and there is nothing in all that that would seem to suggest that it's something genetic but rather enviromental.

I see the mind as an incredibly elastic organ that adapts and "expand" in function of the enviroment. Of course, there's a genetic component to the mind but it's hard to see how it could be overly dominant in such an "epigenetically" formed organ as the mind.

Instead it's well known that lack of stimulation damages the mind, both among the young and the elder. This is nothing surprising as you can also see how muscles weaken with lack of excersise, etc. So guess a good, stimulating, raising is much more likely to get the best of your genetic background in all aspects than a poor, depressing, one, which can also be damaging, maybe with long-lasting effects, as this study seems to show.

terryt said...

"In this ecological study, a robust negative correlation of r = − .62 (P less than .01) is reported between national IQs and consanguinity as measured by the log10 transformed percentage of consanguineous marriages for 72 countries".

So the authors do see some effect of inbreeding, although other factors come into it. And perhaps inbreeding influences some of those other factors.

There are still some who deny inbreeding is ever a problem. Yesterday I went to get some duck eggs off a person who claimed some months ago that, although his ducks are inbred, he doesn't have any problems. I asked yesterday how the season was going. His reply? "Not very well. Half the pairs haven't even nested and fertility on the eggs I've tried is extremely low". I was too much the gentleman to remind him of our earlier discussions regarding the effects of inbreeding.

Cyd the Kid said...

poverty causes mental damage by limited cultural enviroment and emotional stress from Maju

If we are to believe this assertion and Maju's one off, relatively flawed "study" from Berkeley, then it becomes clear Maju is poorer than dirt. Hence the reason for his ignorance.

However, if we are to believe studies done looking at SAT scores and socio-economic status that found black students from relative well to do backgrounds (family income >$70K) doing just as poorly as their poor black brethren, along with many others studies and government programs that found no significant difference in socio-economic status with intelligence, then we KNOW with certainty that Maju is a moron, rich or poor.

The largest thorn in the "study" of Maju's are the Jews. Early 20th century Jews moving from Europe into the US were dirty, smelly, and quite poor. Their children, dirty and smelly as well, absolutely destroyed admission testing standards and in turn caused what was the beginning of changes in admission policies in universities in order to keep Jewish enrollment to a minimum. In other words, they out performed their wealthy Anglo-Saxon peers on these tests.

Let me repeat, Maju is a f*cking moron. Hope this is clear to all.

Maju said...

I can't but "love" your logic. But I really don't expect more from neonazis like you: just ramblings and disrespect.

There's some kind of people with whom it is impossible to dialogue and you epytomize that kind.

Cyd the Kid said...

At least I have logic.

There's some kind of people with whom it is impossible to dialogue and you epytomize that kind.

Kindly repeat this 4 times a day while simultaneously looking in the mirror. Then when your desire to post comments here becomes overwhelming, repeat it again. It will save all of us a lot of trouble. Thanks so much.

Cyd the Kid said...

Oh yes, nor do I expect anything more from the likes of you than impotent cries of "neo-nazi" when caught with your proverbial pants around your fat ankles. Even there, you are dull and unoriginal.