Commenter Lion of the Judah-Sphere informed us of a post by JayMan claiming birth order has no real effect on IQ.
I don’t know whether birth order and has a causal effect on IQ or whether it’s just a proxy for other variables, but in my humble opinion, there is indeed a negative correlation between IQ and birth order.
Using unpublished data on 209 Canadians (aged 19 to 76; IQ 57 to 137) I obtained the following regression equation:
IQ = 104.056 – 1.650(BIRTHORDER)
Assuming a linear relationship, this predicts the following:
Firstborns: average IQ 102
Secondborns: average IQ 101
Thirdborns: average IQ 99
Fourthborns: average IQ 97
Fifthborns: average IQ 96
Sixthborns: average IQ 94
Seventhborns: average IQ 93
Eighthborns: average IQ 91
Ninthborns: average IQ 89
Tenthborns: average IQ 88
Eleventhborns: average IQ 86
Twelfthborns: average IQ 84
Causation
I suspect later-borns average low IQ for the following reasons:
1) r genotype: As the late scholar J.P. Rushton, observed, primitive genotypes are not intelligent or caring enough to have high survival rates for themselves or their kids, so they evolved high birth rates to compensate. Low IQ people are more likely to have these primitive genes, and thus come from families with lots of kids.
2) Prenatal environment: I suspect that each child a woman gives birth to makes subtle changes to her womb. For example, research shows that for males, the more male fetuses have been in your mother’s womb before you, the higher the odds of being gay. Could a similar effect increase the odds of low IQ?
3) Mutation load: Older parents pass on more genetic mutations to their kids, some of which might impair IQ. Later borns are obviously concieved by older parents than newer borns, on average.
Pumpkin Person 
Or… ”dumber” people ON AVERAGE (in the past too) had and have more kids than ”smarter” people. These correlation can express the result about who are the people which have more children and less ” biological birth order have a direct-causal effect”. Would be interesting analyse this effect in smart families specifically to know if it’s true or a demographic-cognitive statistical pollution.
Francis Galton found many cases of extreme personalities, aka, mental disorders, in highly smart families or high number of achievers. I think families with higher heredity for intelligence and or creativity (specially) are more predisposed to have higher incidence of mental disorders and other uncommon features as homossexuality.
I think that what you’re describing here is that the further one’s IQ is from 100, the more likely tey are to be neuroatypical. Notice how a lot of the IQ 50 people (but not all of them) have syndromes or disorders. I bet that that IQ 150 people also have a high rate of syndromes or disorders. The most neurotypical people are the IQ 100 ones.
Yes, i think in the middle of bell curve, there are natural balance. I think, people of very low iq is unable to mate and or tend to be sterile. Many them are sons of smarter couples. I remember to see a german documentary about down syndrome. The two families seems smarter ( well, i think many germans look ”smarter”), a first was a high income family and other, mother and Brother of ”down boy”, look smarter.
High intelligence and creativity heredity is a polimorphism similar to ”anemia falciforme” in negros. Nature give prefference for ”fitness”, not for intelligence or creativity. Not in a ‘natural’ way.
Down syndrome have a chromosomic origine, it is not linked to genes.
Homossexuality specially the kind hiyper sexualized tend to relate with over-masculinization of brain as well autism, schizophrenia and giftedness. But i think both, excess or the lack of testosterone can be a factor to this unusual idiossyncrasies.
”Down syndrome have a chromosomic origine, it is not linked to genes.”
What the real difference*
In the middle of a phenotypical variation as (quantitative) intelligence, by logic and based on idea of natural inclinations to favor health than any other variable (as intelligence), there are less mental complexity than super smarts, on average, as well, more mental complexity than less smarts. AND ”civilization”, i.e, people with power, need many specialized people with average level of complexity. (satanic) ”civilization” as well the nature, tend to favor balance than exceptionality.
that may be entirely due to fertility vs IQ correlation. One needs to control for parents IQ or take data from only a certain set: only 3 child families, or only 5 child families etc…
And homosexuality issue is a bit different. male homosexuality is correlated to the number of older brothers, therefore it is not due to fertility, but as you say due to prenatal environment which might again effect IQ but we need to subtract fertility from that…
Homossexuality correlates with number of older Brothers. On average of course.
Pumpkin you have forgotten the environnemental effect.
Indeed, elder are more intellectualy stimulated because they have to take care of their younger brother(s)/sister(s)
I considered the social environment, but evidence might suggest that only the biological environment can affect adult IQ, though more research is needed.
I don’t really know much about it, but I think social environment can affect IQ scores (not intelligence). Like you said in the article about roms.
It’s cale ba not alcoholicwisdom but there was a bug.
how is it possible that he used my name?
and yeah, social environment effect on IQ is insignificant. Brain is always online, whether you live in a village, or working for NASA. And there is no proven exercise that can increase IQ ever… to my knowledge…
He has a bad habit of posting under other peoples’ names as some kind of joke. When I seem him do this I delete it, but in this case he outed himself, though he tried to blame a fictitious computer bug.
That’s why it’s wise to always post with the same email, so you always get the same coloured design to distinguish yourself. Yours is always a light green diamond for example.
“He has a bad habit of posting under other peoples’ names as some kind of joke.”
wtf ?
“though he tried to blame a fictitious computer bug.”
it’s true but you are free to think what you want, but i don’t see the utility to do this and to correct me after, especially if i post a comment in the continuity of my discution. it would be incredibly stupid.
“That’s why it’s wise to always post with the same email, so you always get the same coloured design to distinguish yourself. Yours is always a light green diamond for example.”
you are a genius.
it’s true but you are free to think what you want, but i don’t see the utility to do this and to correct me after, especially if i post a comment in the continuity of my discution. it would be incredibly stupid.
Well the mistake you made was you forgot to write in a new email so it was obvious you were cale not alcoholicwisdom from the coloured design
Since you knew this would expose you, you decided to out yourself before anyone else did & blame a computer bug
so you think i would write a totally serious comment in the continuity of the precedent and changing my pseudo ?!! and furthemore if you think that i have a bad habit in posting in others names, you don’t think that i should know that i need the mail adress of alcoholicwisdom to have the same gravatar ?
and to finish i know that you have the commenters localisation so i should also have the same localisation than alcoholicwisdom ?
seriously, i didn’t expected you to be particularly smart but there, your lack of logic really disappointed me.
and furthemore if you think that i have a bad habit in posting in others names, you don’t think that i should know that i need the mail adress of alcoholicwisdom to have the same gravatar
You knew you about the email controlling the gravitar but you forgot to change it.
Once you saw that you had posted under your own gravitar but with alcoholicwisdom’s name you thought “damn i forgot to change my email…since they’ll know it’s me I’ll admit it, but blame a computer bug”
And yes I can check locations but others can’t & you know even i will not bother
Maybe I’m wrong…but considering that you’ve pretended to be Blasian, Kate, Robert Lindsay, Robert Mugabe & even went on Lindsay’s blog & pretended to be me, it’s very logical of me to think you did it on purpose
You have made a mistake and you are too arrogant to admit it.
I can understand it, you are not enough masculine in your brain but you are too masculine at the hormonal level.
Btw it’s not because i have live in the same country/city(i dont know a precise this stuff is) of a person that i am actually this person.
Social environnement have indeed an effect on IQ scores but not really on intelligence itself.
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