I made a similar but non-quantitative argument but using the effect of intelligence on child mortality rates. http://charltonteaching.blogspot.com/2011/05/child-death-and-demographic-change-and.html But both models reach the same conclusion: that modernity is self-destroying, and we are currently en route to a return to zero growth agrarian societies (and the Malthusian trap).

Jason Malloy could perhaps give an estimate of the IQ of these Amazonian tribes? - such peoples usually come out around 50-60 - or roughly equivalent in general intelligence to an average 8-10 year old European. IQ therefore should at least be considered as an explanation for much lower complexity of language in such peoples. Does anyone know whether different average levels of average IQ actually has been considered as a potential factor influencing language complexity, by these authors?

The relationship between creativity and psychotic traits was established by Hans J Eysenck - the most cited pyschologist in the world - two or three decades ago. The evidence is summarized in his book Genius, 1995.

Sure I get bored - and it is after these times of boredom I sometimes get (what pass for) my best ideas.  
 
Creativity is linked to getting bored, at least for some people.  
 
e.g. the writer Alasdair Gray - http://en.wikipedia.org/wiki/Alasdair_Gray - once told me that he would sometimes find himself utterly bored by every book he tried to read - wandering around libraries or bookshops, picking up and putting down books in a desultory fashion; and they all seemed dull.  
 
That was when he knew he needed to write something for himself.

It's interesting that intellectuals keep 'discovering' that aspects of universal historic human behaviour are suddenly outrageously immoral. It happens again and again. Funny that... 
 
My guess is that the decline in 'corporal punishment' is mainly related to the fact that children are no longer required to work in the economy - so their behaviour matters less. 
 
My grandmother went into full time employment at age 13 (300 miles away from home, as a servant). Clearly, an education system (both home and school) designed to prepare people for that reality of c 1920 is likely to be much harsher than a modern one which prepares people for launching-out on their own in - what? - their mid-twenties?  
 
According to the anthroplogy of hunter gatherers that I have perused, they have even laxer discipline than moderns - presumably because natural selection has equipped humans with the instincts necessary to develop in an H-G environment without much need for 'education' or other types of behavioural shaping.

This makes an interesting suggestion - but I suspect that the effect of religion on health would have been swamped by other factors.  
 
And until not much more than 100-150 years ago (varying widely between countries), medicine did not exist as a unified profession or concept. In the UK Physicians were gentlemen with a university education (or equivalent) (physicians were almost pure theoreticians, who typically did not touch the patient, nor look at their problems - they would not ask people to undress - and would often practice by correspondence); while surgeons and apothecaries were craftsmen trained by apprenticeship; and midwifery (obstetrics) was a semi-skilled and self-certified activity based on local reputation.  
 
The professional status of surgery and obstetrics began to rise with the Hunter brothers John and William who became exceedingly rich and famous as a result of the science-based practice of (respectively) surgery and being a 'man-midwife'. 
 
Apothecaries mutated into modern style general/ family practitioners during the nineteenth century - and the separate branches were brought together via university and hospital based education - the relic of which can be seen in most UK medical degrees which have separately- named bachelors of medicine and surgery (e.g. BM BS, MB ChB etc - and in Dublin also obstetrics - BAO).  
 
Anyway, my point is that what we consider 'medicine' was - even in the past 200 years in the most advanced societies - practiced by an incredible diversity of people from family friends and neighbours through local 'wise women' or 'cunning men' up to local priests and aristocrats who sometimes used to practice medicine on their tenants as a hobby.  
 
In this sense our modern idea of 'medicine' did not exist as a distinct subject, just 'what people did when other people were sick' or something equally vague.

An alternative explanation would be Geoffrey Miller's idea that IQ is a general 'genetic fitness' indicator - so that the higher the IQ the better are a person's genes (on average); and the less likely more-intelligent people are to get almost any kind of disease (which is what has been found by the same Scottish group who did this work).

While clearly the differences between Irish and English average intelligence are not huge - the only study I have been able to find demonstrated that Irish intelligence is indeed the lowest in the British Isles: 
 
*** 
 
The social ecology of intelligence in the British Isles.Lynn, Richard 
British Journal of Social & Clinical Psychology. Vol 18(1), Feb 1979, 1-12. 
 
Data from 4 studies are presented to show that differences in mean population IQ exist in different regions of the British Isles. Mean population IQs are estimated for 13 subpopulations in the British Isles. Results show that mean population IQ was highest in London and southeast England and tended to drop with distance from this region. Mean population IQs were highly correlated with measures of intellectual achievement, per capita income, unemployment, infant mortality, and urbanization. Regional differences in mean population IQ appear to be due to historical differences dating back to 1751 and to selective migration from the provinces into the London area. (29 ref) (PsycINFO Database Record (c) 2008 APA, all rights reserved)

I think the best examples of this are in the public sector; where PS bureaucrats will always try to offer their product (health care, education, libraries and museums, festivals etc) free at point of use; thereby vastly inflating demand and allowing the PSBs to claims that they are giving the public what they want.  
 
In the UK the National Health Service is mostly free at point of use, and dreadful quality is therefore tolerated. E.g. I know a wealthy middle class health care professional who waited around 6 months for an MRI scan of their back, rather than pay about 300-500 dollars to get this done privately.  
 
This demonstrates the kind of irrational welfare-dependency which can be produced - even among the elite - by 60 years of state provision.  
 
Of course the opportunity costs of the 'free' NHS treatment (in terms of prolonged disability) were vastly more than 500 dollars - and this supports Agnostic's point that _free_ services are profoundly distorting and disorienting of incentives.

Steve Sailer has the right idea - the answer is not to mess about with quibbles over the statistical analysis of single studies, but to replicate. There is no substitute.

Razib said: "give me numbers" 
 
There are plenty of "numbers" suggesting that Western societies will start become more religious soon, as a result of differential reproduction and mass migration; but these numbers come mostly from demographics rather than psychology - such researchers as Eric Kauffman http://sneps.net/RD/religdem.html, David Coleman http://www.spsw.ox.ac.uk/staff/academic/profile/details/coleman.html and and the Second Demographic Transition people http://sdt.psc.isr.umich.edu/.  
 
It is not just theoretical: the reversal of secularism has already happened in Israel - e.g. http://www.foreignpolicy.com/story/cms.php?story_id=4956 
 
One could also factor in the research on the differential relation of IQ and religiousness, and the inverse relationship between IQ and fertility eg from Richard Lynn - http://www.rlynn.co.uk/ (including of course the heritability of IQ).  
 
As TGGP said above, there is need to control for the life history facts of religiousness - that religiousness is lowest among teenagers and young single adults, higher in middle age especially with children. http://www.firmstand.org/books/spiritualmarketplace.html  
 
Then there are assumptions about the political influence of different types of religion, of different degrees of devoutness, in setting a national agenda. The UK and European experience suggests that it may not be necessary to have a majority, nor even a large proportion, of Muslims for the religion to have a large influence upon national policy and social rules. 
 
By contrast, my impression is that atheists and agnostics seem to be individualists of low zeal and even less communitarian or altruistic tendency; including a tendency to accomodate to persistent dissent, or to move away from problems rather than stay and fight them; so that secularists seem to have much less political influence than would be expected from the numbers, or their high average intelligence and socio-economic position.

If the religious outbreed the secular - which they do; and if religiousness is correlated with heritable psychological traits - which it is; then society will get more religious.  
 
The only question is how quickly it will happen.  
 
However, in Western societies, these effects of differential reproduction among the established population will almost certainly be overwhelmed by mass immigration - and mass immigration is currently mostly of more-religious populations than the host societies (especially in Europe and the UK).  
 
So, Western society will be getting more religious, and pretty soon.

"Are there any serious scientific ... arguments against eugenics? " 
 
You have to define what you mean by 'eugenics'. You personally may be referring to the policy of state control over human reproduction (which hardly anyone favours); but politically-correct leftists also use 'eugenics' to refer to most of the things discussed on gnxp.com, even when these are purely scientific.

"TGGP... The political left had been around long before and showed no sign of going away. Why expect it to disappear?" 
 
Because the left had all-but 'achieved' what it set out to achieve in its host nations: equality of opportunity/ meritocracy based on ability, and the abolition of real poverty.  
 
(Actually this was achieved by science, technology and capitalism, not by socialism, but it happened anyway.) 
 
If the left had been honest, it would have wound itself up in - say - 1965. If...

This is covered in the early part of Richard Lynn's Dysgenics (1996), and the same story is found in Hans Eysenck's autobiography Rebel with a cause (1997).  
 
I have also seen the general late sixties counterculture versus science phenomenon using nazi smears documented in the history of psychiatry with respect to electroshock and other treatments (Shock therapy by Edward Shorter and David Healy, 2007).  
 
But the best account is perhaps in Wooldridge A. Measuring the mind: education and psychology in England, c.1860?c.1990. Cambridge, UK: Cambridge University Press; 1994. 
 
Wooldridge describes (for the UK) how the political left shifted from meritocracy towards egalitarianism (from equal opportunities to equal outcomes) in the post 1945 period, in the process rejecting then demonizing IQ testing (which had originally been a leftist project).  
 
So, the elite leftist socio-political intellectuals were already moving against eugenics from the 1940s (when Hamilton became aware of their disapproval), but this took a generation to percolate through to become a mass movement with the student radicals of the late 1960s.  
 
Until the late 1960s plenty of people (including top notch scientists) were working and speculating in eugenics unmolested; but from the late 1960s it became virtually impossible to work on eugenics (and very difficult to work on IQ, for analogous reasons).  
 
I wonder if, when future historians analyze the collapse of our civilization, this shift from meritocracy to egalitarianism on the political left in the leading modernizing societies may be seen as a major factor, or - at least - the final straw?  
 
It seems easily explicable in terms of the need to build electoral alliances by creating victim/ client groups to vote for leftist intellectuals.  
 
Yet without the shift from aiming at equal opportunities to to aiming at equal outcomes, a change underpinned by scientific lies, the political left would by now have disappeared.

kurt9 said: "[Eugenics] became unfashionable ... because of the excesses of the Nazis and their holocaust against the Jews." 
 
Interestingly this is untrue. The 'unfashionability' of eugenics was not due to Nazis but to left wing radicals.  
 
Eugenics was perfectly respectable for more than twenty years following World War Two - and included first rank biolgists such as Julian Huxley, Francis Crick and WD Hamilton.  
 
It was the late 1960s radical counterculture that decided to vilify eugenics by linking it to the Nazis. Very successful propaganda it was.  
 
Now everyone believes the lie.

It was only a few years ago when I was reading everywhere about the 'long tail' phenomenon whereby modern systems of production and marketing supposedly had no problem in catering for minority needs: 
 
http://en.wikipedia.org/wiki/The_Long_Tail

IQ and personality - specifically Conscientiousness - are the best validated psychological features predictive of educational, economic and social status success.  
 
But at present the main method for measuring personality is by self-rating questionnaires - and these can easily be faked; also different cultures seem to have different criteria for self-rating (international studies of personality are a near-random mess IMHO).  
 
So, because it is more reliably and validly measured, IQ works much better than personality as a predictor cross-culturally at present.  
 
But (so far as I am aware) between-culture IQ measures seems to work just as well as within-culture IQ measures as a predictor.  
 
So the above speculations about culturally-determined test-taking attitudes are probably of little significance, or may be irrelevant, to the predictive value of IQ measurements under normal conditions.

I am very familiar with this kind of snide, snippy, sophomoric meta-analysis by generic number-crunchers because it emerged in medical science in the early 1990s, and is now mass-produced.  
 
Medical meta-analysis is currently a research factory assembly-line activity built on extremely dubious assumptions and done as a profession (mostly government-funded in the UK).  
 
In practice medical meta-analysis is corrupt and anti-scientific, because its underlying motivations and aims are neither scientific nor medical - they are political or managerial.  
 
If you look at the discussion section of this papaer you can see the problem. In its effect, the thousands of words of methodology and stats are used only to generate clouds of smoke and obscure the obvious. The message of the paper has been spun in the opposite direction of their findings.  
 
That's mainstream meta-analysis for you: minute but fundamentally-arbitrary methodological accuracy trumps basic scientific honesty.

Lynn is a Kuhnian 'revolutionary scientist' - trailblazing and generating a new new field, a new hypothesis.  
 
Wicherts et al are coming along behind and doing 'normal science' - i.e. testing a hypotheses derived from from revolutionary science using standard methods and techniques, and applying greater resources.  
 
However, Wicherts at al seem to lose track of the fact that all scientific 'testing' is of hypotheses, not of measurements. Hypotheses make predictions, they are tested by observing (and measuring) whether these predictions are fulfilled. The relevance of observed measurements comes from this hypothesis-testing aim.  
 
In their paper, Wicherts et al replicate the hypothesis of Lynn - their results are consistent-with Lynn's hypothesis. That is the primary finding, and this fact should be more clearly emphasized.  
 
Secondarily, Whicherts et al also produce different measurements than Lynn, and this is interesting and useful and we can hope for further clarifying studies to provide further evidence.  
 
But specific measurements can only be interpreted in the light of hypotheses; in other words the significance of IQ measurements comes from the hypotheses the predictions of which these measurements are being used to test.  
 
A hypothesis can only be evaluated and rejected in comparison with an alternative hypothesis which is more powerful. Lynn's hypotheses seem to have withstood this particular test, and I don't see any other comparably explanatory and tested rival hypotheses that are being put forward here - or am I missing something?