Archives for posts with tag: inbreeding and iq

‘Tree of life’ for 2.3 million species released“A first draft of the ‘tree of life’ for the roughly 2.3 million named species of animals, plants, fungi and microbes — from platypuses to puffballs — has been released. A collaborative effort among eleven institutions, the tree depicts the relationships among living things as they diverged from one another over time, tracing back to the beginning of life on Earth more than 3.5 billion years ago. Tens of thousands of smaller trees have been published over the years for select branches of the tree of life — some containing upwards of 100,000 species — but this is the first time those results have been combined into a single tree that encompasses all of life.”

Taste Mutation Helps Monkeys Enjoy Human Food – nice example of recent and local evolution.

SNP hits on cognitive ability from 300k individuals – from steve hsu.

General Cognitive Ability Is Almost Perfectly Stable from Early Adulthood to Late Middle Age“[I]ndividual differences in general intelligence that exist at age 18 are almost perfectly preserved to age 60, after which this stability starts to slowly break down.” – @ human varieties.

Genome-wide autozygosity is associated with lower general cognitive ability“We found that increased levels of autozygosity predicted lower general cognitive ability, and estimate a drop of 0.6 s.d. among the offspring of first cousins (P=0.003–0.02 depending on the model). This effect came predominantly from long and rare autozygous tracts, which theory predicts as more likely to be deleterious than short and common tracts.” – discuss. (~_^)

Study Reports Rare Genetic Mutations Responsible for Almost Half of Autism Cases“Quantitative study identifies 239 genes whose ‘vulnerability’ to devastating de novo mutation makes them priority research targets.”

Genetic transmission of reading ability – h/t to the siberian fox! who tweeted: “Heritability of reading ability is 62%. Previous estimates lower because of assortive mating (r=.38).”

Clannishness – the Series: Zigzag Lightning in the Brain – from jayman. see also: a few thoughts. from me! (^_^)

Inequality among 32 London Boroughs: An S factor analysis and The general religious factor among Muslims: a multi-level factor analysis – from emil kirkegaard.

It’s official: The Maltese are the fattest in all of the European Union“Despite Malta’s weighty problem, the Maltese have a less than average prevalence of premature mortality from cardiovascular diseases, cancer, diabetes and chronic respiratory disease.” – h/t staffan!

Support for linguistic macrofamilies from weighted sequence alignment“This article reports findings regarding the automatic classification of Eurasian languages using techniques from computational biology (such as sequence alignment, phylogenetic inference, and bootstrapping). Main results are that there is solid support for the hypothetical linguistic macrofamilies Eurasiatic and Austro-Tai.”

Our Mental Noise Grows More Intense As We Age, So Our Brains Lose Processing Speed Over Time

Ancient hominid ears were tuned to high frequencies“A. africanus and P. robustus could have heard high-frequency consonants associated with the letters t, k, f and s better than either chimps or present-day people do, the team found.”

Extreme Altruism – The Case of the Pathological Do-Gooder – from helian.

Personal values and intergroup outcomes of concern for group honor – h/t andrew sabisky! who tweeted: “group honour culture = more empathy, lower openness, more endorsement of violence towards Americans.”

Scope Insensitivity in Helping Decisions: Is It a Matter of Culture and Values? – h/t robin hanson! who tweeted: “Contrast to westerners, collectivist Bedouin NOT more willing to help one concrete victim than a group of victims.”

Indigenous Belief in a Just World: New Zealand Māori and other Ethnicities Compared“Māori have more ‘leftist’ beliefs than non-Māori (i.e., nearly 60% of Māori blame an unfair society compared to 41% of non-Māori).”

Tiny mitochondria play outsized role in human evolution and disease

An architecture for encoding sentence meaning in left mid-superior temporal cortex – h/t steve pinker! who tweeted: “The most important paper in cognitive neuroscience in many years: How does the brain represent who did what to whom?”

Sex differences and stress across the lifespan – h/t kevin mitchell!

Does the Welfare State Destroy the Family? Evidence from OECD Member Countries“[A]n expansion in the welfare state increases the fertility, marriage, and divorce rates with a quantitatively stronger effect on the marriage rate. We conclude that the welfare state supports family formation in the aggregate. Further, we find that the welfare state decouples marriage and fertility, and therefore, alters the organization of the average family.”

What is a standard deviation? A definition. – from pumpkin person.

Data analysis yields striking maps of human expansion in North American Holocene“[A] group of paleoclimatologists and anthropologists analyzed data recorded in the Canadian Archaeological Radiocarbon Database (CARD), which aggregates 35,905 radiocarbon samples from archaeological sites across the North American continent, and was created by Dr. Richard Morlan of the Canadian Museum of History. By applying a kernel density estimation method to the data, the researchers produced the first maps of temporally distinct paleo-demographic trends that correspond well to existing evidence of human expansion across North America in the Holocene.”

Scientists Discover 9,000-Year-Old Case of Decapitation in the Americas

Remains of 6,000-year-old first settlers [in ireland] found

Archaeological breakthrough could solve the mystery of Greenland’s Vikings

Regional microbial signatures positively correlate with differential wine phenotypes: evidence for a microbial aspect to terroir

bonus: Growing a penis at 12: the ‘Guevedoce’ boys of the Dominican Republic – (O.O) – h/t @don_arete!

and the tweet of the week! (~_^) :

(note: comments do not require an email. 5-alpha-reductase deficiency.)


via dienekes via jayman:

Genome-wide estimates of inbreeding in unrelated individuals and their association with cognitive ability


“Research on consanguineous marriages, and other forms of inbreeding, has long shown a reduction in cognitive abilities in the offspring of such unions. The presumed mechanism is that detrimental recessive mutations are more likely to be identical by descent in the offspring of such unions and so have a greater chance of being expressed. To date, research on the relationship between inbreeding and cognitive ability has largely been restricted to recent inbreeding events as determined by pedigree…. It has been suggested that intellectual disability is under negative selection, and that recent deleterious mutations have an important role in the underlying aetiology. The wealth of molecular genetic data currently available allows estimates of inbreeding on a genome-wide level and to examine the effects of long-term ancestral levels of inbreeding. Such an association with inbreeding, as measured by runs of homozygous polymorphisms (ROH), has previously been identified with several behavioural traits, such as schizophreniz, Parkinson’s disease and personality measures, as well as non-behavioural traits such as height.

“The relationship between inbreeding on a population level and cognitive ability is particularly interesting due to assortative mating, non-random mating, which is greater for cognitive ability than for other behavioural traits, as well as physical traits such as height and weight. Positive assortative mating has been reported for cognitive ability, particularly for verbal traits, with spousal correlations generally around 0.5. Assortative mating should lead to greater genetic similarity between mates at causal loci for cognitive ability and to a lesser extent across the genome, which in turn reduces heterozygosity at these local. In other words, in contrast to the genome-wide reduction of heterozygosity caused by inbreeding, the reduction of heterozygosity due to assortative mating for a trait is limited to loci associated with the trait…. Another difference between inbreeding and assortative mating is that the effects of inbreeding are expected to be negative, lowering cognitive ability, whereas the effects of assortative mating affect the high, as well as the low end of the ability distribution, thus increasing genetic bariance, that is, when high-ability parents mate assortatively, their children are more likely to be homozygous for variants for high ability, just as offspring of low-ability parents are more likely to be homozygous for variants for low ability….



“The Twins Early Development Study (TEDS) recruited over 11 000 families of twins born within England and Wales between 1994 and 1996…. In this analysis, individuals were excluded if they reported severe current medical problems, as well as children who had suffered severe problems at birth or whose mothers had suffered severe problems during pregnancy. Twins whose zygosity was unknown or uncertain or whose first language was not English were also excluded. Finally, analysis was restricted to twins whose parents reported their ethnicity as ‘white’….

“Cognitive measures

“Verbal and non-verbal tests were administered using web-based testing. The verbal tests consisted the Similarities subtest and the Vocabulary subtests from the Wechsler Intelligence Scale for children (WISC-III-UK). The non-verbal tests were the Picture Completion subtest from the WISC-III-UK and Conceptual Grouping from the McCarthy Scales of Children’s Abilities. A general score was derived from the test battery as the standardized sum of the standardized subtest scores, which correlates 0.99 with a score derived as the first principle component of the test battery score.

“Runs of homozygosity

“FROH was defined as the percentage of an individual’s genome consisted of runs of homozygosity (ROH)…. [O]nly ROH with a minimum of 65 consecutive SNPs covering 2.3Mb were used when calculating the total proportion of the genome covered by ROH. In addition, the required minimum density in a ROH was set at 200kb per SNP, and the maximum gap between two consecutive homozygous SNPs was set at 500kb….


“Table 1 includes descriptive statistics for FROH and the three measures of cognitive ability (general, verbal, and non-verbal). FROH is slightly positively skewed, as it represents the total percentage of the genome that includes runs of homozygosity (ROH). The average percentage of genome covered by ROH was 0.7% (95% CI 0.65-0.72%). Verbal and non-verbal abilities correlate 0.49; because general cognitive ability is the sum of the standardized verbal and non-verbal subtests, they correlate much more highly with general ability (0.87 and 0.86, respectively).

inbreeding and iq - table 01

“Table 2 presents the results of the linear regression analyses. No significant regression was found between FROH and the cognitive measures after correction for multiple testing, although the association with non-verbal cognitive ability was nominally significant (P=0.03). Although this association was not statistically significant, it is noteworthy that every regression in Table 2 is *positive*, indicating that increased homozygosity tends to be associated with *higher* cognitive scores across different measures of cognitive ability (general, verbal and non-verbal).

inbreeding and iq - table 02

“Our analysis identified 87 loci where ROH overlapped in 10 or more individuals. For these overlapping regions we tested for association with each of the cognitive measures and again showed no significant associations after correction for multiple testing (P-values of less than 5.7 x 10-4). A sign test of the direction of effect across all ROH showed a disproportionately large number of *positive* associations, indicating that ROH are associated with higher cognitive ability (P=0.002). The sign test was non-significant for verbal ability but highly significant for non-verbal ability (P<10-6). The sign test for non-verbal ability alone remained significant after correcting for an individual’s genome-wide FROH score (P<10-6).

“As explained earlier, positive assortative mating can also lead to genome-wide homozygosity for trait-specific loci, and, unlike inbreeding, assortative mating can affect the high as well as the low end of the ability distribution. One possible explanation for the trend suggesting a positive correlation between homozygosity and cognitive scores in our data is that positive assortative mating on intelligence might be greater for high cognitive ability individuals….


“Our results show that within a representative UK population sample there was a weak nominally significant association between burden of autosomal runs of homozygosity and higher non-verbal cognitive ability. This nominal association with *increased* cognitive ability is counterintuitive when compared with the results from more extreme inbreeding based on pedigree information. A potential explanation for this direction of effect is that individuals with higher cognitive ability might show greater positive assortative mating, which would lead to increased homozygosity at loci for higher cognitive ability in their offspring. However, in a separate sample we showed that greater positive assortative mating was not associated with higher cognitive ability. While these findings seem to provide clear evidence against this hypothesis, it is possible that the genome-wide genetic finding reflect historical mating habits that no longer exist today. It should also be noted that there was a reduction in the standard deviations for spousal correlations in the increased cognitive ability groups by an average of 6% compared with the decreased cognitive ability group (see Table 3), which could reflect less genetic variability in the high ability couples or a ceiling effect on the cognitive tests. This lesser phenotypic variability at the high ability end would have a small effect in reducing the spouse correlations and potentially confound our analysis….

“Overall, these results highlight the importance of understanding mating habits, such as inbreeding and assortative mating, when investigating the genetic architecture of complex traits such as cognitive ability. The results certainly suggest that there is no large effect of FROH on reduced cognitive ability, the expected direction of effect. The nominally significant associations found in this study may even suggest that in the case of non-verbal cognitive ability, beneficial associations with homozygosity at specific loci might outweigh the negative effects of genome-wide inbreeding and that the relationship between inbreeding and cognitive ability may be more complicated than previously thought.

so, although obviously Further Research is RequiredTM, these researchers have concluded that both the absence of reduced cognitive ability and the slight increase in cognitive ability which they found in individuals who had runs of homozygosity (roh) in their genomes (evidence of matings between genetically similar individuals) were probably NOT due to assortative mating (i.e. smart people mating with smart people).

furthermore, they suggest that the inbreeding-causes-reduced-cognitive-ability meme is incorrect — or at least that the situation is more complicated than the idea that it’s the accumulation of recent deleterious mutations which haven’t been selected away that is the (whole) problem. in fact, a little inbreeding seems to have a positive effect on some cognitive abilities!

i’ve suggested a couple of times one way in which inbreeding might result in a low average iq in a population, and that is if the inbreeding leads to clannish, altruistic behaviors between extended family members which then result in the deleterious mutations NOT being weeded out.

one real world example i’ve offered is how life works in egyptian villages and how the more successful and affluent (and, presumably, more intelligent) members of a clan are obliged to help out their less successful and poorer (and, presumably, less intelligent) clan members. so, apart from mentally retarded individuals not reproducing, where is the negative selection for deleterious mutations here? there is none. or it’s a lot weaker than in more individualistic societies (like gregory clarks’ medieval england) where it’s more every man for himself — in clannish societies, deleterious mutations might be able to hang around for a long time, riding on the coattails of those with fewer deleterious mutations.

(note: comments do not require an email. i’m my own grandpa! [no, I’M not! it’s just the song.])

who knows?

but italy could be another place to look for a possible rapid inbreeding drop-off/rapid iq increase connection (see yesterday’s post) just ’cause the consang data are available. and they did, indeed, have a pretty rapid decrease in cousin marriage rates — at least in northern italy — not so much in the south. (i can’t think of any other examples where consang data are readily available — i mean without delving into church records or something like that.)

no idea if there are any early iq data available for italy, though. i won’t be looking for them (iq questions? – meh) — just wanted to let anyone who might be interested know that the numbers for the drop in inbreeding do exist for italy. (^_^)

look for the consang data here: Consanguinity, Inbreeding and Genetic Drift in Italy (tables also available here).

i put together a table of the first and last lustra in cavalli-sforza’s data set for a previous post, but there are data for each lustrum in between, too. you can get an idea of the scale of the drop-off (in the regions where there was a drop-off) from my nifty table:

1st cousin marriages - cavalli-sforza

previously: japan – reversal of fortune?

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a couple of months ago, greg cochran wrote about how a population (any given population) might raise its average iq quickly — like over two or three generations. one possible method, he suggested, was to quit inbreeding. here’s what he said:

“I’ve been thinking, off and on, about sudden changes in the cognitive abilities of populations: groups low suddenly scoring much higher or lower on a time scale too short to be explained by selection: say, three generations or less…. I can think of two perfectly feasible strategies that *would* cause significant one-generation increases in intelligence, in certain populations. Iodine supplementation, in places where it’s short, has a big payoff…. The other practical, low-tech strategy would be stopping cousin marriage. The next generation would be in much better shape, since the children of first cousins take a substantial IQ hit – maybe six points or so.

i think i may have stumbled across an example of a population rapidly dropping cousin marriage and, also very rapidly, gaining iq points.


yesterday, i was working on a completely different post about japan and cousin marriage, when i rediscovered this [pg. 30] (click on chart for LARGER version):

japan consanguinity rates - decline

that’s the decline in the average national consanguinity rates in japan from 1947 to the early-1980s. but the consang rates were even higher in the 1910s-1920s at 22.4% [pg. 29] (and who knows how high the rates might’ve been even further back?), so the chart above should look something more like this (pardon my crayola — and note that i just eyeballed it — click on chart for LARGER version):

japan consanguinity rates - decline - crayola 02

when i rediscovered this yesterday, i remembered what greg had written, and got to wondering if there were any historic data for japanese iqs and if there’d been any changes in those iqs over time. so i googled (as one does) … and found this:

The Rise of National Intelligence: Evidence from Britain, Japan and the U.S.A. [pdf] – lynn and hampson.

from that article [pgs. 27-31]:

“It has been possible to find five studies providing evidence on the secular trend of intelligence in Japan for the post World War II period….

“(1) Ushijima’s study (1961)….

“Here the Ushijima intelligence test was administered to 1365 children in 1953 and to a comparable sample of 1370 children in 1960 with the objective of determining any change in the mean over this relatively short period. The children were aged 9-15 years.

“(i) All age groups show a rise in scores for all abilities. The overall mean increase was 0.66 standard deviations, the equivalent of 9.9 IQ points, and representing an IQ gain of 14.1 IQ points per decade. This is of course a very considerable increase and much greater than anything found in either Britain or the U.S.A.

“(ii) The IQ increases are in general greater among the younger age groups than among the older….”

see my crayola chart above. kids who were fifteen in 1953 would’ve been born way back in 1938 when the consang rates were above 15% — maybe 17 or 18% (remember, i just eyeballed it, so this is a complete guess really) — while kids who were nine in 1953 would’ve been born in 1944 when consang rates were hovering right around 15%, in other words lower. same for the later cohort from 1960: fifteen year olds would’ve been born in 1945, nine years old in 1951. the younger the kids in the cohorts, the less chances their parents were related.

more from the article…

“(2) Kaneko’s study (1970)….

“Kaneko’s invetigation of a possible rise in the scores on this test was carried out in 1963….

“Hence the mean IQ in these schools has risen 10.38 IQ points over the 9-yr period … represents an IQ gain of 11.4 IQ points per decade. This figure is evidently broadly similar to the rise of 14.1 IQ points per decade for 1953-1960 found by Ushijima and confirms a very considerable rate of IQ gain in Japan in these early post World War II years.

“(3) Sano’s study (1974)….

“It will be seen that in all samples there were considerable increases in mean IQ from 1954 to 1972. The increases appear to be a little greater among the city children than among those from the prefrecture. When the results for 10- and 11-yr olds are combined, city children gained 18.04 IQ points and prefrecture children 15.07 IQ points….”

that the city children had greater gains than the rural kids is not surprising if inbreeding is the factor making the difference here. even up to the 1980s, consanguinity rates have been quite a bit lower in urban areas in japan as compared to rural areas (see table in this post for example). (more on this soon in that upcoming post on japan.)

“The average of the two gains is 16.56 IQ points, representing a gain of approx. 9.15 IQ points per decade for the entire sample.

“Sano also considered the question of whether the IQ gains in Japan have been increasing at a constant rate. For this he used Kaneko’s 1964 data which were available for two of the schools. He calculated that the increase in mean IQ was 10.47 points for 1954-1963 and 3.42 for 1963-1972…. ([I]t will also be noted that the gain of 10.47 IQ points for 1954-1963 is closely similar to Kaneko’s figure of 10.38 for the same period.)

“It is apparent therefore that there was a considerable deceleration in the rate of increase in intelligence over the period 1954-1972….”

again, see my crayola chart. the decline in cousin marriage rates is much sharper in the decades preceding 1954 than during those preceding 1963. in other words, there was a deceleration in the reduction of cousin marriages over time, so perhaps we shouldn’t be surprised at a deceleration in the increases in iq over time.

“(4) Wechsler studies….

“Thus after making these adjustments we have Japanese mean IQs of 101.9 for 1951 and 107.4 for 1975. Hence over this 24-yr period (1951-1975) the Japanese mean IQ increased by 5.5 IQ points relative to the American IQ…. This represents a Japanese IQ gain of 5.75 IQ points per decade. This rate of increase for the period of 1951-1975 is somewhat less than Sano’s result of a 9.15 IQ point per decade increase over approximately the same period (1954-1972)….

“A second Japanese study using the WISC and WISC-R is also available (Anon, 1981)…. This gives a rise of 20.03 IQ points over the 24-yr period, making 8.34 IQ points per decade….”

lynn and hampson conclude:

“The conclusion of the Japanese studies is as follows. Two studies of the early post World War II period show substantial IQ gains of 9.9 and 11.4 IQ points per decade. Three studies of a longer period from approx. 1950-1975 show lower IQ gains of 9.1, 8.3 and 5.7 IQ points per decade, giving an average gain of 7.7 IQ points per decade. Since the early part of this period was characterized by a greater rate of gain, it appears that since around 1960 the IQ gains in Japan have decelerated to approx. 5 IQ points per decade….

“It is not particularly surprising that the Japanese gains should have been the greatest of the three countries. Japan was a relatively underdeveloped country in the 1930s with a per capita income about one eighth of that of the U.S.A.”

but the country was probably relatively underdeveloped because the japanese had a lower average iq at the time, and it’s since increased phenomenally … due to the sharp and rapid decline in inbreeding in japan? and so has their economic success obviously.

i’d be curious to know two things:

– why did the japanese quit marrying their cousins? was there some official policy out there discouraging it — as part of their general modernization, “be more like the westerners” move? did the people just naturally adopt it as part of that westernization package? was it connected to christianity in japan? (japanese catholics historically had lower first cousin marriage rates than other religious groups — i’ll get to this in my upcoming post on japanese cousin marriage — the one that i was working on yesterday!). was it related to industrialization and urbanization? all of the above? none of the above?

– has something similar happened in china and/or korea (or elsewhere for that matter — i mean in modern times)? the cousin marriage rates for china are reportedly very low — today — but i’m pretty sure they were much higher in the past — even the recent past (see mating patterns in asia series below ↓ in the left-hand column), but i don’t have as good data for china as what i’ve presented here for japan. but inquiring minds want to know!

see also: Reversal of Fortune

previously: historic mating patterns in japan

(note: comments do not require an email. cool japanese people!)

today, some classics (and soon-to-be classics?):

Latitude, elevation and the tempo of molecular evolution in mammals“[B]ecause climatic variables change with latitude and elevation in a similar manner, our results suggest that climate has influenced the tempo of genetic change in mammals…. These findings provide new insights into microevolution that are likely to have important implications for understanding global patterns of biodiversity and diversification.”

An Asian perspective on early human dispersal from Africa“Asia might not have been the passive recipient of whatever migrated out of Africa but might have been a major donor to speciation events, as well as dispersals back into Africa. Such two-way traffic is well documented for other mammals in the Pliocene and Early Pleistocene, such as Equus and bovids, with more taxa migrating into than out of Africa. There is no reason why hominin migrations were always from Africa into Asia, and movements in the opposite direction might also have occurred, as has been suggested for the Olduvai OH9 (refs 13, 58) and Daka specimens. We should even allow for the possibility that H. ergaster originated in Asia and perhaps explain its lack of an obvious east African ancestry as the result of immigration rather than a short (and undocumented) process of anagenetic (in situ) evolution (Dennell and Roebroeks 2005:1100-1101).” – see also: Did Early Humans First Arise in Asia, Not Africa?

Recent acceleration of human adaptive evolution“It is sometimes claimed that the pace of human evolution should have slowed as cultural adaptation supplanted genetic adaptation…. Cultural changes have reduced mortality rates, but variance in reproduction has continued to fuel genetic change. In our view, the rapid cultural evolution during the Late Pleistocene created vastly more opportunities for further genetic change, not fewer, as new avenues emerged for communication, social interactions, and creativity.” – hawks, wang, cochran, harpending & moyzis.

Innate Social Aptitudes of Man: An Approach from Evolutionary Genetics [opens pdf] – w.d. hamilton.

How obedience of marriage rules may counteract genetic drift“Continuous unilateral or bilateral cross-cousin mating, reflecting the most common form of prescribed marriage, increases homozygosity but at the same time slows down considerably the loss of gene diversity due to genetic drift.”

It’s All Relative: Race as partly inbred extended family – from steve sailer.

Human genetic diversity: Lewontin’s fallacy [opens pdf] – “In popular articles that play down the genetical differences among human populations, it is often stated that about 85% of the total genetical variation is due to individual differences within populations and only 15% to differences between populations or ethnic groups. … This conclusion, due to R.C. Lewontin in 1972, is unwarranted because the argument ignores the fact that most of the information that distinguishes populations is hidden in the correlation structure of the data and not simply in the variation of the individual factors.”

Discerning the Ancestry of European Americans in Genetic Association Studies“Here we mine much larger datasets (more markers and more samples) to identify a panel of 300 highly ancestry-informative markers which accurately distinguish not just northwest and southeast European, but also Ashkenazi Jewish ancestry.”

Genes predict village of origin in rural Europe“After excluding close kin and inbreeding, village of origin could still be predicted correctly on the basis of genetic data for 89–100% of individuals.”

E Pluribus Unum: Diversity and Community in the Twenty-first Century [opens pdf] – “New evidence from the US suggests that in ethnically diverse neighbourhoods residents of all races tend to ‘hunker down’. Trust (even of one’s own race) is lower, altruism and community cooperation rarer, friends fewer.” – robert putnam.

The Misguided Advocates of Open Borders“Rising diversity within human societies tends to drive people apart, causing them to take sanctuary in individual pursuits and ethnic communities. The practical consequences are reduced public altruism or social capital, evident in falling volunteerism, government welfare for the aged and sick, public health care and a general loss of trust. Ethnic diversity is second only to lack of democracy in predicting civil war. Globally it correlates negatively with governmental efficiency and prosperity.” – frank salter.

Why g Matters: The Complexity of Everyday Life [opens pdf] – linda gottfredson.

State IQ estimates (2009) – from the awesome epigone.

Inbreeding depression and IQ in a study of 72 countries [opens pdf]. see also Consanguinity and national IQ scores.

American Murder Mystery“Why is crime rising in so many American cities? The answer implicates one of the most celebrated antipoverty programs of recent decades.” – h/t anonymous.

bonus: Ethnic differences: Variation in human testis Size – jared diamond.

bonus bonus: Late Middle Eocene primate from Myanmar and the initial anthropoid colonization of Africa

(note: comments do not require an email. boobies!)

jayman said: “M.G., I noticed that your map [of consanguinity rates in twentieth century italy] correlates very well with my map of IQs in Italy here, right down to the large difference between Friuli and Sicily.”

yes, they do correlate well. here is jayman’s map of iqs in europe (click on images for LARGER view):

and, for good measure, here is the reluctant apostate’s map of pisa scores in italy (pisa scores being a good proxy for iq scores):

and here is m.g.’s map of the average consanguinity rates (first-cousin marriage rates) for italy from 1930-1964:

so, yeah — in general, higher consanguinity rates in southern italy + lower iq/pisa scores. meanwhile, lower consanguinity rates in northern italy + higher iq/pisa scores. coincidence? maybe. but, you know, inbreeding depression and lower iqs….

jayman also said: “I wonder what would happen if we made a map of historical consanguinity for Europe as a whole.”

yes, please! or how about … the WHOLE WORLD! that’s what i’m asking santa for christmas this year, anyway — historical consanguinity data for all human societies. (just drop it in my stocking, santa. doesn’t need to be wrapped or anything! i’ve been a really good girl this year — i promise! (~_^) )

the data for consanguinity rates in italy came from cavalli-sforza and co. they collected dispensation records from the catholic church in italy, i.e. permissions granted by the church to cousin couples that wished to marry. cavalli-sforza, et. al., published data going back to 1910 — but they collected data as far back as 1780, but that hasn’t been published as far as i know. (d*mn!)

theoretically, there should be such data for all catholic countries in europe (and elsewhere?) going back — i dunno — for as long as they’ve been keeping records. there seems to be some civil records from the medieval period for parts of italy, too. the protestant nations are trickier since in many it has been ok to marry a cousin, so there are no dispensation records. (d*mn!) some protestant nations did have some anti-cousin marriage laws, though, and also kept really good records — like the efficient swedes. the eastern orthodox church? i don’t really know, but my impression is (after reading about mating patterns in greece) that there aren’t much of any records there, but i could be wrong. i really don’t know.

for anyone who’s curious about mating patterns in europe, you might want to skim through my Inbreeding in Europe series of posts (see links in left-hand column down below ↓). i’ve got some data posted here and there for some countries. there’s also my big timeline of european mating patterns, but that’s (*ahem*) very much a “work in progress.”

footnote: note that there are objections to richard lynn’s iq data as well as to using pisa scores as a proxy for iq scores. see the discussions in this comments thread as well as this one, and italianthro’s blog in general.

(note: comments do not require an email. friûl lībar!)

so, here are regional italian iq scores from lynn based on 2006 pisa scores against the averages of mean inbreeding coefficients for the same regions from 1960-64 (cavalli-sforza, et. al.). correlation is not causation, but i get a negative correlation of 0.85 (-0.85) which is pretty d*mn high.

i know, i know — i’m not comparing the exact same cohorts. but, if you think about it, the comparison is actually between parents and their children. the children are the kids who took the pisa tests in 2006 at age 15 (born in 1991) — and their parents are prolly the children of people who got married in the early 1960s. more-or-less. 1960-64 to 1991 is more like a generation-and-a-half than two generations, but it’s close. and we know that intelligence is in the genes, and we’re talking about families here, so….

like spain, higher iq scores are found to the north in italy, while the farther south you go, the farther south the test scores go. lynn suggests a couple of possible explanations for the differences including latitude and the presence of different populations (both in italy and spain in the medieval period you had germanic peoples settling the northern regions and muslims from north africa and beyond settling in the south). he doesn’t seem to have considered the different degrees of inbreeding between north and south (and possible inbreeding depression) as a potential cause. i’m not saying it’s the only reason behind the different iq scores, but it certainly could be a factor. btw — it was prolly the muslims who introduced strong inbreeding in southern italy as they did in southern spain.

here’s a map of the regions:

here are the data:

and, here are the numbers i used (from cavalli-sforza, et. al.) to get averages of the mean inbreeding coefficients for each region (the averages that i calculated are in bold):

previously: inbreeding in italy and increases in inbreeding in italy after the wars(?) and northern vs. southern spanish iq, redux

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