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Inbreeding depression and IQ in a study of 72 countries
Abstract
In this ecological study, a robust negative correlation of r = - .62 (P < .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 < .01); education index (r = - .40, P < .01); and democracy index (r = - .42, P < .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 > .05) whereas GDP per capita had the highest (β = .35, P > .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.
... Wicherts et al. (2010a) and Borsboom & Dolan (2006) heavily criticized Kanazawa's hypothesis; for reasons they give in detail, we seriously question the ability of linear distance from sub-Saharan Africa to measure evolutionary novelty, undermining the foundation of Kanazawa's hypothesis. Saadat (2008) and Woodley (2009) suggested that inbreeding depression and associated reduced phenotypic quality is a cause of the variation in cognitive ability across the world. They found cross-national correlations of r ¼ 20.77 (n ¼ 35, p , 0.0001) and r ¼ 20.62 (n ¼ 71, p , 0.01), respectively, between average IQ and measures of inbreeding. ...
... They found cross-national correlations of r ¼ 20.77 (n ¼ 35, p , 0.0001) and r ¼ 20.62 (n ¼ 71, p , 0.01), respectively, between average IQ and measures of inbreeding. Woodley (2009), however, noted that rates of consanguineous marriage itself may not account for the magnitude of this variation because (i) the statistical significance of the effect disappears when education and gross domestic product (GDP) are controlled for, and (ii) the effect of inbreeding on intelligence had previously been shown to be relatively small. ...
... Percentage consanguineous marriages was not used in this study because it was the conclusion of Woodley (2009) that this variable is unlikely to account for the worldwide variation in intelligence. Additionally, consanguineous marriage and associated inbreeding may be a strategy for maintaining coadapted gene complexes that defend against local infectious diseases (Denic & Nicholls 2007;Fincher & Thornhill 2008). ...
In this study, we hypothesize that the worldwide distribution of cognitive ability is determined in part by variation in the intensity of infectious diseases. From an energetics standpoint, a developing human will have difficulty building a brain and fighting off infectious diseases at the same time, as both are very metabolically costly tasks. Using three measures of average national intelligence quotient (IQ), we found that the zero-order correlation between average IQ and parasite stress ranges from r ¼ 20.76 to r ¼ 20.82 (p , 0.0001). These correlations are robust worldwide, as well as within five of six world regions. Infectious disease remains the most powerful predictor of average national IQ when temperature, distance from Africa, gross domestic product per capita and several measures of education are controlled for. These findings suggest that the Flynn effect may be caused in part by the decrease in the intensity of infectious diseases as nations develop.
... In Woodley (2009) an analysis was performed in which the ecological relationship between national IQ and the percentage of cousin marriages (consanguinity) was investigated. Bivariate correlations revealed a strong association between the two measures (r = −.61; ...
... In Woodley (2009) log-transformation was employed, however an analysis of skewness in SPSS revealed that this was generally inappropriate as all but one of the variables exhibited insufficient skewness to warrant this (skewness statistic between 1 and − 1). Only education exhibited a marginal skewness (− 1.6), log transformation reduced the skewness (− .34), ...
... Furthermore none of the assumptions of multiple regression actually require log transformation (Allison, 1998, p. 130). The re-analysis (using non-log transformed variables) indicates that the basic pattern of results reported in Woodley (2009) remains unchanged, and that the consanguinity variable is still a non-significant predictor of national IQ once other controlling variables are taken into consideration. This means that the basic conclusion of Woodley (2009)ergo that whilst the bivariate relationship between consanguinity and national IQ is robust, it is of minimal relevance as a predictor of national IQ, remains intact. ...
... Eysenck believes that intelligence type C or measured intelligence has three elements: mental speed, persistence and the ability to recognize mistakes in solutions of a problem. The results of a study by Bashee (1977), as quoted by Woodley (2009) , indicate that the extent to which consanguineous marriages affect IQ depends on the degree of kinship. Based on three cognitive ability tests, he found out that, on average, children of double-first cousins or bilateral relatives by blood up to the third degree of kinship score lower on intelligence compared with children of first cousins or third-degree marriages who, in turn, score lower on intelligence compared with children of non-consanguineous marriages. ...
... Also, Jensen declared that the majority of individuals with an IQ below 70 are children of consanguineous marriages. Buck (1957), as quoted by Woodley (2009), showed that mental retardation in children of third-degree consanguineous marriages is three times more frequent that in children of non-consanguineous marriages among Swedish families. Morton's study (1978) indicated that mental retardation in children of consanguineous marriages is five times more frequent than in normal marriages. ...
Introduction: The present research aims to study and compare intelligence in offspring of consanguineous and non-consanguineous marriages and the relation with Holland personality types.
Method: This is a descriptive study of ex-post facto design. The statistical population was consisted of all students of Tehran province in the school year of 2010-11. The sample size was 1221 individuals, 628 of whom were of consanguineous marriages and 593 were of non-consanguineous marriages. To collect the data in this research Raven and Holland test has been used.
Findings: Results of the t-test indicated that there is no significant difference between intelligence in offspring of consanguineous marriages and that of non-consanguineous marriages. However descriptive data indicated that the average IQ among offspring of consanguineous marriages is one unit lower that of non-consanguineous marriages. Also the results of variance analysis revealed that the difference between the intelligence of different personality types is significant. Tukey’s post hoc test indicated that individuals with investigative personality type have higher intelligence compared to those with other personality types.
Keywords: consanguineous and non-consanguineous marriage, intelligence, personality type, secondary school student
... En aquest cas tenim dades de 2 regions de la Capital i Jahra i s'ha ponderat cada una de les dades per la població que cada regió tenia al 1995 segons el cens del país. Podríem dir que entre les dos regions esta representada el 26,50 % del total de població i ens sembla una dada prou significativa com per tenir en compte.Kyrgyzstan -Tajikistan -Uzbekistan -MongoliaInterval1940/1954 -1955/1964 -1965/1974 Dades extretes deWoodley (2009) [219] provinents de l'índex de minories Bittles, dada poc rigorosa però que serveix per augmentar el nombre de la mostra, pertany a la ètnia dins del país de xina entre els anys 1951/1976.Interval 1965/1975Per aquest interval s'ha utilitzat les dades aportades perKlat & Khudr (1986) [128], el qual distingeix entre Parents y Grandparent, aquests últims son les dades utilitzades per aquest interval. S'ha pogut arribar a l'article original i s'han utilitzat les dades originals de l'article. ...
... En aquest cas tenim dades de 2 regions de la Capital i Jahra i s'ha ponderat cada una de les dades per la població que cada regió tenia al 1995 segons el cens del país. Podríem dir que entre les dos regions esta representada el 26,50 % del total de població i ens sembla una dada prou significativa com per tenir en compte.Kyrgyzstan -Tajikistan -Uzbekistan -MongoliaInterval1940/1954 -1955/1964 -1965/1974 Dades extretes deWoodley (2009) [219] provinents de l'índex de minories Bittles, dada poc rigorosa però que serveix per augmentar el nombre de la mostra, pertany a la ètnia dins del país de xina entre els anys 1951/1976.Interval 1965/1975Per aquest interval s'ha utilitzat les dades aportades perKlat & Khudr (1986) [128], el qual distingeix entre Parents y Grandparent, aquests últims son les dades utilitzades per aquest interval. S'ha pogut arribar a l'article original i s'han utilitzat les dades originals de l'article. ...
... Consanguinity studies concurrently investigating intelligence facets (performance and verbal IQ) and anthropometric traits (height, weight, etc.) have found similar inbreeding depression on both sets of traits (Badaruddoza, 2004). Inbreeding depression of IQ is also discernible from population-level data, as higher national rates of consanguineous marriage correspond to lower national IQ estimates (Saadat, 2008;Woodley, 2009). Even the secular IQ increase ("Flynn effect") that has been observed in many countries during the 20 th century has been attributed to heterosis (Mingroni, 2004(Mingroni, , 2007; but see Woodley, 2011, for counter-arguments and counter-evidence). ...
... As expected, distances were highly positively (leftwards) skewed. To ameliorate this and to enable proper analysis, the standard data transformation for this situation (1 + log 10 ; see Saadat, 2008;Woodley, 2009) was applied (1 was added to all distances prior to taking their logarithms to handle zero distances, i.e., relatives with identical birthplace). Parents vs. grandparents are firstdegree vs. second-degree relatives (about 50% vs. 25% genetically similar to participants). ...
The opposed genetic effects of heterosis and inbreeding depression consist of beneficial augmentations (vs. detrimental reductions) of phenotypic trait values in offspring of genetically distant (vs. related) parents. This is due to increased offspring heterozygosity for heterosis vs. increased homozygosity for inbreeding depression, with the consequence of escape from (vs. falling prey to) the cumulative effects of deleterious recessive alleles. Heterosis/inbreeding depression is well documented for human health outcomes and psychometric intelligence, but has only sporadically been investigated for heritable personality traits. This study of 129 adults from a geographically isolated region in westernmost Austria examined heterosis/inbreeding depression in differentially heritable individual difference variables: personality dimensions (Big Five, sensation seeking), digit ratio (2D:4D), and laterality traits. Consistent with heterosis/inbreeding depression effects, 2D:4D (strongly genetically influenced) of both hands was expressed more sex-typically with farther birthplace distance of relatives (approximating genetic distance) among women (but not men), whereas no effects emerged for directional asymmetry in 2D:4D (almost nonheritable) or laterality traits (only weakly heritable). However, not replicating recent suggestive findings, effects were also largely absent for the (strongly heritable) Big Five and sensation seeking personality dimensions. Future directions for exploring heterosis and inbreeding depression in the personality and individual differences domain are discussed.
... Furthermore it has been argued that the ∝ coefficient may be a poor estimate of the proportion of alleles shared between individuals from a common ancestor (Markert et al., 2004). It is also worth noting that in previous work, these different measures of consanguinity have been found to correlate at r = 0.96 (n = 35), and so are basically isomorphic with respect to one another (Woodley, 2009). In the present study, data for 70 nations were used in total, comprising a combined sample size for that variable of several million individuals. ...
... In the first one, the data were recoded into three categories based on their quality. Based on the protocol used in Woodley (2009), data quality was determined by estimating how representative they were of a whole nation. Data from studies that had been conducted for an entire nation were put into the highest quality category (1). ...
This article examines the hypothesis that although the level of democracy in a society is a complex phenomenon involving many antecedents, consanguinity (marriage and subsequent mating between second cousins or closer relatives) is an important though often overlooked predictor of it. Measures of the two variables correlate substantially in a sample of 70 nations (r = −0.632, p < 0.001), and consanguinity remains a significant predictor of democracy in multiple regression and path analyses involving several additional independent variables. The data suggest that where consanguineous kinship networks are numerically predominant and have been made to share a common statehood, democracy is unlikely to develop. Possible explanations for these findings include the idea that restricted gene flow arising from consanguineous marriage facilitates a rigid collectivism that is inimical to individualism and the recognition of individual rights, which are key elements of the democratic ethos. Furthermore, high levels of within-group genetic similarity may discourage cooperation between different large-scale kin groupings sharing the same nation, inhibiting democracy. Finally, genetic similarity stemming from consanguinity may encourage resource predation by members of socially elite kinship networks as an inclusive fitness enhancing behavior.
... This significantly weakens the case for it resulting from factors operating solely between families such as heterosis, at least within Norway. In another study, Woodley (2009) investigated whether cross-national variability in per capita levels of consanguineous marriage (marriage involving individuals related to one another at the level of second cousin or closer) was in anyway predictive of cross-national variability in the IQ scores reported by Lynn and Vanhanen (2006). Although a significant positive correlation was found between the two variables (r ϭ Ϫ.62, p Ͻ .01), ...
... As Lynn (2009) andFlynn (2009) both pointed out, however, gains of 2 or 3 points due to heterosis are a far cry from the 27-point increase that has been observed in the United States over the last 80 or so years. The only mechanism through which heterosis might substantively influence the Flynn effect might be through a social multiplier effect involving small genetic gains in g having a larger positive effect on developmental factors that might encourage further secular gains amongst abilities (Woodley, 2009). A significant impediment to this model lies in the observation that recent significant inbreeding does not appear to be a characteristic of many of the nations in which the Flynn effect has occurred, however (Flynn, 2009). ...
Mingroni (2007) proposed that heterosis or hybrid vigor may be the principal driver of the Flynn effect--the tendency for IQ scores to increase at a rate of approximately 3 points per decade. This model was presented as a resolution to the IQ paradox--the observation that IQ scores have been increasing despite their high adult heritability--on the basis that substantial changes in IQ can only be accounted for by changes in underlying genetic factors. It is here argued that this model is predicated upon a misconception of the Flynn effect, which is most pronounced on the least g-loaded components of cognitive ability tests and is uncorrelated with genetic effects such as inbreeding depression scores (which are correlated with the g loadings of tests). Evidence supportive of the recently proposed life history model of the Flynn effect is presented. In the discussion, other theoretical objections to the heterosis model are also considered. On this basis, it is concluded that the Flynn effect is strongly entwined with developmental status and that heterosis cannot be its principal cause.
... In general, Oman's population is characterized by large family sizes and consanguineous marriages. The latter is associated with several developmental abnormalities, including those that lead to social and intellectual disabilities (Woodley, 2009). There are also indications that more young Omanis have debilitating medical complications that were typically diagnosed only in elderly citizens, generating the potential to increase disability and dependency . ...
Over the last few decades, Oman has undergone a dramatic transition from an impoverished and inward-looking society to an affluent, globalized one. Demographically, the country is in the second stage of demographic transition, with approximately 50% of the population under the age of 25. Existing literature suggests that cognitive, emotional, and social deficits (CESD) among children and adolescents are becoming increasingly common all over the world. The present review highlights the identified rates of CESD and its covariates in the Omani populace. A literature search on CESD in Oman revealed several studies related to impulse control and externalizing behavioral disorders/attention deficit hyperactivity disorder (ADHD), disordered eating, and autism spectrum disorder (ASD). The rates of ADHD are indicated to be between 5.1% and 8.8%, while disruptive behavior disorders are reported to constitute 12% of the sample. The results indicate that 9.5% of children and adolescents have disordered eating habits. The rate of children with ASD is in the range of 1.4 – 20.35/10,000. Other CESD observed among Omani children and adolescents include depressive symptoms (3% – 17%), bipolar mood disorder (1%), phobias (5.8% – 58%), school bullying (38.9% – 76%), adverse childhood experiences (0.6%), disorders of elimination (2%) and learning disorders (30%). As for psychosocial correlates, childhood CESD in Oman appears to also be influenced by the nature of the childcare-network system, including the creation of a feedback loop phenomenon of triggering poor mental health outcomes as well as adversely impacting the quality of life and psychosocial functioning among the caregivers. These psychosocial correlates ultimately result in suboptimal social and academic performance of the impacted children and adolescents, consequently impacting their general quality of life. Globally, 9 – 13% of child and adolescent age groups have serious CESD, some of which have also been reported in Oman. The magnitude of most types of CESD in Oman appears to generally fall within the range of international prevalence rates, with some outliers. It can be hypothesized that sociocultural factors influence the magnitude of CESD in Oman. As most of the reviewed studies were conducted using non-culturally sensitive measures, it is unclear whether the results might vary if the study instruments were equipped to decipher local idioms of distress. Therefore, future prospective studies employing more robust methodology are required in order to further examine potential rehabilitation and remedial factors for CESD.
... The Global Burden of Diseases, Injuries, And Risk Factors 2015 (Global Burden of Disease Child and Adolescent Health Collaboration 2017) show that population growth and improved medical care in countries such as Oman have significantly increased the number of children with who manifest physical, social and cognitive impairment. Overall, Oman's population is characterized by large family size and consanguineous marriage which is believed to link to several developmental abnormalities including those that lead to life-limiting diseases (Islam 2012;Woodley 2009). A plethora of studies has indicated that children with disabilities are often targeted for maltreatment. ...
In line with international best practice, the Arabian Gulf countries have ratified the Convention on the Right of the Child (CRC), which has some clauses on child abuse and neglect. The present discourse, made from within an Arabian Gulf society, specifically Oman, reviews the socio-cultural differences of the region and explores the potential regional challenges for effectively implementing the CRC mandated child protection legislation. The international best practices evolved for individualistic, “guilt-based” societies, which may need to be modified to suit the “shame-based” collective societies in the Arabian Gulf where the individual autonomy is overridden by that of the family and society. This may mean that the entire spectrum of child abuse may need to be studied in-depth, starting from what constitutes child abuse and neglect, the methods adopted for identifying cases, setting preventive measures in place, applying penal and corrective action on the perpetrators, and helping the victims recover. It is posited that while modifying the laws may be straightforward, implementation of certain clauses may initially come into conflict with deeply engrained socio-cultural conventions on these societies which have different parenting styles and child-rearing practices. The country in focus is Oman. Pointing out the sparsity of research on the topic in the region, the study suggests additional research to understand how to reconcile these sociocultural constraints with the international best practices of protecting child rights.
... Consanguinity measures the percentage of unions to close relatives, i.e., the degree of inbreeding (in biological language). Information was taken from Woodley (2009) and supplemented by Tadmouri et al. (2009). The figures reported in these two sources correlate at r = .87 ...
The Good Country Index ( GCI ) measures countries’ contributions to global prosperity in domains such as peace, climate and health. It is known that political institutions and wealth can enhance a country’s ability to be ‘good’. However, past research has shown that the cognitive ability of a society – and of its intellectual classes in particular – as well as education and background factors such as culture and evolutionary history, may be particularly important for socio-economic development. Using correlations, cross-sectional path analyses and longitudinal path analyses, we examined the GCI ’s relationships with the following variables: average cognitive ability, cognitive level of intellectual classes, evolutionary history, culture (indicated by religion), consanguinity, education, politics (rule of law, freedom, democracy) and wealth ( GDP per capita). There was considerable overlap between measures of politics and the GCI (e.g., freedom; empirically r = .76 to .84). The most important variable for explaining international differences in the GCI was the cognitive level of intellectual classes (around r = .72), followed by indicators of culture ( r = .64 to .69). Benefits and limitations of the intellectual class approach are discussed.
... This inbreeding strategy decreased the genetic variation, thereby increasing the homozygosity in the genomes estimated by the coefficient of inbreeding. 28,29 In addition, backcross and inbreeding enabled us to eliminate phenotypic variation, which might have been due to allelic heterogeneity or mosaicism in the F0 generation. After two generations of backcrosses and inbreeding, we successfully generated Fam83h KO (Fam83h Ko/Ko ) mice ( Figure 3). ...
Family with sequence similarity 83 member H (FAM83H) protein‐coding geneplay an essential role in the structural organization, calcification of developing enamel, and keratin cytoskeleton disassembly by recruiting Casein kinase 1 alpha (CSNK1A1) to keratin filaments. In this study, we have applied CRISPR Cas9 nickase (D10A) to knockout (KO) the Fam83h gene in NMRI outbred mice. We generated homozygous Fam83h KO mice ( Fam83h Ko/Ko) through a premature termination codon, which was validated by Sanger sequencing in F0 generation. Next, we also bred the FAM83H KO for two generations. Reverse‐transcription polymerase chain reaction and Western blot analysis approved the Fam83h KO mice. The Fam83h KO mice had evidence of normal morphology at the cervical loops, secretory and maturation stages, and mandibular molars. In comparison with the normal wild‐type mice ( Fam83h W/W), the F2 homozygous KO ( Fam83h Ko/Ko) had sparse, scruffy coats with small body size and decreased general activity. Also, they had the natural reproductive ability and natural lifespan. In addition, delay in opening the eyes and dry eyes among infant mice were seen. The F1 heterozygous mice looked comparable to the normal wild‐type mice ( Fam83h W/W), which showed autosomal recessive inheritance of these phenotypes. The KO of FAM83H had controversial effects on the development of teeth and the formation of enamel. The phenotype defect in dental development and the enamel formation were seen in three mice among four generations. It can be concluded that null FAM83H in outbred mice not only showed the reported phenotypes in null inbred mouse but also showed normal lifespan and reproductive ability; dental deficiency in three homozygous mice; and the symptoms that were similar to the symptoms of dry eye syndrome and curly coat dog syndrome in all four evaluated KO generations.
... Firstly, it has been demonstrated that consanguineous marriage has a detrimental impact on IQ. Inbreeding leads to a build-up of double doses of mutations that have a small but significant impact on brain functioning (see Woodley, 2009;Brody, 2013, p. 157;Fareed & Afzal, 2014). Shawky et al. (2011) have shown that 35% of marriages contracted in Egypt are consanguineous. ...
Two administrations of the Coloured Progressive Matrices in Egypt were compared. The first was administered to a large, representative national sample between 2011 and 2013. The second was administered to primary school pupils in villages in Menoufia in northern Egypt in 2017. Adjusting for the Flynn Effect, the IQ of the rural northern Egyptians was shown to be statistically significantly higher than the national average. It is demonstrated that this is consistent with regional socioeconomic differences in Egypt, which strongly imply that northern Egypt has a higher average IQ than southern Egypt.
... More Genetic Relatedness will be inhibited by increased Parasite Burden because higher extrinsic sources of mortality will favor genetic diversity (Fincher & Thornhill, 2012;Woodley of Menie, 2009;Figueredo & Wolf, 2009) 3. Super-K will be promoted by: (a) more Genetic Relatedness because it serves as a partial mediator between Super-K and Parasite Burden; (b) greater Population Density as increases in density promote higher levels of competition for resources leading to the production of more competitive offspring; and (c) lower levels of Parasite Burden as fewer sources of extrinsic mortality allow individuals to allocate effort toward circumventing sources of intrinsic mortality. 4. Increased Equality will be promoted by: (a) Super-K because slower life histories will promote more mutualistic social schemata (Figueredo & Jacobs 2010) and (b) more Genetic Relatedness because the more interrelated a state is the more prone it will be to help conspecifics because of inclusive fitness. ...
The purpose of this dissertation is to model biosocial determinants of group-directed altruistic behavior – exploring the nomological net around it. To do this a study will be presented to determine existing associations among various biological and social predictors and test a life-history-derived causal cascade using a partially exploratory and partially confirmatory statistical technique called Sequential Canonical Analysis to ultimately predict living-donor, non-directed kidney donations (NDKD). Toward that end, some important methodological considerations first need to be discussed. The first consideration revolves around the level of analysis and how this frames the cascade model and its interpretation. Following a general discussion, an exercise in some of the general principles is provided – investigating the higher-order factor structure of the Big-5 personality constructs across two levels of analysis. The second consideration is the use of unit-weighted factor scores and their appropriateness. Following the theoretical discussion, a demonstration is provided – deriving an estimate of genetic relatedness from a set of heterogeneous data sets. Once the methodological considerations have been discussed, the primary cascade model is presented in two parts: 1) the measurement model – operationalizing the measures incorporated into 2) the structural model – testing the proposed causal cascade using Sequential Canonical Analysis. A discussion follows in which the results are summarized, limitations are articulated, and further research directions are explored.
... Beyond methodological considerations, we confirmed in this study known associations between increased inbreeding and reduced lung function (PEF), cognitive ability (FIS and MTCIM), and fertility (NCF), which were previously reported, however, using different proxy traits (10,(29)(30)(31). We also replicated the association between inbreeding and decreased height (b UNI − LDMS: −1.71 phenotypic SD for complete inbreeding; P = 0.003) even though it was below the Bonferroni threshold. ...
Significance
Inbreeding depression (ID) is the reduction of fitness in offspring of related parents. This phenomenon can be quantified from SNP data through a number of measures of inbreeding. Our study addresses two key questions. How accurate are the different methods to estimate ID? And how and why should investigators choose among the multiple inbreeding measures to detect and quantify ID? Here, we compare the behaviors of ID estimates from three commonly used SNP-based measures of inbreeding and provide both theoretical and empirical arguments to answer these questions. Our work illustrates how to analyze SNP data efficiently to detect and quantify ID, across species and traits.
... The cause of variation in cognitive ability across the world is said to be due to inbreeding depression and associated reduced [13][14] phenotypic quality. ...
... [12][13][14] Consequently, family studies have shown that offspring of consanguineous marriages have lower cognitive performance than the general population, supporting a role for inbreeding depression on general cognitive ability. [15][16][17][18][19][20] The hypothesized cause of inbreeding depression, directional dominance of alleles that affect fitness, is thought to occur because selection acts more efficiently on additive effects than on recessive effects, which tends to bias deleterious effects toward a recessive mode of action. 21 Inbreeding increases the probability that recessive/partially recessive deleterious mutations are homozygous by increasing the proportion of the genome that is autozygous (stretches of two homologous chromosomes in the same individual that are identical by descent). ...
Inbreeding depression refers to lower fitness among offspring of genetic relatives. This reduced fitness is caused by the inheritance of two identical chromosomal segments (autozygosity) across the genome, which may expose the effects of (partially) recessive deleterious mutations. Even among outbred populations, autozygosity can occur to varying degrees due to cryptic relatedness between parents. Using dense genome-wide single-nucleotide polymorphism (SNP) data, we examined the degree to which autozygosity associated with measured cognitive ability in an unselected sample of 4854 participants of European ancestry. We used runs of homozygosity—multiple homozygous SNPs in a row—to estimate autozygous tracts across the genome. 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. Association mapping of autozygous tracts did not reveal any specific regions that were predictive beyond chance after correcting for multiple testing genome wide. The observed effect size is consistent with studies of cognitive decline among offspring of known consanguineous relationships. These findings suggest a role for multiple recessive or partially recessive alleles in general cognitive ability, and that alleles decreasing general cognitive ability have been selected against over evolutionary time.
... Sarrazin weist auf die genetisch~n Auswirkungen der Heirat von Verwandten hin, was in muslimischen Gesellschaften weni ger verpönt ist, wohl aber in christlich-jüdischen Gesellschaften mit Ausnahme der Adelshäuser. Bei Cousin-Cousinen-Ehen ist im Schnitt die Intelligenz der Nachkommen um drei IQ-Punkte abgesenkt; hinzu kommt ein erhöhtes Risiko für Krankheiten (Woodley, 2009).18 Nach internationalen Statistiken werden in der Türkei 21 % aller Ehen zwischen Verwandten geschlossen, in Afghanistan 55 %, in Pakistan 61 %, im Schnitt der muslimi schen Länder 32 %, in Westeuropa liegt die Häufigkeit unter 1 % (Bittles, 2001 Dieser gemeinsame Ursprung war immer wieder bezweifelt worden, zuletzt von dem israelischen Historiker Shlomo Sand in seinem Buch "Die Erfindung des jüdischen Volkes". ...
Intelligenz als "heißes Eisen" und gesellschaftlich bedeutsames Thema (S. 77-80) - These: Intelligenz ist wichtig für Wohlstand und Wachstum (S. 80-83) - These: Intelligenz ist das Ergebnis von Erb- und Umwelteinflüssen (s. 83-86) - These: Intelligenz kovariiert in modernen Gesellschaften mit sozialer Schichtung (S. 86-88) - Thesen zur Bildung und den kognitiven Fähigkeiten von Muslimen(S. 88-90) - These: Die Intelligenz der nachfolgenden Generation sinkt (S. 91-.92) - Ein kurzes Fazit (S. 92-93) - Anmerkungen (S. 93-96)
... Regarding inbreeding depression, there is a negative correlation between national IQ scores and consanguinity (Woodley, 2009). Of note is that eugenic/dysgenic trends in IQ seem to predict the per capita rate of major innovations over the past 500 years while the Flynn effect appears to be related to per-capita GDP growth (Woodley & Meisenberg, 2013a). ...
When investigating intelligence test score data (commonly referred to as IQ scores) since the 1900s we see that these scores have increased over time. This temporal secular upward trend has been greeted with some amount of positive enthusiasm. The concurrent up- and downward movement of intelligence markers have left us wondering what is going on in intelligence test score data and by implication, our brains.
... The proportion of the autosomal genome in ROHs (F roh ) shows a nominally significant negative association with EA. In the absence of data on parental EA, geographic mobility, and ancestry, this observation could have been interpreted as the result of deleterious effects of inbreeding on cognitive ability, which would fit the existing hypotheses [38,39,40,41]. The effect was considerably more significant however when associating F roh with paternal or maternal EA. ...
Individuals with a higher education are more likely to migrate, increasing the chance of meeting a spouse with a different ancestral background. In this context, the presence of strong educational assortment can result in greater ancestry differences within more educated spouse pairs, while less educated individuals are more likely to mate with someone with whom they share more ancestry. We examined the association between educational attainment and Froh (= the proportion of the genome consisting of runs of homozygosity [ROHs]) in ~2,000 subjects of Dutch ancestry. The subjects’ own educational attainment showed a nominally significant negative association with Froh (p = .045), while the contribution of parental education to offspring Froh was highly significant (father: p < 10-5; mother: p = 9×10-5), with more educated parents having offspring with fewer ROHs. This association was significantly and fully mediated by the physical distance between parental birthplaces (paternal education: pmediation = 2.4 × 10-4; maternal education: pmediation = 2.3 × 10-4), which itself was also significantly associated with Froh (p = 9 × 10-5). Ancestry-informative principal components from the offspring showed a significantly decreasing association with geography as parental education increased, consistent with the significantly higher migration rates among more educated parents. Parental education also showed a high spouse correlation (Spearman’s rho = .66, p = 3 × 10-262). We show that less educated parents are less likely to mate with the more mobile parents with a higher education, creating systematic differences in homozygosity due to ancestry differences not directly captured by ancestry-informative principal components (PCs). Understanding how behaviors influence the genomic structure of a population is highly valuable for studies on the genetic etiology of behavioral, cognitive, and social traits.
... Our results showed a significant decline in cognitive abilities of children due to inbreeding and higher frequency of mental retardation observed among offspring of inbred families, whereas children from non-consanguineous families display higher values of VIQ, PIQ and FSIQ scores and consequently low frequency of mental retardation or ID. Various studies on consanguineous marriages and other forms of inbreeding have cited a discernible reduction in cognitive abilities, with increased mental illness in the offspring of such unions [26,[51][52][53]. A familial study has reported the incidence of mental retardation among the children of firstcousins being four times greater than that in the control group [54]. ...
Background:
Cognitive ability tests are widely assumed to measure maximal intellectual performance and predictive associations between intelligence quotient (IQ) scores and later mental health problems. Very few epidemiologic studies have been done to demonstrate the relationship between familial inbreeding and modest cognitive impairments in children.
Objective:
We aimed to estimate the effect of inbreeding on children's cognitive behavior in comparison with non-inbred children.
Methodology:
A cohort of 408 children (6 to 15 years of age) was selected from inbred and non-inbred families of five Muslim populations of Jammu region. The Wechsler Intelligence Scales for Children (WISC) was used to measure the verbal IQ (VIQ), performance IQ (PIQ) and full scale IQ (FSIQ). Family pedigrees were drawn to access the family history and children's inbred status in terms of coefficient of inbreeding (F).
Results:
We found significant decline in child cognitive abilities due to inbreeding and high frequency of mental retardation among offspring from inbred families. The mean differences (95% C.I.) were reported for the VIQ, being -22.00 (-24.82, -19.17), PIQ -26.92 (-29.96, -23.87) and FSIQ -24.47 (-27.35,-21.59) for inbred as compared to non-inbred children (p<0.001) [corrected].The higher risk of being mentally retarded was found to be more obvious among inbred categories corresponding to the degree of inbreeding and the same accounts least for non-inbred children (p<0.0001). We observed an increase in the difference in mean values for VIQ, PIQ and FSIQ with the increase of inbreeding coefficient and these were found to be statistically significant (p<0.05). The regression analysis showed a fitness decline (depression) for VIQ (R2 = 0.436), PIQ (R2 = 0.468) and FSIQ (R2 = 0.464) with increasing inbreeding coefficients (p<0.01).
Conclusions:
Our comprehensive assessment provides the evidence for inbreeding depression on cognitive abilities among children.
... Such cultural practices have significantly prevented public health problems that can result from consanguineous marriages. For example, consanguineous marriages (marriage between close family members) increases the risks of several genetic disorders including birth defects, still births, infant mortality, disabilities, different forms of eye diseases, deafness (Hamamy, 2012) and mental retardation (Woodley, 2009). ...
The health of the Oromo people is determined by complex and intertwined social and
natural environments. Modifying or entirely changing these environments necessitates
developing effective organizations and leadership. Colonial socio-cultural-structural
impositions conditioned the Oromo people to adopt the Euro-centric discourses and its
top-down organizational structure. The top-down organizational structure is
incompatible with the Oromo episteme; it is inaccessible, inequitable and
unsustainable. Such a structure does not foster full participation of community
members and promote healthy social conditions. This paper provokes a discussion as
to whether or not the Oromo people and other indigenous people need to adopt the
Euro-centric organizational structure or maintain their indigenous structures to
transform their society and promote health. The Oromo indigenous organizational
structures are framed in an Oromo paradigm of thinking and they are in a better
position to understand the social problems of the Oromo people. In addition, they
foster the participation of people, create a stable, transparent and dynamic society and
help to continuously improve the social environments in which the Oromo people work
and live. This can prevent illness and injuries in the first place and helps implement the
principles of health promotion strategies and creates supportive environments i.e.
nagaa (peace), haaqa (social justice) and tasgaabi (social order).
... Research on consanguineous marriages, and other forms of inbreeding, has long shown a reduction in cognitive abilities in the offspring of such unions. [1][2][3] 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, although one genome-wide study of ancestral inbreeding has been reported for 10 unrelated families each with two mentally retarded siblings. ...
The consequence of reduced cognitive ability from inbreeding has long been investigated, mainly restricted to cousin-cousin marriages. Molecular genetic techniques now allow us to test the relationship between increased ancestral inbreeding and cognitive ability in a population of traditionally unrelated individuals. In a representative UK sample of 2329 individuals, we used genome-wide SNP data to estimate the percentage of the genome covered by runs of homozygous SNPs (ROH). This was tested for association with general cognitive ability, as well as measures of verbal and non-verbal ability. Further, association was tested between these traits and specific ROH. Burden of ROH was not associated with cognitive ability after correction for multiple testing, although burden of ROH was nominally associated with increased non-verbal cognitive ability (P = 0.03). Moreover, although no individual ROH was significantly associated with cognitive ability, there was a significant bias towards increased cognitive ability in carriers of ROH (P = 0.002). A potential explanation for these results is increased positive assortative mating in spouses with higher cognitive ability, although we found no evidence in support of this hypothesis in a separate sample. Reduced minor allele frequency across the genome was associated with higher cognitive ability, which could contribute to an apparent increase in ROH. This may reflect minor alleles being more likely to be deleterious.
... cold winters, seasonal temperature variation) believed necessary to facilitate the transition toward higher levels of cognitive ability. Additionally, certain cultural practices strongly associated with these populations (such as consanguineous marriages) may also have subsequently impaired increases in cognitive ability through negative culture-gene co-evolutionary feedback (Woodley, 2009). ...
... And of course, if a more or less strong impact of identified genes is eventually found further causes are not excluded, like culture stimulating diligence, learning and thinking (Rindermann, 2009;Steppan, 2010). The same is true for reciprocal effects (e.g. from culture and intelligence to genes by inbreeding; Woodley, 2009). ...
Cognitive ability theory claims that peoples’ competences are decisive for economic wealth. For a large number of countries Lynn and Vanhanen (2002) have published data on mean intelligence levels and compared them to wealth and productivity indicators. The correlation between intelligence and wealth was supported by studies done by different authors using different countries and controls. Based on their pioneering research two research questions were developed: does intelligence lead to wealth or does wealth lead to intelligence or are other determinants involved? If a nation’s intelligence increases wealth, how does intelligence achieve this? To answer them we need longitudinal studies and theoretical attempts, investigating cognitive ability effects at the levels of individuals, institutions and societies and examining factors which lie between intelligence and growth. Two studies, using a cross-lagged panel design or latent variables and measuring economic liberty, shares of intellectual classes and indicators of scientific-technological accomplishment, show that cognitive ability leads to higher wealth and that for this process the achievement of high ability groups is important, stimulating growth through scientific-technological progress and by influencing the quality of economic institutions. In modernity, wealth depends on cognitive resources enabling the evolution of cognitive capitalism.
... With regards to song learning, Forstmeier et al. (2009) showed that syllable repertoire size and motif duration, learned song traits that are thought to be sexually selected, have very low heritabilities in male zebra finches. Inbreeding has been found to negatively affect the Intelligence Quotient (IQ) in various human populations (reviewed by Woodley 2009). In nonhuman vertebrates, the effect of inbreeding and domestication on learning performance differs depending on the species and particular tests used. ...
To what extent do individuals assess the cognitive abilities of the opposite sex when choosing a mate? With the exception of song learning in birds, the hypothesis that cognitive traits are under sexual selection has received attention only recently. Here, we evaluate the evidence for this hypothesis in nonhuman vertebrates. We first briefly review the literature on brain development, which shows that cognition may be a sensitive indicator of early developmental conditions. We then consider the empirical evidence that females choose mates with better cognitive skills, which may be reflected in males' courtship displays, foraging performance, courtship feeding, or diet-dependent morphological traits. There is very little research that assesses whether females discriminate between males through direct observation of cognitively demanding behavior. Instead, several studies support female choice on the basis of morphological traits correlated with cognitive abilities. We conclude by highlighting key questions for future research: 1) To what extent do cognitive skills determine foraging success, courtship feeding, and the expression of diet-dependent morphological traits? 2) Do behavioral courtship displays depend on motor development and physiological maturation or learning through practice and experience? 3) How do cognitive abilities affect survival and mating success? Studies on a range of vertebrate taxa, with their diverse mating systems and cognitive ecologies, offer great potential to tackle these questions and deepen our understanding of sexual selection on cognition. Copyright 2011, Oxford University Press.
... This estimate features prominently in several evolutionary theories of intelligence (Kanazawa, 2004;Lynn, 2006;Rushton, 2000). Moreover, Vanhanen's (2002, 2006) estimates of national IQ have featured in over twenty scientific studies (Barber, 2005;Dickerson, 2006;Gelade, 2008a,b;Jones & Schneider, 2006;Kanazawa, 2006Kanazawa, , 2008Kirkcaldy, Furnham, & Siefen, 2004;Lynn, Harvey, & Nyborg, 2009;Meisenberg, 2004;Morse, 2006;Ram, 2007;Rindermann, 2006Rindermann, , 2007Rindermann, , 2008aRindermann & Meisenberg, in press;Rushton & Templer, in press;Shatz, 2008;Templer, 2008;Templer & Arikawa, 2006a,b;Voracek, 2004;Weede & Kampf, 2002;Whetzel & McDaniel, 2006;Woodley, 2009). ...
On the basis of several reviews of the literature, Lynn [Lynn, R., (2006). Race differences in intelligence: An evolutionary analysis. Augusta, GA: Washington Summit Publishers.] and Lynn and Vanhanen [Lynn, R., & Vanhanen, T., (2006). IQ and global inequality. Augusta, GA: Washington Summit Publishers.] concluded that the average IQ of the Black population of sub-Saharan Africa lies below 70. In this paper, the authors systematically review published empirical data on the performance of Africans on the following IQ tests: Draw-A-Man (DAM) test, Kaufman-Assessment Battery for Children (K-ABC), the Wechsler scales (WAIS & WISC), and several other IQ tests (but not the Raven's tests). Inclusion and exclusion criteria are explicitly discussed. Results show that average IQ of Africans on these tests is approximately 82 when compared to UK norms. We provide estimates of the average IQ per country and estimates on the basis of alternative inclusion criteria. Our estimate of average IQ converges with the finding that national IQs of sub-Saharan African countries as predicted from several international studies of student achievement are around 82. It is suggested that this estimate should be considered in light of the Flynn Effect. It is concluded that more psychometric studies are needed to address the issue of measurement bias of western IQ tests for Africans.
... Cross-national research in mean IQ is a relatively new field but has already produced a number of studies which have sought predictors of variation in IQ. Such putative predictors have included temperature and skin colour (Templer & Arikawa, 2006), evolutionary novelty (Kanazawa, 2008), irreligion (Lynn, Harvey, & Nyborg, 2009), inbreeding (Woodley, 2009) and a range of economic factors (e.g. Dickerson, 2006). ...
Cross-national comparisons of IQ have become common since the release of a large dataset of international IQ scores. However, these studies have consistently failed to consider the potential lack of independence of these scores based on spatial proximity. To demonstrate the importance of this mission, we present a re-evaluation of several hypotheses put forward to explain variation in mean IQ among nations namely: (i) distance from central Africa, (ii) temperature, (iii) parasites, (iv) nutrition, (v) education, and (vi) GDP. We quantify the strength of spatial autocorrelation (SAC) in the predictors, response variables and the residuals of multiple regression models explaining national mean IQ. We outline a procedure for the control of SAC in such analyses and highlight the differences in the results before and after control for SAC. We find that incorporating additional terms to control for spatial interdependence increases the fit of models with no loss of parsimony. Support is provided for the finding that a national index of parasite burden and national IQ are strongly linked and temperature also features strongly in the models. However, we tentatively recommend a physiological – via impacts on host–parasite interactions – rather than evolutionary explanation for the effect of temperature. We present this study primarily to highlight the danger of ignoring autocorrelation in spatially extended data, and outline an appropriate
approach should a spatially explicit analysis be considered necessary.
... is. Saadat (2008) and Woodley (2009) suggested that inbreeding depression and associated reduced phenotypic quality is a cause of the variation in cognitive ability across the world. They found cross-national correlations of r ¼ 20.77 (n ¼ 35, p , 0.0001) and r ¼ 20.62 (n ¼ 71, p , 0.01), respectively, between average IQ and measures of inbreeding. Woodley (2009), however, noted that rates of consanguineous marriage itself may not account for the magnitude of this variation because (i) the statistical significance of the effect disappears when education and gross domestic product (GDP) are controlled for, and (ii) the effect of inbreeding on intelligence had previously been shown to be relativel ...
In this study, we hypothesize that the worldwide distribution of cognitive ability is determined in part by variation in the intensity of infectious diseases. From an energetics standpoint, a developing human will have difficulty building a brain and fighting off infectious diseases at the same time, as both are very metabolically costly tasks. Using three measures of average national intelligence quotient (IQ), we found that the zero-order correlation between average IQ and parasite stress ranges from r=-0.76 to r=-0.82 (p<0.0001). These correlations are robust worldwide, as well as within five of six world regions. Infectious disease remains the most powerful predictor of average national IQ when temperature, distance from Africa, gross domestic product per capita and several measures of education are controlled for. These findings suggest that the Flynn effect may be caused in part by the decrease in the intensity of infectious diseases as nations develop.
Countries differ with respect to human rights. Using the cross-country CIRI data (Cingranelli & Richards), the authors tested two theories. The cognitive-moral enlightenment theory going back to Piaget and Socrates postulates that individuals and nations with higher levels of cognitive ability think and behave in a way more conducive to human rights. The culture-religion theory going back to Weber, Sombart and Voltaire postulates that different religious beliefs shape attitudes, and propel societies toward institutions that are more or less supportive of human rights. Cognitive ability had a positive impact on human rights but its effect varied depending on the country sample. More important was religion, both in cross-sectional and longitudinal models. Percentage of Christians had a positive impact (r = .62, total effect β = .63), percentage of Muslima negative one (r = -.57, total effect β = -.59). Political institutions are highly correlated with human rights, but religion is the decisive background factor.
The results of two previously published Arabic language administrations of the Standard Progressive Matrices (SPM) are compared. The first is an administration of the SPM in 2006 to a probability sample of 6529 Kuwaitis aged between 8 and 15 from all regions of Kuwait. The second is an administration to a comparable sample of 6431 Kuwaitis in 2015. We find a significant Negative Flynn Effect in each age cohort and an overall Negative Flynn Effect amounting to a loss of 6.2 points in a decade. Possible reasons for this are discussed. It is proposed that the most persuasive explanation is increasing religious emphasis in the Kuwaiti school curriculum.
In three rural Ecuadorian schools from" different regions (central highlands in the Andes, hinterland of Quito, and Amazonian lowlands) N = 161 pupils aged 9-14 with about 86% Amerindian background were tested for cognitive ability. Fluid intelligence was measured using culture-reduced Raven's SPM, while crystallized intelligence was measured using school-near tasks from PIRLS-Reading and TIMSS-Mathematics. Parental education, parental wealth (family assets), number Of books in the home, parenting style, discipline in school, and height (relative to age and sex) were also measured. Average IQusing British FLynn-corrected 1979 SPM norms was equal to 71, with the figure being lower in the central highlands (IQ= 65) than in the hinterland of Quito and the Amazonian lowlands (IQ= 75). Raw perforinance only weakly increased with age (r =.11 to.18) indicating limited cognitive development and resulting in lower normed IQs at higher ages (r =.17 to 22). Individual differences in cognitive ability were better explained by parental education (beta(Ed) =.53 to.54) than by parental wealth (beta(We) =.14 to.15). Height per-age-and-sex had an effect of beta(He) =.13 to.14. Number of books, discipline and authoritative parenting also had positive impacts. Explanations for the low average performance and for differences between regions are discussed.
This paper summarises the author's friendship and collaboration with Hans Eysenck over forty years with particular reference to their work on racial and national differences in personality and intelligence and its subsequent development by the author and others. Eysenck was one of the first to accept a genetically based black–white difference in intelligence. Later work has developed this further by documenting IQs for all races.
Prior studies of studentsqqaposxx and adultsqqaposxx cognitive competence have shown large differences between nations, equivalent to a difference of 5 to 10 years of schooling. These differences seem to be relevant because studies using different research paradigms have demonstrated that population-level cognitive abilities are related to a number of important societal outcomes, including productivity, democratization, and health. In this overview of transnational differences, we document a number of positive predictors of international differences in student competence, including the amount of preschool education, student discipline, quantity of education, attendance at additional schools, early tracking, the use of centralized exams and high-stakes tests, and adult educational attainment. We found rather negative relationships for grade retention rates, age of school onset, and class size. Altogether, these results, when combined with the outcomes of earlier studies, demonstrate that international differences in cognitive competence can be explained in part by aspects of the respective countriesqqaposxx educational systems and that these differences consequently can be reduced by reform of their educational policy. This has important implications not just for closing gaps in educational achievement, but for narrowing international gaps in wealth, health, and democracy.
© 2009 Association for Psychological Science.
Across 177 countries around the world, the Failed State Index, a measure of state vulnerability, was reliably negatively associated with the estimates of national intelligence. Psychometric analysis of the Failed State Index, compounded of 12 social, economic, and political indicators, suggested factorial unidimensionality of this index. The observed correspondence of higher national intelligence figures to lower state vulnerability might arise through these two macro-level variables possibly being proxies of even more pervasive historical and societal background variables that affect both.
This paper summarizes the results of 244 correlates of national IQs that have been published from 2002 through 2012 and include educational attainment, cognitive output, educational input, per capita income, economic growth, other economic variables, crime, political institutions, health, fertility, sociological variables, and geographic and climatic variables.
In this study, we tested the parasite-stress hypothesis for the distribution of intelligence among the USA states: the hypothesis proposes that intelligence emerges from a developmental trade-off between maximizing brain vs. immune function. From this we predicted that among the USA states where infectious disease stress was high, average intelligence would be low and where infectious disease stress was low, average intelligence would be high. As predicted, we found that the correlation between average state IQ and infectious disease stress was − 0.67 (p < 0.0001) across the 50 states. Furthermore, when controlling the effects of wealth and educational variation among states, infectious disease stress was the best predictor of average state IQ.Highlights► We compared rates of infectious disease with average IQ across USA states. ► We controlled for education and wealth. ► Infectious disease was the best predictor of average IQ.
An essential guide to this major contemporary issue, Consanguinity in Context is a uniquely comprehensive account of intra-familial marriage. Detailed information on past and present religious, social, and legal practices and prohibitions is presented as a backdrop to the preferences and beliefs of the 1100+ million people in consanguineous unions. Chapters on population genetics, and the role of consanguinity in reproductive behaviour and genetic variation, set the scene for critical analyses of the influence of consanguinity in the early years of life. The discussion on consanguinity and disorders of adulthood is the first review of its kind and is particularly relevant given the ageing of the global population. Incest is treated as a separate issue, with historical and present-day examples examined. The final three chapters deal in detail with practical issues, including genetic testing, education and counselling, national and international legislation and imperatives, and the future of consanguineous marriage worldwide.
The question of cognitive differences between human populations is one of the most contentious issues in the study of human diversity. After reviewing the worldwide patterns of cognitive test performance, this article evaluates alternative causal hypotheses and evolutionary mechanisms. Racial affiliation and latitude correlate with IQ test performance, as does economic development. Religion, a history of colonialism, and a history of Communist rule are important in some cases. This article proposes mechanisms of gene-culture co-evolution that can explain the worldwide patterns. The genetic component of these mechanisms is likely to become testable with further advances in molecular genetics.
Lynn and Vanhanen test the hypothesis on the causal relationship between the average national intelligence (IQ) and the gap between rich and poor countries by empirical evidence. Based on an extensive survey of national IQ tests, the results of their work challenge the previous theories of economic development and provide a new basis to evaluate the prospects of economic development throughout the world.
They begin by reviewing and evaluating some major previous theories. The concept of intelligence is then described and intelligence quotient (IQ) introduced. Next they show that intelligence is a significant determinant of earnings within nations, and they connect intelligence with various economic and social phenomena. The sociology of intelligence at the level of sub-populations in nations is examined, and the independent (national IQ) and dependent (various measures of per capita income and economic growth rates) variables are defined and described. They then provide empirical analyses starting from the 81 countries for which direct evidence of national IQs is available; the analysis is then extended to the world group of 185 countries. The hypothesis is tested by the methods of correlation and regression analyses. The results of statistical analyses support the hypothesis strongly. The results of the analyses and various means to reduce the gap between rich and poor countries are discussed. A provocative analysis that all scholars, students, and researchers involved with economic development need to confront.
Birthweight correlations were analysed among 505 intergenerational pairs of first births to women aged 18-25 identified from a large obstetric data bank. After standardisation for fetal sex, maternal height, gestational age, and proteinuric pre-eclampsia residual correlations of between 0.1402 and 0.1725 were found, suggesting only a small genetic effect. It is concluded that genetic factors play only a small part in determining birth weight.
This study presents the assessment of inbreeding depression on the intelligence quotient among north Indian Muslim Children of school age. The Wechsler Intelligence Scale for Children (WISC-R)-74 was given to the children in both groups (50 each non-inbred and inbred of the first-cousin status), aged 6 to 11 years and from the same socio-economic status. The change of the mean follows genetic theory; however, the nature of the change in variance seems to be somewhat different.
PIP
The level of inbreeding depression on the intelligence quotient (IQ) of North Indian Muslim schoolchildren was assessed in a survey conducted in Aligarh. The 50 inbred children were products of marriages between first cousins; their mean age was 7.7 years (range, 6-11 years). A significant (p 0.001) negative association was found between inbreeding and score on the Weschler Intelligence Scale for Children (WISC-C). In addition, the weighted mean IQ of inbred children )88.4 + or - 1.37) differed significant (p 0.001) from that recorded among 50 noninbred controls of similar age and socioeconomic status (99.6 + or - 2.0). The group means for both verbal and performance IQ subscales differed significantly and in the expected direction between subjects and controls, but the lower variance recorded in the inbred group did not conform to genetic theory. However, data do not always demonstrate a clear trend of linear increase in phenotypic variance with inbreeding in human populations. Additional surveys in other populations and for various inbreeding levels are recommended.
Consanguineous marriages are strongly preferred in much of West and South Asia. This paper examines the prevalence and sociodemographic correlates of consanguineous unions in Pakistan using local and national data. Information from 1011 ever-married women living in four multi-ethnic and multi-lingual squatter settlements of Karachi, the main commercial centre of the country, are compared with data from the national 1990/91 Pakistan Demographic and Health Survey (PDHS), based on information provided by 6611 women. Both sets of results indicate that approximately 60% of marriages were consanguineous, over 80% of which were between first cousins. The mean coefficients of inbreeding (F) in the present generation were 0.0316 and 0.0331 for the Karachi and PDHS data respectively. In both surveys the prevalence of consanguineous unions appeared to be unchanged over the past three to four decades. Consanguineous unions were more common among women who were illiterate or had only primary level education, were first or second generation migrants from rural areas of Pakistan or, in the PDHS, lived in rural areas, and whose parents were also consanguineously married.
Although the recent Pakistan Demographic and Health Survey (DHS) show that two-thirds of marriages in Pakistan are consanguineous, the sociocultural determinants of such marriages remain largely unexplored. This paper examines the relative importance of the three commonly perceived reasons for such marriages: religious, economic and cultural. The analysis is based on qualitative data collected in 1995 from multi-ethnic and multi-religious communities in Karachi, the largest city of Pakistan. Results show that consanguineous marriages are preferred across all ethnic and religious groups to a varying degree, and that parents continue to be the prime decision-makers for marriages of both sons and daughters. The major reasons for a preference for consanguineous marriages are sociocultural rather than any perceived economic benefits, either in the form of consolidation of family property or smaller and less expensive dowries. Among Muslims, following religious traditions is the least commonly cited reason for such marriages. Despite the reported sociocultural advantages of consanguineous marriages, such unions are perceived to be exploitative as they perpetuate the existing power structures within the family.
Some argue that the high heritability of IQ renders purely environmental explanations for large IQ differences between groups implausible. Yet, large environmentally induced IQ gains between generations suggest an important role for environment in shaping IQ. The authors present a formal model of the process determining IQ in which people's IQs are affected by both environment and genes, but in which their environments are matched to their IQs. The authors show how such a model allows very large effects for environment, even incorporating the highest estimates of heritability. Besides resolving the paradox, the authors show that the model can account for a number of other phenomena, some of which are anomalous when viewed from the standard perspective.
In most Western countries there is a widespread belief, fostered in part by historical prejudice and religious proscription, that inbreeding in human populations causes a reduction in fertility. Support for this belief has been claimed in HLA-based studies, with increased rates of fetal losses suggested in HLA-compatible unions. To critically assess the overall status of fertility in consanguineous unions, data on 30 populations resident in six countries were collated from a systematic review of the literature. The mean numbers of live births were then compared in four consanguinity test categories, ranging from second cousin to uncle-niece/double first cousin, and corresponding non-consanguineous reference groups. Linear regressions indicated a positive association between consanguinity and fertility at all levels of inbreeding, attaining statistical significance at first cousin level (p < 0.0001). The results were, however, subject to a number of potential limitations, in particular lack of control for important socio-demographic variables. To overcome this problem, data on first cousin marriages were abstracted from the National Family and Health Survey conducted in India during 1992-1993. Multivariate analysis showed that fertility in first cousin unions was positively influenced by a number of variables, including illiteracy, earlier age at marriage and lower contraceptive uptake, but the most important of these parameters were duration of marriage and reproductive compensation. In net terms, consanguinity was not found to be associated either with a significant positive or negative effect on fertility.
Consanguineous marriages have been practiced for hundreds of years in many parts of the world. The rate of congenital malformations among the offspring is 2.5 times higher than that among the offspring of unrelated parents, mainly due to the expression of autosomal-recessive disorders, and hospitalization for these reasons causes a major financial burden. An increase in sterility and in the rates of abortion, stillbirths, perinatal losses and neonatal deaths has been reported by some authors but not by others. It is generally accepted that the advantages of consanguinity outweigh the disadvantages; however, strategies for reducing the burden require a unique approach as discussed in this article.
Consanguineous marriage has had considerable attention as a causative factor in the prevalence of genetic disorders. Iran, with its majority Muslim population, has a high rate of consanguineous marriage. In Iranian tradition, first cousin marriage is an acceptable and appreciated custom. However, there seems to be no encouragement of consanguineous marriage in the Islamic context; it is merely mentioned as a traditional and common custom. This paper may help medical professionals providing premarital genetic counselling, who are regularly asked about consanguineous marriage, especially in Islamic communities. Increased public awareness via the mass media would seem to be a priority.
This paper examines the relationship of the national IQs reported by Lynn & Vanhanen (2002, 2006) to national achievement in mathematics and science among 8th graders in 67 countries. The correlation between the two is 0.92 and is interpreted as establishing the validity of the national IQs. The correlation is so high that national IQs and educational achievement appear to be measures of the same construct. National differences in educational achievement are greater than differences in IQ, suggesting an amplifier effect such that national differences in IQs amplify differences in educational achievement. Controlling for national differences in IQ, slight inverse relationships of educational achievement are observed with political freedom, subjective well-being, income inequality, and GDP. However, public expenditure on education (as % of GDP) was not a significant predictor of differences in educational achievement.
IQ test scores have risen steadily across the industrialized world ever since such tests were first widely administered, a phenomenon known as the Flynn effect. Although the effect was documented more than 2 decades ago, there is currently no generally agreed-on explanation for it. The author argues that the phenomenon heterosis represents the most likely cause. Heterosis, often referred to as hybrid vigor, is a genetic effect that results from matings between members of genetically distinct subpopulations, such as has been occurring in human populations through the breakup of small, relatively isolated communities owing to urbanization and greater population mobility. In Part 1 of the article, empirical findings are listed that are consistent with a heterosis hypothesis but render other hypotheses either implausible or very difficult to test. In Part 2, a formal model of the process of heterosis is presented. The goal of the modeling is to develop a quantitatively rigorous method for estimating the potential contribution of heterosis in the Flynn effect, as well as trends observed in other heritable traits and conditions.
Previous studies have reported that related human couples tend to produce more children than unrelated couples but have been unable to determine whether this difference is biological or stems from socioeconomic variables. Our results, drawn from all known couples of the Icelandic population born between 1800 and 1965, show a significant positive association between kinship and fertility, with the greatest reproductive success observed for couples related at the level of third and fourth cousins. Owing to the relative socioeconomic homogeneity of Icelanders, and the observation of highly significant differences in the fertility of couples separated by very fine intervals of kinship, we conclude that this association is likely to have a biological basis.
In their book, IQ and the Wealth of Nations, Lynn and Vanhanen ([Lynn, R. and Vanhanen, T. (2002). IQ and the wealth of nations. Westport, CT: Praeger.]) proposed the hypothesis that “the intelligence of the populations has been a major factor responsible for the national differences in economic growth and for the gap in per capita income between rich and poor nations” (p. xv). They presented analyses showing that national wealth can be predicted by IQ, democracy, economic freedom, and oil production. This paper has four goals. First, we examine the robustness of Lynn and Vanhanen findings using updated IQ and wealth variables and updated sources of democracy, economic freedom, and oil production. Second, we evaluate the curvilinear relationship between IQ and national wealth. Third, we address concerns over the accuracy of IQ estimates in low IQ countries by evaluating whether the relationship between IQ and national wealth is dependent on precise estimates of IQ. Fourth, we extend the predictor space of national wealth by examining its correlates with public expenditures on health and education.
Population genetics is the study of genetic variation in human populations, and IQ population genetics is the population-level study of those genetic variations that influence mental ability. Admittedly, this field does not yet exist as an area of established scientific inquiry because hardly any of the genetic variations that influence human cognition in the non- pathological range are known at the present time. However, the first reports about intelligence-related genetic traits have appeared in the literature (Egan et al., 2001, 2003), and more information is likely to become available in the not too distant future. At this point in time we can only chart the worldwide variations in people's performance on standardized cognitive tests, and evaluate the plausibility of causal hypotheses. In this article I review the available evidence, not to advance one or another explanation but to provide a road map for future studies that will increasingly rely on the methods of molecular
Recurrent digital fibroma of infancy generally is considered a sporadic tumor of childhood. We describe the case of a mother with recurrent digital fibroma at a young age who gave birth to a daughter with focal dermal hypoplasia, coloboma of the iris and eyelids, anal atresia, and extensive limb malformations. When the infant was 3 months old, fibromas started to appear at the fingertips. The cases of three additional patients are described, with a similar combination of multiple digital fibromas, pigmented marks on the temporal region, and limb malformations. One of these patients has consanguineous parents. The clinical findings overlap partially with Gorlin-Goltz syndrome, which has been renamed by some authors “microphthalmia with linear skin defects” (MLS). Since the skin signs are clearly different, however—more like those of Setleis syndrome (“forceps mark” temporal dysplasia)—the patients described here seem to have a new combination of congenital malformations. Deletion of distal Xp, known to occur in some MLS patients, was not detected using cosmids in fluorescence in situ hybridization. This pattern of digital fibroma with congenital malformations seems to represent a new syndrome. Am. J. Med. Genet. 94:91–101, 2000. © 2000 Wiley-Liss, Inc.
International cognitive ability and achievement comparisons stem from different research traditions. But analyses at the interindividual data level show that they share a common positive manifold. Correlations of national ability means are even higher to very high (within student assessment studies, r = .60–.98; between different student assessment studies [PISA-sum with TIMSS-sum] r = .82–.83; student assessment sum with intelligence tests, r = .85–.86). Results of factor analyses indicate a strong g-factor of differences between nations (variance explained by the first unrotated factor: 94–95%). Causes of the high correlations are seen in the similarities of tests within studies, in the similarities of the cognitive demands for tasks from different tests, and in the common developmental factors at the individual and national levels including known environmental and unknown genetic influences. Copyright © 2007 John Wiley & Sons, Ltd.
The differential effects of inbreeding on 11 subtests of the WISC, in a Japanese (Hiroshima) population, are related to the factor structure of the tests. The degree of inbreeding depression on mental abilities is most strongly correlated with the subtests' loadings on the General factor, g, which is common to all of the subtests. Loadings on the Verbal factor are also positively correlated with inbreeding depression. The (non-verbal) Performance factor, however, is slightly enhanced by inbreeding. One possible inference from these findings is that at least the General factor shows genetic dominance, which is theoretically consistent with natural selection for g in the course of human evolution. It is also noted that the factor structure of the WISC in the Japanese population is highly similar to that of the U.S. standardization sample.
Empirical studies demonstrate that individuals perceive physically attractive others to be more intelligent than physically unattractive others. While most researchers dismiss this perception as a “bias” or “stereotype,” we contend that individuals have this perception because beautiful people indeed are more intelligent. The conclusion that beautiful people are more intelligent follows from four assumptions. (1) Men who are more intelligent are more likely to attain higher status than men who are less intelligent. (2) Higher-status men are more likely to mate with more beautiful women than lower-status men. (3) Intelligence is heritable. (4) Beauty is heritable. If all four assumptions are empirically true, then the conclusion that beautiful people are more intelligent is logically true, making it a proven theorem. We present empirical evidence for each of the four assumptions. While we concentrate on the relationship between beauty and intelligence in this paper, our evolutionary psychological explanation can account for a correlation between physical attractiveness and any other heritable trait that helps men attain higher status (such as aggression and social skills).
Cognitive abilities are important for the economic and non-economic success of individuals and societies. For international analyses, the collection of IQ-measures from Lynn and Vanhanen was supplemented and meliorated by data from international student assessment studies (IEA-Reading, TIMSS, PISA, PIRLS). The cognitive level of a nation is highly correlated with its educational level (r = .78, N = 173). In international comparisons, it also shows a high correlation with gross domestic product (GDP, r = .63, N = 185). However, in cross-sectional studies, the causal relationship between intelligence and national wealth is difficult to determine. In longitudinal analyses with various samples of nations, education and cognitive abilities appear to be more important as developmental factors for GDP than economic freedom. Education and intelligence are also more relevant to economic welfare than vice versa, but at the national level the influence of economic wealth on cognitive development is still substantial.
Both decline of IQ and increase of mental retardation are consistent with rare recessive alleles at about 325 loci. There is no suggestion of a discrepancy that might be due to polygenic dominance or confounding of consanguinity with unfavorable environment. These data indicate that the risk for mental retardation in matings of normal parents increases from 0.012 with random mating to 0.062 for first-cousin parentage but that dominance deviations are a negligible cause of family resemblance of IQ. Implications for frequencies, mutation rates, and radiation response are detailed.
THE few studies1,2 in which the effects of inbreeding on cognitive performance have been examined revealed that offspring of first-cousin marriages had lower IQ scores than offspring of unrelated parents. These studies were, however, performed in societies where the population engaging in such marriages is a small (1%, 6%)2,3 and unrepresentative proportion of the total population. Possible confounding of the effects of inbreeding with the effects of other intelligence-related variables such as socioeconomic status may lead the effects of inbreeding to be overestimated2. Unfortunately statistical control may either over- or under-correct for the correlates of the independent variables, leaving one in doubt about the true effect of inbreeding. I have now examined the effects of inbreeding on cognitive performance in an Arab population with a high rate of consanguinous marriage which minimised the distortions due to non-genetic variables. I show here that offspring of unrelated parents performed better than offspring of first-cousin marriages in intelligence and achievement tests administered at grades 4 and 6. The lowest level of performance and a higher variance were found for offspring of double-cousin marriages. The inbreeding depression found in this study is consistent and cannot be explained by the effects of socioeconomic status. I drew a nationally representative sample of 3,203 children in grades four and six (approximate ages 10 and 12 yr) of the Arab educational system in Israel. This sample constitutes about 10% of the total population in these grades and includes only normal (not retarded) children. Column 1 in Table 1 shows the division of the subjects according to grade level and consanguinity of the parents. A first-cousin marriage is between children of siblings. Children of first cousins have, on average, 1/16 pairs of genes by common descent. Double first cousins are children of siblings married to unrelated siblings. When they marry, their children have, on the average, 2/16 pairs of genes by common descent.
A survey in the Lebanese schools for the blind revealed that 77% of childhood blindness in the country was genetically determined. Two thirds of the hereditary blindness cases were due to autosomal recessive conditions; the high frequency of consanguineous marriages in Lebanon was the underlying cause of this finding. There is marked similarity in the etiology of childhood blindness in Cyprus and Lebanon, for both countries are somewhere between the highly developed and the developing countries.
To study the effects of parental HLA sharing on pregnancy outcome, we initiated population-based studies in the Hutterites. We previously reported longer intervals from marriage to each birth among couples sharing HLA, particularly HLA-DR. In the present report, we present the results of a prospective, 5-year study of fecundability and fetal loss rates in this population. Between April 1986 and April 1991, 154 pregnancies were observed in 104 couples. The median number of months of unprotected intercourse to a positive pregnancy test was significantly longer among couples sharing HLA-DR who stopped nursing prior to the first menses as compared with couples not sharing HLA-DR who stopped nursing prior to the first menses (5.1 vs. 2.0 mo, respectively; P = .016). Fetal loss rates were increased among couples sharing HLA-B as compared with couples not sharing HLA-B (.23 vs. .12, respectively; P = .041, adjusted for age, gravidity, and kinship). These data suggest that our earlier observations of increased birth interval lengths among Hutterite couples sharing HLA were predominantly due to longer intervals until a clinical pregnancy among couples sharing HLA-DR and, to a lesser degree, were due to increased fetal loss rates among couples sharing HLA-B.
Consanguinity among parents as a cause of mental retardation in their children is debatable. The present study was conducted to find out the effect of consanguinity on mental retardation where the causative factor is not established. A total of 517 mentally retarded persons and their families were studied out of which 160 were born of consanguineous marriage and 357 were of non-consanguineous marriage. The results indicated that, when there is a history of mental retardation in the family and if the parents are consanguineously married, the risk of mental retardation in the offspring is significantly high (chi 2 = 11.52; P less than 0.001). Among the consanguineously married families, the blood relationship of uncle-niece seems to have the highest risk of affecting the offsprings. The implications are discussed in detail.
Effects of consanguineous marriages on offspring's gestational age and anthropometrics at birth were investigated in Beirut through a hospital-based survey of 1,252 newborns. Twenty-five percent of all newborns were inbred, and the mean inbreeding coefficient was 1.25%. Neither prematurity rate nor weight, length, head circumference, and chest circumference (considered individually, or as a whole) showed a significant pattern by type of parental consanguinity. Failure to demonstrate significant inbreeding effects is reported in several other studies and generally interpreted as the long-term result of continued inbreeding practices.
Specific factors in a couple's history may influence the recurrence risk following repeated pregnancy loss (RPL). Couples with RPL were contacted several years following evaluation and information concerning subsequent pregnancies was obtained. Linear regression analysis was utilized to determine which factors in the history were significant predictors of pregnancy outcome following evaluation. A family history of RPL or a "genetic defect" was a highly significant predictor of subsequent unsuccessful pregnancies. Surgical, but not medical, treatment for RPL was a significant predictor of eventual successful outcome. The number of abortions prior to evaluation for RPL, presence of a liveborn child, maternal age at evaluation, and intercurrent infertility all failed to be significant predictors of pregnancy outcome after evaluation.
Indian Muslim school boys, ages 13 to 15 years, whose parents are first cousins, were compared with classmates whose parents are genitically unrelated on the Raven Standard Progressive Matrices, a nonverbal test of intelligence. The inbred group (N=86) scored significantly lower and had significantly greater variance than the noninbred group (N=100), both on raw scores and on scores statistically adjusted to control for age and socioeconomic status. Genetic theory predicts both of these effects for a polygenic trait with positive directional dominance.
To some authorities, studies of inbreeding depression and IQ represent "unassailable" or "impressive" evidence for the heritability of IQ; to other authorities, the same evidence is "meager and ambiguous." To study this discrepancy, a detailed review is made of 6 studies of the children of cousin marriages and 3 studies of the children of incestuous matings. These studies, taken as a whole, provide no substantial evidence for an inbreeding depression effect within the polygenic system that is commonly asserted to determine IQ. (24 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Two siblings who exhibited hereditary parkinsonism with pyramidal signs and cerebellar ataxia are reported. Anticholinergics had a dramatic beneficial effect in both cases, but levodopa did not. This responsiveness, which is similar to that reported in patients with Joseph's disease, suggests dysfunction of an "indirect pathway" involving the globus pallidus and the subthalamic nucleus, in addition to that of the nigrostriatal system. We propose a new hereditary variant of early onset Parkinson's disease distinct from the levodopa sensitive forms of juvenile Parkinson's disease.
Turkey has a high rate of consanguineous marriage (21.1%), indicating strong preference for this traditional form of marital union. Social and cultural factors are especially important in marriages between first and second cousins. Fertility is high, the closed birth interval is long, and the sterility rate is low among these couples. Post-neonatal, infant and under-5 mortalities are high in first cousin unions by comparison with non-consanguineous marriages. According to the results of the study, first cousin marriage is a significant determinant underlying the high total fertility and infant mortality rates in Turkey.
Wolcott-Rallison syndrome (OMIM 226980) is a rare
autosomal recessive disorder characterised by permanent
insulin requiring diabetes developing in the
newborn period or early infancy, an early tendency to skeletal
fractures, and spondyloepiphyseal dysplasia. The syndrome
results from mutations in the gene encoding the eukaryotic
translation initiation factor 2-a kinase 3 (EIF2AK3, also called
PERK or PEK). This enzyme phosphorylates EIF2A at Ser51
to regulate the synthesis of unfolded proteins in the
endoplasmic reticulum. Targeted disruption of the Eif2ak3
gene in mice also causes diabetes because of the accumulation
of unfolded proteins triggering b cell apoptosis.
Although these murine models have provided significant
insight into the pathogenesis of Wolcott-Rallison syndrome,
only three human cases have been characterised genetically.
Here, we report genetic analysis of two further cases,
and demonstrate new features of the expression pattern of
human EIF2AK3 that offer possible explanations for important
clinical features of the syndrome that are not apparent in
the transgenic mouse models.
The effects of inbreeding in humans on the intelligence has been investigated in the present study of offspring of second cousin matings (F=0.0156, n=138 male, 132 female), first cousins once removed (F=0.03125, n=148 male, 138 female), first cousins (F=0.0625, n=161 male, 151 female), and unrelated (F=0, n=194 male, 182 female) among North Indian Muslims. The Weschler Intelligence Scale for Children (WISC-R)-74 was given to the children in the both groups. An overall significant (p<0.001) reduction of means has been observed in inbred series. The results of this study confirm the appreciable inbreeding depression especially among the offspring of first cousins.
Generally, inbreeding is associated with loss of biological fitness. For countries such as Iran, where consanguineous marriages are common,1 the association between consanguinity and intelligence is very important for public health programmes.
National IQs were calculated in relation to a mean IQ of 100 and standard deviation of 15 in Britain.2 The inbreeding coefficient is the probability that an individual has received both alleles of a pair from an identical ancestor. At the population level, the mean of inbreeding coefficient (α) was calculated for 35 countries. …
Defining and measuring democracy. Working Paper, International Political Science Association
- M Coppedge
Coppedge, M. (2005, April). Defining and measuring democracy. Working
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The Economist Intelligence Unit's index of democracy. [WWW document Inbreeding effects on fetal growth in Beirut
- L Kekic
Kekic, L. (2007). The Economist Intelligence Unit's index of democracy. [WWW document]. URL http://www.economist.com/media/pdf/ DEMOCRACY_INDEX_2007_v3.pdf Khlat, M. (1989). Inbreeding effects on fetal growth in Beirut, Lebanon. American Journal of Physical Anthropology, 80, 481−484.
Hereditary parkinsonism with multiple system degeneration: Beneficial effect of anticholinergics, but not of levodopa
- T Mitsui
- H Kawai
- S Sakoda
- M Miyata
- S Saitio
Mitsui, T., Kawai, H., Sakoda, S., Miyata, M., & Saitio, S. (1994). Hereditary
parkinsonism with multiple system degeneration: Beneficial effect of
anticholinergics, but not of levodopa. Journal of the Neurological Sciences,
125, 153−157.
The prevalence and demographic charac-teristics of consanguineous marriages in Pakistan The impact of consanguinity worldwide
- R Hussain
- A H Bittles
- −
- L Jaber
- G J Halpern
- M Shohat
Hussain, R., & Bittles, A. H. (1998). The prevalence and demographic charac-teristics of consanguineous marriages in Pakistan. Journal of Biosocial Science, 30, 261−275. Jaber, L., Halpern, G. J., & Shohat, M. (1998). The impact of consanguinity worldwide. Community Genetics, 1, 12−17.