Ancestry of Latinos

As they say, Hispanic is not a race. Latin Americans are a three-way mix of Europeans (from Spain), Native American Indians, and Sub-Saharan Africans, but proportions of these genetic components vary a lot both among and within different groups.

We find that the most likely source of the indigenous ancestry in Caribbean islanders is a Native South American component shared among coastal tribes from Venezuela, Central America, and the Yucatan peninsula, suggesting extensive gene flow across the Caribbean in pre-Columbian times. We find evidence of two pulses of African migration. The first pulse — which today is reflected by shorter, older ancestry tracts — consists of a genetic component more similar to coastal West African regions involved in early stages of the trans-Atlantic slave trade. The second pulse — reflected by longer, younger tracts — is more similar to present-day West-Central African populations, supporting historical records of later transatlantic deportation. Surprisingly, we also identify a Latino-specific European component that has significantly diverged from its parental Iberian source populations, presumably as a result of small European founder population size.

[...]

Figure 1B shows the distribution in PCA space of each individual, recapitulating clustering patterns previously observed in Hispanic/Latino populations: Mexicans cluster largely between European and Native American components, Colombians and Puerto Ricans show three-way admixture, and Dominicans principally cluster between the African and European components. Ours is the first study to characterize genomic patterns of variation from (1) Hondurans, which we show have a higher proportion of African ancestry than Mexicans, (2) Cubans, which show extreme variation in ancestry proportions ranging from 2% to 78% West African ancestry, and (3) Haitians, which showed the largest average proportion of West African ancestry (84%).

Assuming a K=3 admixture model, population admixture patterns are driven by continental reference samples with no continental subdivision (Figure 1C, top panel). However, higher Ks show substantial substructure in all three continental components. [...] At K=8, when the clinal gradient of differentiation between Southern and Northern Europeans appears, the Latino European component is seen only in low proportions in individuals from Portugal and Spain, whereas it is the major European component among Latinos (Figure 1C, bottom panel).

ADMIXTURE clustering analysis using the high-density dataset containing approximately 390K autosomal SNP loci in common across admixed and reference panel populations. Unsupervised models assuming K=3 and K=8 ancestral clusters are shown. At K=3, Caribbean admixed populations show extensive variation in continental ancestry proportions among and within groups. At K=8, sub-continental components show differential proportions in recently admixed individuals. A Latino-specific European component accounts for the majority of the European ancestry among Caribbean Latinos and is exclusively shared with Iberian populations within Europe. Notably, this component is different from the two main gradients of ancestry differentiating southern from northern Europeans. Native Venezuelan components are present in higher proportions in admixed Colombians, Hondurans, and native Mayans.

Moreno-Estrada et al. "Reconstructing the Population Genetic History of the Caribbean". arXiv:1306.0558 [q-bio.PE], 2013.

King Richard III Reconstruction

Link to story

Racial Composition and History of India

DNA evidence confirms what historians, linguists and anthropologists have long known but nationalists have denied: that Indians are mainly a mix of indigenous Australoids and intrusive Caucasoids. They're composed of two genetic components, one related to Andaman Islanders and the other to Western Eurasians. And the estimated dates of admixture between the two are consistent with the introduction of Indo-Aryan languages from the northwest and probably also earlier events related to the spread of Dravidian languages and even agriculture.

India has been underrepresented in genome-wide surveys of human variation. We analyse 25 diverse groups in India to provide strong evidence for two ancient populations, genetically divergent, that are ancestral to most Indians today. One, the "Ancestral North Indians" (ANI), is genetically close to Middle Easterners, Central Asians, and Europeans, whereas the other, the "Ancestral South Indians" (ASI), is as distinct from ANI and East Asians as they are from each other. By introducing methods that can estimate ancestry without accurate ancestral populations, we show that ANI ancestry ranges from 39-71% in most Indian groups, and is higher in traditionally upper caste and Indo-European speakers. Groups with only ASI ancestry may no longer exist in mainland India. However, the Andamanese are an ASI-related group without ANI ancestry, showing that the peopling of the islands must have occurred before ANI-ASI gene flow on the mainland. Allele frequency differences between groups in India are larger than in Europe, reflecting strong founder effects whose signatures have been maintained for thousands of years owing to endogamy. We therefore predict that there will be an excess of recessive diseases in India, which should be possible to screen and map genetically.

Reich et al. "Reconstructing Indian Population History". Nature, 2009.


Metspalu et al. "Shared and Unique Components of Human Population Structure and Genome-Wide Signals of Positive Selection in South Asia". Am J Hum Genet, 2011.

Linguistic and genetic studies have shown that most Indian groups have ancestry from two genetically divergent populations, Ancestral North Indians (ANI) and Ancestral South Indians (ASI). However, the date of mixture still remains unknown. We analyze genome-wide data from about 60 South Asian groups using a newly developed method that utilizes information related to admixture linkage disequilibrium to estimate mixture dates. Our analyses suggest that major ANI-ASI mixture occurred in the ancestors of both northern and southern Indians 1,200-3,500 years ago, overlapping the time when Indo-European languages first began to be spoken in the subcontinent. These results suggest that this formative period of Indian history was accompanied by mixtures between two highly diverged populations, although our results do not rule out other, older ANI-ASI admixture events. A cultural shift subsequently led to widespread endogamy, which decreased the rate of additional population mixtures.

Moorjani et al. "Estimating a date of mixture of ancestral South Asian populations", Evolutionary and Population Genetics, 2012.

The paper provides an overview of the spatial and temporal aspects of human morphological variation in India. Four morphological types — Australoids, Negritos, Mongoloids and Caucasoids — have been discerned in the contemporary Indian population. The Australoids appear to be the oldest and have evolved in India. The Caucasoids are physically heterogeneous and suggests incorporation of more than one physical type involving more than one migration. The within-type variance compared to between-type variance for characters studied is smaller. The paper further discusses the observed variability in terms of Indian social organization as well as in terms of endogamy, small numerical strength of the groups and varying ecological conditions prevalent in India.

K.C. Malhotra. "Morphological Composition of the People of India". J Hum Evol, 1978.

Indian Male Composite

Indian Female Composite

Assumed parental groups:

Andamanese Australoid

Iranian Caucasoid

Degrees of admixture:

Austroasiatic speaker (Juang)

Austroasiatic speaker (Santhal)

Dravidian speaker (Paniya)

Dravidian speaker (Hallaki)

Indo-European speaker (Meghawal)

Indo-European speaker (Kashmiri Pandit)

Welsh Are the Most Ancient Britons

The Welsh (and Cornish) may be the Sardinians of the UK: relatively pure descendants of prehistoric Britons, minimally altered by post-Neolithic gene flow. Interestingly, they and Sardinians are each the darkest and most racially Mediterranean populations in their respective countries, having the highest rates of black hair and brown eyes and the lowest rates of blondism (Coon, 1939: Ch. X, Sec. 3 and Ch. XI, Sec. 16).

Welsh people could lay claim to be the most ancient Britons, according to scientists who have drawn up a genetic map of the British Isles.

Research suggests the Welsh are genetically distinct from the rest of mainland Britain.

Professor Peter Donnelly, of Oxford University, said the Welsh carry DNA which could be traced back to the last Ice Age, 10,000 years ago.

The project surveyed 2,000 people in rural areas across Britain.

Participants, as well as their parents and grandparents, had to be born in those areas to be included in the study.

Prof Donnelly, a professor of statistical science at Oxford University and director of the Wellcome Trust centre for human genetics, said DNA samples were analysed at about 500,000 different points.

After comparing statistics, a map was compiled which showed Wales and Cornwall stood out.

Prof Donnelly said: "People from Wales are genetically relatively distinct, they look different genetically from much of the rest of mainland Britain, and actually people in north Wales look relatively distinct from people in south Wales."

While there were traces of migrant groups across the UK, there were fewer in Wales and Cornwall.

He said people from south and north Wales genetically have "fairly large similarities with the ancestry of people from Ireland on the one hand and France on the other, which we think is most likely to be a combination of remnants of very ancient populations who moved across into Britain after the last Ice Age.

"And potentially also, people travelling up the Atlantic coast of France and Spain and settling in Wales many thousands of years ago".

Mountains

He said it was possible that people came over from Ireland to north Wales because it was the closest point, and the same for people coming to south Wales from the continent, as it was nearer.

However he added: "We don't really have the historical evidence about what those genetic inputs were."

The geography of Wales made it more likely that ancient DNA would be retained.

Because of its westerly position and mountainous nature, Anglo-Saxons who moved into central and eastern England after the Romans left did not come that far west, and neither did the Vikings who arrived in around 900AD.

The professor said modern people from central and southern England had many genetic similarities to modern people in Denmark and Germany.

The mountains were also the reason why DNA may have remained relatively unchanged, as people would have found it harder to get from north to south Wales or into England compared with people trying to move across the flatter southern English counties, making them more likely to marry locally and conserve more ancient DNA.

"In north Wales, there has been relative isolation because people moved less because of geographical barriers," Prof Donnelly said.

He added that some of these factors also held true for the extreme edges of Scotland, while the Orkney islands showed DNA connections to Norway.

The next stage of the research will looking at physical similarities between different groups, in which the team will use photographs of people and make 3D models to measure quantitative similarities between related groups.

"Welsh people could be most ancient in UK, DNA suggests". BBC News, June 19, 2012.

Separate Origin of Blondism in Oceania

Science can't yet tell us whether they have more fun — but it has uncovered a new genetic change that makes people blonde. And contrary to long held belief, it seems golden hair hasn't simply been introduced across the globe by travelling tow heads, but instead evolved separately in different human populations.

Indigenous people of the Solomon Islands in the South Pacific have some of the darkest skin pigmentation outside of Africa. But unlike most other tropical populations, they also have a high prevalence of blonde hair. Up to 10 per cent of the population is fair haired, the highest proportion outside of Europe. Until now, this odd trait had generally been attributed to the introduction of blonde genes by European explorers and traders in preceding centuries. "We originally thought, well that must be a Captain Cook allele," says Carlos Bustamante at Stanford University.

Yet a closer look revealed that the genetics behind blonde hair in Brussels are distinct from those leading to flaxen locks in the South Pacific.

Bustamante, Sean Myles and colleagues at Stanford discovered this after analysing saliva samples from 43 blondes and 42 dark-haired Solomon Islanders. A genome-wide scan pointed to a single strong difference between the groups at a gene called TYRP1. Further analysis revealed that a single-letter change in the gene accounted for 46 per cent of the population's hair colour variation, with the blonde allele being recessive to the dark hair allele. The blonde mutation wasn't found in any of the 900 other individuals sampled from outside the South Pacific (Science, DOI: 10.1126/science.1217849).

TYRP1 is known to be involved in skin and hair pigmentation in several species. In normally black mice, for example, a mutation in the gene produces light brown coats. A rare kind of human albinism is also caused by mutations in TYRP1, which produces reddish skin colour and ginger hair. TYRP1 isn't, however, one of the genes that produces blonde hair in Europeans. The novel blonde mutation in Solomon Islanders is likely to have cropped up around 10,000 years ago, and it appears to be the same one behind blondness in Fiji and other regions of the South Pacific.

"Before this, everybody would have thought, blonde hair evolved once in humans," says Bustamante. "This tells us we can't really assume that even these common mutations are common across different human populations. Non-European populations are critical to study to find mutations that may be underlying the vast phenotypic variation of humans."

Lisa Raffensperger. "Blonde hair evolved independently in Pacific islands". NewScientist, May 3, 2012.

EU Overweight and Obesity Statistics

This article presents recent statistics on overweight and obesity in the European Union (EU). Weight problems and obesity are increasing at an alarming rate: over the last decade the proportion of the population that is overweight has increased considerably in most Member States, resulting in more than half the EU population being overweight or obese.

Obesity is a serious public health problem, as it significantly increases the risk of chronic diseases such as cardiovascular disease, type-2 diabetes, hypertension, coronary-heart diseases and certain cancers. For individuals, psychological problems associated with obesity are common, wide-ranging and potentially serious. For society, obesity has substantial direct and indirect costs that put a strain on healthcare and social resources.

Among the 19 Member States for which data are available, the proportion of overweight and obese people in the adult population varied in 2008/09 between 36.9 % and 56.7 % for women and between 51 % and 69.3 % for men.

For both women and men aged 18 years and over, the lowest shares of obesity in 2008/09 were observed in Romania (8.0 % for women and 7.6 % for men), Italy (9.3 % and 11.3 %), Bulgaria (11.3 % and 11.6 %) and France (12.7 % and 11.7 %). The highest proportions of obese women were recorded in the United Kingdom (23.9 %), Malta (21.1 %), Latvia (20.9 %) and Estonia (20.5 % in 2006), and of men in Malta (24.7 %), the United Kingdom (22.1 %), Hungary (21.4 %) and the Czech Republic (18.4 %).

There is no systematic difference in obesity between women and men across the Member States available. The proportion of obesity was higher for women in eight Member States, higher for men in ten and equal in one. However, for overweight there is a clear gender difference: in all Member States available the proportion of overweight men is much higher than for women (differences from 8.5 % in Hungary to 18.2 % in Slovenia).

The share of overweight and obese persons increases with age. The average difference between the youngest and oldest age groups is for men around 44 % and for women around 53 %. For women there is a clear pattern in all the Member States available: the older the age group, the higher the share of overweight and obese persons. For men, the pattern is a little different: increase of overweight and obesity is systematic till 65. For the age group 65-74 the picture is less uniform: For seven of the Member States available the highest share of overweight and obese men was recorded for the age group 65-74.

The share of overweight and obese persons tends to fall with educational level. For women, the pattern is clear in all Member States available: the proportion of women who are obese or overweight falls as the educational level rises. For women the differences between lower and upper education level vary between 12.8 and 36.7 %. For men, the pattern is again slightly different. Differences are smaller and the distribution is different: in 8 of the available Member States, the highest share of overweight and obese men is observed for those with the lowest educational level, in six Member States for those with a medium educational level while in 4 countries it is for those with a high educational level.

Overweight and Obesity — BMI Statistics. Eurostat — Statistics Explained, 2012.

Geography and Industry

Continuing on the theme of environment significantly shaping development and history, here we see how the uneven distribution, quality and accessibility of coal reserves determined the course of the industrial revolution, and how geography also had a major impact on the newer alternative energy source of hydroelectricity, determining which countries (or parts of countries) would be able to play catch up.

The objective of this article is to analyse the importance of one of the new energy sources, electricity, since the end of the nineteenth century until 1945, from the point of view of natural resource endowments. Not all countries had good or equivalent endowments of coal, the energy-producing mineral of the nineteenth century, and for this reason not all of them had the same opportunities to use it, given that the transport cost was very high due to its weight in relation to its caloric power. Electricity reduced the dependence on coal resources as it could be produced not only from coal but also from water.

[...]

The accessible coal endowments available at that time can be proxied by the reserve estimates elaborated by the Geological Survey of Canada in a monograph prepared for the Twelfth International Geological Congress, which was held in Canada in 1913. These estimations are presented in Table 1, both in the form of total coal reserves and coal reserves per capita in each country. Well endowed in coal were Canada and the US in North America and Germany, the UK, Austria and — in an intermediate position — France in Europe. The Northern European countries Denmark and Sweden and the Southern European countries Italy, Greece and Portugal all had poor coal endowments. Looking at coal quality, Spain and especially Italy lacked good quality coal; as for the cost of extraction, this was particularly high in France and Spain, due to the characteristics of its seams.

The differences of national coal endowments are reflected by the levels of coal prices at colliery (see Table 2). We find lower coal prices in the USA, the UK and Germany than in France and Spain, and these differences were substantial. We can see how in the case of France and Spain, where extraction costs were significantly higher, the prices at colliery were too. However, in France, contrary to Spain, the coal reserves were closer to the industrial centres, and these centres were also closer to other coal producing countries. Italy, due to her scarcity of coal, imported coal from the UK through Genoa, with the resulting difference in prices with respect to the other above mentioned countries (see Table 2).

Despite the reduction in transport cost at the end of the nineteenth century, resort to imported coal significantly increased its price. Coal is heavy and bulky in relation to its unit value. Moreover, the differences in transport costs between countries close to and far away from coal production centres persisted over time. In Table 3 the average freight rates from Cardiff to different ports in 1909-1911 are shown. The freight rates to the closest continental harbours were about 4.5 shillings (s.) per tonne on average, but they ranked from 5.5 s. to 7 s. per tonne to the Mediterranean. For example, in the case of Barcelona, the industrial centre of Spain, the rate was 7.42 s. per tonne, and in Genoa it was 7.08 s., both of them being amongst the highest.

[...]

Natural resources also had effects on the type of electricity being produced in these countries when electricity eventually arrived. In the case of the USA, the main thermoelectric power plants were located in the regions along the Mid-Atlantic coast and in the North-East-Central industrial belt. In 1932, they represented 57 per cent of total installed power, 65 per cent of the electricity production in the USA, and 70 per cent and 75 per cent of the installed power and production, respectively, of thermoelectricity. The main hydroelectricity power plants clustered in the coastal regions of the Atlantic (New York State, Pennsylvania, Maryland, North and South Carolina, Georgia and Alabama) and along the Pacific (in California). In 1932, the former regions represented 45 per cent of the hydroelectricity production, and California 30 per cent.

In the UK, as mentioned above, the coal resources were extensive and of good quality. This country had less access to waterpower with the exception of the Highlands in Scotland. Even the locations of coal seams were favourable, as they were distributed all over the country. This created a great advantage in terms of low coal prices for the country as a whole. In the advent of electricity, the main primary energy source became steam to produce thermoelectricity, and small local plants were established close to the location of coal mines.

In France, however, the coal fields were located in the regions of Pas de Calais, the North, Lorraine (Moselle), the Central Massif (Saint-Etienne, Creusot, Gard, etc.) and the Saar (between 1925 and 1935). National production represented around two-thirds of the needs of the country, and the rest was imported from countries near to centres of production and consumption. The coal mining districts mentioned above were important industrial centres, which, time passing, became users of thermoelectricity. Water resources were substantial in the regions of the Alps and the Pyrenees, both well endowed with high falls of little flow, and in the Central Massif, where there were wide rivers. These regions, situated far from the important coal seams, used hydroelectric energy and were centres of the electrochemical and the electrometallurgical industries, which require cheap and abundant supplies of electric energy. The proportion of thermoelectricity was 57.3 per cent, the remainder being hydroelectricity.

The situation was worst in Italy because of the scarcity of coal and its low caloric power. As a result, coal had to be imported. For that reason, electricity was generated by hydraulic power, once the problem of long distance transmission was solved by means of the alternating current. The most important hydraulic resources were concentrated in the Alps and the Po Valley, between the Alps and the Apennines in the North of the country. The regions endowed with the most important sources of waterpower were the Piedmont and Lombardy, the Po Valley (Adda, Adige, Ticino, Tevere, etc.), the Venetia region and that of Umbria.

The situation was different in Spain. As we have seen in Table 1, the coal resources were better than those of Sweden and Italy, worse than those in the United Kingdom and Germany, and similar — in per capita terms — to the case of France. The problem was the quality of Spanish coal as well as its difficult extraction and, hence, its high cost of production. Moreover, the most important coal resources were located in the Asturias region, in the North of Spain, close to the sea side but difficult to transport out because of the mountains that enclose the region. Given its inaccessibility, a substantial part of coal consumption was supplied through foreign trade with the inconvenience of high transport costs. Spain's hydraulic resources were better than its coal resources, but not as abundant as in Italy, Sweden, Norway or Switzerland. Falls were located in the Pyrenees and the Penibetic range. The rivers had small flows, but they did occupy high grounds, which represented an advantage for electricity production. The rivers with the best flow conditions were the Ebro, the Douro and the Tagus. The disadvantage of a low flow is that this makes it very much dependent on year over weather conditions, making a substantial investment in dams necessary to stock water.

We have calculated the proportion of hydroelectricity and thermoelectricity in the total electricity production of each country. As shown in Figure 1, at the top of the countries using hydroelectricity were Canada, Italy and Spain. Hydroelectricity accounted for over 80 per cent of their electricity production. At the bottom, using less than 60 per cent, as already commented, were the coal intensive countries, i.e. the UK, the USA, and France, although, France had a lesser proportion of thermoelectricity.

[...]

In short, an advanced electrification process is observed in the countries less endowed with coal, such as in Spain, Italy and the Northern European countries, in spite of their different levels of economic development. On the other hand, the countries that were the last ones in electrifying their industries were the countries blessed with better coal endowments, such as the UK, Germany and France. The exception among them corresponds to the USA, which had good endowments of both resources.

[...]

The degree of electrification advanced substantially from the end of the nineteenth century until WWII, the height of the process being 1925, after WWI, when real electricity prices fell considerably. The behaviour of the relative prices electricity-coal, coupled with the new technical opportunities for electrification in the manufacturing sector where electricity competed with steam, produced important possibilities for economic growth. There was also a relationship between the accumulation of physical capital and electrification process and the increase in labour productivity, manufacturing and income per capita, especially in the countries that were badly endowed with coal deposits, but enjoyed better opportunities for the production of electricity.

Concha Betrán. "Natural Resources, Electrification and Economic Growth from the End of the Nineteenth Century until World War II". Revista de Historia Económica, 2005.

Bollywood Indians vs. Ordinary Indians

South Asians have varying degrees of Caucasoid and Australoid ancestry, and actors in Bollywood tend to come from regions and castes with more of the former. They also use plastic surgery and skin bleaching, not just to look younger and more attractive for the screen, but as part of a growing trend in India to appear more Caucasoid. The difference in phenotype between "enhanced" Bollywood stars and ordinary Indians is visible in these facial composites:

Indian male

South Indian male

Bollywood male

Indian female

South Indian female

Bollywood female

Source: The Postnational Monitor – World of Facial Averages

Northern Polish Facial Composites

I've been trying out this new morphing software that detects faces automatically and puts the control points in place for you. It has a few kinks but it saves a lot of time, so I made these quick composites of some students from northern Poland.

207 males

192 females

Software: Abrosoft FaceMixer

African IQ and the Flynn Effect

Average IQ in Sub-Saharan Africa is about 20 points lower than average IQ in Europe, and not the 30+ points proposed by Richard Lynn and his gang. Though that may still seem huge and insurmountable, it's actually normal when placed in the proper historical context. As happened in Europe during the 20th century, it's expected that when living conditions improve in Sub-Saharan Africa, IQ levels will increase, narrowing or even eliminating the gap. This process is known as the Flynn Effect.

In the western world, average IQs have shown remarkable gains over the course of the twentieth century (Flynn, 1984, 1987, 2007). These gains have been largest for non-verbal tests once considered relatively impervious to cultural influences, such as the Raven's (Brouwers et al., 2009). For instance, in the Netherlands an unaltered version of the SPM [Raven's Standard Progressive Matrices] was administered to male military draftees from 1952 to 1982. The 1982 cohort scored approximately 20 IQ points higher than the 1952 cohort (Flynn, 1987). In this section, we consider whether a Flynn Effect has occurred among Africans on the Raven's tests.

[...]

Proposed causes of the Flynn Effect include improvements in test-specific skills (Greenfield, 1998; Wicherts et al., 2004), improvements in nutrition (Lynn, 1989, 1990), urbanization (Barber, 2005), improvements in health care (Williams, 1998), a trend towards smaller families (Zajonc & Mullally, 1997), increases in educational attainment (Ceci, 1991), greater environmental complexity (Schooler, 1998), and the working of genotype by environment correlation in the increasing presence of more intelligent others (Dickens & Flynn, 2001). Many of these environmental variables have not undergone the improvement in developing sub-Saharan African countries that they have in the developed world over the last century. This suggests that the Flynn Effect has great potential in sub-Saharan Africa (Wicherts, Borsboom, & Dolan, 2010b).

[...]

Although the implications of our psychometric findings for the potential of the Flynn Effect in sub-Saharan Africa remain unclear, the Raven's tests and other IQ tests have shown robust increases in many populations (Daley et al., 2003; Flynn, 2007). So suppose that there were a well-validated IQ test that showed measurement invariant scores between westerners and Africans. Even then, lower IQs of Africans still would not support Lynn and Vanhanen's (2002, 2006) assertion that countries in sub-Saharan Africa are poorly developed economically because of their low "national IQ". Wicherts, Borsboom, and Dolan (2010b) found that "national IQs" are rather strongly confounded with the developmental status of countries. Given the well-documented Flynn Effect, we know that "national IQs" are subject to change. An average IQ around 80 among Africans may appear to be low, but from a historical perspective this average is not low at all. A representative sample of British adults, who took the SPM in 1948 would have an average IQ of 81 in terms of the British norms of 1992 (J. C. Raven, 1960; J. C. Raven et al., 1996). Using older British norms, the average IQ of Africans would be much closer to 100. This is evident in Figure 2, where we compared SPM scores of Africans to older norms. In this figure, the average IQ of several African samples is near or above 100.

Present-day sub-Saharan Africa is one of the poorest regions in the world and the home to some of the world's most deprived children. The majority of sub-Saharan children are chronically malnourished, not only from lack of food but particularly from food lacking vital elements related to both physical growth and intellectual development. It has been estimated that up to 70 percent of rural children live in absolute poverty and 90 percent suffer severe deprivation (Gordon, Nancy, Pantazis, Pemberton, & Townsend, 2003). A substantial number of sub-Saharan African children are under-educated. According to Garcia, Gillian, and Dunkelberg (2008), only about 12 percent of sub-Sahara African children have attended preschool, and this generally for well less than a year. They note that children who do not attend or have only minimal experience in pre-primary school tend to do less well in primary school than children who have had that experience. Further, it is important that the preschool experience be successful. For example, Jaramillo and Mingat (2008) have shown that children who have a poor experience in preschool and have to repeat a year or part of a year have a high drop-out rate in primary school (r = -0.875). The probability of preschool without repetition and who complete primary school is low but positive (r = 0.209). With or without preschool experience, approximately only fifty-five percent of 10-14 year-olds in sub-Saharan Africa complete primary school.

[...]

Many of the variables that have been proposed as causes of the Flynn Effect (e.g., Barber, 2005; Ceci, 1991; Dickens & Flynn, 2001; Greenfield, 1998; Lynn, 1989; Schooler, 1998; Williams, 1998) have yet to undergo improvement in developing sub-Saharan African countries that they have enjoyed in the developed world over the last century. Because the environmental variables that potentially contribute to enhanced IQ have yet to improve in the countries of sub-Saharan Africa, we regard the Flynn Effect as still in its infancy. There is in fact considerable empirical support that (mal)nutrition (Grantham-McGregor & Baker-Henningham, 2007; Sigman & Whaley, 1998), health (Williams, 1998), sanitation (Boivin et al., 1993), and schooling (Ceci, 1991) have an effect on IQ. The UN have included such variables in the so-called Millennium Goals, i.e., they are targeted for improvement by 2015 (United Nations, 2005). The formulation of the Millennium Goals provides an interesting opportunity to evaluate the effect of these factors on IQ levels in sub-Saharan Africa. There is now a clear indication that the Flynn Effect seems to have come to a halt in developed nations (Flynn, 2007). It is, therefore, reasonable to think that as circumstances in sub-Saharan Africa improve, the IQ gap between western samples and African samples will diminish.

[...]

The vast literature on IQ testing with the Raven's tests in Africa does not support James Watson's pessimism concerning the prospects of Africa. It is true that Africans show lower average IQs as compared to contemporary western norms, although the IQ gap is substantially smaller than Lynn (and Vanhanen) have maintained. More importantly, there is little scientific basis for the assertion that the observed lower IQs of Africans are evidence of lower levels of general intelligence or g. The validity of the Raven's tests among Africans needs to be studied further before these tests can be used to assess Africans' cognitive ability in educational and professional settings. There are several reasons to expect increases in IQ levels among sub-Saharan Africans in the coming decades.

Wicherts et al. "Raven's Test Performance of Sub-Saharan Africans: Average Performance, Psychometric Properties, and the Flynn Effect". Learning and Individual Differences, 2010.

Related: Parasite prevalence and cognitive development