The Great Decline

 

Mean polygenic score of Icelanders by year of birth (Kong et al. 2017, Fig. 2)

 

Three polygenic studies have shown that cognitive ability declined among European Americans, British people, and Icelanders during the 20th century. The decline briefly stopped during the postwar baby boom and again with the liberalization of abortion laws.

 

 

How can we measure the genetic component of cognitive ability? For a long time, the only way was to administer an IQ test, but the result would inevitably be influenced by the test-taker’s environment—not only culture and life history but also familiarity with taking tests and answering questions in rapid-fire succession. Yes, twin studies and adoption studies suggest that genetic factors largely explain variation in IQ between individuals. But the same is not necessarily true for variation in IQ between populations. That could be 100% environmental.

 

Recent years have seen the advent of a direct measure of innate cognitive ability: the educational attainment polygenic score. It’s a summation of the predicted effects of genetic variants that together explain 11-13% of the variance in educational attainment among individuals (Lee et al. 2018). It’s especially suited for predicting the mean IQ of a population—the correlation is 98% with the actual mean IQ (Piffer 2019).  Polygenic data predict a mean IQ of about 85 for sub-Saharan Africans, 100 for Europeans, and 105 for East Asians. There is also variation within each of those geographic groups. Among Europeans, predicted IQ varies from 97 for southern Europeans to 102 for Finns and 110 for Ashkenazi Jews. Among sub-Saharan Africans, it seems to be higher among groups who were more advanced during precolonial times, particularly those, like the Igbo, who lived along the Niger and took part in trade between the coast and the interior (Frost 2022).

 

The above predictions should be viewed with some caution. Because the genetic variants have been identified only in people of European descent, the polygenic score is less valid for non-Europeans, particularly those of sub-Saharan African descent. It thus predicts the IQ of African Americans with five times less accuracy than that of European Americans (Lasker et al. 2019).

 

Generational change

 

In addition to predicting differences in mean IQ across space, we can do the same across time. That begs the question: were past generations as intelligent as the latest one? We can answer that question by examining past generations who are still alive. That approach, however, raises the issue of survivorship bias: people who live to an old age are generally smarter than those who do not (Gottfredson and Deary 2004).

 

Beauchamp (2016) deals with this issue point by point when he discusses polygenic data from the Health and Retirement Study (HRS), a longitudinal study of 20,000 Americans shortly before and during retirement:

 

·         The HRS participants are people who have lived to the age of 50; however, about 10% of American women and 15% of American men born in 1940 were already dead by the age of 50.

·         Thus, in Beauchamp’s sample, 85% of the original participants were still alive in 2008, 69% were asked to be genotyped, and 59% consented to be genotyped.

·         Nonetheless, no important differences emerged when he compared the genotyped participants with the total sample. 

 

European Americans

 

Beauchamp found evidence that alleles associated with high educational attainment had declined in frequency among European Americans between the 1931 and 1953 birth cohorts. “[M]y results strongly suggest that genetic variants associated with EA have slowly been selected against among both female and male Americans of European ancestry born between 1931 and 1953.”

 

That decline is attributed to differences in fertility: “individuals with high EA typically have children at a more advanced age, which may further reduce their fitness.”

 

Icelanders

 

The above findings have been replicated by Kong et al. (2017) in their study of Icelanders born since 1910. Although survivorship bias is still a problem, it does not easily explain the decline in cognitive ability between the last two cohorts, i.e., Icelanders born in the 1970s and those born in the 1980s. In that decline, any survivorship bias would be due to deaths of people less than 44 years old, and in most cases less than 36 years old. “The samples studied here were collected between 1998 and 2014, with a majority (68%) ascertained before 2006” (Kong et al, 2017, p. E729).

 

Iceland’s cognitive decline had two “pauses”: one in the 1950s and another in the 1970s. The first pause coincides with the postwar economic boom and a corresponding improvement in the ability of middle class couples to start families early in life. The second pause may reflect the passage in 1975 of Iceland’s abortion law, which, while not allowing abortion on demand, did allow it for cases of rape, mental disability of the mother, and “difficult family situation” (Wikipedia 2022)

 

Kong et al. (2017) concluded that the cognitive decline was due only in part to more intelligent Icelanders staying in school longer and postponing reproduction. In fact, a high educational level, unlike a high polygenic score, was actually associated with somewhat higher fertility among males. A high polygenic score seems to reduce fertility independently of whether one pursues or does not pursue higher education, perhaps because higher intelligence goes hand in hand with greater ability to plan ahead and thus foresee, with trepidation, the costs of raising a family. 

 

British of European descent

 

In a study of British of European origin, using the UK Biobank, Hugh-Jones and Abdellaoui. (2022) found that mean cognitive ability had declined between two successive generations, particularly in lower-income groups. The median birth year was 1950 for the second generation and unknown for the first. The authors also looked at genetic variants that influence non-cognitive traits. In general, the bulk of the population seems to be getting dumber, fatter, and nuttier.

 

The authors nonetheless warn against excessive pessimism:

 

Many people would probably prefer to have high educational attainment, a low risk of ADHD and major depressive disorder, and a low risk of coronary artery disease, but natural selection is pushing against genes associated with these traits. Potentially, this could increase the health burden on modern populations, but that depends on effect sizes.

 

The authors go on to argue that the effect sizes are “small,” although one wonders: smaller than what? They then make the obvious point that generational change can accumulate from one generation to the next: “Although effects on our measured polygenic scores are small even after weighting, individually small disadvantages can cumulate to create larger effects” (Hugh-Jones and Abdellaoui 2022). Beauchamp (2016) makes a similar comment that seems reassuring on first thought, and then not so reassuring on second thought: “natural selection has thus been occurring in that population—albeit at a rate that pales in comparison with the rapid changes that have occurred in recent generations.”

 

Finally, Hugh-Jones and Abdellaoui (2022) point out that their data may suffer from ascertainment bias. For instance, the first generation of their dataset is composed of the parents of the second generation. The dataset thus excludes the childless individuals of the first generation. Were they more intelligent or less intelligent on average than the succeeding generation? Furthermore, participation in the UK Biobank is voluntary. Could that factor also be a source of bias? If so, in what direction?

 

Conclusion

 

As time goes by, intergenerational genetic datasets will become more complete, and the problem of survivorship bias will diminish. Ideally, we should conduct a “genetic census” of each generation, perhaps by collecting a DNA sample from everyone at the time of death. We will thus be able to see how we are evolving.

 

We now have intergenerational polygenic studies from three different Western countries: the U.S., the U.K., and Iceland. In all three cases, the genetic component of cognitive ability declined during the 20th century, with the exception of two pauses: one during the postwar baby boom and the other with the liberalization of access to abortion.

 

If we wish to halt the cognitive decline, we should push for the following measures:

 

·         A return to the protected high-wage economy that prevailed during the postwar era;

·         Free access to abortion, at least for cases of rape, mental disability of either parent, and difficult economic circumstances;

·         Pro-natalist measures to counteract the fear of not having the means to support a family. This fear is particularly strong among people who like to plan and are oriented toward the future.

 

 

References

 

Beauchamp, J.P. (2016). Genetic evidence for natural selection in humans in the contemporary United States. Proceedings of the National Academy of Sciences 113(28): 7774-7779. https://doi.org/10.1073/pnas.1600398113    

 

Frost, P. (2022). Recent cognitive evolution in West Africa: the Niger’s role. Evo and Proud, April 30. https://evoandproud.blogspot.com/2022/04/recent-cognitive-evolution-in-west.html  

 

Gottfredson, L. S., and I.J. Deary. (2004). Intelligence Predicts Health and Longevity, but Why? Current Directions in Psychological Science 13(1): 1–4. https://doi.org/10.1111/j.0963-7214.2004.01301001.x

 

Hugh-Jones, D., and A. Abdellaoui. (2022). Human Capital Mediates Natural Selection in Contemporary Humans. Behavior Genetics. https://doi.org/10.1007/s10519-022-10107-w  

 

Kong, A., M.L. Frigge, G. Thorleifsson, H. Stefansson, A.I. Young, F. Zink, G.A. Jonsdottir, A. Okbay, P. Sulem, G. Masson, D.F. Gudbjartsson, A. Helgason, G. Bjornsdottir, U. Thorsteinsdottir, and K. Stefansson. (2017). Selection against variants in the genome associated with educational attainment. Proceedings of the National Academy of Sciences 114(5): E727-E732. https://doi.org/10.1073/pnas.1612113114   

 

Lasker, J., B.J. Pesta, J.G.R. Fuerst, and E.O.W. Kirkegaard. (2019). Global ancestry and cognitive ability. Psych 1(1). https://doi.org/10.3390/psych1010034    

 

Lee, J. J., Wedow, R., Okbay, A., Kong, E., Maghzian, O., Zacher, et al. (2018). Gene discovery and polygenic prediction from a genome-wide association study of educational attainment in 1.1 million individuals. Nature Genetics 50(8): 1112-1121. https://doi.org/10.1038/s41588-018-0147-3  

 

Piffer, D. (2019). Evidence for Recent Polygenic Selection on Educational Attainment and Intelligence Inferred from Gwas Hits: A Replication of Previous Findings Using Recent Data. Psych 1(1): 55-75. https://www.mdpi.com/2624-8611/1/1/5   

 

Wikipedia (2022). Abortion in Iceland. https://en.wikipedia.org/wiki/Abortion_in_Iceland    

 

Declining intelligence in the 20th century: the case of Estonia

Soviet-era stamp. In Estonia, cranial volume shrank between the cohort of girls born in 1937 and those born in 1962, apparently because the intellectually gifted were more likely to pursue higher education and postpone childbearing.

 

Is the genetic basis for intelligence declining from one generation to the next? That’s the conclusion of several recent studies on alleles associated with high educational attainment. By adding up such alleles over the genome, we can get a person's "polygenic score." By calculating the mean polygenic score for each generation, we can then find out whether this genetic basis is declining.

The polygenic score has declined among Icelanders since the cohort born in 1910 and among Euro Americans between the 1931 and 1953 cohorts (Beauchamp 2016; Kong et al. 2017). The Icelandic study is especially interesting because that country took in very few immigrants during the period under study. The decline was thus driven by internal factors. One reason seems to be the tendency of university-educated people to delay reproduction and have fewer children. But that's not the whole story. Even among Icelanders who didn’t pursue higher education, fertility was lower among the intellectually gifted, apparently because their intelligence was associated with a desire to plan for the future and delay gratification.

Before the twentieth century, such forward-looking people were reproductively successful. They were the ones who had enough resources to survive disasters of one sort or another: famine, disease, the Little Ice Age, etc. Today, such disasters are a lot less deadly, and it no longer matters so much whether one is a grasshopper or an ant.

Moreover, because of demographic and cultural changes during the twentieth century, it’s no longer possible to count on the same degree of assistance for child-raising from relatives and grandparents. With childbearing at later ages, grandparents are either dead or too frail to help. With people moving around more, not all relatives live nearby. If you’re the sort of person who plans for the future and delays gratification, you may be a lot more intimidated than your forbears by the costs of raising a family.

Shrinking cranial volume in Estonians

Cranial volume correlates with IQ and with educational attainment, albeit imperfectly (see Frost 2020). Has it been declining in tandem with the decline in alleles for educational attainment?

In Soviet-era Estonia, cranial volume was one of several anthropometric traits that were measured in girls born between 1937 and 1962. Because the measurements were mandatory, there was no volunteer basis; mortality bias was minimal because all the participants were younger than 20. In this respect, the study is better than Western biobank studies. On the other hand, the results may be less applicable to Western populations, given the differences in demographic history. Estonia had no postwar baby boom. Fertility then rose from the late 1960s until the breakup of the Soviet Union. By the late 1980s, fertility was actually higher in Estonia than in any other major region of Europe.

Nonetheless, there were demographic similarities between Soviet Estonia and the West, particularly the rising prevalence of single mothers and the influence of education on fertility:

- Divorce rates began to rise during the interwar years, equalling or exceeding those of Scandinavia from the 1970s onward.

- Throughout the twentieth century, Estonian women with only primary education bore 0.5 to 0.75 more children on average than women with tertiary education. In the population under study, taller children and those with larger crania were more likely to go on to secondary and/or tertiary education, independently of sex, socioeconomic position, and rural vs urban origin (Valge et al. 2019).

The second factor seems to explain why cranial volume declined from the older cohorts to the younger ones:

[...] the majority of selection for smaller cranial volume acted indirectly via educational attainment, whereas the direct path of selection in the SEM model was non-significant (Figs. 2 and 4). In other words, consistent with our prior expectations, girls with larger heads were selected against because they were more likely to obtain higher education than girls with smaller heads. Lower education (Tiit, 2013) and rural origin (Kulu, 2005) have been independently and additively associated with higher fertility in Estonia throughout the past century. The reason for the link between education and fertility is that early reproduction, a major determinant of LRS, is not compatible with schooling for both cultural and genetic reasons. (Valge 2020)

 It is doubtful that this decline is due to ethnic change. All of the girls were from Estonian schools (Russian-speakers had their own schools). Nonetheless some of them were of mixed background. According to a personal communication from the corresponding author, 84% of the fathers and 93% of the mothers were Estonian. Ideally, the study should be redone without individuals of mixed parentage. The problem here is not only that one of the parents was non-Estonian but also that such individuals were disproportionately economic migrants who had trouble finding suitable work elsewhere in the Soviet Union.

Other anthropomorphic changes

Height also declined. Unlike cranial volume, this decline was not wholly explained by educational/socioeconomic differences:

Notably, higher reproductive success of shorter girls in Estonia could not be entirely ascribed to indirect selection via educational attainment, nor via other measured socioeconomic variables such as rural/urban origin, although indirect selection via education did account for a large portion of total selection (Fig. 4). The finding that selection against height remains after controlling for education or income (that favours less-educated individuals who are generally shorter than highly-educated ones) is consistent with findings of studies reviewed by Stulp and Barrett (2016).

 

Female hips and female jaws became narrower even after controlling for educational/socioeconomic differences. There seems to have been selection for rounder female faces, but this selection is significant only if one allows for nonlinear effects. Finally, there was no direct selection on two markers of overall health and nutritional status: handgrip strength and lung capacity.

In general, "direct selection favoured shorter, slimmer and lighter girls with smaller heads, more masculine facial and body shapes and slower rates of sexual maturation."

Conclusion

The genetic basis for intelligence has declined in European populations, apparently since the early twentieth century. This decline is attested by two "hard" measures: 1) alleles associated with educational attainment; and 2) cranial volume. Furthermore, it is attested in two relatively homogenous societies, i.e., Iceland and Estonia.

In Estonia, the decline seems entirely due to the intellectually gifted going to university and postponing family formation. In Iceland, this factor explains only part of the decline: the intellectually gifted chose to postpone family formation even when they didn't go to university. Perhaps the Soviet system was better at steering gifted individuals into higher education.

On a final note, this problem will not go away on its own. If we wish to have large numbers of intellectually gifted people who plan for the future and delay gratification, we will need to reverse certain social and cultural changes of the twentieth century.

Comments by Peeter Horak

In an email, Peeter pointed out that the decrease in height due to natural selection might be offset by an increase in height due to lower pathogen load (as a result of vaccination and antibiotics, see Hõrak and Valge 2015). In addition, we currently don't know the direction of selection on boys. It may entirely cancel out natural selection on girls if men's income and education correlate positively with their reproductive success. In the sample under study, taller boys and those with larger heads went on to obtain more education; if they were reproductively successful, there would be sexually antagonistic selection: selection would favor larger boys and smaller girls at the same time.

References

Beauchamp, J.P. (2016). Genetic evidence for natural selection in humans in the contemporary United States. Proceedings of the National Academy of Sciences 113(28): 7774-7779 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4948342/

Frost, P. (2020). Did women jumpstart recent cognitive evolution? Evo and Proud, July 1 https://evoandproud.blogspot.com/2020/07/did-women-jumpstart-recent-cognitive.html

Hõrak, P., and M. Valge. (2015). Why did children grow so well at hard times? The ultimate importance of pathogen control during puberty, Evolution, Medicine, and Public Health, 2015 (1): 167–178, https://doi.org/10.1093/emph/eov017

Kong, A., M.L. Frigge, G. Thorleifsson, H. Stefansson, A.I. Young, F. Zink, G.A. Jonsdottir, A. Okbay, P. Sulem, G. Masson, D.F. Gudbjartsson, A. Helgason, G. Bjornsdottir, U. Thorsteinsdottir, and K. Stefansson. (2017). Selection against variants in the genome associated with educational attainment. Proceedings of the National Academy of Sciences 114(5): E727-E732 https://core.ac.uk/download/pdf/154416179.pdf

Valge, M., P. Horak, and J.M. Henshaw. (2020). Natural selection on anthropometric traits of Estonian girls. Evolution and Human Behavior in press. https://doi.org/10.1016/j.evolhumbehav.2020.07.013

Valge, M, R. Meitern, and P. Horak. (2019). Morphometric traits predict educational attainment independently of socioeconomic background. BMC Public Health 19: 1696. https://link.springer.com/article/10.1186/s12889-019-8072-7

Between Europe and America

Iceland had pre-Columbian contacts with North America. Did they lead to intermarriage? (Wikicommons)



Did the Norse have sustained contacts with the indigenous peoples of the Americas, including intermarriage? Or was Vinland a fleeting encounter?

Steve Sailer touched on this question in a recent column, citing an Icelandic study. Although Iceland’s gene pool is overwhelmingly from Scandinavia and the British Isles, there are also traces of a lineage normally found among the indigenous peoples of northeast Asia and the Americas. Preliminary genealogical analyses have shown that this lineage was present in Iceland at least 300 years ago. 

This raised the intriguing possibility that the Icelandic C1 lineage could be traced to Viking voyages to the Americas that commenced in the 10th century. In an attempt to shed further light on the entry date of the C1 lineage into the Icelandic mtDNA pool and its geographical origin, we used the deCODE Genetics genealogical database to identify additional matrilineal ancestors that carry the C1 lineage and then sequenced the complete mtDNA genome of 11 contemporary C1 carriers from four different matrilines. Our results indicate a latest possible arrival date in Iceland of just prior to 1700 and a likely arrival date centuries earlier. Most surprisingly, we demonstrate that the Icelandic C1 lineage does not belong to any of the four known Native American (C1b, C1c, and C1d) or Asian (C1a) subclades of haplogroup C1. Rather, it is presently the only known member of a new subclade, C1e. (Ebenesersdóttir et al. 2011)

I doubt the hypothesis of Amerindian admixture. As the authors note, the C1e subclade has not been found in any indigenous population of the Americas. Perhaps this is because those populations have not been studied as thoroughly as the Icelandic one. Perhaps it is present among Amerindians, but at a frequency too low to be detected by studies done to date.

But why, then, do we see no other Amerindian subclades in Icelanders? That population has been studied so exhaustively that even low frequencies of other subclades should have been detected by now. This point is made by Der Sarkissian et al. (2014):

Among other hypotheses including that of a European origin, an American origin was favoured on the basis that most of the hg C1 diversity is found on the American continent, despite the fact that no sequence belonging to hg C1e could be detected in the Americas (or anywhere else). This lack of match was explained by under-sampling of the American mtDNA genome diversity [10]. In any case, if admixture between Native Americans and Vikings did occur, it must have been limited, as no other American-specific lineage (e.g. hg A2, B2, D1, C1b, C1c, C1d) was detected in Iceland.

The authors of the same study point out that a sister subclade, C1f, has been found in human remains from Mesolithic northeast Europe. Moreover, it is not excluded that these two sister subclades, C1e and C1f, still exist in northeast Europe. The Icelandic population has been studied much more than almost any other population, so C1e might still exist somewhere in northeast Europe but hasn't been found because of its low frequency. The authors conclude:

... we suggest that the Icelandic-specific C1e sub-clade could have had a recent origin in northern Europe rather than an American origin. This hypothesis is relevant with regard to the origins of the Icelandic population, as Iceland was discovered and first settled by Scandinavian Vikings around 1,130 years ago. Vikings raids extended as far from their homeland in Scandinavia as France, Spain and Sicily, but their main expansion range comprised western Russia, the Baltic region, Scandinavia, and the British Isles.

In fact, we know that some of Iceland's settlers had trading contacts with Russia and may have had slaves of Slavic origin:

No name given in Landnámabók resembles any Slavic form. But the settlers who came from Sweden and Gotland (e.g. S. 209) must have had various contacts with the Slavs. This would be the case also with some Norwegians who like Skinna-Bjöm 'used to go trading to Novgorod' before he went to Iceland. His son Miðjarðar-Skeggi 'went to plunder in the Baltic' (S. 174 and H. 140). Such people were very likely to have aboard their ships Slavic slaves and/or companions recruited from among southern Baltic pirates or inhabitants of the multiethnic emporia like Wolin/Jómsborg or Truso. (Urbanczyk 2002, p. 160)

A Slavic presence in Iceland is further suggested by the existence of "sunken huts"—rectangular-like depressions in the ground with vertical walls, stone ovens placed in one of the corners, and roof constructions supported by corner posts. To date, the remains of eighteen such huts have been discovered in Iceland, and they seem to date to the settlement period. They are also typically Slavic:

Considering the houses they built there is little alternative to the conclusion that they were Slavs or, at least, people who grew up among the Slavs which made them 'Slavs' culturally. Such houses, distinctively different from the Germanic sunken huts are known in thousands from all the lands settled by early Slavs in Eastern, Southern and Central Europe. (Urbanczyk 2002, p. 163)

It should be pointed out that the Norse were major players in the early medieval slave trade, particularly in supplying North African and Middle Eastern clients with fair-skinned women. One of the largest slave markets was at Hederby, on what is now the Danish-German border. It was largely to cash in on the demand for slaves that the Norse began launching their infamous raids across Europe (Holm 1986; Raffield 2019; Skirda 2010, 143-146). Regular visits by Muslim merchants likely explain the influx of Middle Eastern silver coins into Scandinavia during the ninth and tenth centuries (Raffield 2019). 

Such visits may also explain the presence of low levels of North African ancestry in the Icelandic gene pool. Ásmundsdóttir (2017) argues that this North African ancestry entered the Icelandic gene pool by way of the initial Scandinavian settlers. It may thus have its origins in merchants from Muslim Spain and North Africa who regularly came to trading centers like Hederby.


References

Ásmundsdóttir R.D. (2017). The African L3e5a haplogroup in the Icelandic population.
Skemman repository of dissertations
https://skemman.is/handle/1946/27644

Der Sarkissian, C., P. Brotherton, O. Balanovsky, J.E. Templeton, B. Llamas, J. Soubrier, V. Moiseyev, V. Khartanovich, A. Cooper, W. Haak, and Genographic Consortium (2014). Mitochondrial genome sequencing in Mesolithic North East Europe Unearths a new sub-clade within the broadly distributed human haplogroup C1. PloS one 9(2), e87612. 
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3913659/ 

Ebenesersdóttir, S.S., Á. Sigurðsson, F. Sánchez-Quinto, C. Lalueza-Fox, K. Stefánsson, and A. Helgason, (2011). A new subclade of mtDNA haplogroup C1 found in icelanders: Evidence of pre-columbian contact? American Journal of Physical Anthropology 144: 92-99.
https://onlinelibrary.wiley.com/doi/abs/10.1002/ajpa.21419

Holm, P. (1986). The Slave trade of Dublin, Ninth to Twelfth Centuries. Peritia 5: 317-45.

Raffield, B. (2019). The Slave Markets of the Viking World: Comparative Perspectives on an 'Invisible Archaeology'. Slavery & Abolition 40(4)

Sailer, S. (2020). Are Any Living Humans Descended from Pre-1492 Trans-Atlantic Contacts? The Unz Review, February 20
https://www.unz.com/isteve/are-any-living-humans-descended-from-pre-1492-trans-atlantic-contacts/#new_comments

Skirda, A. (2010). La traite des Slaves. L'esclavage des Blancs du VIII^e au XVIII^e siècle. Paris: Les Éditions de Paris Max Chaleil.

Urbanczyk, P. (2002). Ethnic aspects of the settlement of Iceland. Collegium medievale: interdisciplinary journal of medieval research 15:155-166
http://www.mgh-bibliothek.de/dokumente/b/b071118.pdf

Yes, the decline is genetic

Average polygenic score for educational attainment, by year of birth in Iceland. The blue line is a quadratic fit for the full range of birth years. The red line is a linear fit for people born in or after 1940. (Kong et al. 2017)

For most of the 20th century mean IQ went up at the rate of 3 points per decade throughout the Western world. This is the Flynn effect (Rindermann 2018, pp. 85-89). Much of the increase seems to have involved a change in mental priorities rather than a rise in intelligence: a culture of doing as we're told has given way to a culture of having several possible responses and picking the right one. But some of the increase seems real, being perhaps due to better nutrition and a more stimulating learning environment.

The Flynn effect is now running out of steam (Flynn 2007, p. 143). In Scandinavia, mean IQ peaked during the late 1990s and has since declined (Teasdale and Owen 2005). Using the Norwegian population registry, two economists, Bernt Bratsberg and Ole Rogeberg, attribute this decline largely, if not entirely, to "within-family variation." In other words, IQ has been declining even among people of similar genetic background, i.e., siblings. So this decline is not due to the poor outbreeding the rich or immigrants outbreeding natives.

All the same, a genetic cause cannot be excluded. In Norway, siblings are less and less genetically similar; they are increasingly half-siblings. This factor can especially affect the methodology of Bratsberg and Rogeberg (2018) because the IQ decline is most measurable between siblings who are born farther apart. As this birth interval increases, so does the probability that the younger siblings is a half-sibling.

This is not a minor factor. Bratsberg and Rogeberg were looking at pairs of brothers. (The IQ data come from the military conscript register, and only men are subject to conscription). To produce a pair of brothers, a woman has to have three children on average. Among Norwegian women with three children, 36.2% have had them by two or more men (Thomson et al. 2014). Furthermore, because those children tend to be born farther apart than children born to the same father, they contribute more to within-family variation.

If the genetic basis of intelligence has been declining within Norwegian families, specifically between older and younger half-siblings, two things must be happening:

1. The average divorced mother has her second child by a man who belongs to a lower-IQ segment of the Norwegian population.

2. Such men have been contributing more than other men to succeeding generations of Norwegians, at least during the last forty years. This point is important. Even if we look only at first-born sons, mean IQ has steadily declined among Norwegians born since c. 1975 (Bratsberg and Rogeberg 2018).

The first point has been proven by Lappegård et al. 2011) in their study of fatherhood and fertility in Norway. Multi-partner fatherhood is most common among men with the lowest level of education (10 years of schooling, "i.e., compulsory education"). Second place goes to men with college or university education (14 to 17 years of schooling, "tertiary degree"), and third place goes to men with upper secondary (11 to 13 years of schooling). 

At age 45, about 15 percent of all men in the 1960-62 cohort with a compulsory education had had children with more than one woman, compared to about 5 percent among men with a tertiary degree. If looking at fathers only (Figure 6), the pattern becomes even more pronounced. At the lowest educational level, 19.3 percent of those who had become fathers, had children with more than one woman, compared to 6.1 percent of those at the highest educational level. (Lappegård et al. 2011)

As for the second point, Lappegård et al. (2011) found that reproductive success is more variable among men with the lowest level of education. Such men have the highest rate of childlessness of all three groups, while having the highest level of multi-partner fertility. Moreover, multi-partner fertility has increased over time among these men, while childlessness has remained constant. Their overall reproductive success has thus gone up:

Like childlessness, multi-partner fertility has increased across cohorts, but unlike childlessness it has increased more among men with lower education than among those with higher education. From the 1940-44 cohort to the 1960-62 cohort the proportion of fathers who had children with more than one woman more than doubled (from 8.9% to 19.3%) in the compulsory schooling group, while it only rose by about 30% in the highest tertiary group, from 4.7 to 6.1 percent. (Lappegård et al. 2011)

Thomson et al. (2014) made the same observation:

In all countries [Australia, United States, Norway, Sweden], however, education is negatively associated with childbearing across partnerships, and the differentials increased from the 1970s to the 2000s.

Moreover, official statistics do not fully capture multi-partner fatherhood. It can be difficult to identify the paternity of children whose biological father is little more than a sperm donor. Lappegård et al. (2011) allude to this difficulty: "some of these men have never been in a stable relationship with the mother." This is less of a problem in Norway, where "only about 1-1.5 percent of the total number of children has no registered father."  The registered "father" may nonetheless be a cuckolded husband or a boyfriend who has agreed to assume paternity of the unborn child. The second situation is not uncommon if the woman is still young and attractive.

It seems, then, that modern Norwegian culture is facilitating the reproductive success of low IQ men. One such man was Anders Breivik's stepfather:

My stepfather Tore, one of my best friends Marius and my more distant friends Kristoffer, Sturla and Ronny are all living manifestations of the complete breakdown of sexual moral. All five have had more than 300 sexual partners (two of them more than 700) and I know for a fact that three of them have one or more STDs (probably all of them).

[...] My mother was infected by genital herpes by her boyfriend (my stepfather), Tore, when she was 48. Tore, who was a captain in the Norwegian Army, had more than 500 sexual partners and my mother knew this but suffered from lack of good judgement and moral due to several factors (media - glorification of certain stereotypes being one).

[...] Tore, my stepfather, worked as a major in the Norwegian military and is now retired. I still have contact with him although now he spends most his time (retirement) with prostitutes in Thailand. He is a very primitive sexual beast, but at the same time a very likable and good guy. (Breivik 2011)

The evidence from Iceland

Iceland isn't Norway but it is culturally similar. According to a recent study, the genetic basis of intelligence has been declining in that country since the cohort born in 1910. The authors used a "polygenic score," based on alleles associated with high educational attainment, to measure the genetic potential for academic achievement from generation to generation:

Here, we investigate the effect of this genetic component on the reproductive history of 109,120 Icelanders and the consequent impact on the gene pool over time. We show that an educational attainment polygenic score, POLYEDU, constructed from results of a recent study is associated with delayed reproduction (P < 10-100) and fewer children overall. The effect is stronger for women and remains highly significant after adjusting for educational attainment. Based on 129,808 Icelanders born between 1910 and 1990, we find that the average POLYEDU has been declining at a rate of ~0.010 standard units per decade, which is substantial on an evolutionary timescale.

This is the same polygenic score I've discussed in previous posts, such as Frost (2018). Certain genetic variants are associated with high educational attainment and others with low educational attainment. Do these variants determine our capacity for intelligence? For the most part, yes, but I suspect that many of them have a stronger bearing on time preference or willingness to sit still in a classroom. The authors concede this point:

We postulate that, in addition to being correlated with cognitive ability (32, 33), POLYEDU is capturing a portion of the propensity to long-term planning and delayed gratification. (Kong et al. 2017)

These other traits still matter. Together, they form a mental/behavioral package that coevolved with the rising middle class over the last millennium, eventually spreading through all social strata (Clark 2007; Clark 2009a; Clark 2009b). That evolution is now unravelling. Reproductive success is shifting toward individuals with "fast life-history": lower cognitive ability, weaker orientation toward the future, and, for men, a larger number of sexual partners with less investment in the resulting offspring (Frost 2012; but see also JayMan 2012). This shift began seventy years before the decline in IQ scores.

It seems, then, that the Flynn effect has masked a longer-term decline in the genetic basis of intelligence and other mental/behavioral traits. This is in line with other recent findings. Woodley et al. (2013) argue that mean reaction time has increased in Great Britain by 13 points since Victorian times, although this finding may be an artefact of better sampling of the general population over time (hbd* chick, 2013). Another study, however, using Swedish subjects, has confirmed this lengthening of reaction time, particularly in cohorts born since the 1970s (Madison 2014; Madison et al. 2016).

Conclusion

The recent reversal of the Flynn effect seems to result from two trends:

1. a positive trend based on increasing familiarity with tests and test-taking, as well as improvements in nutrition and a more stimulating learning environment;

2. a negative trend due to dysgenic factors.

For most of the 20th century the positive trend overwhelmed the negative trend. In Norway, the negative trend has had the upper hand in post-1975 cohorts, partly because the positive trend has exhausted all room for improvement and partly because the current culture is facilitating the reproductive success of sexy, low-IQ men.

I've long believed that human evolution didn't stop in the Pleistocene. Nor did it slow down. In fact, we've changed much more over the past 10,000 years than over the previous 100,000, and I'm talking here not only about our outward appearance but also about our inward qualities of mind and behavior. But we can quickly lose what we so quickly gained. This reverse evolution is now taking place, and it’s visible even in the relatively closed system of Iceland's gene pool.

I used to be unconcerned about dysgenics. Any negative trends would surely take hundreds of years to produce serious consequences. So we would have plenty of time to get all of the relevant facts, discuss everything thoroughly with everyone, and reach a consensus. Well, I was wrong. Our dystopic future is close at hand.

References

Bratsberg, B., and O. Rogeberg. (2018). Flynn effect and its reversal are both environmentally caused. Proceedings of the National Academy of Sciences Jun 2018, DOI: 10.1073/pnas.1718793115

https://sci-hub.tw/https://doi.org/10.1073/pnas.1718793115  

Breivik, A. (2011). A European declaration of independence.

https://publicintelligence.net/anders-behring-breiviks-complete-manifesto-2083-a-european-declaration-of-independence/

Clark, G. (2007). A Farewell to Alms. A Brief Economic History of the World. Princeton University Press: Princeton and Oxford.

Clark, G. (2009a) The indicted and the wealthy: surnames, reproductive success, genetic selection and social class in pre-industrial England.

http://www.econ.ucdavis.edu/faculty/gclark/Farewell%20to%20Alms/Clark%20-Surnames.pdf

Clark, G. (2009b). The domestication of man: The social implications of Darwin. ArtefaCTos 2: 64-80.

https://www.researchgate.net/publication/277275046_The_Domestication_of_Man_The_Social_Implications_of_Darwin

Flynn, J.R. (2007). What is Intelligence? Beyond the Flynn Effect. Cambridge University Press.

https://books.google.ca/books?id=qvBipuypYUkC&printsec=frontcover&hl=fr&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false

Frost, P. (2018). A new yardstick. Evo and Proud, May 14

http://evoandproud.blogspot.com/2018/05/a-new-yardstick.html

Frost, P. (2012). Are the cads outbreeding the dads? Evo and Proud, November 3

http://evoandproud.blogspot.com/2012/11/are-cads-outbreeding-dads.html

Hbd* chick (2013). a response to a response to two critical commentaries on woodley, te nijenhuis & murphy (2013), hbd* chick, May 27

http://hbdchick.wordpress.com/2013/05/27/a-response-to-a-response-to-two-critical-commentaries-on-woodley-te-nijenhuis-murphy-2013/

JayMan (2012). It's not the cads, it's the tramps. JayMan's Blog, December 28

https://jaymans.wordpress.com/2012/12/28/its-not-the-cads-its-the-tramps/

Kong, A., M.L. Frigge, G. Thorleifsson, H. Stefansson, A.I. Young, F. Zink, G.A. Jonsdottir, A. Okbay, P. Sulem, G. Masson, D.F. Gudbjartsson, A. Helgason, G. Bjornsdottir, U. Thorsteinsdottir, and K. Stefansson. (2017). Selection against variants in the genome associated with educational attainment. Proceedings of the National Academy of Sciences 114(5): E727-E732.

http://www.pnas.org/content/early/2017/01/10/1612113114.full

Lappegård, T., Rønsen, M., & Skrede, K. (2011). Fatherhood and fertility. Fathering 9: 103-120.

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.839.2752&rep=rep1&type=pdf

Madison, G. (2014). Increasing simple reaction times demonstrate decreasing genetic intelligence in Scotland and Sweden, London Conference on Intelligence, Psychological comments, April 25

#LCI14 Conference proceedings

http://www.unz.com/jthompson/lci14-questions-on-intelligence/

Madison, G., M.A. Woodley of Menie, and J. Sänger. (2016). Secular Slowing of Auditory Simple Reaction Time in Sweden (1959-1985). Frontiers in Human Neuroscience, August 18

https://www.frontiersin.org/articles/10.3389/fnhum.2016.00407/full

Teasdale, T.W., and D.R. Owen. (2005). A long-term rise and recent decline in intelligence test performance: The Flynn Effect in reverse. Personality and Individual Differences 39(4): 837-843.

https://doi.org/10.1016/j.paid.2005.01.029

Thomson, E., T. Lappegård, M. Carlson, A. Evans, and E. Gray (2014). Childbearing across partnerships in Australia, the United States, Norway, and Sweden. Demography 51(2): 485-508

https://link.springer.com/article/10.1007/s13524-013-0273-6

Woodley, M.A., J. Nijenhuis, and R. Murphy. (2013). Were the Victorians cleverer than us? The decline in general intelligence estimated from a meta-analysis of the slowing of simple reaction time. Intelligence 41: 843-850.

https://pdfs.semanticscholar.org/e8cc/634169c7c5d3e4738fe08091c86177be1380.pdf