New evidence of dysgenic fertility for intelligence in the United States

Lynn, Richard; Court, Marian Van

doi:10.1016/j.intell.2003.09.002

Cited by 48 publications

(15 citation statements)

References 17 publications

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“…This is consistent with the co-occurrence model, as it is performance on the most difficult (and therefore most g -loaded) words that is declining. These trends would furthermore be congruent with the presence of persistent negative associations between IQ and fertility on WORDSUM vocabulary knowledge, which have been found in GSS birth cohorts dating back to 1880–1899 (van Court and Bean, 1985; Lynn and van Court, 2004). …”

Section: Introductionsupporting

confidence: 67%

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By their words ye shall know them: Evidence of genetic selection against general intelligence and concurrent environmental enrichment in vocabulary usage since the mid 19th century

2015

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It has been theorized that declines in general intelligence (g) due to genetic selection stemming from the inverse association between completed fertility and IQ and the Flynn effect co-occur, with the effects of the latter being concentrated on less heritable non-g sources of intelligence variance. Evidence for this comes from the observation that 19th century populations were more intellectually productive, and also exhibited faster simple reaction times than modern ones, suggesting greater information-processing ability and therefore higher g. This co-occurrence model is tested via examination of historical changes in the utilization frequencies of words from the highly g-loaded WORDSUM test across 5.9 million texts spanning the period 1850–2005. Consistent with predictions, words with higher difficulties (δ parameters from Item Response Theory) and stronger negative correlations between pass rates and completed fertility declined in use over time whereas less difficult and less strongly selected words, increased in use over time, consistent with a Flynn effect stemming in part from the vocabulary enriching effects of increases in population literacy. These findings persisted when explicitly controlled for word age, changing literacy rates and temporal autocorrelation. These trends constitute compelling evidence for the co-occurrence model.

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Section: Introductionsupporting

confidence: 67%

“…Early use of IQ testing seemed to confirm Galton’s (1869) predictions, as most studies found that IQ was inversely related to fertility, suggesting directional genetic selection for lower intelligence (Lynn, 2011) – a trend that persists into the present (Lynn and van Court, 2004; Meisenberg, 2010; Reeve et al, 2013; Kanazawa, 2014). …”

Section: Introductionmentioning

confidence: 99%

By their words ye shall know them: Evidence of genetic selection against general intelligence and concurrent environmental enrichment in vocabulary usage since the mid 19th century

2015

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“…This process eventually led to the Industrial Revolution in Europe (28,29). The millennia long directional selection favouring higher GCA not only ceased, but went into reverse among Europeanderived populations living in the 19 th century (30), largely in response to factors such as the asymmetric use of birth control and prolonged exposure to education among those with high GCA (31). Consistent with this, it has been found that various POLY COG negatively predict fertility in contemporary Western populations (21,22,23,24).…”

Section: Discussionmentioning

confidence: 99%

Holocene selection for variants associated with cognitive ability: Comparing ancient and modern genomes

Younuskunja

Balan²,

Piffer

2017

Preprint

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Human populations living in Eurasia during the Holocene experienced considerable microevolutionary change. It has been predicted that the transition of Holocene populations into agrarianism and urbanization brought about culture-gene coevolution that favoured via directional selection genetic variants associated with higher general cognitive ability (GCA). To examine whether GCA might have risen during the Holocene, we compare a sample of 99 ancient Eurasian genomes (ranging from 4.56 to 1.21 kyr BP) with a sample of 503 modern European genomes, using three different cognitive polygenic scores. Significant differences favouring the modern genomes were found for all three polygenic scores (Odds Ratios=0.92, p=0.037; 0.81, p=0.001 and 0.81, p=0.02). Furthermore, a significant increase in positive allele count over 3.25 kyr was found using a subsample of 66 ancient genomes (r=0.217, p one-tailed =0.04). These observations are consistent with the expectation that GCA rose during the Holocene.peer-reviewed)

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“…Research on the IQ -fertility relationship has largely focused on the USA, with some studies using nationally representative samples and others focusing upon data from the Midwest, though a smaller number of studies have examined other high-income countries [6,[17][18][19][20][21]. These studies suggest that there has been a transition in the relationship between intelligence and fertility over time, from no clear gradient among cohorts born in the first half of the twentieth century, to a small to moderate negative gradient (i.e.…”

Section: (A) Previous Research On Intelligence and Fertilitymentioning

confidence: 99%

Cognitive ability and fertility among Swedish men born 1951–1967: evidence from military conscription registers

Kolk

Barclay

2019

Proc. R. Soc. B.

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We examine the relationship between cognitive ability and childbearing patterns in contemporary Sweden using administrative register data. The topic has a long history in the social sciences and has been the topic of a large number of studies, many reporting a negative gradient between intelligence and fertility. We link fertility histories to military conscription tests with intelligence scores for all Swedish men born 1951-1967. We find a positive relationship between intelligence scores and fertility, and this pattern is consistent across the cohorts we study. The relationship is most pronounced for the transition to a first child, and men with the lowest categories of IQ scores have the fewest children. Using fixed effects models, we additionally control for all factors that are shared by siblings, and after such adjustments, we find a stronger positive relationship between IQ and fertility. Furthermore, we find a positive gradient within groups at different levels of education. Compositional differences of this kind are therefore not responsible for the positive gradient we observe-instead, the relationship is even stronger after controlling for both educational careers and parental background factors. In our models where we compare brothers to one another, we find that, relative to men with IQ 100, the group with the lowest category of cognitive ability have 0.56 fewer children, and men with the highest category have 0.09 more children.

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New evidence of dysgenic fertility for intelligence in the United States

Cited by 48 publications

References 17 publications

By their words ye shall know them: Evidence of genetic selection against general intelligence and concurrent environmental enrichment in vocabulary usage since the mid 19th century

By their words ye shall know them: Evidence of genetic selection against general intelligence and concurrent environmental enrichment in vocabulary usage since the mid 19th century

Holocene selection for variants associated with cognitive ability: Comparing ancient and modern genomes

Cognitive ability and fertility among Swedish men born 1951–1967: evidence from military conscription registers

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