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Proc Natl Acad Sci U S A. 1978 Aug; 75(8): 3906–3908.
PMCID: PMC392897

Effect of inbreeding on IQ and mental retardation.

N E Morton
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Abstract

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.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Rao DC, Morton NE, Yee S. Resolution of cultural and biological inheritance by path analysis. Am J Hum Genet. 1976 May;28(3):228–242. [PMC free article] [PubMed]
  • Morton NE, Miki C, Yee S. Bioassay of population structure under isolation by distance. Am J Hum Genet. 1968 Sep;20(5):411–419. [PMC free article] [PubMed]
  • MORTON NE. The mutational load due to detrimental genes in man. Am J Hum Genet. 1960 Sep;12:348–364. [PMC free article] [PubMed]
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