Heritability of IQ

Research on the heritability of IQ inquires into the degree of variation in IQ within a population that is due to genetic variation between individuals in that population. There has been significant controversy in the academic community about the heritability of IQ since research on the issue began in the late nineteenth century.[1][2] Intelligence in the normal range is a polygenic trait, meaning that it is influenced by more than one gene,[3][4] and in the case of intelligence at least 500 genes.[5] Further, explaining the similarity in IQ of closely related persons requires careful study because environmental factors may be correlated with genetic factors.

Early twin studies of adult individuals have found a heritability of IQ between 57% and 73%,[6] with some recent studies showing heritability for IQ as high as 80%.[7] IQ goes from being weakly correlated with genetics for children, to being strongly correlated with genetics for late teens and adults. The heritability of IQ increases with the child's age and reaches a plateau at 14–16[8] years old, continuing at that level well into adulthood. However, poor prenatal environment, malnutrition and disease are known to have lifelong deleterious effects.[9][10]

Although IQ differences between individuals have been shown to have a large hereditary component, it does not follow that disparities in IQ between groups have a genetic basis.[11][12][13][14] The scientific consensus is that genetics does not explain average differences in IQ test performance between racial groups.[15][16][17][18][19][20]

  1. ^ Cite error: The named reference devlin was invoked but never defined (see the help page).
  2. ^ Rose, Steven P R (June 2006). "Commentary: Heritability estimates—long past their sell-by date". International Journal of Epidemiology. 35 (3): 525–527. doi:10.1093/ije/dyl064. PMID 16645027.
  3. ^ Alice Marcus. 2010. Human Genetics: An Overview. Alpha Science section 14.5
  4. ^ Davies, G.; Tenesa, A.; Payton, A.; Yang, J.; Harris, S. E.; Liewald, D.; Deary, I. J. (2011). "Genome-wide association studies establish that human intelligence is highly heritable and polygenic". Molecular Psychiatry. 16 (10): 996–1005. doi:10.1038/mp.2011.85. PMC 3182557. PMID 21826061.
  5. ^ Association, New Scientist staff and Press. "Found: more than 500 genes that are linked to intelligence". New Scientist. Archived from the original on 2019-12-13. Retrieved 2018-11-29.
  6. ^ Cite error: The named reference pmid12486697 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference Bouchard2013W was invoked but never defined (see the help page).
  8. ^ Icenogle, G.; Steinberg, L.; Duell, N.; Chein, J.; Chang, L.; Chaudhary, N.; Di Giunta, L.; Dodge, K. A.; Fanti, K. A.; Lansford, J. E.; Oburu, P.; Pastorelli, C.; Skinner, A. T.; Sorbring, E.; Tapanya, S.; Tirado, L. M.; Alampay, L. P.; Al-Hassan, S. M.; Takash, H. M.; Bacchini, D. (2019). "Adolescents' Cognitive Capacity Reaches Adult Levels Prior to Their Psychosocial Maturity: Evidence for a "Maturity Gap" in a Multinational, Cross-Sectional Sample". Law and Human Behavior. 43 (1): 69–85. doi:10.1037/lhb0000315. PMC 6551607. PMID 30762417.
  9. ^ Lutter, C. K.; Lutter, R. (2012). "Fetal and Early Childhood Undernutrition, Mortality, and Lifelong Health". Science. 337 (6101): 1495–1499. Bibcode:2012Sci...337.1495L. doi:10.1126/science.1224616. hdl:1903/24471. PMID 22997328. S2CID 45170027.
  10. ^ Daniele, V. (2013). "The burden of disease and the IQ of nations". Learning and Individual Differences. 28: 109–118. doi:10.1016/j.lindif.2013.09.015.
  11. ^ Visscher, Peter M.; Hill, William G.; Wray, Naomi R. (2008). "Heritability in the genomics era – concepts and misconceptions". Nature Reviews Genetics. 9 (4): 255–266. doi:10.1038/nrg2322. PMID 18319743. S2CID 690431.
  12. ^ Cite error: The named reference :9 was invoked but never defined (see the help page).
  13. ^ Nisbett, Richard E.; Aronson, Joshua; Blair, Clancy; Dickens, William; Flynn, James; Halpern, Diane F.; Turkheimer, Eric (2012). "Intelligence: New findings and theoretical developments". American Psychologist. 67 (2): 130–159. doi:10.1037/a0026699. ISSN 1935-990X. PMID 22233090.
  14. ^ Mitchell, Kevin (2 May 2018). "Why genetic IQ differences between 'races' are unlikely: The idea that intelligence can differ between populations has made headlines again, but the rules of evolution make it implausible". The Guardian. Archived from the original on 29 June 2020. Retrieved 13 June 2020.
  15. ^ Ceci, Stephen; Williams, Wendy M. (1 February 2009). "Should scientists study race and IQ? YES: The scientific truth must be pursued". Nature. 457 (7231): 788–789. Bibcode:2009Natur.457..788C. doi:10.1038/457788a. PMID 19212385. S2CID 205044224. There is an emerging consensus about racial and gender equality in genetic determinants of intelligence; most researchers, including ourselves, agree that genes do not explain between-group differences.
  16. ^ Panofsky, Aaron; Dasgupta, Kushan; Iturriaga, Nicole (28 September 2020). "How White nationalists mobilize genetics: From genetic ancestry and human biodiversity to counterscience and metapolitics". American Journal of Physical Anthropology. 175 (2): 387–398. doi:10.1002/ajpa.24150. PMC 9909835. PMID 32986847. [T]he claims that genetics defines racial groups and makes them different, that IQ and cultural differences among racial groups are caused by genes, and that racial inequalities within and between nations are the inevitable outcome of long evolutionary processes are neither new nor supported by science (either old or new).
  17. ^ Hunt, Earl (2010). Human Intelligence. Cambridge University Press. p. 447. ISBN 978-0-521-70781-7. OL 24384631M – via Open Library. [N]o genes related to the difference in cognitive skills across the various racial and ethic groups have ever been discovered.
  18. ^ Mackintosh, N. J. (2011). IQ and human intelligence (2nd ed.). Oxford: Oxford University Press. pp. 334–338, 344. ISBN 978-0-19-958559-5. OCLC 669754008. OL 25211083M – via Open Library.
  19. ^ Nisbett, Richard E.; Aronson, Joshua; Blair, Clancy; Dickens, William; Flynn, James; Halpern, Diane F.; Turkheimer, Eric (2012). "Group differences in IQ are best understood as environmental in origin" (PDF). American Psychologist. 67 (6): 503–504. doi:10.1037/a0029772. ISSN 0003-066X. PMID 22963427. Archived (PDF) from the original on 23 January 2015. Retrieved 22 July 2013.
  20. ^ Kaplan, Jonathan Michael (January 2015). "Race, IQ, and the search for statistical signals associated with so-called "X"-factors: environments, racism, and the "hereditarian hypothesis"". Biology & Philosophy. 30 (1): 1–17. doi:10.1007/s10539-014-9428-0. ISSN 0169-3867. S2CID 85351431.