Re:Most Reported Genetic Associations with Intelligence are ...
by bayesianhorse on Tuesday October 08, 2013 @11:56AM
(#6515811)
One example for the trouble with genetics in intelligence is the issue of Malaria: If a child gets Malaria, it will have a lower intelligence quotient. Resistance/resilience of Malaria sure has genetic factors. Would those factors show up in genetic studies about intelligence? Betcha.
Should we accept this variance in IQ as genetic and unavoidable? Or should we just buckle down, eradicate Malaria and stop worrying about these factors?
Studies of the issue of "missing heritability" have often investigated height (bodily stature), which has a very high calculated heritability (resemblance among close relatives) but which must be influenced by hundreds of genes, many of very small effect. Even very extensive genome-wide association studies (GWAS) in large samples find NO gene with large effect on height, and fail to detect most of the presumed associations with height in gene associations investigated in such studies.
The review article Johnson, W. (2010). Understanding the Genetics of Intelligence: Can Height Help? Can Corn Oil?. Current Directions in Psychological Science, 19(3), 177-182
http://apsychoserver.psych.arizona.edu/JJBAReprints/PSYC621/...
looks at some famous genetic experiments to show how little is explained by gene frequencies even in thoroughly studied populations defined by artificial selection.