Underlying heterogeneity: a problem for biological, philosophical, and other analyses of heritability?
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Claims that some human trait, say, IQ test score at age 18, show high heritability derive from analysis of data from relatives. For example, the similarity of monozygotic twins (which share all their genes) can be compared with the similarity of dizygotic twins (which do not share all their genes). The more that the former quantity exceeds the latter, the higher the trait’s “heritability.” Researchers and commentators often describe such calculations as showing how much a trait is “heritable” or “genetic.” However, no genes or measurable, transmissable genetic factors (e.g., alleles, tandem repeats, chromosomal inversions) are examined in deriving heritability estimates, nor does the method of analysis suggest where to look for them. Moreover, even if the similarity among twins or a set of close relatives is associated with similarity of yet-to-be-identified genetic factors, the factors may not be the same from one set of relatives to the next, or from one situation to the next. In...
KeywordsHeritability Estimate Underlying Factor High Heritability Selective Breeding Dizygotic Twin
This letter is based on research supported by the National Science Foundation under grant SES-0634744.
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