The accuracy of current heritability estimates is also important, because experimentally identified variants could never explain all the variance in an erroneously inflated heritability estimate. Heritability of quantitative traits, formally defined as the proportion of phenotypic variance in a population attributable to additive genetic factors (narrow-sense heritability, h2 (ref. 36)) is typically estimated from family studies, and can be expected to vary across environments. Narrow-sense heritability estimates in humans can be inflated if family resemblance is influenced by non-additive genetic effects (dominance and epistasis, or gene–gene interaction), shared familial environments, and by correlations or interactions among genotypes and environment36,37. However, heritabilities estimated from pedigree studies in animals agree well with heritability estimated from response to artificial selection, suggesting that estimates from family studies are not necessarily inflated.
