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The heritability of human longevity was investigated in a sample of 218 pairs of monozygotic (MZ) and 382 pairs of like-sex dizygotic (DZ) Danish twin pairs born 1870-1880. Twin similarity for age at death was significant for MZ twins but nonsignificant for DZ twins. The heritability (h2) of life span estimated from the best-fitting biometrical model was statistically significant but moderate in magnitude (h2 = .333 +/- .058). Heritability of longevity did not vary by gender, and the pattern of twin resemblance was more consistent with nonadditive as compared to additive genetic effects. In addition, evidence for a genetic association between premature and senescent deaths was observed. Although environmental factors accounted for a majority of the variance in life span, the relevant environmental factors appeared to be those that create differences rather than similarities among reared-together relatives. Findings are discussed in terms of their relevance for understanding the inheritance and evolution of human life span.
McGue et al. (Mon,) studied this question.