LONGEVITY IS MODERATELY HERITABLE IN A SAMPLE OF DANISH TWINS BORN 1870-1880

The heritability of human longevity was investigated in a sample of 21 8 pairs of monozygotic (MZ) and 382 pairs of like-sex dizygotic (DZ) D anish twin pairs born 1870-1880. Twin similarity for age at death was significant for MZ twins but nonsignificant for DZ twins. The heritabi lity (h2) of life span estimated from the best-fitting biometrical mod el was statistically significant but moderate in magnitude (h2 = .333 +/- .058). Heritability of longevity did not vary by gender, and the p attern of twin resemblance was more consistent with nonadditive as com pared to additive genetic effects. In addition, evidence for a genetic association between premature and senescent deaths was observed. Alth ough environmental factors accounted for a majority of the variance in life span, the relevant environmental factors appeared to be those th at create differences rather than similarities among reared-together r elatives. Findings are discussed in terms of their relevance for under standing the inheritance and evolution of human life span.