Figure 3. Epidemiological evidence for a genetic component to variation in human lifespan. a.
Similarity in lifespan for monozygotic and dizygotic Danish twins of the same sex from cohorts born between 1870 and 1900 and who survived to at least the age of 6. Each dot in the graphs represents a twin pair. The pattern indicates that approximately one-quarter of the variation in lifespan can be attributed to genetic factors. Data are from REF. 27. b. Similarity in longevity between siblings in a US population. The relative chance of survival until the age of 60–94 for siblings of centenarians versus siblings of individuals who died at 73 years of age20.