Rethinking the heritability of aging.

Life span varies strikingly across the tree of life. Baker's yeast survive for days, fruit flies for weeks to months, bowhead whales for more than two centuries, and bristlecone pines for millennia (1). Comparative studies have uncovered conserved biological mechanisms that regulate aging (2), leaving little doubt that genetics places strong constraints on how long organisms live. Nevertheless, classical aging experiments in animals show that there is considerable variability in life span, even among isogenic littermates, indicating that there's more to aging than genetics (3). Indeed, population-level studies on twins estimate that the heritability of human life span may be as little as 10 to 25% (4, 5), as do studies on pedigrees (6, 7). The prevailing view is that individual longevity is influenced largely by environmental factors and lifestyle. On page 504 of this issue, Shenhar et al. (8) challenge this notion, reporting that human heritability is 55%, considerably higher than previous estimates. [ABSTRACT FROM AUTHOR]