Mortality Leveling

One of the oldest but still debated question in evolutionary demography is about the shape of the mortality trajectory for humans at extreme ages. Several studies suggested that for humans adult and early-old death rates rise exponentially up to about age 80 and thereafter decelerate. Other studies, however, found that the exponential increase of the mortality risk with age continues at advanced ages in humans. Recent studies on exceptionally long-lived individuals have shown that the trajectory of mortality levels off at extreme ages. This is consistent with the theory of the selective survival in heterogeneous populations. However, other evolutionary explanations are possible.