Negative senescence is characterized by a decline in mortality with age after reproductive maturity, generally accompanied by an increase in fecundity. Hamilton (1966) ruled out negative senescence: we adumbrate the deficiencies of his model. We review empirical studies of various plants and...

Humans, and many other species, suffer senescence: mortality increases and fertility declines with adult age. Some species, however, enjoy sustenance: mortality and fertility remain constant. Here we develop simple but general evolutionary-demographic models to explain the conditions that favor...

The evolution of different life history strategies and thus different ageing patterns essentially depends on the nature of the underlying trade-offs between survival and reproduction. To fully comprehend ageing, we need to understand these trade-offs.

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Hamilton quantified the force of selection on an age-specific mutation. Hamilton’s indicators of the age-specific force of selection always decline with age. This result is of profound importance to the theory of the evolution of senescence. Here I derive alternative indicators within...

The ratio (RMR) is the standard measure of sex differentials in mortality. It is commonly known that the RMR was historically small and increased throughout the 20th century. However, numerical properties might account for the trend in the RMR rather than sex differences in risk factors. In this...

Patterns of diversity in age at death are examined using e†, a dispersion measure that also equals the average expected lifetime lost at death. We apply two methods for decomposing differences in e†. The first method estimates the contributions of average levels of mortality and mortality...

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We study inter-individual variability in number of children among women. Concentration ratio (CR) and percentile measures are used. In most countries CR has increasing from cohorts of the 1930s-40s onward due to rise in childlessness. In cohorts of the early 1960s CR varies from 0.24 to 0.46...