  Standard evolutionary theories of aging and mortality, implicitly based on
assumptions of spatial averaging, hold that natural selection cannot favor
shorter lifespan without direct compensating benefit to individual reproductive
success. Here we show that both theory and phenomenology are consistent with
programmed death. Spatial evolutionary models show that self-limited lifespan
robustly results in long-term benefit to a lineage; longer-lived variants may
have a reproductive advantage for many generations, but shorter lifespan
ultimately confers long-term reproductive advantage through environmental
feedback acting on much longer time scales. Numerous model variations produce
the same qualitative result, demonstrating insensitivity to detailed
assumptions; the key conditions under which self-limited lifespan is favored
are spatial extent and locally exhaustible resources. Numerous empirical
observations can parsimoniously be explained in terms of long-term selective
advantage for intrinsic mortality. Classically anomalous empirical data on
natural lifespans and intrinsic mortality, including observations of longer
lifespan associated with increased predation, and evidence of programmed death
in both unicellular and multicellular organisms, are consistent with specific
model predictions. The generic nature of the spatial model conditions under
which intrinsic mortality is favored suggests a firm theoretical basis for the
idea that evolution can quite generally select for shorter lifespan directly.
