Hamilton's Age-Specific Force of Natural Selection

Selection drove early-life survival toward one in the simulations, matching the theory of ageing. Hamilton's formula provides a linear approximation to the fitness cost of deleterious mutations that increase mortality at a specific age. Standard evolutionary theory predicts that selection weakens with age because fewer individuals survive to old age. The timing of care benefits determines whether selection maintains late-life survival. The same age-specific logic applies to descendant investment because potential care receivers vary across the caregiver's lifespan. Hamilton's age-specific force of natural selection links genetics and demography in theories of senescence.