Beneficial cumulative effects of old parental age on offspring fitness

Old parental age is commonly associated with negative effects on offspring
life-history traits. Such parental senescence effects are predicted to
have a cumulative detrimental effect over successive generations. However,
old parents may benefit from producing higher quality offspring when these
compete for seasonal resources. Thus, old parents may choose to increase
investment in their offspring, thereby producing fewer but larger and more
competitive progeny. We show that Caenorhabditis elegans hermaphrodites
increase parental investment with advancing age, resulting in fitter
offspring who reach their reproductive peak earlier. Remarkably, these
effects increased over six successive generations of breeding from old
parents and were subsequently reversed following a single generation of
breeding from a young parent. Our findings support the hypothesis that
offspring of old parents receive more resources and convert them into
increasingly faster life-histories. These results contradict the theory
that old parents transfer a cumulative detrimental “ageing factor” to
their offspring.