and the Grandmother Hypothesis

Evolutionary life-history theory and demography provide strong reasons to suppose that long human life spans are not a recent novelty. Here we focus on one robust model of mammalian life history evolution, and a grand-mother hypothesis about our own lineage that is based upon it. This hy-pothesis takes long adult life spans to be an ancient human trait. Claims that few adults survived to old age until the last century are a serious challenge to it. Such claims are generally based on the inference that when life expectancy is less than forty, most adults die before they grow old. We use demographic evidence to show that inference is wrong. Findings in paleo-demography also show that ancient skeletal assemblages do not reflect the age structure of past populations. By contrasting human and chimpanzee age structures, we further underline that point. The comparison with chim-panzees also serves to highlight the likely importance of ancestral grand-mothers in human evolution. Life History Evolutio