At the present time, postmenopausal women represent more than fifteen percent of the world's population and this figure is likely to grow. From an evolutionary perspective, these demographic numbers pose some intriguing questions. Darwinian theory holds that a successful life is measured in terms of reproduction. How is it, then, that a woman's lifespan can greatly exceed her childbearing and childrearing years? Is this phenomenon simply a byproduct of improved standards of living, or do older women-grandmothers in particular-play a measurable role in increasing their family members'...