Grandmotherhood: The Evolutionary Significance of the Second Half of Female LifeBy the year 2030, the average life expectancy of women in industrialized countries could reach ninety exceeding that of men by about ten years. 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