Fig. 1.

Schematic diagram depicting approximate ages at puberty, menopause, and maximum life span of female macaques (Macaca spp.), chimpanzees (Pan troglodytes), and humans (Homo sapiens). Bars are aligned to the age at menopause; shading indicates the fertile time span between onset of puberty and menopause. Approximate ages used are based upon references [15, 16, 18, 48, 49] : puberty: 3.5, 8, 12.5 years; median life span: 16, 26, 80 years; menopause: 25, 50, 50 years; life span: 35, 60, 100 years. The age of 100 years was arbitrarily chosen for the human life span because survival to this age is very rare; only about 2 years of life expectancy remain in 20th century European and North American cohorts [50].