| Description |
Chimpanzees (Pan troglodytes) are the best studied of the great apes and one of our closest living relatives. That makes them a preferred living referent for modeling life history characteristics of the first members of the human radiation. We share similarities in oldest ages of parturition and ovarian follicle decline, which are consistent with the hypothesis that humans retained ancestral patterns of ovarian aging while longevity increased in our lineage. Still, we know very little about aging and reproductive function in chimpanzees. To improve quantitative comparisons between chimpanzees and humans associated with the biology of menopause this dissertation employed a three-pronged approach: assessing ovarian follicle numbers, reproductive hormone levels, and grip strength across adulthood in captive female chimpanzees. The first chapter reports postmortem ovarian follicle stock sizes in 67 chimpanzees (age range 0-51 years), showing that depletion rates are similar to those published for women until around age 35, after which the human counts rapidly fall while the chimpanzee data show little age-dependent decline. The second chapter reports reproductive hormonal and cycling profiles of 16 aged female chimpanzees (mean age = 41.25 years), as well as one exceptionally old iv female (estimated age ~76 years). Results from this analysis once again show species differences: contrary to human patterns of the menopausal transition, chimpanzees do not experience hyperestrogenemia or decline in Pregnanediol-3-Glucuronide (PdG) with advancing age, nor do they exhibit an increase in follicle stimulating hormone (FSH). Additionally, whereas menstrual cycles shorten in women approaching menopause, chimpanzee cycles show very little change with advancing age. The third chapter reports the rate and timing of changes in female chimpanzee grip strength across adulthood. Grip strength is a widely used index of overall somatic vigor in women. Our comparisons are consistent with observations of earlier geriatric symptoms in chimpanzees. Taken together, these lines of evidence implicate different perimenopausal physiology in humans and chimpanzees, a difference that emerged as physiological aging slowed in the evolution of our human lineage. |
