How Did the Human Menopause Arise

Abstract

Both an anxious public and a concerned medical profession wonder about the human menopause: essentially, is it normal or abnormal? Through a proposed natural history, the present study explores this problem. When, 2.5 million years ago, the great East African geologic change occurred altering ancestral human habitats from wet nonseasonal rainforest to dry biseasonal savannah, human evolution came to be shaped by two major forces: one, dry season hardship; the other, lengthening of periods of dependency of human young. Commencing at this juncture, premature ovarian failure in older women would have served both to permit an increase in years of postfertile reproductive care and, at the expense of reduced numbers of progeny, to increase rates of survival of existing children. With years of dependency of human young subsequently lengthening, prematurity of ovarian failure advanced, producing longer periods of ovarian hormone deficiency. Tapering from approximately age 50 onward, the use of hormone replacement therapy with a projected termination in the eighth decade appears physiologically appropriate to the life-course trajectory of a modern woman