A new study finds the timing of menopause is probably a function of how long it takes a female to raise her offspring. The longer it takes to rear an infant, the earlier menopause sets in....which could be nature's way of making sure young are mature before their mother dies of old age. University of Minnesota Ecology Professor and study co-author, Craig Packer, based his findings on research on baboons and lions, two mammals that take a relatively long time to raise their young.