<P> The mother hypothesis suggests that menopause was selected for humans because of the extended development period of human offspring and high costs of reproduction so that mothers gain an advantage in reproductive fitness by redirecting their effort from new offspring with a low survival chance to existing children with a higher survival chance . </P> <P> The grandmother hypothesis suggests that menopause was selected for humans because it promotes the survival of grandchildren . According to this hypothesis, post-reproductive women feed and care for children, adult nursing daughters, and grandchildren whose mothers have weaned them . Human babies require large and steady supplies of glucose to feed the growing brain . In infants in the first year of life, the brain consumes 60% of all calories, so both babies and their mothers require a dependable food supply . Some evidence suggests that hunters contribute less than half the total food budget of most hunter - gatherer societies, and often much less than half, so that foraging grandmothers can contribute substantially to the survival of grandchildren at times when mothers and fathers are unable to gather enough food for all of their children . In general, selection operates most powerfully during times of famine or other privation . So although grandmothers might not be necessary during good times, many grandchildren cannot survive without them during times of famine . Arguably, however, there is no firm consensus on the supposed evolutionary advantages (or simply neutrality) of menopause to the survival of the species in the evolutionary past . </P> <P> Indeed, analysis of historical data found that the length of a female's post-reproductive lifespan was reflected in the reproductive success of her offspring and the survival of her grandchildren . Another study found comparative effects but only in the maternal grandmother--paternal grandmothers had a detrimental effect on infant mortality (probably due to paternity uncertainty). Differing assistance strategies for maternal and paternal grandmothers have also been demonstrated . Maternal grandmothers concentrate on offspring survival, whereas paternal grandmothers increase birth rates . </P> <P> Some believe a problem concerning the grandmother hypothesis is that it requires a history of female philopatry, while in the present day the majority of hunter - gatherer societies are patrilocal . However, there is disagreement split along ideological lines about whether patrilineality would have existed before modern times . Some believe variations on the mother, or grandmother effect fail to explain longevity with continued spermatogenesis in males (oldest verified paternity is 94 years, 35 years beyond the oldest documented birth attributed to females). Notably, the survival time past menopause is roughly the same as the maturation time for a human child . That a mother's presence could aid in the survival of a developing child, while an unidentified father's absence might not have affected survival, could explain the paternal fertility near the end of the father's lifespan . A man with no certainty of which children are his may merely attempt to father additional children, with support of existing children present but small . Note the existence of partible paternity supporting this . Some argue that the mother and grandmother hypotheses fail to explain the detrimental effects of losing ovarian follicular activity, such as osteoporosis, osteoarthritis, Alzheimer's disease and coronary artery disease . </P>

Who will most likely have marked symptoms of menopause