An evolutionary perspective on the origin and ontogeny of menopause

Trajectories and phenotypes with estrogen exposures across the lifespan: What does Goldilocks have to do with it?

“…Though whales and elephants may have a comparable post-reproductive lifespan to humans (Kuhle, 2007; Lahdenperä et al, 2014; Ward et al, 2009), they are not close relatives to our species, and extended longevity after reproductive senescence has not been observed in non-human primates (Gems, 2014; Sievert, 2014). Cooperative social dynamics and relatedness to other conspecifics within each species can also be a tool to understand longevity beyond reproductive senescence (Johnstone and Cant, 2010).…”

“…The prevalent though debated “Grandmother Hypothesis,” popularized by G.C. Williams in 1957, states that menopause — which was thought to be uniquely human at that time — might be a result of natural selection because it is an adaptive advantage for non-reproducing females to continue to care for, and put resources into, the survival of their genealogical lineage (Kuhle, 2007; Williams, 1957). A grandmother's contribution of resources, particularly food resources, to mothers and children could increase the children's potential to survive to reproductive age as well as maintain the heath of the mother (Hawkes et al, 1998).…”

“…This is in line with the closely related “Mother Hypothesis,” which postulates that births are riskier for the mother at a later age, so it is more advantageous to cease reproductive ability early and invest in surviving children due to the extended period of infancy in humans which necessitates a large parental investment (Hawkes and Coxworth, 2013; Pavard et al, 2008; Wu et al, 2005). As a social species, devoting food resources and continued care to offspring that have a greater chance of survival is more advantageous than continued reproduction of children that may not survive infancy; likewise, mother mortality can compromise survival rates of immature children so maternal maintenance is also an important factor (Hawkes et al, 1998; Kuhle, 2007; Pavard et al, 2008). In sum, the “Grandmother” and “Mother” hypotheses are based on the idea that menopause is an evolutionarily adaptive trait that prevents maternal mortality and supports surviving children to maturity and reproductive age.…”

“…Additionally, the rate at which chimpanzees (the closest living relatives to humans) and human females’ ovarian follicles deplete is remarkably similar, yet a chimpanzee's lifespan is much shorter than modern humans and they lack an extended post-menopausal life stage, indicating that humans’ unique capacity for longevity evolved long ago (Gems, 2014). Despite the fact that the average life expectancy started to increase in the twentieth century (Hawkes and Coxworth, 2013), anthropological evidence suggests that “menopause and post-reproductive life are not new phenomena” (Sievert, p. 1153, 2014) even in early civilizations and other hominid ancestors (Kuhle, 2007; Sievert, 2014). Information obtained from female ancient Egyptian mummies indicates that women lived into their forties (Allam et al, 2011), and estimates in early hunter-gatherer populations suggest that some women lived beyond 45 years of age (Hawkes, 2004).…”

“…The “Patriarch Hypothesis” postulates that older men continue to reproduce late in life with younger women, and this selection for older male fathers increases the probability for offspring to also have a long lifespan. According to this hypothesis, longevity in women is a byproduct of selective mating with older males (Gems, 2014; Kuhle, 2007). This theory also leads to evidence for antagonistic pleiotropy, or the effect that a particular genetic trait may have benefits early in life (e.g.…”