Grandmothering and cognitive resources are required for the emergence of menopause and extensive post-reproductive lifespan

Abstract

Menopause, the permanent cessation of ovulation, occurs in humans well before the end of the expected lifespan, leading to an extensive post-reproductive period which remains a puzzle for evolutionary biologists. All human populations display this particularity; thus, it is difficult to empirically evaluate the conditions for its emergence. In this study, we used artificial neural networks to model the emergence and evolution of allocation decisions related to reproduction in simulated populations. When allocation decisions were allowed to freely evolve, both menopause and extensive post-reproductive life-span emerged under some ecological conditions. This result allowed us to test various hypotheses about the required conditions for the emergence of menopause and extensive post-reproductive life-span. Our findings did not support the Maternal Hypothesis (menopause has evolved to avoid the risk of dying in childbirth, which is higher in older women). In contrast, results supported a shared prediction from the Grandmother Hypothesis and the Embodied Capital Model. Indeed, we found that extensive post-reproductive lifespan allows resource reallocation to increase fertility of the children and survival of the grandchildren. Furthermore, neural capital development and the skill intensiveness of the foraging niche, rather than strength, played a major role in shaping the age profile of somatic and cognitive senescence in our simulated populations. This result supports the Embodied Capital Model rather than the Grand-Mother Hypothesis. Finally, in simulated populations where menopause had already evolved, we found that reduced post-reproductive lifespan lead to reduced children’s fertility and grandchildren’s survival. The results are discussed in the context of the evolutionary emergence of menopause and extensive post-reproductive life-span.

A reformulated contextual model of psychotherapy for treating anxiety and depression

“…When drones (male honey bees) lose their reproductive function in the autumn they are expelled from the hive and die. Paleolithic grandparents, despite their weaker physique, provided selective advantage as information providers and educators carers of grandchildren ( Aimé, André, & Raymond, 2017 ; Thouzeau & Raymond, 2017 ), a grandparenting function that differs from those of animals where there are reproductive grandparents ( Péron et al, 2019 ). The evolutionary history of humans shows that, although relationships are important, survival depended on much more, for example, exploration and discovery, planning, nurturing, hunting and aggression, technological skills, education, remembering, problem solving etc., which are summarised to some extent by the primary motives of self-determination theory, connection, autonomy and competence ( Deci & Ryan, 2012 ).…”

Can postfertile life stages evolve as an anticancer mechanism?

“…Another (and probably the most popular explanation for reproductive cessation) is the “grandmother hypothesis.” It posits that a long postfertile life span in females improves the likelihood that their grandchildren (who carry a quarter of their genes on average) reach the age of sexual maturity. Thus, by helping their relatives to survive and reproduce, perhaps through the transmission of cultural knowledge [16], postreproductive females may increase their inclusive fitness through kin selection [17–19]. Adaptive hypotheses proposed to explain the evolution of postfertile life span converge toward the idea that reproduction through time progressively compromises the health and survival prospects of females (e.g., [20] [21], see also [22] for a synthesis in women), which ultimately jeopardizes the fate of their offspring and grandoffspring, as observed in Asian elephants, Elephas maximus [23,24].…”

O conhecimento produzido acerca de climatério, família e envelhecimento

“…A análise da influência da família enquanto participante do envelhecimento feminino no climatério destacou a correlação entre a menopausa, o cessar definitivo da ovulação e o fim da expectativa de vida. Foram discutidas a Hipótese Materna, que versa sobre a regulação da fertilidade a partir da menopausa em sua evolução natural, defendendo que essa regulação deva acontecer, já que quanto mais velha fica uma mulher, maior é seu risco de morrer no parto 11 ; e a Hipótese da Avó, que traz uma abertura à longevidade quando subsidiada a fertilidade de suas filhas através da previsão dos netos, sendo esta uma possibilidade de se viver fértil por muitos anos 12 . Para além da reprodução, as avós são presenças capazes de promover a cognição e o engajamento social de suas filhas, quando oferecem assistência e companhia a seus netos 13 .…”

“…Origem dos estudos Abordagem metodológica Grand mothering and cognitive resources are required for the emergence of menopause and extensive post-reproductive lifespan 11 .…”