Grandmotherhood across the demographic transition

Abstract

Grandmothers provide key care to their grandchildren in both contemporary and historic human populations. The length of the grandmother-grandchild relationship provides a basis for such interactions, but its variation and determinants have rarely been studied in different contexts, despite changes in age-specific mortality and fertility rates likely having affected grandmotherhood patterns across the demographic transition. Understanding how often and long grandmothers have been available for their grandchildren in different conditions may help explain the large differences between grandmaternal effects found in different societies, and is vital for developing theories concerning the evolution of menopause, post-reproductive longevity, and family living. Using an extensive genealogical dataset from Finland spanning the demographic transition, we quantify the length of grandmotherhood and its determinants from 1790–1959. We found that shared time between grandmothers and grandchildren was consistently low before the demographic transition, only increasing greatly during the 20th century. Whilst reduced childhood mortality and increasing adult longevity had a role in this change, grandmaternal age at birth remained consistent across the study period. Our findings further understanding of the temporal context of grandmother-grandchild relationships, and emphasise the need to consider the demography of grandmotherhood in a number of disciplines, including biology (e.g. evolution of the family), sociology (e.g. changing family structures), population health (e.g. changing age structures), and economics (e.g. workforce retention).

Limits to Fitness Benefits of Prolonged Post-reproductive Lifespan in Women

“…Throughout the study period, a grandmother and grandchild would live at the same time for an average of between 5-10 years [19]. The population was predominantly patrilocal [20,21], with the eldest son typically inheriting the farm, and dispersal rates were generally low, such that most adult siblings lived nearby [22], and therefore, both maternal and paternal grandmothers would often be close to their grandchildren, but typically only paternal grandmothers were co-resident [23].…”

Offspring fertility and grandchild survival enhanced by maternal grandmothers in a pre-industrial human society

“…We initially controlled for social class, region, birth order, quadratic (mean-centred) age, and number of living siblings, while entering mother ID as a random effect to account for shared family effects between siblings. We did not control for birth cohort in the final model, because age at first birth did not vary across time in this population 48 (though running the model with this random term included did not affect the results). After model selection, we dropped the social class and region terms.…”

“…Together, these factors contributed to decreases in birth rates and childhood mortality 45 from the high levels typical of pre-demographic transition societies 46,47 . Adult life expectancy was greater than 60 years 41 , and an average grandmother and grandchild would live at the same time (and therefore could help and be helped, respectively) for less than 10 years across the study period 48 . Residence was typically patrilocal, and migration was constrained such that both sets of grandparents typically lived nearby and marital partners came from the same or nearby villages.…”

Counting on Potential Grandparents? Adult Children’s Entry Into Parenthood Across European Countries

“…In light of the increase in both age at first birth and longevity, parents are more likely than in the past to live for many years while their children are adults. Thus, today’s parents are in a better position than previous generations to assume an important role in the lives of their children and grandchildren (Bengtson 2001 ; Bengtson et al 1990 ; Chapman et al 2018 ; Gauthier 2002 ; Margolis and Wright 2017 ; Silverstein 2005 ). When it comes to fertility, parental characteristics might materially influence the fertility outcomes of their adult children.…”