Twenty-first century grandparents: global perspectives on changing roles and consequences

Human menopause is ubiquitous among women and is uninfluenced by modernity. In addition, it remains an evolutionary puzzle: studies have largely failed to account for diminishing selection on reproduction beyond 50 years. Using a 200-year dataset on pre-industrial Finns, we show that an important component is between-generation reproductive conflict among unrelated women. Simultaneous reproduction by successive generations of in-laws was associated with declines in offspring survivorship of up to 66%. An inclusive fitness model revealed that incorporation of the fitness consequences of simultaneous intergenerational reproduction between in-laws, with those of grandmothering and risks of dying in childbirth, were sufficient to generate selection against continued reproduction beyond 51 years. Decomposition of model estimates suggested that the former two were most influential in generating selection against continued reproduction. We propose that menopause evolved, in part, because of age-specific increases in opportunities for intergenerational cooperation and reproductive competition under ecological scarcity. © 2012 Blackwell Publishing Ltd/CNRS.

Objectives To examine the effect of parental rural-to-urban internal migration on nutritional status of left-behind children and how this is related to guardianship. Methods We used UNICEF China’s maternal and child health survey data to investigate stunting prevalence and feeding practices in children left behind by rural-to-urban internal migrant parents. We also assessed the effects of primary guardianship which is related closely with parental migration. Results Of 6136 children aged 0–3 years, over one-third was left behind by one or both parents. About 13 % were left behind by mothers, leaving guardianship primarily to grandmothers. Left-behind status was not associated with stunting, yet children who were cared for primarily by their fathers had a 32 % increase of stunting compared to children cared for by the mothers [adjusted odds ratio (aOR) = 1.32; 95 % confidence interval = 1.04–1.67]. Children with migrant mothers were less likely to receive age-appropriate breastfeeding (aOR = 0.04;0.02–0.10) and a minimum acceptable diet (aOR = 0.56;0.39–0.79) compared with non-left-behind children. Conclusions Guardian’s feeding behaviours varied, and was inappropriate for both children affected and not affected by parent’s rural-to-urban internal migration. Community-based infant and young child feeding counselling and support should be provided to all caregivers. Electronic supplementary material The online version of this article (doi:10.1007/s00038-016-0844-6) contains supplementary material, which is available to authorized users.