Levels of reproductive skew vary in wild primates living in multimale groups depending on the degree to which high-ranking males monopolize access to females. Still, the factors affecting paternity in egalitarian societies remain unexplored. We combine unique behavioral, life history, and genetic data to evaluate the distribution of paternity in the northern muriqui (Brachyteles hypoxanthus), a...

Two classes of explanation have been advanced to explain women’s long post-menopausal life span – that it is an epiphenomenon of increased longevity or an evolved adaptation. While there is no decisive evidence to choose between them, the latter appears more likely. Two mechanisms for the evolved adaptation have been proposed, the ‘mother effect’ and the ‘grandmother effect’. It is argued that ...

Results We identified 21 putative candidate variants that are both novel and consistent with dominant inheritance. Sanger sequencing validated all 21 variants. Three variants identified in TNFRSF9, MGEA5, and TNFAIP3 genes were confirmed to have arisen de novo in the affected mother based on the genotyping of the healthy maternal grandmother, the maternal unaffected brother, and the unaffected ...

In the United States, about 25% of women choose not to initiate breastfeeding, yet little is known about how opinions of individuals in a woman's support network influence her decision to breastfeed. In the 2005-2007 Infant Feeding Practices Study II, women completed questionnaires from the last trimester of pregnancy until 12 months postpartum. Mothers indicated prenatally their family members...

We conducted a meta-analysis of 17 studies that tested for an association between grandparental survival and grandchild survival in patrilineal populations. Using two different methodologies, we found that the survival of the maternal grandmother and grandfather, but not the paternal grandmother and grandfather, was associated with decreased grandoffspring mortality. These results are consisten...

Using multivariate techniques, the authors investigate how age, family type, and race/ethnicity affect grandmother-headed families’ economic resources. The authors examine four grandmother-headed family types that are classified on the basis of two features: parents’ presence and the caregiving relationship of the grandmother and grandchild. Using data from the 2000 census (Public Use Microdata...

Grandmothers play a crucial role in families enhancing grandchild wellbeing and survival but their effects can be context-dependent, the children born poor conditions are most likely to benefit from investments made by helping grandmothers. In this study, we examined, for first time, whether grandmothers' presence modified associations between adverse birth status up 5 years of age. detail, ver...

Usually animals reproduce into old age, but a few species such as humans and killer whales can live decades after their last reproduction. The grandmother hypothesis proposes that such life-history evolved through older females switching to invest in their existing (grand)offspring, thereby increasing their inclusive fitness and selection for post-reproductive lifespan. However, positive grandm...