Evolutionary adaptation perspectives on childcare with references to life history plasticity in the modern world: Brazil, Russia, and the USA

Introduction. The cooperative breeding framework suggests that help from extended family members with childrearing is important adaptation for our species survival, and it is universal. However, the degree of alloparental help may vary between societies, families, and over time. We hypothesized that maternal and paternal effort, as well as alloparental carе, would depend both upon resource availability (SЕS) and different mating opportunities for males and females in three countries: Brazil, Russia, and the USA. Methods. We analyzed the intergenerational interactions between family members during childcare via Structural Equation Modeling (SEM) in R-software. Online samples were collected from Brazil (N = 603), Russia (N = 620), and the USA (N = 314). Results and discussion. The results of our study are consistent with previous research on life history (LHT) plasticity, which has shown a negative correlation between low SES and parental effort. However, our models indicated a possible cultural difference in the estimates of poverty paths: in Brazilian and American samples, SES had a greater impact on paternal care than on maternal, while in Russia, poverty had a greater effect on mothers’ effort. This reversed effect size on maternal versus paternal effort in Russia may suggest that Russian mothers experience a trade-off between working outside the home and direct childcare, while Russian fathers may adopt a “faster” LHT strategy as they are the limited sex in the mating pool. Our findings also demonstrate that the parental effort of both parents was positively associated, indicating their mutualistic relationship. We also found that maternal grandparents usually compensate the lack of paternal effort, but their help, as well as the help of paternal grandparents, was indifferent to the poverty cues.