Familial allomaternal care exposure is predictive of infant development

Alloparental Support and Infant Psychomotor Developmental Delay

Receiving social support from community and extended family has been typical for mothers with infants in human societies past and present. In non-industrialised contexts, infants of mothers with extended family support often have better health and higher survival through the vulnerable infant period, and hence shared infant care has a clear fitness benefit. However, there is scant evidence that these benefits continue in industrialised contexts. Better infant health and development with allocare support would indicate continued evolutionary selection for allocare. The research reported here used multiple logistic regression analysis to test whether a lack of family and other social support for mothers was associated with an increased risk of developmental delay in 9-month-old infants in the UK Millennium Cohort (analysis sample size, 15,696 infants). Extended family-based childcare during work hours and more maternal time spent with friends were the most influential kin and social support variables: infants of mothers with kin-based childcare versus all other childcare arrangements had a lower risk of developmental delay (OR = 0.61, 95% CIs: 0.46-0.82). Infants of mothers who spent no time with friends when compared with those who saw friends every day had double the odds of delay. Greater paternal involvement in infant care was associated with a lower odds of developmental delay. In conclusion, shared care of infants and social support for mothers may influence fitness-related traits in industrialised societies rather than being factors that influenced selection only in the past and in societies which retain close kin networks and a strong local community focus.

Learning Through Shared Care : Allomaternal Care Impacts Cognitive Development in Early Infancy in a Western Population

This study investigates how allomaternal care (AMC) impacts human development outside of energetics by evaluating relations between important qualitative and quantitative aspects of AMC and developmental outcomes in a Western population. This study seeks to determine whether there are measurable differences in cognitive and language outcomes as predicted by differences in exposure to AMC via formal (e.g., childcare facilities) and informal (e.g., family and friends) networks. Data were collected from 102 mothers and their typically developing infants aged 13-18 months. AMC predictor data were collected using questionnaires, structured daily diaries, and longitudinal interviews. Developmental outcomes were assessed using the Cognitive, Receptive Language, and Expressive Language subtests of the Bayley III Screening Test. Additional demographic covariates were also evaluated. Akaike Information Criterion (AIC)-informed model selection was used to identify the best-fitting model for each outcome across three working linear regression models. Although AMC variables had no significant effects on Receptive and Expressive Language subtest scores, highly involved familial AMC had a significant medium effect on Cognitive subtest score (β = 0.23, p < 0.01, semi-partial r = 0.28). Formal childcare had no effect on any outcome. This study provides preliminary evidence that there is a measurable connection between AMC and cognitive development in some populations and provides a methodological base from which to assess these connections cross-culturally through future studies. As these effects are attributable to AMC interactions with networks of mostly related individuals, these findings present an area for further investigation regarding the kin selection hypothesis for AMC.