February 11, 2019

Human infant feeding: evolved strategies, individual optimums, and public health

Melanie Martin, University of Washington

Across past and present human populations, breastfeeding and weaning practices have been demonstrably varied. Though this variation is largely influenced by ecological and socioeconomic factors, comparative primate and human biological and cross-cultural evidence further suggests that flexible mixed-feeding is an evolved human strategy. In this talk, I review the differences in infant energetic needs and maternal time, physical, and reproductive constraints that favor individual optimums for exclusive and total breastfeeding durations. I draw on my work with indigenous Tsimane and Qom/Toba families to illustrate that (1) early (“suboptimal”) mixed-feeding can still be compatible with long-term, intensive breastfeeding and (2) that more discreet measures of feeding trajectories and their multidirectional effects on growth and other biological processes should be considered in assessing relationships to health outcomes. In closing I emphasize that these positions are not incompatible with current age-delineated feeding recommendations, which are essential for uniform public health messaging and related policy development. Instead, an evolutionary and biocultural perspective may inform parallel dialogs among families and health care providers that acknowledge diverse needs and circumstances in shaping individual feeding optimums.