Who we are -- our behavior, physiology, and health throughout our lives -- is strongly influenced by our early life. Decades of experimental research in animal taxa and epidemiological studies of humans have demonstrated that nutrition in the womb and behavioral care after birth are instrumental for the developing young. Mother's milk sustains infant growth, development, and behavioral activity, but little is known about the effects of milk on offspring brain and behavior, especially after weaning during adolescence and adulthood. Importantly, mother's milk is food, medicine, and hormonal signal. This project will investigate how mother's milk ingested in infancy influences neurobiology and social behavior in adolescence and adulthood by programming behavior during early life. Longitudinal, interdisciplinary research on how mother's milk shapes offspring, not only addresses key theoretical questions in animal behavior, but has important implications for infant nutrition, clinical recommendations, and human well-being. Such knowledge will inform maternal decisions about breast-feeding initiation and duration, improve replacement and supplemental formula compositions, influence clinical interventions during early life, and can shape institutional policy (e.g., parental leave). Researchers in the Comparative Lactation Lab create research opportunities for undergraduate, graduate, and post-doctoral trainees, particularly through minority tracks of the PRISE (Program for Research in Science & Engineering) and HGWISE (Harvard Graduate Women in Science and Engineering). The results will be communicated to the general public through "Mammals Suck... Milk!" a blog written accessibly for clinical and lay audiences, as well as science outreach lectures in K-12 classrooms, natural history museums, and science centers.

The study will address two key questions in rhesus monkeys (Macaca mulatta): 1) How does early life nutrition and hormonal signaling via mother's milk affect social behavior, particularly social networks, mating, and maternal behavior during transitions from adolescence to adulthood and 2) How are these behavioral effects mediated through the organization of temperament and neurobiology during infancy. Neurobiological (PET and MRI) and behavioral investigations of lactocrine programming, both nutritional and hormonal, are needed in long-lived, socially-complex, singleton-rearing taxa. This project provides an unparalleled and ephemeral opportunity to prospectively assess neurobiological and behavioral outcomes in a targeted cohort of adolescent and adult rhesus monkeys that were intensively studied as infants, including systematic analysis of the milk their mothers produced. Longitudinal integration of early life experiences with neurobiology, behavioral phenotype, and fitness outcomes addresses fundamental aspects of maternal effects and developmental programming and advances an understanding of how selection has shaped maternal investment strategies and consequences for offspring. Results generated from the proposed research will be disseminated to the scholarly and clinical community via open access publication and data will be made searchable, available, and citable through the online Dryad Data Repository.