This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book seeks to spark new research and theoretical innovation that bridges anthropological subfields around breastfeeding. It highlights some key themes that have influenced recent work on breastfeeding. The chapters of the book are organized around four key themes: relationality and interembodiment; cultural ideologies and biocultural practices; variability and adaptability; and ecological and political economic considerations. The chapters on cultural ideologies use a case study from American Samoa to demonstrate how cultural preferences for a larger infant body size shape breastfeeding practices, ultimately leading to the shorter duration of exclusive breastfeeding and increasing the vulnerability of this population to obesity and its health consequences. The next group highlights variation and adaptability as a key feature of human lactation and infant feeding. Finally, the book highlights the considerable overlap in ecological modes of inquiry in biological anthropology, and political economic approaches in sociocultural anthropology.