To contribute to the creation of a new theoretical synthesis about the relationship between the biological and social dimensions of breastfeeding, categorizing it as a nature-nurture hybrid.The methodological approach of the present article was based on the qualitative health research frame, and data were analyzed on the basis of dialectic-hermeneutic principles. Primary sources, comprising historical documents, books, scientific articles and medical theses written in the 19th and 20th centuries were analyzed.Depending on the moment in history and on the expectations that surround the act of breastfeeding, the aspects related to nature and nurture, i.e., to biology and society, sometimes separate out and sometimes intermingle. A comprehensive approach to breastfeeding makes possible to see that it had to be considered instinctive, natural and biological in order to be assimilated as a cultural habit, and thus, it is not open to any kind of questioning. On other occasions, particularly in the course of the past decade, there has been a steady tendency to supplant traditional biological reductionism, which yielded cultural interpretations that do not reduce the human being to the status of a mammal like any other. Under this point of view, breastfeeding, in addition to being biologically determined, is socially conditioned, and thus constitutes an act embedded in ideologies and determinants resulting from the concrete conditions of life. In real life, however, a process apparently so natural, so loaded with affection and emotion is, in fact, affected by the most aggressive market interests, very often presented as scientific knowledge and decked out as health provisions.Breastfeeding focused as a nature-culture hybrid symbolizes the theoretical and methodological changes in the field, especially in the late 1990s. These changes reflect a renewed appreciation of biology and a more in-depth approach to interdisciplinary processes.